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Open Habitats (open + habitat)

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Animal Science & Zoology	6%
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Selected Abstracts

Evaluating the Predicted Local Extinction of a Once-Common Mouse

CONSERVATION BIOLOGY, Issue 4 2005
OLIVER R.W. PERGAMS
Chicago; declinación de especies comunes; extinción pronosticada; Peromyscus leucopus; Peromyscus maniculatus bairdii Abstract:,In an earlier paper (Pergams & Nyberg 2001) we found that the proportion of the prairie deer mouse (Peromyscus maniculatus bairdii), among all local Peromyscus museum specimens collected in the Chicago region, had significantly declined over time. This proportion changed from about 50% before 1900 to <10% in the last 25 years. Based on this proportion a regression model predicted the local extinction of the prairie deer mouse in 2009. To evaluate that prediction, we estimated current deer mouse abundance by live trapping small mammals at 15 preserves in Cook and Lake counties, Illinois (USA) at which prairie deer mice had previously been caught or that still contained their preferred open habitat. In 1900 trap nights, 477 mammals were caught, including 251 white-footed mice (P. leucopus), but only one prairie deer mouse. The observed proportion of Peromyscus that were prairie deer mice, 0.4%, was even lower than the 4.5% predicted for 2000. Here we also introduce a simple, new community proportions model, which for any given geographic region compares the proportions of species recently caught with the proportions of species in museums. We compared proportions of seven species collected in Cook and Lake counties and examined by Hoffmeister (1989) with proportions of these species that we caught. Ten percent of the museum community was prairie deer mice, but only 0.2% of our catch was. The current local scarcity of the prairie deer mouse is consistent with the regression-based prediction of its eminent local extinction. More conservation attention should be paid to changes in relative abundance of once-common species. Resumen:,En un artículo previo (Pergams & Nyberg 2001) encontramos que la proporción de Peromyscus maniculatus bairdii, entre todos los especimenes de museo de Peromyscus recolectados en la región de Chicago, había declinado significativamente. Esta proporción cambió de 50% antes de 1900 a <10% en los últimos 25 años. Con base en esta proporción, un modelo de regresión pronosticó la extinción local de P. m. bairdii en 2009. Para evaluar esa predicción, estimamos la abundancia actual de P. m. bairdii mediante el trampeo de mamíferos pequeños en 25 reservas en los condados Cook y Lake, Illinois (E.U.A.) en las que se había capturado a P. m. bairdii previamente o que aun contenían su hábitat abierto preferido. En 1900 noches-trampa, capturamos a 477 mamíferos, incluyendo a 251 P. leucopus pero solo a un P. m. bairdii. La proporción observada de P. m. bairdii, 0.4%, fue menor a 4.5% pronosticado para 2000. Aquí también introducimos un modelo, nuevo y sencillo, de proporciones de la comunidad que compara, para cualquier región geográfica, las proporciones de especies recientemente capturadas con la proporciones de especies en los museos. Comparamos las proporciones de siete especies recolectadas en los condados Cook y Lake y examinadas por Hoffmeister (1989) con las proporciones de especies que capturamos. Diez por ciento de la comunidad de museos era P. m. bairdii, pero solo 0.2% de nuestra muestra lo fue. La actual escasez local de P. m. bairdii es consistente con la predicción de su inminente extinción local con base en la regresión. La conservación debe prestar mayor atención a los cambios en la abundancia relativa de una especie anteriormente común. [source]

A Historical Perspective and Future Outlook on Landscape Scale Restoration in the Northwest Wisconsin Pine Barrens

RESTORATION ECOLOGY, Issue 2 2000
Volker C. Radeloff
Abstract The concurrent discussions of landscape scale restoration among restoration ecologists, and of historic disturbance pattern as a guideline for forest management among forest scientists, offer a unique opportunity for collaboration between these traditionally separated fields. The objective of this study was to review the environmental history, early restoration projects, and current plans to restore landscape patterns at broader scales in the 450,000 ha northwest Wisconsin Pine Barrens. The Pine Barrens offer an example of a landscape shaped by fire in the past. In northwestern Wisconsin historically the barrens were a mosaic of open prairie, savanna, and pine forests on very poor, sandy soils. The surrounding region of better soils was otherwise heavily forested. Six restoration sites have been managed since the middle of this century using prescribed burns to maintain the open, barrens habitat. However, these sites are not extensive enough to mimic the shifting mosaic of large open patches previously created by fire. Extensive clear-cuts may be used as a substitute for these large fire patches so that presettlement landscape patterns are more closely approximated in the current landscape. We suggest that such silvicultural treatments can be suitable to restore certain aspects of presettlement landscapes, such as landscape pattern and open habitat for species such as grassland birds. We are aware that the effects of fire and clear-cuts differ in many aspects and additional management tools, such as prescribed burning after harvesting, may assist in further approximating the effect of natural disturbance. However, the restoration of landscape pattern using clear-cuts may provide an important context for smaller isolated restoration sites even without the subsequent application of fire, in this formerly more open landscape. [source]

Remnant habitats for grassland species in an abandoned Swedish agricultural landscape

APPLIED VEGETATION SCIENCE, Issue 3 2010
Anna Dahlström
Abstract Questions: Which factors influence the persistence of vascular grassland plants in long-abandoned (at least 50 yr) arable fields and meadows? What might be the implications of current levels of species richness on abandoned arable fields and meadows for future restoration? Location: Forested highlands of Kilsbergen, south central Sweden. Methods: The abundance of all vascular plant species was investigated in three habitat types: former arable fields, hay meadows and outlands (pastures) at 27 farms, abandoned for either approximately 50 yr or 90 yr. Time since abandonment, tree cover, soil depth, degree of soil podsol development, size of the infield area and two measures of connectivity were used as predictors for species richness and species composition. Results: Former outland had denser tree cover, fewer species and fewer grassland species than former arable fields and hay meadows, irrespective of time since abandonment. Former hay meadows and arable fields with a longer time since abandonment were less rich in species, more wooded and had greater podsolization than meadows and fields abandoned at a later stage. Species richness was higher in hay meadows and arable fields at farms with larger infield area and deeper soils compared with farms with smaller infield area and shallower soils. The greatest richness of species and most open habitat were former arable fields at larger farms abandoned 50 yr before the study. Former arable fields had the highest number of grassland species. Conclusion: After 50 yr of abandonment, former arable fields were the most important remnant habitats for grassland species and may be a more promising target for restoration than formerly managed grasslands. [source]

Comparison and Origin of Forest and Grassland Ant Assemblages in the High Plateau of Madagascar (Hymenoptera: Formicidae),

BIOTROPICA, Issue 1 2002
Brian L. Fisher
ABSTRACT We assessed species richness and composition of ant assemblages in adjacent montane forest and secondary (anthropogenic) grassland habitats in the central plateau of Madagascar. We used five quantitative methods (leaf litter sifting, two types of pitfall traps, beating low vegetation, and soil digging) and compared methods within and across habitats. Sample,based and occurrence,based accumulation curves demonstrated that die efficiency of ant inventory methods is habitat specific. Litter sifting, however, was the single most efficient method in both habitats. Overall, our analyses of the relative efficiency of methods recommend the use of sifting and beating in the montane forest site, and sifting alone in the grassland site. In four of five methods, more species were collected in the grassland site (31 spp.) than in the forest site (26 spp.). Occurrence,based accumulation curves based on all methods demonstrated that species richness was similar in the two habitats, reaching a maximum difference of approximately one species. Only five species were shared between the grassland and forest sites. The presence of a high number of ant species restricted to the grassland site (18 spp.) is the first record of high endemism in this habitat in Madagascar and may have strong implications for the reconstruction of the natural vegetation types at the time humans arrived. Their presence suggests that a comparable open habitat, such as montane woodland, shrubland, or thicket, was present on Madagascar long before humans developed the secondary grasslands less than 2000 years ago. These results are contrary to the "classical hypothesis" that the central plateau was a continuous region of closed forest. These results support the hypothesis that the montane regions, including the central plateau, once contained areas of habitat with an open structure and that the endemic ants now found in the secondary grasslands were originally native to such a habitat. RéSUMé La richesse en espéces et la composition des fourmis ont été inventoriées dans la for,t montagneuse du plateau central de Madagascar et dans la prairie secondaire adjacente. Cinq méthodes quantitatives ont été utilisées (tamisage des litières, deux types de trous-pièges, battage des végétations basses et lavage de terre). Nous avons comparé I'efficacité de ces méthodes dans chacun et entre les deux habitats. Les courbes d'accumulation d'espèces basées sur I'échantillon et sur I'occurrence ont montré que I'efficacité des méthodes d'inventaire de fourmis est habitat-dépendant. Cependant, le tamisage des litières se montrait la méthode la plus efficace dans les deux habitats. Nos analyses sur I'efficacité relative des méthodes recommandent I'utilisation combinée du tamisage des litières et du battage de végétation dans la for,t montagneuse, et I'utilisation seule du tamisage des litières dans la prairie secondaire. Dans quatre des cinq méthodes, plus d'espèces ont été collectées dans la prairie (31 spp.) que dans la for,t (26 spp.). Les courbes d'accumulation d'occurrence basées sur routes les méthodes ont démontré que la richesse en espèces de ces deux habitats est similaire, atteignant seulement une difference maximale d'approximativement une espèce. Pourtant, seulement cinq espèces parta-geaient les deux habitats. La présence de plusieurs espèces de fourmis uniquement trouvées dans la prairie (18 spp.) est la première observation d'une forte endémicité de cet habitat et peut avoir une importante implication pour la restauration des types de végétation naturelle initiale de I'ile. Leur présence suggère que des habitats ouverts similaires tels que les formations arbustives de montagnes et les fourrés, étaient présentsà Madagascar longtemps avant la transformation de ces habitats en prairie secondaire par les humains. Ces résultats contredisent I'hypothèse classique qui avance que le plateau central a é té uniquement composé d'une région de for,t dense. Ainsi, ces résultats supportent I'hypothese que la région montagneuse contenant le plateau central, renfermait des habitats àstructure ouverte et que les fourmis endémiques actuellement trouvées dans la prairie secondaire sont, a I'origine natives de ces habitats. [source]

One Hundred Fifty Years of Change in Forest Bird Breeding Habitat: Estimates of Species Distributions

CONSERVATION BIOLOGY, Issue 6 2005
LISA A. SCHULTE
aptitud del hábitat; ecología aviar; ecología de paisaje; planificación de conservación Abstract:,Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant change. We propose pre-Euro-American settlement as an alternative baseline for assessing changes in bird populations. We evaluated the amount, quality, and distribution of breeding bird habitat during the mid-1800s and early 1990s for three forest birds: the Pine Warbler (Dendroica pinus), Blackburnian Warbler (D. fusca), and Black-throated Green Warbler (D. virens). We constructed models of bird and habitat relationships based on literature review and regional data sets of bird abundance and applied these models to widely available vegetation data. Original public-land survey records represented historical habitat conditions, and a combination of forest inventory and national land-cover data represented current conditions. We assessed model robustness by comparing current habitat distribution to actual breeding bird locations from the Wisconsin Breeding Bird Atlas. The model showed little change in the overall amount of Pine Warbler habitat, whereas both the Blackburnian Warber and the Black-throated Green Warbler have experienced substantial habitat losses. For the species we examined, habitat quality has degraded since presettlement and the spatial distribution of habitat shifted among ecoregions, with range expansion accompanying forest incursion into previously open habitats or the replacement of native forests with pine plantations. Sources of habitat loss and degradation include loss of conifers and loss of large trees. Using widely available data sources in a habitat suitability model framework, our method provides a long-term analysis of change in bird habitat and a presettlement baseline for assessing current conservation priority. Resumen:,La evaluación de tendencias de las poblaciones de aves requiere de datos de referencia. En Norte América, los primeros datos disponibles de poblaciones son del final de la década de 1960. Sin embargo, las condiciones de los bosques en los estados de los Grandes Lagos (E.U.A.) han experimentado sucesión desde que la región fue talada en los inicios del siglo veinte, y se espera que las poblaciones de aves hayan experimentado cambios concomitantes. Proponemos que se considere al período previo a la colonización euro americana como referencia alternativa para evaluar los cambios en las poblaciones de aves. Evaluamos la cantidad, calidad y distribución del hábitat para reproducción de tres especies de aves de bosque (Dendroica pinus, D. fusca y D. virens) a mediados del siglo XIX e inicios del XX. Construimos modelos de las relaciones entre las aves y el hábitat con base en la literatura y conjuntos de datos de abundancia de aves y los aplicamos a los datos de vegetación ampliamente disponibles. Los registros topográficos de tierras públicas originales representaron las condiciones históricas del hábitat, y una combinación de datos del inventario forestal y de cobertura de suelo representaron las condiciones actuales. Evaluamos la robustez del modelo mediante la comparación de la distribución de hábitat actual con sitios de reproducción de aves registrados en el Wisconsin Breeding Bird Atlas. El modelo mostró poco cambio en la cantidad total de hábitat de Dendroica pinus, mientras que tanto D. fusca como D. virens han experimentado pérdidas sustanciales de hábitat. Para las especies examinadas, la calidad del hábitat se ha degradado desde antes de la colonización y la distribución espacial del hábitat cambió entre ecoregiones, con la expansión del rango acompañando la incursión de bosques en hábitats anteriormente abiertos o el reemplazo de bosques nativos con plantaciones de pinos. Las fuentes de pérdida y degradación de hábitats incluyen la pérdida de coníferas y de árboles grandes. Mediante la utilización de fuentes de datos ampliamente disponibles en un modelo de aptitud de hábitat, nuestro método proporciona un análisis a largo plazo de los cambios en el hábitat de aves y una referencia precolonización para evaluar prioridades de conservación actuales. [source]

Land-cover and land-use change and its contribution to the large-scale organization of Puerto Rico's bird assemblages

DIVERSITY AND DISTRIBUTIONS, Issue 1 2008
Miguel A. Acevedo
ABSTRACT Global biodiversity is changing rapidly driven by human alteration of habitat, and nowhere this is more dramatic than in insular habitats. Yet land-cover change is a complex phenomenon that not only involves habitat destruction but also forest recovery over different time scales. Therefore, we might expect species to respond in diverse ways with likely consequences for the reorganization of regional assemblages. These changes, however, may be different in tropical islands because of their low species richness, generalist habits and high proportion of endemics. Here, we focus on the island of Puerto Rico and ask how island-wide changes in land cover and land use has influenced the large-scale organization of bird assemblages. To address this question, we combined in a Geographical Information System (GIS) the first 6 years (1997,2002) of the Puerto Rican Breeding Bird Survey (PR-BBS) with land-cover and land-use data extracted from a published digital map derived from the classification of Landsat images. A Non-metric Multidimensional Scaling (NMS) ordination based on the composition and abundance of birds, and percentage land-use types showed that land use followed by climate could explain most of the variation observed among routes in terms of species composition and abundance. Moreover, endemic and exotic species were widely distributed throughout the island, but the proportion of endemic species is higher in closed forests while exotic species are more abundant in open habitats. However, historical accounts from the early 1900s indicate that endemic species were distributed across the entire island. Today, most of the land cover transformation in Puerto Rico occurs in the lowlands which may explain the high abundance of endemic species in cloud forests and the high abundance of exotic species in open habitats in the lowlands. [source]

Conservation value of degraded habitats for forest birds in southern Peninsular Malaysia

DIVERSITY AND DISTRIBUTIONS, Issue 5 2006
Kelvin S.-H.
ABSTRACT Clearance of tropical forest for agricultural purposes is generally assumed to seriously threaten the survival of forest species. In this study, we quantified the conservation value, for forest bird species, of three degraded habitat types in Peninsular Malaysia, namely rubber tree plantations, oil palm plantations, and open areas. We surveyed these degraded habitats using point counts to estimate their forest bird species richness and abundance. We assessed whether richness, abundance, and activities of different avian dietary groups (i.e. insectivores and frugivores) varied among the habitats. We identified the critical habitat elements that accounted for the distribution of forest avifauna in these degraded habitats. Our results showed that these habitats harboured a moderate fraction of forest avifauna (approximately 46,76 species) and their functions were complementary (i.e. rubber tree plantations for moving; open habitats for perching; shrubs in oil palm plantations for foraging). In terms of species richness and abundance, rubber tree plantations were more important than oil palm plantations and open habitats. The relatively high species richness of this agricultural landscape was partly due to the contiguity of our study areas with extensive forest areas. Forecasts of forest-species presence under various canopy cover scenarios suggest that leaving isolated trees among non-arboreal crops could greatly attract relatively tolerant species that require tree canopy. The conservation value of degraded habitats in agricultural landscapes seems to depend on factors such as the type of crops planted and distance to primary forest remnants. [source]

The effects of green tree retention and subsequent prescribed burning on ground beetles (Coleoptera: Carabidae) in boreal pine-dominated forests

ECOGRAPHY, Issue 5 2006
Petri Martikainen
We studied how two methods to promote biodiversity in managed forests, i.e. green tree retention and prescribed fire, affect the assemblages of carabid beetles. Our experiment consisted of 24 study sites, each 3,5 ha in size, which had been prepared according to factorial design. Each of the eight treatment combinations determined by the two factors explored , tree retention level (0, 10, 50 m3/ha,1 and uncut controls) and prescribed use of fire (yes/no) , was replicated three times. We sampled carabids using pitfall traps one year after the treatments. Significantly more individuals were caught in most of the burned sites, but this difference was partially reflective of the trap-catches of Pterostichus adstrictus. The fire did not increase no. of P. adstrictus in the uncut sites as much as in the other sites. Species richness was significantly affected by both factors, being higher in the burned than in the unburned sites and in the harvested than in the unharvested sites. Many species were concentrated in the groups of retention trees in the burned sites, but only a few were in the unburned sites. The species turnover was greater in the burned than in the unburned sites, as indicated by the NMDS ordinations. Greater numbers of smaller sized species and proportion of brachypterous species were present in the burned sites. Fire-favored species, and also the majority of other species that prefer open habitats were more abundantly caught in the burned sites than in the unburned sites. Dead wood or logging waste around the traps did not correlate with the occurrence of species. We conclude that carabids are well adapted to disturbances, and that frequent use of prescribed fire is essential for the maintenance of natural assemblages of carabid beetles in the boreal forest. Small retention tree groups can not maintain assemblages of uncut forest, but they can be important by providing food, shelter and breeding sites for many species, particularly in the burned sites. [source]

Post-fire recovery of ant communities in Submediterranean Pinus nigra forests

ECOGRAPHY, Issue 2 2006
Anselm Rodrigo
This study analyzes the variations in the structure and composition of ant communities in burned Pinus nigra forests in central Catalonia (NE Spain). Pinus nigra forests do not recover after fire, changing to shrublands and oak coppices. For this reason, we suggest that ant communities of burned P. nigra forests will change after fire, because the post-fire scenario, in particular with the increase of open areas, is different to the unburned one, and more favourable for some species than for others. In four locations previously occupied by P. nigra forests where different fires occurred 1, 5, 13 and 19 yr before the sampling, we sampled the structure and composition of ant communities with pitfall traps, tree traps and net sweeping in unburned plots and in plots affected by canopy and understory fire. The results obtained suggest that canopy and understory fire had little effect on the structure of ant communities. Thus, many variables concerning ant communities were not modified either by fire type (understory or canopy fire) or by time since fire. However, a number of particular species were affected, either positively or negatively, by canopy fire: three species characteristic of forest habitats decreased after fire, while eight species characteristic of open habitats increased in areas affected by canopy fire, especially in the first few years after fire. These differences in ant community composition between burned and unburned plots imply that the maximum richness is achieved when there is a mixture of unburned forests and areas burned with canopy fire. Moreover, as canopy cover in P. nigra forests burned with canopy fire is not completed in the period of time studied, the presence of the species that are characteristic of burned areas remains along the chronosequence studied, while the species that disappear after fire do not recover in the period of time considered. Overall, the results obtained indicate that there is a persistent replacement of ant species in burned P. nigra forests, as is also the case with vegetation. [source]

Detection and Avoidance of Predators in White-Tailed Deer (Odocoileus virginianus) and Mule Deer (O. hemionus)

ETHOLOGY, Issue 2 2001
Susan Lingle
In this paper, we investigate the relationship between early detection of predators and predator avoidance in white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus), two closely related species that differ in their habitat preferences and in their anti-predator behavior. We used observations of coyotes (Canis latrans) hunting deer to test whether the distance at which white-tails and mule deer alerted to coyotes was related to their vulnerability to predation. Coyote encounters with both species were more likely to escalate when deer alerted at shorter distances. However, coyote encounters with mule deer progressed further than encounters with white-tails that alerted at the same distance, and this was not due to species differences in group size or habitat. We then conducted an experiment in which a person approached groups of deer to compare the detection abilities and the form of alert response for white-tails and mule deer, and for age groups within each species. Mule deer alerted to the approacher at longer distances than white-tails, even after controlling for variables that were potentially confounding. Adult females of both species alerted sooner than conspecific juveniles. Mule deer almost always looked directly at the approacher as their initial response, whereas white-tails were more likely to flee or to look in another direction with no indication that they pinpointed the approacher during the trial. Mule deer may have evolved the ability to detect predators earlier than white-tails as an adaptation to their more open habitats, or because they need more time to coordinate subsequent anti-predator defenses. [source]

Predator perches: a visual search perspective

FUNCTIONAL ECOLOGY, Issue 2 2009
Malte Andersson
Summary 1Predators hunting by sight often search for prey from elevated perches or hovering positions above the prey habitat. Theory suggests that prey visibility depends strongly on predator perch height and distance, but their quantitative effects have not been experimentally tested in natural habitats. 2We estimate for the first time how prey visibility depends on predator perch height, distance and vegetation height in an open natural habitat, based on visibility measurements of two targets: a mounted bird and a graduated plate, from five perch heights (0·2,8 m) and six distances (5,120 m). 3For both targets, their proportion visible increases strongly with observer perch height and proximity. From the lowest perch, visibility of the target bird declines to < 5% beyond 20 m distance, but 40% of it remains visible from the highest perch even at 120 m. 4Models of predator search suggest that hunting success and predation rate depend strongly on the prey detection rate, which is expected to decline with distance r approximately as r,d. However, d, the distance decay parameter, has not previously been empirically estimated in natural predator habitats. For distance , prey visibility relationships similar to those observed here, we find a realistic estimate of d to be 2·1,2·4. 5The results demonstrate the crucial role of relative perch and vegetation height for prey visibility, which is of relevance for habitat management. The strong increase of prey visibility with predator search height suggests that removal of predator perches can improve the survival of endangered prey populations in open habitats. Conversely, perch preservation or addition can improve habitat suitability for some predator species where perches are rare or lacking. [source]

Vigilance and fitness in grey partridges Perdix perdix: the effects of group size and foraging-vigilance trade-offs on predation mortality

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2007
MARK WATSON
Summary 1Vigilance increases fitness by improving predator detection but at the expense of increasing starvation risk. We related variation in vigilance among 122 radio-tagged overwintering grey partridges Perdix perdix (L.) across 20 independent farmland sites in England to predation risk (sparrowhawk Accipiter nisus L., kill rate), use of alternative antipredation behaviours (grouping and use of cover) and survival. 2Vigilance was significantly higher when individuals fed in smaller groups and in taller vegetation. In the covey period (in early winter when partridges are in flocks), vigilance and use of taller vegetation was significantly higher at sites with higher sparrowhawk predation risk, but tall vegetation was used less by larger groups. Individuals were constrained in reducing individual vigilance by group size and habitat choice because maximum group size was determined by overall density in the area during the covey period and by the formation of pairs at the end of the winter (pair period), when there was also a significant twofold increase in the use of tall cover. 3Over the whole winter individual survival was higher in larger groups and was lower in the pair period. However, when controlling for group size, mean survival decreased as vigilance increased in the covey period. This result, along with vigilance being higher at sites with increasing with raptor risk, suggests individual vigilance increases arose to reduce short-term predation risk from raptors but led to long-term fitness decreases probably because high individual vigilance increased starvation risk or indicated longer exposure to predation. The effect of raptors on survival was less when there were large groups in open habitats, where individual partridges can probably both detect predators and feed efficiently. 4Our study suggests that increasing partridge density and modifying habitat to remove the need for high individual vigilance may decrease partridge mortality. It demonstrates the general principle that antipredation behaviours may reduce fitness long-term via their effects on the starvation,predation risk trade-off, even though they decrease predation risk short-term, and that it may be ecological constraints, such as poor habitat (that lead to an antipredation behaviour compromising foraging), that cause mortality, rather than the proximate effect of an antipredation behaviour such as vigilance. [source]

Butterfly life history and temperature adaptations; dry open habitats select for increased fecundity and longevity

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2005
BENGT KARLSSON
Summary 1Evidence suggests that changes of temperature-related performance curves can trigger a selective response in life-history traits. Hence, it should be expected that insects adapted to different temperature regimes should exhibit optimal performance at the temperature to which they are adapted. 2To test this idea we investigated how fecundity and longevity are influenced by ambient temperatures in a set of satyrine butterflies adapted to live in dry open landscapes or in closed forest landscapes, respectively, by keeping egg-laying adult females at five different constant temperatures ranging between 20 and 40 °C. 3We studied four species, two of which are confined to dry and hot open habitats, namely the grayling (Hipparchia semele) and the small heath (Coenonympha pamphilus), and two of which are shade dwelling, namely the ringlet (Aphantopus hyperantus) and the speckled wood butterfly (Pararge aegeria). 4As predicted, the results showed that lifetime fecundity exhibited bell-shaped curves in relation to temperature with the open landscape group peaking at a higher temperature, 30 °C, compared with the shade-dwelling group that peaked at 25 °C. Longevity decreased with increasing temperatures among all species, but the open landscape living species survived better at higher temperatures. Moreover, although the magnitude of reproductive effort measured as lifetime egg mass did not differ between the two ecological groups, lifetime fecundity did with open landscape species laying more and smaller eggs than the shade-dwelling species. 5This difference in life-history character traits suggests either that dry and relatively warm open habitats open life-history opportunities in terms of higher fecundity and longevity that remain closed to butterflies adapted to cooler temperatures, or that life in dry open habitats actively selects for higher fecundity and survival as a result of increased offspring mortality. [source]

Wildfires and the expansion of threatened farmland birds: the ortolan bunting Emberiza hortulana in Mediterranean landscapes

JOURNAL OF APPLIED ECOLOGY, Issue 4 2008
Lluís Brotons
Summary 1It has been argued that wildfires are one of the major agents involved in landscape transformation in many European regions and their impact is expected to increase in the near future. Despite the recognized impact of fire on wildlife at a local scale, we lack information on the species responses to fire at larger spatial scales. 2In this study, we used the ortolan bunting Emberiza hortulana to evaluate the potential effects of wildfires on open-habitat species distribution. In contrast to most European countries, this farmland species has experienced a consistent range expansion during the last decades in Catalonia (northeast Iberian peninsula). Distribution data of the species collected at different time periods allowed us to test the role of fires in determining range expansions at a regional scale, and to evaluate the importance of dispersal constraints on distribution changes. 3Analyses of distribution data from 1975,1983 and 1999,2002 showed a consistent expansion of the ortolan bunting in Catalonia. After correcting for differences in sampling effort, changes in distribution showed a strong spatial pattern with colonization and stability, but not local extinction, being clumped in space. Patterns of change were also strongly and significantly associated with the amount of shrubland burnt between the two time periods, since areas that experienced a larger impact of fires in terms of burnt area showed a much higher probability of maintaining species presence or of being colonized. Colonization events appeared to be more likely in areas affected by fire especially when surrounding areas had already been colonized by the species. 4Synthesis and applications. Overall, our results support the hypothesis that wildfires, especially those affecting open woodlands or shrubby areas, play a critical role in the ecology of the ortolan bunting and have contributed to the recent expansion of the species in Catalonia. Furthermore, we have shown that colonization appears to be limited, not only by the availability of new burnt habitat but also by specific dispersal constraints. We suggest that, for several European threatened species associated with open habitats, burnt areas may partially compensate for the widespread loss and deterioration of farmland habitat, opening new management opportunities for their conservation. [source]

A multilocus study of pine grosbeak phylogeography supports the pattern of greater intercontinental divergence in Holarctic boreal forest birds than in birds inhabiting other high-latitude habitats

JOURNAL OF BIOGEOGRAPHY, Issue 4 2010
Sergei V. Drovetski
Abstract Aim, Boreal forest bird species appear to be divided into lineages endemic to each northern continent, in contrast to Holarctic species living in open habitats. For example, the three-toed woodpecker (Picoides tridactylus) and the winter wren (Troglodytes troglodytes) have divergent Nearctic and Palaearctic mitochondrial DNA clades. Furthermore, in these species, the next closest relative of the Nearctic/Palaearctic sister lineages is the Nearctic clade, suggesting that the Palaearctic may have been colonized from the Nearctic. The aim of this study is to test this pattern of intercontinental divergence and colonization in another Holarctic boreal forest resident , the pine grosbeak (Pinicola enucleator). Location, The Holarctic. Methods, We sequenced the mitochondrial ND2 gene and Z -specific intron 9 of the ACO1 gene for 74 pine grosbeaks collected across the Holarctic. The sequences were used to reconstruct the phylogeographical history of this species using maximum likelihood analysis. Results, We discovered two distinct mitochondrial and Z -specific lineages in the Nearctic and one in the Palaearctic. The two Nearctic mtDNA lineages, one in the northern boreal forest and one in south-western mountain forest, were more closely related to each other than either was to the Palaearctic clade. Two Nearctic Z-chromosome clades were sympatric in the boreal and south-western mountain forests. Unlike the topology of the mtDNA tree, the relationship among the Z-chromosome clades was the same as in the three-toed woodpecker and winter wren [Nearctic (Nearctic, Palaearctic)]. The Palaearctic Z-chromosome clade had much lower genetic diversity and a single-peak mismatch distribution with a mean < 25% of that for either Nearctic region, both of which had ragged mismatch distributions. Main conclusions, Our data suggest that, similar to the other boreal forest species, the pine grosbeak has divergent lineages in each northern continent and could have colonized the Palaearctic from the Nearctic. Compared with many Holarctic birds inhabiting open habitats, boreal forest species appear to be more differentiated, possibly because the boreal forests of the Nearctic and Palaearctic have been isolated since the Pliocene (3.5 Ma). [source]

What is the origin of the carabid beetle fauna of dry, anthropogenic habitats in western Europe?

JOURNAL OF BIOGEOGRAPHY, Issue 4 2000
Johan Andersen
Abstract Aim To study the origin of the carabid beetle fauna of dry, open anthropogenic habitats. Location Various parts of Europe. Methods Collecting by hand in habitats influenced by humans (arable land, sand pits, ruderal places, road verges, meadows) and naturally open habitats such as talus, supralittoral sand dunes, alvar as well as littoral habitats in south and central Scandinavia. Studies made in other parts of Europe were included in the discussion. Results and conclusion The material comprises about 37,700 specimens. About 8% of the Scandinavian species occurring in anthropogenic habitats may have a littoral origin, about 10% may originate from forests whereas about 9% are euryoecious. A majority of the species (about 66%) originate from primarily open, dry habitats and many of them constitute a steppe or steppe-like element. They invaded the bare landscape soon after the deglaciation and probably survived in naturally open habitats (supralittoral sand dunes, talus, alvar, old riverbeds) during the postglacial warm period, but some species have a recent origin in Scandinavia. [source]

Habitat availability, hunting or poaching: what affects distribution and density of large mammals in western Tanzanian woodlands?

AFRICAN JOURNAL OF ECOLOGY, Issue 4 2009
Matthias Waltert
Abstract Game reserves (GR) in Tanzania have been found to support similar or lower densities of large mammals compared with National parks (NP). But as these areas usually differ considerably not only in regard to management but also to environmental factors, we assessed the relative importance of vegetation cover, species-specific habitat preferences and legal (trophy hunting) and illegal off-take for observed differences in species-specific densities. In the Katavi ecosystem, open habitats were characteristic elements of Katavi NP, while Rukwa GR was dominated by miombo forest. In an inter-specific comparison, density differences were moderately correlated with preferences for open habitats, and with estimates of combined legal and illegal off-take but not with one of these separately. In a multiple linear regression, open habitat preference was found to explain 39.6% of the density differences between the two protected areas. This analysis suggests that the broad-scale pattern of most species' distributions is governed by differing vegetation cover but that several species are overexploited by illegal (elephant, giraffe, buffalo, bush pig, warthog) or combined off-take (hippopotamus, eland, waterbuck), thus emphasizing the need for quota readjustments and a more efficient anti-poaching control. Résumé En Tanzanie, on a découvert que les réserves de chasse, comparées aux parcs nationaux, abritaient des densités semblables ou inférieures de grands mammifères. Mais étant donné que ces zones diffèrent d'habitude considérablement, en termes non seulement de gestion mais aussi de facteurs environnementaux, nous avons évalué l'importance relative de la couverture végétale, des préférences spécifiques des espèces en matière d'habitat, et des prélèvements légaux (chasse aux trophées) et illégaux dans les différences constatées des densités spécifiques. Dans l'écosystème de Katavi, les habitats ouverts sont des éléments caractéristiques du Parc National de Katavi (PN) alors que la Réserve de Chasse de Rukwa (RC) est dominée par la forêt à miombo. Dans une comparaison interspécifique, les différences de densitéétaient modérément liées à la préférence pour des habitats ouverts et aux estimations de prélèvements légaux et illégaux combinés, mais pas avec les estimations séparées des uns ou des autres. Dans une régression linéaire multiple, on a découvert que la préférence pour un habitat ouvert expliquait 39.6% des différences de densité entre les deux aires protégées. Cette analyse suggère que le schéma, à grande échelle, de la distribution de la plupart des espèces est régi par une différence de couverture végétale, mais que plusieurs espèces semblent être surexploitées par les prélèvements illégaux (éléphants, girafes, buffles, potamochères, phacochères) ou combinés (hippopotames, élands, waterbucks), ce qui souligne la nécessité de réajuster les quotas et d'exercer des contrôles anti-braconnage plus efficaces. [source]

Status of the Mara Woodlands in Kenya

AFRICAN JOURNAL OF ECOLOGY, Issue 3 2004
Matthew J. Walpole
Abstract The woodlands of the Masai Mara National Reserve in Kenya have suffered dramatic declines over four decades as a result of elephant and fire pressure. This study examined the current status of woody resources in the Reserve and browse pressure thereon, using both classification (TWINSPAN) and ordination (DCA) techniques. From 333 widespread regular plots used to survey the vegetation, a total of 62 woody species were identified. Thirteen woody habitats were identified on the basis of species composition, varying from species-rich closed thickets and forest to less diverse open grasslands. A NW/SE stratification of the more open habitats was observed, possibly as a result of differences in soils, rainfall and drainage. Both plant density and diversity were lower than in communal and privately managed areas outside the Reserve. Moreover, browser pressure was substantially higher than that observed previously in the ecosystem, and suggests increased competition for scarcer woody resources within the Reserve. This has implications for the management of the ecosystem as a whole. As woodland and thickets continue to decline, long-term monitoring should expand to encompass the wider habitat diversity of the open grasslands and unprotected areas where much of the regeneration potential resides. Résumé Les forêts de la Réserve Nationale de Masai Mara, au Kenya, ont subi des réductions dramatiques depuis quatre décennies, suite à la pression des éléphants et des feux. Cette étude a examiné le statut actuel des ressources en bois dans la Réserve et la pression du pâturage qui s'y ajoute, en utilisant les techniques de classification (TWINSPAN) et d'ordination (DCA). Dans 333 plots régulièrement dispersés, utilisés pour étudier la végétation, on a identifié 62 espèces ligneuses. On a identifié aussi 13 habitats forestiers sur la base de la composition des espèces, depuis les buissons et les forêts fermés riches en espèces jusqu'aux prairies ouvertes moins diverses. On a observé une stratification NO/SE dans les habitats plus ouverts, résultat peut-être de différences de sols, de chutes de pluies et de drainage. La densité et la diversité des plantes étaient plus faibles que dans les aires gérées en commun ou de façon privée en dehors de la Réserve. Qui plus est, la pression des animaux qui mangent les buissons y était substantiellement plus élevée que celle qu'on observait jadis dans cet écosystème, et elle laisse penser qu'il y a une compétition plus forte pour des ressources ligneuses plus rares dans la Réserve. Ceci a des implications pour la gestion de l'écosystème dans son ensemble. Si les forêts et les buissons continuent à se rèduire, le monitoring à long terme devrait s'élargir pour englober la plus grande diversité d,habitat des prairies ouvertes et des aires non protégées où réside l'essentiel du potentiel de régénération. [source]

Evolutionary relationships of sprint speed in Australian varanid lizards

JOURNAL OF ZOOLOGY, Issue 4 2009
C. J. Clemente
Abstract Ecomorphological studies often seek to link morphology and performance to relevant ecological characteristics. Varanid lizards are unique in that species can vary in body size by almost four orders of magnitude within a single genus, and a question of considerable interest is whether similar ecomorphological relationships exist when constraints on body size are reduced. We studied sprint speed in relation to size, shape and ecology for 18 species of varanid lizards. Maximal speed scaled positively with mass0.166 using least squares regression, and mass0.21 using reduced major-axis regression. However, a curvilinear trend better described this relationship, suggesting an optimal mass of 2.83 kg with respect to speed. Including data for the komodo dragon Varanus komodoensis moves the optimum mass to 2.23 kg. We use this relationship to predict the sprint speed of the Komodo's giant extinct relative Varanus (Megalania) prisca to be 2.6,3 m s,1 similar to that of extant freshwater crocodiles Crocodylus johnstoni. When differences in speed were compared to ecological characteristics, species from open habitats were significantly faster than species from semi-open or closed habitat types, and remained so after correction for size and phylogeny. Thus, despite large variation in body size, varanids appear to share similar associations between performance and ecology as seen in other lizard groups. Varanids did, however, differ in morphological relationships with sprint speed. Differences in relative speed were not related to relative hindlimb length, as is commonly reported for other lizard groups. Instead, size-free forefoot length was negatively related to speed as was the size-free thorax,abdomen length. While shorter forefeet were thought to be an adaptation to burrowing, and thus open habitats, rather than speed per se, the reduction in the thorax,abdomen length may have significant advantages to increasing speed. Biomechanical models predicting this advantage are discussed in relation to a trade-off between speed and manoeuvrability. [source]

Taxonomic and biogeographical status of guanaco Lama guanicoe (Artiodactyla, Camelidae)

MAMMAL REVIEW, Issue 2 2006
BENITO A. GONZÁLEZ
ABSTRACT 1We review the status of the four currently recognized guanaco Lama guanicoe subspecies, and provide information about their taxonomy and distribution. The success of guanaco in inhabiting open habitats of South America is based mainly on the flexibility of their social behaviour and ecophysiological adaptations to harsh environments. 2Lönnberg described the first subspecies, L. g. cacsilensis, at the beginning of the 20th century. Forty years later Krumbiegel described L. g. voglii, based on skull measurements and pelage colouration. The other two subspecies, L. g. huanacus and L. g. guanicoe, were classified as subspecies by Krumbiegel based on pelage colouration and body size, while maintaining the original Latin names and descriptors. 3Further guanaco populations have been incorporated into each of these subspecies, based on their proximity to the type locality but without attention to the homogeneity of phenotype or habitat and only limited consideration of Bergmann's rule based on scarce skulls. Two alternative geographical ranges were proposed in the middle and towards the end of the 20th century. Discrepancies occur in the geographical range of each subspecies. 4Molecular studies based on mitochondrial DNA cytochrome b sequences recognized only two subspecies: the Peruvian L. guanicoe cacsilensis and the rest of the populations grouped in the clade recognized as L. g. guanicoe. We conclude that the evolutionary biology of L. guanicoe requires a significant revision with respect to biogeography. Phylogeographical data hold particular value in developing conservation strategies, particularly for some of the reduced and marginal populations and/or subspecies and will support IUCN (The World Conservation Union) Red List classification. [source]

Ecological distribution and phenology of an invasive species, Cardamine hirsuta L., and its native counterpart, Cardamine flexuosa With., in central Japan

PLANT SPECIES BIOLOGY, Issue 1 2003
YOSHINORI YATSU
Abstract Cardamine hirsuta is a European species that was recently introduced into Japan and its wide distribution has been confirmed in the Kanto district. To understand mechanisms of the recent spread of C. hirsuta in Japan, a comparative study of the alien species and its native congeneric species, C. flexuosa, was conducted. Habitat preferences, phenology and seed germination were examined. Cardamine hirsuta and C. flexuosa showed distinctive habitat-preferences; the former was most common in open habitats created by recent man-made constructions, and the latter was common in rice paddy fields and surrounding areas. The results indicate that C. flexuosa is a year-long annual, with a mixed phenology of summer and winter germination and growth. Seed dormancy during summer was relatively weak for C. flexuosa, and some plants that germinated early in summer reproduced during the same summer,autumn period. Plants that germinated in late summer and autumn behaved as winter annuals. In rice paddy fields, C. flexuosa is a winter annual because germination is prevented by submergence during summer. Plants flower during the following spring and complete their life cycle before the fields are flooded for rice cultivation. Cardamine hirsuta showed strong seed dormancy during summer and behaved as a typical winter annual. Seeds of C. hirsuta were intolerant to submergence in water, a condition that breaks seed dormancy of C. flexuosa. The results explain the absence of C. hirsuta from rice paddy fields. It was concluded that the spread of C. hirsuta is attributable to the recent expansion of urban habitats created by human activity and has occurred without direct competition with C. flexuosa. Considering recent urbanization in many areas, it is suggested that C. hirsuta has been spreading rapidly in Japan. [source]

Dionaea muscipula (Venus Flytrap) Establishment, Release, and Response of Associated Species in Mowed Patches on the Rims of Carolina Bays

RESTORATION ECOLOGY, Issue 4 2005
James O Luken
Abstract Carolina bays are depression wetlands of high conservation value that occur across the Southeastern Coastal Plain of the United States. Venus flytrap (Dionaea muscipula) is one rare carnivorous plant that grows in open habitats on the rims of Carolina bays. Without frequent burning, vegetation on bay rims becomes dominated by evergreen shrubs and Venus flytrap populations decline. This project examined the utility of mechanical mowing, soil clearing, transplanting, and seeding as an approach to restoring populations of Venus flytraps when fire is precluded. Mowing of patches on bay rims produced open sites with little ground-layer vegetation. After two growing seasons, adult Venus flytraps transplanted to mowed patches showed high survivorship and relatively high leaf number/plant. Suppressed Venus flytraps existing on-site quickly initiated growth in response to mowing. These volunteers and the transplants had higher flowering percentages than plants in reference populations. Seeds of Venus flytraps were scattered in mowed and cleared plots. Seedling establishment was low, but seedlings persisted into the second growing season. Mowing created suitable habitat for growth and flowering of adult Venus flytraps and facilitated establishment of two other carnivorous species, Sundew (Drosera capillaris) and Bladderwort (Utricularia subulata). But, mowing and clearing also facilitated invasion by four species of grasses and rushes; evergreen shrubs resprouted quickly after mowing. Maintaining persistent openings by mowing the rims of Carolina bays will be an ongoing challenge due to availability of potential invaders and rapid regrowth of shrubs. [source]

Effect of agro-forestry and landscape changes on common buzzards (Buteo buteo) in the Alps: implications for conservation

ANIMAL CONSERVATION, Issue 1 2005
Fabrizio Sergio
In Italy, pre-Alpine forests, once managed through coppice silviculture, are being converted to mature woodland, while land abandonment is causing woodland expansion and erosion of open habitats. Based on habitat-selection analyses, we predicted the impact of such changes on common buzzards (Buteo buteo), which depend on forested and open areas for nesting and foraging. Compared to availability, at a micro-scale buzzards selected nests higher above ground and on trees frequently covered by ivy. At the landscape-scale, buzzards avoided roads and conspecifics, while selecting rugged areas with high habitat heterogeneity, probably related to a varied food supply. Productivity was related to the availability of arid habitats, probably because of their richness in main prey species. Finally, population density was negatively related to the abundance of eagle owls (Bubo bubo), a potential predator of adults and nestlings, and positively related to the availability of woodland, a low predation-risk habitat rich in food and nest-sites. Therefore, buzzard settlement, density and productivity depended on the complex interplay of food availability, human persecution and predation risk. Thus, the current landscape changes would benefit buzzards by providing more nest-sites, but would be detrimental because of the lower productivity associated with the disappearance of dry open areas. Proposed conservation guidelines focus on conversion of coppice woodland to mature forests and active management of dry heath, a conservation sensitive habitat, through controlled burning. [source]

The conservation value for birds of cacao plantations with diverse planted shade in Tabasco, Mexico

ANIMAL CONSERVATION, Issue 2 2000
Russell Greenberg
We surveyed birds in cacao (Theobroma cacao) plantations in the state of Tabasco, Mexico. The shade canopy was planted by farmers and consisted of approximately 60 species of trees with no single dominant species. Canopy height averaged 15 m and the structure was multi-storied. We conducted 220 ten minute, 25 m radius point counts for birds and detected 1550 individuals from 81 species. The average number of birds/point and the expected diversity in a fixed number of individuals within the cacao surveyed were well within the range of other lowland habitats, including agricultural sites, that we have surveyed previously in neighbouring Chiapas. In the Tabascan cacao, the migrant group was composed, in part, of forest species, and dimorphic species were represented primarily by males, which in other areas are known to dominate forest or forest-like habitats. In contrast to the composition of migrant species, we found few resident forest specialists in Tabascan cacao. Instead, the tropical resident group was composed of large-bodied generalist species that use small patches of trees in open habitats. These results (moderate diversity, low numbers of forest specialists) differ from the few studies completed in ,rustic' cacao systems located near large tracts of forest. The planted shade cacao agroecosystem , at least in the absence of nearby forest , may have a limited value for conserving lost tropical forest bird diversity, but it provides habitat for woodland-associated migratory species. Our results also indicate that the planted shade cacao plantations supported few small omnivorous or frugivorous species, probably because cacao itself, as well as the dominant shade trees, produce primarily mammal or wind dispersed fruit and seeds. [source]

Temporal changes in the island flora at different scales in the archipelago of SW Finland

APPLIED VEGETATION SCIENCE, Issue 4 2010
Jens-Johan Hannus
Abstract Question: How have species richness and vegetation patterns changed in a group of islands in the northern Baltic Sea over a 58-yr period of changing land use and increasing eutrophication? Location: A group of 116 islands, the Brunskär sub-archipelago, in SW Finland. Methods: A complete survey of vascular plant species performed in 1947,1949 by Skult was repeated by our group using the same methodology in 2005,2007 (historical versus contemporary, respectively). DCAs were performed and total number of species, extinction,colonization rates, species frequency changes and mean Ellenberg indicator values for light, moisture and nitrogen and Eklund indicator values for dependence of human cultural influence were obtained for each island and relevé. Results: Species richness has declined on large islands and increased on small islands. The increase in number of species on small islands is driven by a strong increase in frequency of shore species, which in turn is induced by more productive shores. The decrease in species richness on large islands is related to overgrowth of open semi-natural habitats after cessation of grazing and other agricultural practices. Conclusions: After the late 1940s, open habitats, which were created and maintained by cattle grazing and other traditional agricultural activities, have declined in favour of woody shrub and forest land. Shores have been stabilized and influenced by the eutrophication of the Baltic Sea, and the vegetation has become more homogeneous. This development, resulting in lower species diversity, poses a challenge for the preservation of biodiversity both on a local and on a landscape level. [source]

Effects of natural barriers on the spillover of a marine mollusc: implications for fisheries reserves

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2003
Alexander Tewfik
Abstract 1.The movement of organisms and dispersal of propagules is fundamental to the maintenance of populations over time. However, the existence of barriers, created through the spatial configuration of habitats, may significantly affect dispersal patterns and thus influence community dynamics and resource sustainability. 2.Within marine environments unstructured or open habitats may form partial or complete ecological barriers due to elevated risk of predation or physical stresses associated with them. The existence and effects of such barriers may be of particular importance when considering the establishment of marine protected areas with a fisheries enhancement focus. 3.In this paper, the spillover of post-settlement queen conch (Strombus gigas) from a protected area in the Turks and Caicos Islands is investigated. It is hypothesized that the reserve boundaries overlap with a series of shallow, sand habitats that effectively enclose the protected population, reducing the spillover of conch into the adjacent fished areas. 4.To test this, density gradient maps for juvenile and adult conch populations were constructed using underwater visual survey data at 68 sites within and surrounding the protected area. These maps illustrate very low densities coinciding with poor, shallow sand habitats along the two marine boundaries of the reserve where spillover is expected to take place. 5.These sand habitats are thought to create ecological barriers to a slow, sedentary gastropod largely due to their shallowness (physical stresses of solar exposure or anoxia) and lack of food reducing the tendency of individuals to move across these areas, despite the 10-times higher density of adult queen conch observed in the protected area compared with outside. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Local richness and distribution of the lizard fauna in natural habitat mosaics of the Brazilian Cerrado

AUSTRAL ECOLOGY, Issue 1 2009
CRISTIANO NOGUEIRA
Abstract We investigate local lizard richness and distribution in central Brazilian Cerrado, harbouring one of the least studied herpetofaunas in the Neotropical region. Our results are based on standardized samplings at 10 localities, involving 2917 captures of 57 lizard species in 10 families. Local richness values exceeded most presented in earlier studies and varied from 13 to 28 species, with modal values between 19 and 28 species. Most of the Cerrado lizard fauna is composed of habitat-specialists with patchy distributions in the mosaic of grasslands, savannas and forests, resulting in habitat-structured lizard assemblages. Faunal overlap between open and forested habitats is limited, and forested and open areas may act as mutual barriers to lizard distribution. Habitat use is influenced by niche conservatism in deep lineages, with iguanians and gekkotans showing higher use of forested habitats, whereas autarchoglossans are richer and more abundant in open habitats. Contrary to trends observed in Cerrado birds and large mammals, lizard richness is significantly higher in open, interfluvial habitats that dominate the Cerrado landscape. Between-localities variation in lizard richness seems tied to geographical distance, landscape history and phylogenetic constraints, factors operating in other well-studied lizard faunas in open environments. Higher richness in dominant, open interfluvial habitats may be recurrent in Squamata and other small-bodied vertebrates, posing a threat to conservation as these habitats are most vulnerable to the fast, widespread and ongoing process of habitat destruction in central Brazil. [source]

Contrasting patterns of variation in urban populations of Cepaea (Gastropoda: Pulmonata): a tale of two cities

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009
ROBERT A. D. CAMERON
The shell colour and banding polymorphisms in urban populations of Cepaea snails were studied in Sheffield (England) and Wroc,aw (Poland), which are two cities of similar size. Both Cepaea nemoralis and Cepaea hortensis were found in Sheffield, but only C. nemoralis was found in Wroc,aw. In neither city was variation with habitat apparent, nor was there evidence of large-scale geographical patterns. Spatial autocorrelation analyses revealed only vaguely defined local clusters. There was a greater degree of among-population variation in Sheffield, and more cases of extreme frequencies and low levels of polymorphism. Wroc,aw populations were more uniform and highly polymorphic. These differences can be related to the history of these snails in each city. Sheffield has been colonized mainly in the last 20 years, and some parts of the city with apparently suitable habitat remain unoccupied. Leptokurtic dispersal of small propagules followed by local spread appears likely. Values of FST resemble those seen in districts elsewhere with ,Area Effects'. Although there are ancient woodlands within the city, they have been colonized too recently for selection to achieve a new balance. Wroc,aw has held Cepaea populations for at least 100 years, and they are denser and more continuous. Shaded habitats are recent and temporary; the overall pattern of variation matches that seen in open habitats in districts elsewhere in which variation with habitat is apparent, and values of FST also correspond. Population history and the character of dispersal clearly affect the patterns of variation observed. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 27,39. [source]