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Sympatry
Selected AbstractsGIS-based niche models identify environmental correlates sustaining a contact zone between three species of European vipersDIVERSITY AND DISTRIBUTIONS, Issue 3 2008F. Martínez-Freiría ABSTRACT The current range of European vipers is mostly parapatric but local-scale allopatric distribution is common and few cases of sympatry are known. In the High Course of Ebro River, northern Spain, there is a contact zone between Vipera aspis, V. latastei, and V. seoanei. Sympatry was detected between aspis and latastei and also specimens with intermediate morphological traits. Presence-data at a local scale (1 × 1 km) and ecological niche-based models manipulated in a GIS were used to (1) identify how environmental factors correlate with the distribution of the three vipers and with the location of the sympatry area, and (2) identify potential areas for viper occurrence and sympatry. Ensemble for casting with 10 Maximum Entropy models identified a mixture of topographical (altitude, slope), climatic (precipitation, evapotranspiration, and minimum and maximum temperature), and habitat factors (land cover) as predictors for viper occurrence. Similar predicted probabilities according to the variation of some environmental factors (indicating probable sympatry) were observed only for aspis-latastei and aspis-seoanei. In fact, areas of probable occurrence of vipers were generally allopatric but probable sympatry between vipers was identified for aspis-latastei in 76 UTM 1 × 1 km squares, for aspis-seoanei in 23 squares, and latastei-seoanei in two squares. Environmental factors correlate with the location of this contact zone by shaping the species range: some enhance spatial exclusion and constrain distribution to spatially non-overlapping ranges, while others allow contact between species. The distribution in the contact zone apparently results from the balance between the pressures exerted by the different environmental factors and in the sympatry area probably by interspecific competition. Further ecological and genetical data are needed to evaluate the dynamics of the probable hybrid zone. GIS and niche-modelling tools proved to be powerful tools to identify environmental factors sustaining the location of contact zones. [source] Sympatry with the devil: reproductive interference could hamper species coexistenceJOURNAL OF ANIMAL ECOLOGY, Issue 4 2007AXEL HOCHKIRCH Summary 1As species are often considered discrete natural units, interspecific sexual interactions are often disregarded as potential factors determining community composition. Nevertheless reproductive interference, ranging from signal jamming to hybridization, can have significant costs for species sharing similar signal channels. 2We combined laboratory and field experiments to test whether the coexistence of two congeneric ground-hopper species with overlapping ranges might be influenced by sexual interactions. 3In the laboratory experiment the number of conspecific copulations of Tetrix ceperoi decreased substantially in the presence of Tetrix subulata. Males of T. ceperoi performed more mating attempts with heterospecific females, whereas females of T. subulata rejected these heterospecific approaches more often than those of conspecifics. Although no heterospecific matings occurred in the laboratory, the reproductive success of T. ceperoi was reduced substantially in field experiments. Negative effects on T. subulata were found only at high densities. 4Our results suggest that reproductive interference could have similar consequences as competition, such as demographic displacement of one species (,sexual exclusion'). As reproductive interference should be selected against, it may also drive the evolution of signals (reproductive character displacement) or promote habitat, spatial or temporal segregation. [source] Habitat differentiation within the large-carnivore community of Norway's multiple-use landscapesJOURNAL OF APPLIED ECOLOGY, Issue 5 2008Roel May Summary 1The re-establishment of large carnivores in Norway has led to increased conflicts and the adoption of regional zoning for these predators. When planning the future distribution of large carnivores, it is important to consider details of their potential habitat tolerances and strength of inter-specific differentiation. We studied differentiation in habitat and kill sites within the large-carnivore community of south-eastern Norway. 2We compared habitat selection of the brown bear Ursus arctos L., Eurasian lynx Lynx lynx L., wolf Canis lupus L. and wolverine Gulo gulo L., based on radio-tracking data. Differences in kill site locations were explored using locations of documented predator-killed sheep Ovis aries L. We modelled each species' selection for, and differentiation in, habitat and kill sites on a landscape scale using resource selection functions and multinomial logistic regression. Based on projected probability of occurrence maps, we estimated continuous patches of habitat within the study area. 3Although bears, lynx, wolves and wolverines had overlapping distributions, we found a clear differentiation for all four species in both habitat and kill sites. The presence of bears, wolves and lynx was generally associated with rugged, forested areas at lower elevations, whereas wolverines selected rugged terrain at higher elevations. Some degree of sympatry was possible in over 40% of the study area, although only 1·5% could hold all four large carnivores together. 4Synthesis and applications. A geographically differentiated management policy has been adopted in Norway, aimed at conserving viable populations of large carnivores while minimizing the potential for conflicts. Sympatry of all four carnivores will be most successful if regional zones are established of adequate size spanning an elevational gradient. High prey densities, low carnivore densities, low dietary overlap and scavenging opportunities have most probably led to reduced competitive exclusion. Although regional sympatry enhances the conservation of an intact guild of large carnivores, it may well increase conflict levels and resistance to carnivore conservation locally. [source] THE GEOGRAPHICAL PATTERN OF SPECIATION AND FLORAL DIVERSIFICATION IN THE NEOTROPICS: THE TRIBE SINNINGIEAE (GESNERIACEAE) AS A CASE STUDYEVOLUTION, Issue 7 2007Mathieu Perret The geographical pattern of speciation and the relationship between floral variation and species ranges were investigated in the tribe Sinningieae (Gesneriaceae), which is found mainly in the Atlantic forests of Brazil. Geographical distribution data recorded on a grid system of 0.5 × 0.5 degree intervals and a near-complete species-level phylogenetic tree of Sinningieae inferred from a simultaneous analysis of seven DNA regions were used to address the role of geographical isolation in speciation. Geographical range overlaps between sister lineages were measured across all nodes in the phylogenetic tree and analyzed in relation to relative ages estimated from branch lengths. Although there are several cases of species sympatry in Sinningieae, patterns of sympatry between sister taxa support the predominance of allopatric speciation. The pattern of sympatry between sister taxa is consistent with range shifts following allopatric speciation, except in one clade, in which the overlapping distribution of recent sister species indicates speciation within a restricted geographical area and involving changes in pollinators and habitats. The relationship between floral divergence and regional sympatry was also examined by analyzing floral contrasts, phenological overlap, and the degree of sympatry between sister clades. Morphological contrast between flowers is not increased in sympatry and phenological divergence is more apparent between allopatric clades than between sympatric clades. Therefore, our results failed to indicate a tendency for sympatric taxa to minimize morphological and phenological overlap (geographic exclusion and/or character displacement hypotheses). Instead, they point toward adaptation in phenology to local conditions and buildup of sympatries at random with respect to flower morphology. Additional studies at a lower geographical scale are needed to identify truely coexisting species and the components of their reproductive isolation. [source] The ethnoprimatological approach in primatology,AMERICAN JOURNAL OF PRIMATOLOGY, Issue 10 2010Agustin Fuentes Abstract Recent and long-term sympatries between humans and nonhuman primates (hereafter primates) are central to the behavioral ecology, conservation, and evolutionary trajectories of numerous primate species. Ethnoprimatology emphasizes that interconnections between humans and primates should be viewed as more than just disruptions of a "natural" state, and instead anthropogenic contexts must be considered as potential drivers for specific primate behavioral patterns. Rather than focusing solely on the behavior and ecology of the primate species at hand, as in traditional primatology, or on the symbolic meanings and uses of primates, as in socio-cultural anthropology, ethnoprimatology attempts to merge these perspectives into a more integrative approach. As human pressures on environments continue to increase and primate habitats become smaller and more fragmented, the need for a primatology that considers the impact of human attitudes and behavior on all aspects of primate lives and survival is imperative. In this special issue, we present both data-driven examples and more general discussions that describe how ethnoprimatological approaches can be both a contribution to the core theory and practice of primatology and a powerful tool in our goal of conservation action. Am. J. Primatol. 72:841,847, 2010. © 2010 Wiley-Liss, Inc. [source] GIS-based niche models identify environmental correlates sustaining a contact zone between three species of European vipersDIVERSITY AND DISTRIBUTIONS, Issue 3 2008F. Martínez-Freiría ABSTRACT The current range of European vipers is mostly parapatric but local-scale allopatric distribution is common and few cases of sympatry are known. In the High Course of Ebro River, northern Spain, there is a contact zone between Vipera aspis, V. latastei, and V. seoanei. Sympatry was detected between aspis and latastei and also specimens with intermediate morphological traits. Presence-data at a local scale (1 × 1 km) and ecological niche-based models manipulated in a GIS were used to (1) identify how environmental factors correlate with the distribution of the three vipers and with the location of the sympatry area, and (2) identify potential areas for viper occurrence and sympatry. Ensemble for casting with 10 Maximum Entropy models identified a mixture of topographical (altitude, slope), climatic (precipitation, evapotranspiration, and minimum and maximum temperature), and habitat factors (land cover) as predictors for viper occurrence. Similar predicted probabilities according to the variation of some environmental factors (indicating probable sympatry) were observed only for aspis-latastei and aspis-seoanei. In fact, areas of probable occurrence of vipers were generally allopatric but probable sympatry between vipers was identified for aspis-latastei in 76 UTM 1 × 1 km squares, for aspis-seoanei in 23 squares, and latastei-seoanei in two squares. Environmental factors correlate with the location of this contact zone by shaping the species range: some enhance spatial exclusion and constrain distribution to spatially non-overlapping ranges, while others allow contact between species. The distribution in the contact zone apparently results from the balance between the pressures exerted by the different environmental factors and in the sympatry area probably by interspecific competition. Further ecological and genetical data are needed to evaluate the dynamics of the probable hybrid zone. GIS and niche-modelling tools proved to be powerful tools to identify environmental factors sustaining the location of contact zones. [source] A morphological reappraisal of Tubifex blanchardi Vejdovský, 1891 (Clitellata: Tubificidae)ACTA ZOOLOGICA, Issue 2 2009Roberto Marotta Abstract Tubifex blanchardi Vejdovský, 1891 is a freshwater tubificid, often living in sympatry with Tubifex tubifex (Müller 1774). Although considered from its discovery as a species on its own, its biological status is debated. During the early seventies T. blanchardi was reduced to a mere form of T. tubifex, as a particular case of polymorphism in chaetal pattern. Using classical histological techniques, microdissections of portions of the male genital apparatus and phalloidin staining of dissected copulatory organs we investigated 163 mixed individuals of T. blanchardi and T. tubifex belonging to sympatric populations from the Lambro River (Milan, Northern Italy). The internal morphology of T. blanchardi is described for the first time. Our results show that T. tubifex and T. blanchardi differ in several characters concerning both their external and internal morphology, and in the fine organization of their copulatory organs. Several independent character sets support the separation of T. blanchardi from T. tubifex, suggesting that it is an independent species. This study also supports the idea that T. blanchardi and T. bergi (Hrab,, 1935), another species closely related to T. tubifex, are not conspecific. The observed morphological differences between allopatric populations of T. tubifex are discussed. [source] Genetic divergence and ecological specialisation of seed weevils (Exapion spp.) on gorses (Ulex spp.)ECOLOGICAL ENTOMOLOGY, Issue 3 2008MYRIAM BARAT Abstract 1.,Reproductive isolation of sympatric populations may result from divergent selection of populations in different environments, and lead to ecological specialisation. In Brittany (France), the gorse Ulex europaeus (Fabaceae, Genisteae), may be encountered in sympatry with one of the two other gorse species present: U. gallii and U. minor. A recent study based on morphological identification of seed predators of gorse has shown that two weevil species (Curculionoidea, Apionidae) infest gorse pods at different seasons and have different host ranges: Exapion ulicis infests U. europaeus in spring, whereas E. lemovicinum infests U. gallii and U. minor in autumn. Weevil populations may thus have diverged in sympatry. 2.,As morphological identification of weevils is often difficult and some of the characters used may exhibit individual or environmental variation, mitochondrial and nuclear sequences of weevils collected within pods of the three gorse species in 10 populations of Brittany were used to reconstruct their phylogeny. 3.,The results reveal that species differentiation based on morphological characters is confirmed by the two molecular data sets, showing that E. ulicis and E. lemovicinum are distinct species, and suggesting the absence of host races. Finally, E. ulicis was able to use U. gallii and U. minor pods in spring in some years in some populations, which appeared to depend on the availability of pods present during its reproductive period. 4.,Divergence between E. ulicis and E. lemovicinum may have resulted from temporal isolation of reproductive periods of weevil populations followed by specialisation of insects to host phenology. [source] Competition and character displacement in two species of scincid lizardsECOLOGY LETTERS, Issue 3 2002Jane Melville Abstract The role of competition in habitat occupation and character displacement is investigated in two species of alpine lizards (Niveoscincus microlepidotus and N. greeni), using both controlled competition experiments and field-based ecological work. Competition experiments demonstrate that interspecific aggression occurs between these closely related species, with the larger and more aggressive N. greeni being socially dominant. When these species occur in sympatry, N. microlepidotus was found to shift its habitat occupation to the heathlands, which provide less thermal opportunities. In addition, a reduction in body size occurred in both adult and neonatal N. microlepidotus at sympatric field sites. Differences in body size between N. microlepidotus and N. greeni in sympatry were significantly greater than in allopatry, indicating that character displacement is occurring. Results, combined with previous molecular and biogeographical data, suggest that there is a trend towards a reduction in body size and a restriction in habitat occupation in N. microlepidotus in the north-east periphery of its distribution, which is shaped by competition with N. greeni. [source] Foraging specialisms, prey size and life-history patterns: a test of predictions using sympatric polymorphic Arctic charr (Salvelinus alpinus)ECOLOGY OF FRESHWATER FISH, Issue 1 2008D. Fraser Abstract,,, We use arguments based on optimal foraging theory to predict body size constraints and the consequences of these on a range of life-history traits in three trophic specialist morphs of Arctic charr, Salvelinus alpinus, living in sympatry in Loch Rannoch, Scotland. As predicted, foraging specialists feeding on small prey items with a narrow size range showed evidence of deterministic growth; the ultimate body size of macrobenthos feeders being larger (L, = 238 mm) than that of planktivores (L, = 216 mm). In contrast, the piscivorous morph showed no evidence of reaching a maximal body size. The two size-constrained morphs (benthivores and planktivores) matured earlier and died younger (living for up to 11 and 7 years, respectively, in this study) than did the piscivorous charr which showed continuous growth up to at least 17 years. The pattern of annual reproductive investment in maturing individuals was complex. Planktivores invested in larger eggs than the other two forms, but benthivores produced a greater number of eggs than planktivores, which in turn produced more than piscivores. Planktivorous males had a greater investment in mean testis weight than the other two forms. Lifetime reproductive output was the greatest in the benthivorous charr, intermediate in planktivorous and the lowest in the piscivorous charr when measured either as fecundity or as gonadal weight. We conclude that constraints imposed upon foraging specialists by foraging efficiency is a significant driver of body size and ultimately reproductive investment in gape-limited foraging salmonids. [source] Stream habitat use and diet of juvenile (0+) brown trout and grayling in sympatryECOLOGY OF FRESHWATER FISH, Issue 4 2000E. Degerman Abstract , Electrofishing survey data and experiments carried out in a semi-natural stream were used to test the hypothesis that interactions between underyearling (0+) trout and grayling during their first summer affect habitat use and diet. The survey data revealed a general difference in habitat use, with 0+ grayling being more common than 0+ trout in large streams and deeper sections. It was also found that in the presence of trout, finer substrate and shallower sections were utilised more by grayling. Field experiments were carried out with three treatments; trout alone, grayling alone and the two species together. In both the July and September experiments grayling tended to occupy deeper sections than trout. Trout abundance was higher in shallow areas in sympatry, while no such difference was found in allopatry. The rate of disappearance of grayling from the study sections was significantly higher in sympatry in July, while no difference was found in September. In July the size difference between species and the degree of dietary overlap were small and non-significant, respectively, indicating that the two species were strongly competing., [source] Ecological niche partitioning in the picoplanktonic green alga Micromonas pusilla: evidence from environmental surveys using phylogenetic probesENVIRONMENTAL MICROBIOLOGY, Issue 9 2008Elodie Foulon Summary Very few studies have analysed the niches of pelagic protist in details. This is because for most protists, both an accurate species definition and methods for routine detection and quantification of cells are lacking. The morphospecies Micromonas pusilla, a marine unicellular green alga, is the most ubiquitous and cosmopolitan picoeukaryote described to date. This species comprises several independent genetic lineages or clades, which are not currently distinguishable based on comparison of their morphology or biogeographical distribution. Molecular probes were used to detect and quantify the genetic clades of M. pusilla in samples from temperate, polar and tropical environments in order to assess potential ecological niche partitioning. The three clades were detected in all biogeographical regions studied and were commonly found in sympatry. Cell abundances recorded for clades A and B were high, especially at coastal stations. Clade C, when detected, was always at low abundances and is suggested to be a low-light clade. Shifts in the contribution of clades to total M. pusilla abundance were observed along environmental gradients, both at local and basin-wide scales. This suggests that the phylogenetic clades occupy specific niches and confirms the existence of cryptic species within the morphospecies M. pusilla. Parameters which can precisely explain the distribution of these cryptic species remain to be elucidated. [source] EVOLUTION OF CHARACTER DISPLACEMENT IN SPADEFOOT TOADS: DIFFERENT PROXIMATE MECHANISMS IN DIFFERENT SPECIESEVOLUTION, Issue 8 2010David W. Pfennig Character displacement occurs when two species compete, and those individuals most dissimilar from the average resource-use phenotypes of the other species are selectively favored. Few studies have explored the sequence of events by which such divergence comes about. We addressed this issue by studying two species of spadefoot toads that have undergone ecological character displacement with each other. Previous research revealed that phenotypic shifts between sympatric and allopatric populations of one species, Spea multiplicata, reflect a condition-dependent maternal effect. Here, we show that analogous shifts in the other species, S. bombifrons, cannot similarly be explained by such a maternal effect, and that these shifts instead appear to be underlain by allelic differences. We hypothesize that these two species have evolved different mechanisms of character displacement because they differ in duration in sympatry. Specifically, because they occur at the edge of a range expansion, populations of S. bombifrons have been exposed to S. multiplicata for a longer period. Consequently, S. bombifrons have likely had more time to accumulate genetic changes that promote character displacement. Generally, character displacement may often progress through an initial phase in which trait differences are environmentally induced to one in which they are constitutively expressed. [source] SIMULATING RANGE EXPANSION: MALE SPECIES RECOGNITION AND LOSS OF PREMATING ISOLATION IN DAMSELFLIESEVOLUTION, Issue 1 2010Maren Wellenreuther Prolonged periods of allopatry might result in loss of the ability to discriminate against other formerly sympatric species, and can lead to heterospecific matings and hybridization upon secondary contact. Loss of premating isolation during prolonged allopatry can operate in the opposite direction of reinforcement, but has until now been little explored. We investigated how premating isolation between two closely related damselfly species, Calopteryx splendens and C. virgo, might be affected by the expected future northward range expansion of C. splendens into the allopatric zone of C. virgo in northern Scandinavia. We simulated the expected secondary contact by presenting C. splendens females to C. virgo males in the northern allopatric populations in Finland. Premating isolation toward C. splendens in northern allopatric populations was compared to sympatric populations in southern Finland and southern Sweden. Male courtship responses of C. virgo toward conspecific females showed limited geographic variation, however, courtship attempts toward heterospecific C. splendens females increased significantly from sympatry to allopatry. Our results suggest that allopatric C. virgo males have partly lost their ability to discriminate against heterospecific females. Reduced premating isolation in allopatry might lead to increased heterospecific matings between taxa that are currently expanding and shifting their ranges in response to climate change. [source] A THEORETICAL INVESTIGATION OF SYMPATRIC EVOLUTION OF TEMPORAL REPRODUCTIVE ISOLATION AS ILLUSTRATED BY MARINE BROADCAST SPAWNERSEVOLUTION, Issue 11 2007Maurizio Tomaiuolo Recent theory suggests that frequency-dependent disruptive selection in combination with assortative mating can lead to the establishment of reproductive isolation in sympatry. Here we explore how temporal variation in reproduction might simultaneously generate both disruptive selection and assortative mating, and result in sympatric speciation. The conceptual framework of the model may be applicable to biological systems with negative frequency-dependent selection, such as marine broadcast spawners or systems with pollinator limitation. We present a model that is motivated by recent findings in marine broadcast spawners and is parameterized with data from the Montastraea annularis species complex. Broadcast spawners reproduce via external fertilization and synchronous spawning is required to increase the probability of successful fertilization, but empirical evidence shows that as density increases, so does the risk of polyspermy. Polyspermy is the fusion of multiple sperm with an egg at fertilization, a process that makes the embryo unviable. Synchrony can therefore also act as a source of negative density-dependent disruptive selection. Model analysis shows that the interaction between polyspermy and spawning synchrony can lead to temporal reproductive isolation in sympatry and that, more generally, increased density promotes maintenance of genetic variation. [source] THE GEOGRAPHICAL PATTERN OF SPECIATION AND FLORAL DIVERSIFICATION IN THE NEOTROPICS: THE TRIBE SINNINGIEAE (GESNERIACEAE) AS A CASE STUDYEVOLUTION, Issue 7 2007Mathieu Perret The geographical pattern of speciation and the relationship between floral variation and species ranges were investigated in the tribe Sinningieae (Gesneriaceae), which is found mainly in the Atlantic forests of Brazil. Geographical distribution data recorded on a grid system of 0.5 × 0.5 degree intervals and a near-complete species-level phylogenetic tree of Sinningieae inferred from a simultaneous analysis of seven DNA regions were used to address the role of geographical isolation in speciation. Geographical range overlaps between sister lineages were measured across all nodes in the phylogenetic tree and analyzed in relation to relative ages estimated from branch lengths. Although there are several cases of species sympatry in Sinningieae, patterns of sympatry between sister taxa support the predominance of allopatric speciation. The pattern of sympatry between sister taxa is consistent with range shifts following allopatric speciation, except in one clade, in which the overlapping distribution of recent sister species indicates speciation within a restricted geographical area and involving changes in pollinators and habitats. The relationship between floral divergence and regional sympatry was also examined by analyzing floral contrasts, phenological overlap, and the degree of sympatry between sister clades. Morphological contrast between flowers is not increased in sympatry and phenological divergence is more apparent between allopatric clades than between sympatric clades. Therefore, our results failed to indicate a tendency for sympatric taxa to minimize morphological and phenological overlap (geographic exclusion and/or character displacement hypotheses). Instead, they point toward adaptation in phenology to local conditions and buildup of sympatries at random with respect to flower morphology. Additional studies at a lower geographical scale are needed to identify truely coexisting species and the components of their reproductive isolation. [source] TESTING THE ROLE OF INTERSPECIFIC COMPETITION IN THE EVOLUTIONARY ORIGIN OF ELEVATIONAL ZONATION: AN EXAMPLE WITH BUARREMON BRUSH-FINCHES (AVES, EMBERIZIDAE) IN THE NEOTROPICAL MOUNTAINSEVOLUTION, Issue 5 2007Carlos Daniel Cadena Interspecific competition might drive the evolution of ecological niches and result in pairs of formerly competing species segregating along ecological gradients following a process of character displacement. This mechanism has been proposed to account for replacement of related species along gradients of elevation in many areas of the world, but the fundamental issue of whether competition is responsible for the origin of elevational replacements has not been tested. To test hypotheses about the role of interspecific competition in the origin of complementary elevational ranges, I combined molecular phylogenetics, phylogeography, and population genetic analyses on Buarremon torquatus and B. brunneinucha (Aves, Emberizidae), whose patterns of elevational distribution suggest character displacement or ecological release. The hypothesis that elevational distributions in these species changed in opposite directions as a result of competition is untenable because: (1) a historical expansion of the range of B. brunneinucha into areas occupied by B. torquatus was not accompanied by a shift in the elevational range of the former species; (2) when B. brunneinucha colonized the range of B. torquatus, lineages of the latter distributions had already diverged; and (3) historical trends in effective population size do not suggest populations with elevational ranges abutting those of putative competitors have declined as would be expected if competition caused range contractions. However, owing to uncertainty in coalescent estimates of historical population sizes, the hypothesis that some populations of B. torquatus have declined cannot be confidently rejected, which suggests asymmetric character displacement might have occurred. I suggest that the main role of competition in elevational zonation may be to act as a sorting mechanism that allows the coexistence along mountain slopes only of ecologically similar species that differ in elevational distributions prior to attaining sympatry. The contrasting biogeographic histories of B. brunneinucha and B. torquatus illustrate how present-day ecological interactions can have recent origins, and highlights important challenges for testing the hypothesis of character displacement in the absence of data on population history and robust reconstructions of the evolution of traits and geographic ranges. [source] CHARACTER DISPLACEMENT AS THE "BEST OF A BAD SITUATION": FITNESS TRADE-OFFS RESULTING FROM SELECTION TO MINIMIZE RESOURCE AND MATE COMPETITIONEVOLUTION, Issue 10 2005Karin S. Pfennig Abstract Character displacement has long been considered a major cause of adaptive diversification. When species compete for resources or mates, character displacement minimizes competition by promoting divergence in phenotypes associated with resource use (ecological character displacement) or mate attraction (reproductive character displacement). In this study, we investigated whether character displacement can also have pleiotropic effects that lead to fitness trade-offs between the benefits of avoiding competition and costs accrued in other fitness components. We show that both reproductive and ecological character displacement have caused spadefoot toads to evolve smaller body size in the presence of a heterospecific competitor. Although this shift in size likely arose as a by-product of character displacement acting to promote divergence between species in mating behavior and larval development, it concomitantly reduces offspring survival, female fecundity, and sexual selection on males. Thus, character displacement may represent the "best of a bad situation" in that it lessens competition, but at a cost. Individuals in sympatry with the displaced phenotype will have higher fitness than those without the displaced trait because they experience reduced competition, but they may have reduced fitness relative to individuals in allopatry. Such a fitness trade-off can limit the conditions under which character displacement evolves and may even increase the risk of "Darwinian extinction" in sympatric populations. Consequently, character displacement may not always promote diversification in the manner that is often expected. [source] CHARACTER DISPLACEMENT IN POLYPHENIC TADPOLESEVOLUTION, Issue 5 2000David W. Pfennig Abstract Biologists have long known that closely related species are often phenotypically different where they occur together, but are indistinguishable where they occur alone. The causes of such character displacement are controversial, however. We used polyphenic spadefoot toad tadpoles (Spea bombifrons and S. multiplicata) to test the hypothesis that character displacement evolves to minimize competition for food. We also sought to evaluate the role of phenotypic plasticity in the mediation of competitive interactions between these species. Depending on their diet, individuals of both species develop into either a small-headed omnivore morph, which feeds mostly on detritus, or a large-headed carnivore morph, which specializes on shrimp. Laboratory experiments and surveys of natural ponds revealed that the two species were more dissimilar in their tendency to produce carnivores when they occurred together than when they occurred alone. This divergence in carnivore production was expressed as both character displacement (where S. multiplicata's propensity to produce carnivores was lower in sympatry than in allopatry) and as phenotypic plasticity (where S. multiplicata facultatively enhanced carnivore production in S. bombifrons, and S. bombifrons facultatively suppressed carnivore production in S. multiplicata). In separate experiments, we established that S. bombifrons (the species for which carnivore production was enhanced) was the superior competitor for shrimp. Conversely, S. multiplicata (the species for which carnivore production was suppressed and omnivore production enhanced) was the superior competitor for detritus. These results therefore demonstrate that selection to minimize competition for food can cause character displacement. They also suggest that both character displacement and phenotypic plasticity may mediate competitive interactions between species. [source] Feeding methods, visual fields and vigilance in dabbling ducks (Anatidae)FUNCTIONAL ECOLOGY, Issue 4 2002M. Guillemain Summary 1.,Visual fields were determined in two species of dabbling ducks (Anatini): Shoveler Anas clypeata L. (planktivore whose foraging is guided mainly by tactile cues) and Wigeon A. penelope L. (herbivore whose foraging is guided mainly by visual cues). 2.,The binocular fields of Shoveler and Wigeon are of similar maximum width (20°), but they differ in their position and vertical extent. The bill of the Shoveler lies in the very periphery of its frontal binocular field, which extends through 220° thus providing comprehensive visual coverage about the head. In Wigeon the bill is positioned more centrally in the frontal binocular field, which extends through 150° and results in the birds having a narrow blind area behind the head. 3.,The vigilance behaviour of Shoveler and Wigeon when foraging simultaneously was studied using a focal observation procedure at sites where the two species winter in sympatry. Focal Wigeon almost only fed by grazing. Only Shoveler feeding by dabbling (filtering the first centimetres of water) were used in the analyses. Wigeon spent significantly more time in head-up vigilance than Shoveler (F1,75 = 14·70, P = 0·0003). 4.,It is proposed that this interspecific difference in the proportion of time spent in vigilance behaviour may be an adaptive response to differences in the visual field topography of these species, particularly with respect to the presence/absence of a blind area to the rear of the head. 5.,The ability of foragers to combine part of their vigilance behaviour with head-down feeding has recently been recognized as influencing the trade-offs related to vigilance while foraging. This study shows that this ability may vary significantly between species, even within the same genus, and that these variations are likely to be due to contrasted visual fields, themselves related to the type of feeding techniques employed by the different duck species. [source] Foraging behaviour and habitat partitioning of two sympatric cormorants in Patagonia, ArgentinaIBIS, Issue 3 2008ESTEBAN FRERE Radiotelemetry was used to assess the distribution and diving behaviour of Rock Shags Phalacrocorax magellanicus and Red-legged Cormorants Phalacrocorax gaimardi breeding in sympatry, and Rock Shags breeding in isolation. When breeding in sympatry there was little overlap in the foraging locations of the two species, with the highest densities of each species separated by 10 km. Red-legged Cormorants fed significantly closer to the breeding colony than did Rock Shags and undertook shorter foraging trips, making almost twice as many foraging trips per day as Rock Shags. Rock Shags breeding in isolation had a shorter foraging range than the birds breeding in sympatry with Red-legged Cormorants and foraging trip duration was significantly shorter. However, the number of feeding trips per day was similar between areas of sympatry and allopatry. Differences in the foraging ecology of Rock Shags in areas of sympatry and allopatry may be due to interspecific competition, which forces niche differentiation. The distance between foraging sites, the speed of movement of the prey, a species tendency to move into prey-depleted areas and the length of the breeding season (during which the birds are constrained to be in the same area) may play critical roles in determining the extent to which differential area use by competitors is a strategy that benefits both parties. [source] Disruption of the Wolbachia surface protein gene wspB by a transposable element in mosquitoes of the Culex pipiens complex (Diptera, Culicidae)INSECT MOLECULAR BIOLOGY, Issue 2 2007Y. O. Sanogo Abstract Culex pipiens quinquefasciatus Say and Culex pipiens pipiens Linnaeus are sibling species incriminated as important vectors of emerging and re-emerging infectious diseases worldwide. The two forms differ little morphologically and are differentiated mainly based upon ecological, behavioural, physiological and genetic traits. Within the North American zone of sympatry, populations of Cx. p. quinquefasciatus and Cx. p. pipiens undergo extensive introgression and hybrid forms have been reported in nature. Both Cx. p. quinquefasciatus and Cx. p. pipiens are infected with the endosymbiotic bacteria Wolbachia pipientis. Here, we report the presence of a transposable element belonging to the IS256 family (IS256wPip) associated with Wolbachia in both Cx. p. quinquefasciatus and Cx. p. pipiens populations. Using reverse transcriptase PCR and sequence analysis, we show that IS256wPip has disrupted the wspB locus, a paralogue of the Wolbachia outer membrane protein (wspA) gene. The inactivation of the wspB appears to be specific to Cx. p. quinquefasciatus and to hybrids of the two forms, and was not observed in the surveyed Cx. p. pipiens mosquitoes. Our results support the hypothesis of a different origin of North American Cx. p. quinquefasciatus and Cx. p. pipiens populations. The flux of mobile genetic elements in the Wolbachia wPip genome could explain the high level of crossing types observed among different Culex populations. The insertion of IS256wPip into wspB may comprise a genetic candidate for discriminating Wolbachia symbionts in Culex. [source] An unusual distribution of the kdr gene among populations of Anopheles gambiae on the island of Bioko, Equatorial GuineaINSECT MOLECULAR BIOLOGY, Issue 6 2005L. J. Reimer Abstract In West Africa, Anopheles gambiae exists in discrete subpopulations known as the M and S molecular forms. Although these forms occur in sympatry, pyrethroid knock-down resistance (kdr) is strongly associated with the S molecular form. On the island of Bioko, Equatorial Guinea we found high frequencies of the kdr mutation in M form individuals (55.8%) and a complete absence of kdr in the S form. We also report the absence of the kdr allele in M and S specimens from the harbour town of Tiko in Cameroon, representing the nearest continental population to Bioko. The kdr allele had previously been reported as absent in populations of An. gambiae on Bioko. Contrary to earlier reports, sequencing of intron-1 of this sodium channel gene revealed no fixed differences between M form resistant and susceptible individuals. The mutation may have recently arisen independently in the M form on Bioko due to recent and intensive pyrethroid application. [source] Evidence for genetic differentiation between the molecular forms M and S within the Forest chromosomal form of Anopheles gambiae in an area of sympatryINSECT MOLECULAR BIOLOGY, Issue 1 2002C. Wondji Abstract We studied genetic variation at ten microsatellite DNA loci in Anopheles gambiae populations from the Forest chromosomal form collected in four villages in Cameroon (Central Africa). Both recently described M and S molecular forms occur in sympatry in this area. Geographic differentiation within form was low (Fst < 0.017) despite geographical distance between collection sites ranging from 35 to 350 km. However, higher (Fst > 0.035) and statistically significant levels of genetic differentiation were observed between forms, being the highest between sympatric M and S populations collected within the same village. Results were consistent across all loci spread throughout the genome, therefore reflecting a genome-wide pattern. Considering previous findings of strong assortative mating within forms and general lack of hybrids in areas of sympatry, we propose that there is now sufficient direct and indirect evidence to consider both M and S molecular forms of An. gambiae as distinct species that have probably speciated recently. [source] Using presence signs to discriminate between similar speciesINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 3 2009Sara M. SANTOS Abstract The Lusitanian and the Mediterranean pine voles (Microtus lusitanicus Gerbe, 1879 and Microtus duodecimcostatus de Selys-Longchamps, 1839) are fossorial sister species and have an allopatric pattern of distribution in Portugal, which includes a potential sympatry area in the centre of the country. The present study aimed to determine the validity of using presence signs in the field for discrimination of the two species in an area of sympatry (Northern Alentejo) and the characteristics that achieve the best classification accuracy. A total of 175 trapping plots were sampled across the study area. Prior to the set up of traps, ten presence signs were randomly selected for measurements of four variables: proportion of soil mounds, mean diameter of mounds, proportion of burrow openings and mean diameter of burrow openings. On the basis of a classification tree analysis, results showed that presence signs can be used to discriminate plots inhabited by one or the other species in the studied sympatry area. The characteristic that most accurately enables species identification is the proportion of burrow openings: for every ten presence signs found in a plot, if more than eight have an opening, then it is inhabited by M. lusitanicus (i.e. mostly burrow openings with few or no mounds present); if eight or fewer have an opening, M. duodecimcostatus is present (i.e. mostly mounds with few or no burrow openings). [source] Habitat differentiation within the large-carnivore community of Norway's multiple-use landscapesJOURNAL OF APPLIED ECOLOGY, Issue 5 2008Roel May Summary 1The re-establishment of large carnivores in Norway has led to increased conflicts and the adoption of regional zoning for these predators. When planning the future distribution of large carnivores, it is important to consider details of their potential habitat tolerances and strength of inter-specific differentiation. We studied differentiation in habitat and kill sites within the large-carnivore community of south-eastern Norway. 2We compared habitat selection of the brown bear Ursus arctos L., Eurasian lynx Lynx lynx L., wolf Canis lupus L. and wolverine Gulo gulo L., based on radio-tracking data. Differences in kill site locations were explored using locations of documented predator-killed sheep Ovis aries L. We modelled each species' selection for, and differentiation in, habitat and kill sites on a landscape scale using resource selection functions and multinomial logistic regression. Based on projected probability of occurrence maps, we estimated continuous patches of habitat within the study area. 3Although bears, lynx, wolves and wolverines had overlapping distributions, we found a clear differentiation for all four species in both habitat and kill sites. The presence of bears, wolves and lynx was generally associated with rugged, forested areas at lower elevations, whereas wolverines selected rugged terrain at higher elevations. Some degree of sympatry was possible in over 40% of the study area, although only 1·5% could hold all four large carnivores together. 4Synthesis and applications. A geographically differentiated management policy has been adopted in Norway, aimed at conserving viable populations of large carnivores while minimizing the potential for conflicts. Sympatry of all four carnivores will be most successful if regional zones are established of adequate size spanning an elevational gradient. High prey densities, low carnivore densities, low dietary overlap and scavenging opportunities have most probably led to reduced competitive exclusion. Although regional sympatry enhances the conservation of an intact guild of large carnivores, it may well increase conflict levels and resistance to carnivore conservation locally. [source] Niche overlap between marsupial and eutherian carnivores: does competition threaten the endangered spotted-tailed quoll?JOURNAL OF APPLIED ECOLOGY, Issue 2 2008A. S. Glen Summary 1The significance of top-down regulation by carnivores is receiving increasing global recognition. As a consequence, key objectives in many programmes that seek to maintain ecosystem function now include conserving carnivores and understanding their interactions. This study examined overlap in resource use (space and diet) of introduced eutherian carnivores and an endangered marsupial carnivore, the spotted-tailed quoll Dasyurus maculatus, in eastern Australia. We also investigated mechanisms of niche partitioning and evidence for interspecific aggression. 2Dietary overlap between quolls, red foxes Vulpes vulpes and wild dogs Canis lupus ssp. was assessed by analysis of scats. Trapping, radio-tracking and direct observations were used to quantify spatial overlap between quolls, foxes, wild dogs and feral cats Felis catus. 3Dietary overlap among the carnivores was extensive. Medium-sized mammals were the most important prey for all three predators, indicating potential for exploitative interactions. However, hunting of different size classes of secondary prey and consumption by quolls of more arboreal prey than their counterparts may assist coexistence. Remains of quoll were found in two dog scats, and cat hair in another, possibly indicating intraguild predation. 4We observed extensive spatial overlap between quolls and eutherian carnivores. However, we inferred from dietary data that quolls foraged primarily in forested habitat, while canids foraged mainly in cleared habitat. 5Synthesis and applications. Our results indicate strong potential for competition between spotted-tailed quolls and eutherian carnivores, and thus a situation where control of introduced predators may be desirable, not only for the conservation of prey species but also for the protection of native carnivores. Concern over potential non-target mortality of quolls has hindered efforts to control foxes in eastern Australia using poison baits. We contend that, rather than harming quoll populations, baiting for foxes should aid the conservation of quolls and should be implemented in areas of sympatry where fox numbers are high. [source] Hydrological disturbance benefits a native fish at the expense of an exotic fishJOURNAL OF APPLIED ECOLOGY, Issue 5 2006F. LEPRIEUR Summary 1Some native fish in New Zealand do not coexist with introduced salmonids. Previous studies of disjunct distributions of exotic brown trout Salmo trutta and native galaxiids demonstrated native extirpation except where major waterfalls prevented upstream migration of trout. In the Manuherikia River system, we predicted that water abstraction might be a further factor controlling the spatial distribution of both the invader and a native fish. 2We applied multiple discriminant function analyses to test for differences in environmental conditions (catchment and instream scales) at sites with roundhead galaxias Galaxias anomalus and brown trout in sympatry and allopatry. We then used a supervised artificial neural network (ANN) to predict the presence,absence of G. anomalus and brown trout (135 sites). The quantification of contributions of environmental variables to ANN models allowed us to identify factors controlling their spatial distribution. 3Brown trout can reach most locations in the Manuherikia catchment, and often occur upstream of G. anomalus. Their largely disjunct distributions in this river are mediated by water abstraction for irrigation, together with pool habitat availability and valley slope. Trout are more susceptible than the native fish to stresses associated with low flows, and seem to be prevented from eliminating galaxiid populations from sites in low gradient streams where there is a high level of water abstraction. 4Synthesis and applications. In contrast to many reports in the literature, our results show that hydrological disturbance associated with human activities benefits a native fish at the expense of an exotic in the Manuherikia River, New Zealand. Water abstraction is also known to have negative impacts on native galaxiids, therefore we recommend restoring natural low flows to maintain sustainable habitats for native galaxiids, implementing artificial barriers in selected tributaries to limit trout predation on native fish, and removing trout upstream. [source] Assortative mating also indicates that common crossbill Loxia curvirostra vocal types are speciesJOURNAL OF AVIAN BIOLOGY, Issue 1 2008Pim Edelaar Compared to most other birds, the taxonomy of crossbills (Loxia) is still highly unsettled. However, much progress seems to be achievable when data on vocalisations is included. In a recent paper, Summers et al. (2007) argued that strong assortative mating indicated that parrot crossbill Loxia pytyopsittacus, Scottish crossbill Loxia scotica and common crossbill Loxia curvirostra behave as good species when breeding in sympatry. Here I argue that their data, when placed in the context of other studies, also indicate that three vocally differentiated European populations within the common crossbill are species (following the biological species concept of Mayr (1963): species are groups of interbreeding natural populations that are reproductively isolated from other such groups). If this tentative conclusion remains to be upheld, it might have large repercussions for our understanding of the speciation process as well as for a number of more applied issues such as the discovery and description of biodiversity and the conversation of mobile, cryptic species. [source] Areography of the genus Dendroctonus (Coleoptera: Curculionidae: Scolytinae) in MexicoJOURNAL OF BIOGEOGRAPHY, Issue 7 2004Yolanda Salinas-Moreno Abstract Objective, To analyse whether the geographical ranges of Dendroctonus species are (1) associated with factors such as host species or elevation, and (2) in agreement with Halffter's Nearctic distribution pattern. (3) To identify and discuss the factors that are likely to act as barriers to the genus' geographical distribution. (4) To explore whether there is an association between the size of the geographical ranges of Dendroctonus species and the number of Pinus host species used by each of them, and (5) to assess if these host species are most common at the elevations preferred by the individual Dendroctonus species. Site, Mexico. Methods, Records of 12 species of Dendroctonus were gathered from entomological collections in Mexico. Distribution ranges were defined by using the propinquity method (Rapoport, 1975a). Analysed parameters were: (1) geographical distribution of single species, (2) overlapping of species ranges, (3) disjunction patterns and barriers by means of isoprobabilistic lines, based on the morphotectonic subdivision of Mexico (Ferrusquía-Villafranca, 1998), (4) spatial variation in species richness with respect to latitude and altitude, (5) size of geographical ranges, and (6) host species for each Dendroctonus species. A correlation was determined between area size and number of pine host species. Results, The species ranges varied in shape and size. Geographical ranges tend to be discontinuous in shape. Composite patterns showed that disjunctions among ranges do not closely follow Mexico's morphotectonic subdivision. There are repeated discontinuities among individual distributions, which define five areas: (1) Baja California Peninsula, (2) Sierra Madre Occidental (SMOC), (3) northern Sierra Madre Oriental (SMOR), (4) Sierra Madre de Chiapas, and (5) SMOR + Faja Volcanica Transmexicana (FVT) + Sierra Madre del Sur. The isoprobabilistic lines confirm that the inner part of SMOC provides an optimal environment for the genus, and the FVT province constitutes the broader corridor for it in the country. Richness does not directly decrease or increase with latitude. Richness behaviour of the insect is not associated with that of its host. Elevation distributions showed that most Dendroctonus species move within broad margins of tolerance and species richness is concentrated in the montane interval. Dendroctonus attack 24 of the 47 Pinus species distributed in Mexico. Preferred pine species belong predominantly to Leiophyllae, Ponderosae and Oocarpae subsections. The Spearman rank correlation between area size and number of pine host species was not significant. Dendroctonus clearly belongs to a Nearctic distribution pattern (sensuHalffter, 1987). Main conclusions,Dendroctonus is present in all montane systems of Mexico and its species coexist within a high geographical sympatry. Overlapping of species distribution appears to be the result of two elements , generalized polyphagy inside Pinus and a wide elevation tolerance within mountainous environments. This behaviour, linked to a high vagility, has allowed the genus Dendroctonus to expand its distribution across Mexico and to employ mountainous systems as corridors separated by barriers that exert a low selective filter effect. [source] | ||||||||||||||||||||||||||||||||||||||||