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Ecological Traits (ecological + trait)
Selected AbstractsAntioxidant and Pigment Composition during Autumnal Leaf Senescence in Woody Deciduous Species Differing in their Ecological TraitsPLANT BIOLOGY, Issue 5 2003J. I. García-Plazaola Abstract: Photoprotection mechanisms have been studied during autumnal senescence in sun and shade leaves of woody plants with different ecological characteristics and senescence patterns. Three of them belonging to the same family, Betulaceae: the shade-intolerant and early successional species (Betula alba L.), the shade-tolerant and late successional species (Corylus avellana L.), and an N-fixing tree with low N resorption efficiency (Alnus glutinosa L.). The other two species: a shade-intolerant (Populus tremula L.) and a shade-tolerant (Cornus sanguinea L.), were chosen because of their ability to accumulate anthocyanins during autumnal leaf senescence. The study of plants with different ecological strategies allowed us to establish general trends in photoprotection mechanisms during autumnal senescence, when nutrient remobilisation occurs, but also during whole leaf ontogeny. We have not found a clear relationship between shade tolerance and the level of photoprotection; the main difference between both groups of species being the presence of ,-carotene in shade leaves of shade-tolerant species. Preceding autumn, nitrogen resorption started in mid-summer and occurred in parallel with a slight and continuous ascorbate, chlorophyll and carotenoid degradation. However, the ascorbate pool remained highly reduced and lipid oxidation did not increase at this time. Contrasting with ascorbate, ,-tocopherol accumulated progressively in all species. Only during the last stages of senescence was chlorophyll preferentially degraded with respect to carotenoids, leading to the yellowing of leaves, except in A. glutinosa in which a large retention of chlorophyll and N took place. Senescing leaves were characterised, except in C. sanguinea, by a relative increase in the proportion of de-epoxidised xanthophylls: zeaxanthin, antheraxanthin and lutein. The light-induced accumulation of anthocyanins in C. sanguinea could play an additional protective role, compensating for the low retention of de-epoxidised xanthophylls. These different strategies among deciduous species are consistent with a role for photoprotective compounds in enhancing nitrogen remobilization and storage for the next growing season. [source] EVOLUTION OF DOMINANCE UNDER FREQUENCY-DEPENDENT INTRASPECIFIC COMPETITION IN AN ASSORTATIVELY MATING POPULATIONEVOLUTION, Issue 2 2010Stephan Peischl We study the evolution of higher levels of dominance as a response to negative frequency-dependent selection. In contrast to previous studies, we focus on the effect of assortative mating on the evolution of dominance under frequency-dependent intraspecific competition. We analyze a two-locus two-allele model, in which the primary locus has a major effect on a quantitative trait that is under a mixture of frequency-independent stabilizing selection, density-dependent selection, and frequency-dependent selection caused by intraspecific competition for a continuum of resources. The second (modifier) locus determines the degree of dominance at the trait level. Additionally, the population mates assortatively with respect to similarities in the ecological trait. Our analysis shows that the parameter region in which dominance can be established decreases if small levels of assortment are introduced. In addition, the degree of dominance that can be established also decreases. In contrast, if assortment is intermediate, sexual selection for extreme types can be established, which leads to evolution of higher levels of dominance than under random mating. For modifiers with large effects, intermediate levels of assortative mating are most favorable for the evolution of dominance. For large modifiers, the speed of fixation can even be higher for intermediate levels of assortative mating than for random mating. [source] Phylogenetic relatedness and plant invader success across two spatial scalesDIVERSITY AND DISTRIBUTIONS, Issue 3 2009Marc W. Cadotte ABSTRACT Aim, Successful invaders often possess similar ecological traits that contribute to success in new regions, and thus under niche conservatism, invader success should be phylogenetically clustered. We asked if the degree to which non-native plant species are phylogenetically related is a predictor of invasion success at two spatial scales. Location, Australia , the whole continent and Royal National Park (south-eastern Australia). Methods, We used non-native plant species occupancy in Royal National Park, as well as estimated continental occupancy of these species from herbarium records. We then estimated phylogenetic relationships using molecular data from three gene sequences available on GenBank (matK, rbcL and ITS1). We tested for phylogenetic signals in occupancy using Blomberg's K. Results, Whereas most non-native plants were relatively scarce, there was a strong phylogenetic signal for continental occupancy, driven by the clustering of successful species in Asteraceae, Caryophyllaceae, Poaceae and Solanaceae. However, we failed to detect a phylogenetic signal at the park scale. Main Conclusions, Our results reveal that at a large spatial scale, invader success is phylogenetically clustered where ecological traits promoting success appear to be shared among close relatives, indicating that phylogenetic relationships can be useful predictors of invasion success at large spatial scales. At a smaller, landscape scale, there was no evidence of phylogenetic clustering of invasion success, and thus, relatedness plays a much reduced role in determining the relative success of invaders. [source] Invasive exotic aoudad (Ammotragus lervia) as a major threat to native Iberian ibex (Capra pyrenaica): a habitat suitability model approachDIVERSITY AND DISTRIBUTIONS, Issue 5 2007Pelayo Acevedo ABSTRACT The introduction of alien species to new environments is one of the main threats to the conservation of biodiversity. One particularly problematic example is that of wild ungulates which are increasingly being established in regions outside their natural distribution range due to human hunting interests. Unfortunately, we know little of the effects these large herbivores may have on the host ecosystems. This study deals with a first comparative analysis of the habitat requirements of two ungulate species that may be facing competition for resources in the south of Europe: the native Iberian ibex (Capra pyrenaica) and the exotic aoudad (Ammotragus lervia). The aoudad is a North African caprid introduced in 1970 as a game species in south-eastern Spain. It has adapted well, and populations have been freely expanding since then. Ecological Niche Factor Analysis is used to describe the realized niche of both species where their distribution ranges merge. Both species occupy marginal areas of rugged terrain in the region. Marginality is higher for the Iberian ibex, which also presents a higher tolerance of secondary environmental gradients than the aoudad. Highly suitable areas for each species are secondarily suitable for the other. Reclassified and cross-tabulated habitat suitability maps showing the areas of potential spatial coexistence and differences in ecological traits between both species are provided. The results obtained do not allow inferring resource competition between these species. However, current aoudad expansion could result in it invading the favoured habitats of the ibex. Inadequate hunting policy and monitoring, and increasing climatic resemblance of the study region to the native aoudad areas, due to a strong desertification process, are facilitating a high rate of expansion. We strongly recommend to eradicate or, at least, monitor these exotic populations, and promote active conservation practices, if one wants to preserve the unique natural resources present in this European region. [source] Multivariate correlates of extinction proneness in a naturally fragmented landscapeDIVERSITY AND DISTRIBUTIONS, Issue 4 2007James I. Watling ABSTRACT Habitat loss and fragmentation threaten a large proportion of terrestrial biodiversity, and identifying the ecological traits associated with extinction proneness is of widespread interest. We used a multivariate statistical approach to identify combinations of ecological traits that best allowed us to identify extinction-prone amphibians and reptiles in a fragmented landscape in north-eastern Bolivia. Extinction-prone amphibians were rare and did not utilize the savannah matrix separating forest islands, whereas extinction-prone reptiles were trophically specialized. Rarity and matrix aversion are among the most widely reported correlates to extinction proneness, and we argue that an increased understanding of their role as drivers of extinction processes is necessary. We suggest that the absence of reptilian vertebrate predators may exacerbate trophic cascades in habitat patches. [source] Effects of species' ecology on the accuracy of distribution modelsECOGRAPHY, Issue 1 2007Jana M. McPherson In the face of accelerating biodiversity loss and limited data, species distribution models , which statistically capture and predict species' occurrences based on environmental correlates , are increasingly used to inform conservation strategies. Additionally, distribution models and their fit provide insights on the broad-scale environmental niche of species. To investigate whether the performance of such models varies with species' ecological characteristics, we examined distribution models for 1329 bird species in southern and eastern Africa. The models were constructed at two spatial resolutions with both logistic and autologistic regression. Satellite-derived environmental indices served as predictors, and model accuracy was assessed with three metrics: sensitivity, specificity and the area under the curve (AUC) of receiver operating characteristics plots. We then determined the relationship between each measure of accuracy and ten ecological species characteristics using generalised linear models. Among the ecological traits tested, species' range size, migratory status, affinity for wetlands and endemism proved most influential on the performance of distribution models. The number of habitat types frequented (habitat tolerance), trophic rank, body mass, preferred habitat structure and association with sub-resolution habitats also showed some effect. In contrast, conservation status made no significant impact. These findings did not differ from one spatial resolution to the next. Our analyses thus provide conservation scientists and resource managers with a rule of thumb that helps distinguish, on the basis of ecological traits, between species whose occurrence is reliably or less reliably predicted by distribution models. Reasonably accurate distribution models should, however, be attainable for most species, because the influence ecological traits bore on model performance was only limited. These results suggest that none of the ecological traits tested provides an obvious correlate for environmental niche breadth or intra-specific niche differentiation. [source] Holly leaf-miners on two continents: what makes an outbreak species?ECOLOGICAL ENTOMOLOGY, Issue 2 2001Sabine Eber Summary 1. Some herbivore species periodically undergo damaging, high-density outbreak phases followed by less damaging low-density phases. Others maintain steady, low to moderate density levels that do little damage to their hosts. 2. Two closely related holly leaf-miner species were compared that share many ecological traits and have very similar life cycles, but only one of which exhibits outbreaks. Phytomyza ilicicola in the eastern U.S.A. varied widely in mortality and infestation levels, reaching local densities of over 10 mines per leaf. In contrast, Phytomyza ilicis in the U.K. showed low infestation and high mortality at all sites. Using data from the literature and from field studies, the factors responsible for these contrasting dynamics were sought. 3. Phytomyza ilicicola oviposits into the leaf lamina, and experiences weak larval competition only at high densities. Phytomyza ilicis oviposits into the leaf midrib, which leads to high mortality of young larvae before mine formation. Multiply mined leaves were therefore very common in P. ilicicola but rare in P. ilicis. 4. Differences in the parasitoid complexes of the two systems accounted for further differences in survival to adulthood. The main (larval) parasitoid, which was found to impose high, density-dependent mortality on P. ilicis, is missing on P. ilicicola. It is replaced by an egg,pupal parasitoid, which varies in its impact at differe,t sites. Multiple emergence of adults from multiply mined leaves is therefore widespread in P. ilicicola but does not occur in P. ilicis. 5. The differences in oviposition behaviour and in the parasitoid complexes are likely to allow P. ilicicola to outbreak when habitat conditions are favourable, while P. ilicis is always tightly regulated. [source] Predicting competition coefficients for plant mixtures: reciprocity, transitivity and correlations with life-history traitsECOLOGY LETTERS, Issue 4 2001R.P. Freckleton There are few empirical or theoretical predictions of how per capita or per individual competition coefficients for pairs of plant species should relate to each other. In contrast, there are a considerable number of general hypotheses that predict competitive ability as a function of a range of ecological traits, together with a suite of increasingly sophisticated models for competitive interactions between plant species. We re-analyse a data set on competition between all pairwise combinations of seven species and show that competition coefficients relate strongly to differences between the maximum sizes, root allocation, emergence time and seed size of species. Regressions suggest that the best predictor of competition coefficients is the difference in the maximum size of species and that correlations of the other traits with the competition coefficients occur through effects on the maximum size. We also explore the patterns of association between coefficients across the competition matrix. We find significant evidence for coefficient reciprocity (inverse relationships between the interspecific coefficients for species pairs) and transitivity (numerically predictable hierarchies of competition between species) across competition matrices. These results therefore suggest simple null models for plant community structure when there is competition for resources. [source] Disclosing arbuscular mycorrhizal fungal biodiversity in soil through a land-use gradient using a pyrosequencing approachENVIRONMENTAL MICROBIOLOGY, Issue 8 2010Erica Lumini Summary The biodiversity of arbuscular mycorrhizal fungi (AMF) communities present in five Sardinian soils (Italy) subjected to different land-use (tilled vineyard, covered vineyard, pasture, managed meadow and cork-oak formation) was analysed using a pyrosequencing-based approach for the first time. Two regions of the 18S ribosomal RNA gene were considered as molecular target. The pyrosequencing produced a total of 10924 sequences: 6799 from the first and 4125 from the second target region. Among these sequences, 3189 and 1003 were selected to generate operational taxonomic units (OTUs) and to evaluate the AMF community richness and similarity: 117 (37 of which were singletons) and 28 (nine of which were singletons) unique AMF OTUs were detected respectively. Within the Glomeromycota OTUs, those belonging to the Glomerales order were dominant in all the soils. Diversisporales OTUs were always detected, even though less frequently, while Archaeosporales and Paraglomerales OTUs were exclusive of the pasture soil. Eleven OTUs were shared by all the soils, but each of the five AMF communities showed particular features, suggesting a meaningful dissimilarity among the Glomeromycota populations. The environments with low inputs (pasture and covered vineyard) showed a higher AMF biodiversity than those subjected to human input (managed meadow and tilled vineyard). A reduction in AMF was found in the cork-oak formation because other mycorrhizal fungal species, more likely associated to trees and shrubs, were detected. These findings reinforce the view that AMF biodiversity is influenced by both human input and ecological traits, illustrating a gradient of AMF communities which mirror the land-use gradient. The high number of sequences obtained by the pyrosequencing strategy has provided detailed information on the soil AMF assemblages, thus offering a source of light to shine on this crucial soil microbial group. [source] SEXUAL DIMORPHISM AND ADAPTIVE SPECIATION: TWO SIDES OF THE SAME ECOLOGICAL COINEVOLUTION, Issue 11 2003Daniel I. Bolnick Abstract Models of adaptive speciation are typically concerned with demonstrating that it is possible for ecologically driven disruptive selection to lead to the evolution of assortative mating and hence speciation. However, disruptive selection could also lead to other forms of evolutionary diversification, including ecological sexual dimorphisms. Using a model of frequency-dependent intraspecific competition, we show analytically that adaptive speciation and dimorphism require identical ecological conditions. Numerical simulations of individual-based models show that a single ecological model can produce either evolutionary outcome, depending on the genetic independence of male and female traits and the potential strength of assortative mating. Speciation is inhibited when the genetic basis of male and female ecological traits allows the sexes to diverge substantially. This is because sexual dimorphism, which can evolve quickly, can eliminate the frequency-dependent disruptive selection that would have provided the impetus for speciation. Conversely, populations with strong assortative mating based on ecological traits are less likely to evolve a sexual dimorphism because females cannot simultaneously prefer males more similar to themselves while still allowing the males to diverge. This conflict between speciation and dimorphism can be circumvented in two ways. First, we find a novel form of speciation via negative assortative mating, leading to two dimorphic daughter species. Second, if assortative mating is based on a neutral marker trait, trophic dimorphism and speciation by positive assortative mating can occur simultaneously. We conclude that while adaptive speciation and ecological sexual dimorphism may occur simultaneously, allowing for sexual dimorphism restricts the likelihood of adaptive speciation. Thus, it is important to recognize that disruptive selection due to frequency-dependent interactions can lead to more than one form of adaptive splitting. [source] Convergence of fish communities from the littoral zone of reservoirsFRESHWATER BIOLOGY, Issue 6 2009KEITH B. GIDO Summary 1.,Understanding factors that regulate the assembly of communities is a main focus of ecology. Human-engineered habitats, such as reservoirs, may provide insight into these assembly processes because they represent novel habitats that are subjected to colonization by fishes from the surrounding river basin or transported by humans. By contrasting community similarity within and among reservoirs from different drainage basins to nearby stream communities, we can test the relative constraints of reservoir habitats and regional species pools in determining species composition of reservoirs. 2.,We used a large spatial database that included intensive collections from 143 stream and 28 reservoir sites within three major river basins in the Great Plains, U.S.A., to compare patterns of species diversity and community structure between streams and reservoirs and to characterize variation in fish community structure within and among major drainage basins. We expected reservoir fish faunas to reflect the regional species pool, but would be more homogeneous that stream communities because similar species are stocked and thrive in reservoirs (e.g. planktivores and piscivores), and they lack obligate stream organisms that are not shared among regional species pools. 3.,We found that fish communities from reservoirs were a subset of fishes collected from streams and dominant taxa had ecological traits that would be favoured in lentic environments. Although there were regional differences in reservoir fish communities, species richness, patterns of rank abundance and community structure in reservoir communities were more homogonous across three major drainage basins than for stream communities. 4.,The general pattern of convergence of reservoir fish community structure suggests their assembly is constrained by local factors such as habitat and biotic interactions, and facilitated by the introduction of species among basins. Because there is a reciprocal transfer of biota between reservoirs and streams, understanding factors structuring both habitats is necessary to evaluate the long-term dynamics of impounded river networks. [source] Biological and ecological traits of benthic freshwater macroinvertebrates: relationships and definition of groups with similar traitsFRESHWATER BIOLOGY, Issue 2 2000Philippe Usseglio-Polatera Summary 1Relating species traits to habitat characteristics can provide important insights into the structure and functioning of stream communities. However, trade-offs among species traits make it difficult to predict accurately the functional diversity of freshwater communities. Many authors have pointed to the value of working with groups of organisms as similar as possible in terms of relationships among traits and have called for definition of groups of organisms with similar suites of attributes. 2We used multivariate analyses to examine separately the relationships among 11 biological traits and among 11 ecological traits of 472 benthic macroinvertebrate taxa (mainly genera). The main objective was to demonstrate (1) potential trade-offs among traits; (2) the importance of the different traits to separate systematic units or functional groupings; and (3) uniform functional groups of taxa that should allow a more effective use of macroinvertebrate biological and ecological traits. 3We defined eight groups and 15 subgroups according to a biological trait ordination which highlighted size (large to small), reproductive traits (K to r strategists), food (animal to plant material) and feeding habits (predator to scraper and/or deposit feeder) as ,significant' factors determining the ordination of taxa. This ordination partly preserved phylogenetic relationships among groups. 4Seven ecological groups and 13 ecological subgroups included organisms with combinations of traits which should be successively more adequate in habitats from the main channel to temporary waters, and from the crenon to the potamic sections of rivers, and to systems situated outside the river floodplain. These gradients corresponded to a gradual shift from (1) rheophilic organisms that lived in the main channel of cold oligotrophic mountain streams to (2) animals that preferred eutrophic habitats of still or temporary waters in lowlands. The groups with similar ecological traits had a more diverse systematic structure than those with similar biological traits. 5Monitoring and assessment tools for the management of water resources are generally more effective if they are based on a clear understanding of the mechanisms that lead to the presence or absence of species groups in the environment. We believe that groups with similar relationships among their species traits may be useful in developing tools that measure the functional diversity of communities. [source] Local extent of old-growth woodland modifies epiphyte response to climate changeJOURNAL OF BIOGEOGRAPHY, Issue 2 2009Christopher J. Ellis Abstract Aim, To quantify the interaction between climate and woodland continuity in determining the bioclimatic response of lichen epiphytes. Location, Northern Britain (Scotland). Methods, Indicator-species analysis was used to pre-select lichen epiphytes along parallel gradients in climate and the extent of old-growth woodland. Nonparametric multiplicative regression was used to describe in a predictive model the individualistic response of selected species, which were projected based on climate-change scenarios and contrasting patterns of simulated woodland loss or gain. Species with a similar response were grouped using a novel application of cluster analysis to summarize the potentially huge number of projected outcomes. Projected patterns of occurrence under climate-change scenarios were examined for different levels of old-growth woodland extent. Results, Forty-two lichen species were statistically significant indicator species in oceanic woodlands, and old-growth indicators under suboptimal climatic conditions. Responses to climate-change scenarios were contrasting, with one group comprising species projected to increase in extent in response to climate warming, and other response groups projected to decrease in occurrence, possibly in response to shifting rainfall patterns. The occurrence of all response groups had a positive relationship with old-growth woodland extent. Main conclusions, An ,oceanic' biogeographical group of epiphytes identified using the baseline climatic and present-day woodland setting comprised species with a cyanobacterial photobiont or tropical phytogeographical affinities. However, within this group the individual species responses to climate-change scenarios were contrasting. Additionally, group responses may be poorly matched with simple ecological traits. However, the studied interaction between climate and habitat continuity suggests that the impact of climate change might be offset for certain lichen epiphytes by appropriate management of woodland resources, for example, expansion of native woodland around remnant old-growth stands. [source] Patch occupancy of North American mammals: is patchiness in the eye of the beholder?JOURNAL OF BIOGEOGRAPHY, Issue 8 2003Robert K. Swihart Abstract Aim Intraspecific variation in patch occupancy often is related to physical features of a landscape, such as the amount and distribution of habitat. However, communities occupying patchy environments typically exhibit non-random distributions in which local assemblages of species-poor patches are nested subsets of assemblages occupying more species-rich patches. Nestedness of local communities implies interspecific differences in sensitivity to patchiness. Several hypotheses have been proposed to explain interspecific variation in responses to patchiness within a community, including differences in (1) colonization ability, (2) extinction proneness, (3) tolerance to disturbance, (4) sociality and (5) level of adaptation to prevailing environmental conditions. We used data on North American mammals to compare the performance of these ,ecological' hypotheses and the ,physical landscape' hypothesis. We then compared the best of these models against models that scaled landscape structure to ecologically relevant attributes of individual species. Location North America. Methods We analysed data on prevalence (i.e. proportion of patches occupied in a network of patches) and occupancy for 137 species of non-volant mammals and twenty networks consisting of four to seventy-five patches. Insular and terrestrial networks exhibited significantly different mean levels of prevalence and occupancy and thus were analysed separately. Indicator variables at ordinal and family levels were included in models to correct for effects caused by phylogeny. Akaike's information criterion was used in conjunction with ordinary least squares and logistic regression to compare hypotheses. Results A patch network's physical structure, indexed using patch area and isolation, received the greatest support among models predicting the prevalence of species on insular networks. Niche breadth (diet and habitat) received the greatest support for predicting prevalence of species occupying terrestrial networks. For both insular and terrestrial systems, physical features (patch area and isolation) received greater support than any of the ecological hypotheses for predicting species occupancy of individual patches. For terrestrial systems, scaling patch area by its suitability to a focal species and by individual area requirements of the species, and scaling patch isolation by species-specific dispersal ability and niche breadth, resulted in models of patch occupancy that were superior to models relying solely on physical landscape features. For all selected models, unexplained levels of variation were high. Main conclusions Stochasticity dominated the systems we studied, indicating that random events are probably quite important in shaping local communities. With respect to deterministic factors, our results suggest that forces affecting species prevalence and occupancy may differ between insular and terrestrial systems. Physical features of insular systems appeared to swamp ecological differences among species in determining prevalence and occupancy, whereas species with broad niches were disproportionately represented in terrestrial networks. We hypothesize that differential extinction over long time periods in highly variable networks has driven nestedness of mammalian communities on islands, whereas differential colonization over shorter time-scales in more homogeneous networks probably governed the local structure of terrestrial communities. Our results also demonstrate that integration of a species' ecological traits with physical features of a patch network is superior to reliance on either factor separately when attempting to predict the species' probability of patch occupancy in terrestrial systems. [source] Interactions between non-native plant species and the floristic composition of common habitatsJOURNAL OF ECOLOGY, Issue 6 2006L. C. MASKELL Summary 1We investigated the role of non-native species (neophytes) in common British plant communities using botanical data from two stratified random surveys carried out in 1990 and 1998. 2We found that from 16 851 plots surveyed in 1998 there were 123 non-native species found mostly in arable, tall grass/herb and fertile grassland habitats. Invasive non-native species, e.g. Fallopia japonica, Impatiens glandulifera and Rhododendron ponticum, were uncommon in this survey. 3Between 1990 and 1998 the total number of non-native species increased but the mean number of species per sample plot decreased. The mean cover of non-natives increased from 1.2% to 1.9%. 4There were positive spatial and temporal relationships between non-native and native species diversity. However, there was a weak negative relationship between changes in non-native cover and native diversity. 5The species composition and ecological traits of communities containing non-natives were very different from those that did not contain them. 6In the British countryside non-native species were mainly found in habitats with anthropogenic associations, high fertility, high number of ruderal species and high diversity. There is also an indication that successional shifts where competitive invasive species dominate involve non-native species. 7National-scale changes in plant community composition are likely to be closely correlated with external land-use impacts. Changes such as eutrophication, nitrogen deposition and increased fertility in infertile habitats are likely to benefit both native and non-native invasive species; however, currently these trends benefit native species much more often than non-natives. 8Non-native species are known to have significant effects on native species at local scales in many countries; however, at the landscape scale in Great Britain they are best considered as symptoms of disturbance and land-use change rather than a direct threat to biodiversity. [source] Ecological speciation in marine v. freshwater fishesJOURNAL OF FISH BIOLOGY, Issue 5 2009O. Puebla Absolute barriers to dispersal are not common in marine systems, and the prevalence of planktonic larvae in marine taxa provides potential for gene flow across large geographic distances. These observations raise the fundamental question in marine evolutionary biology as to whether geographic and oceanographic barriers alone can account for the high levels of species diversity observed in marine environments such as coral reefs, or whether marine speciation also operates in the presence of gene flow between diverging populations. In this respect, the ecological hypothesis of speciation, in which reproductive isolation results from divergent or disruptive natural selection, is of particular interest because it may operate in the presence of gene flow. Although important insights into the process of ecological speciation in aquatic environments have been provided by the study of freshwater fishes, comparatively little is known about the possibility of ecological speciation in marine teleosts. In this study, the evidence consistent with different aspects of the ecological hypothesis of speciation is evaluated in marine fishes. Molecular approaches have played a critical role in the development of speciation hypotheses in marine fishes, with a role of ecology suggested by the occurrence of sister clades separated by ecological factors, rapid cladogenesis or the persistence of genetically and ecologically differentiated species in the presence of gene flow. Yet, ecological speciation research in marine fishes is still largely at an exploratory stage. Cases where the major ingredients of ecological speciation, namely a source of natural divergent or disruptive selection, a mechanism of reproductive isolation and a link between the two have been explicitly documented are few. Even in these cases, specific predictions of the ecological hypothesis of speciation remain largely untested. Recent developments in the study of freshwater fishes illustrate the potential for molecular approaches to address specific questions related to the ecological hypothesis of speciation such as the nature of the genes underlying key ecological traits, the magnitude of their effect on phenotype and the mechanisms underlying their differential expression in different ecological contexts. The potential provided by molecular studies is fully realized when they are complemented with alternative (e.g. ecological, theoretical) approaches. [source] Functional evolutionary developmental biology (evo-devo) of morphological novelties in plantsJOURNAL OF SYSTEMATICS EVOLUTION, Issue 2 2010Jisi ZHANG Abstract The origin of morphological and ecological novelties is a long-standing problem in evolutionary biology. Understanding these processes requires investigation from both the development and evolution standpoints, which promotes a new research field called "evolutionary developmental biology" (evo-devo). The fundamental mechanism for the origin of a novel structure may involve heterotopy, heterochrony, ectopic expression, or loss of an existing regulatory factor. Accordingly, the morphological and ecological traits controlled by the regulatory genes may be gained, lost, or regained during evolution. Floral morphological novelties, for example, include homeotic alterations (related to organ identity), symmetric diversity, and changes in the size and morphology of the floral organs. These gains and losses can potentially arise through modification of the existing regulatory networks. Here, we review current knowledge concerning the origin of novel floral structures, such as "evolutionary homeotic mutated flowers", floral symmetry in various plant species, and inflated calyx syndrome (ICS) within Solanaceae. Functional evo-devo of the morphological novelties is a central theme of plant evolutionary biology. In addition, the discussion is extended to consider agronomic or domestication-related traits, including the type, size, and morphology of fruits (berries), within Solanaceae. [source] Plant traits as predictors of woody species dominance in climax forest communitiesJOURNAL OF VEGETATION SCIENCE, Issue 3 2001Fumito Koike Satake et al. (1989) Abstract. The dominance of a given tree or shrub species in a particular forest community may be determined by many ecological traits of the target species, as well as those of the surrounding species as its potential competitors. The present study was conducted to evaluate the possibility of predicting community status (species composition and dominance) on the basis of traits of local flora using statistical methods, and to visualize the mathematical function which determines species dominance. A general linear model and logistic regression were used for the statistical analysis. Dependent variables were designated as dominance and presence/absence of species in climax forest, with independent variables as vegetative and reproductive traits. Subalpine, cool-temperate, warm-temperate and subtropical climax rain forests in East Asia were studied. Quantitative prediction of climax community status could readily be made based on easily measured traits of local flora. Species composition and 74.6% of the total variance of species dominance were predicted based on two traits; maximum height and shade tolerance. Through application of this method, the capacity of an alien species to invade a climax forest community could possibly be predicted prior to introduction of the alien species. [source] The use of taxonomic distinctness indices in assessing patterns of biodiversity in modular organismsMARINE ECOLOGY, Issue 2 2009Stanislao Bevilacqua Abstract Estimating diversity of modular organisms may be problematic due to actual difficulties in discriminating between ,individuals' and quantifying their abundances. Quantitative data, when available, are collected through methods that could preclude the application of classical diversity indices, making comparisons among studies difficult. Taxonomic distinctness indices, such as the ,Average Taxonomic Distinctness' (,+) and the ,Variation in Taxonomic Distinctness' (,+) may represent suitable tools in investigating diversity beyond the simple species number. The potential usefulness of such indices has been explored almost exclusively on unitary organisms, neglecting modular ones. In this study, we employed ,+ and ,+ to analyse patterns of diversity of epiphytic hydroid assemblages living on Cystoseira seaweeds at a hierarchy of spatial scales, along 800 km of rocky coast (SE Italy). ANOVA on species richness and ,+ showed no significant difference in sample diversity at the investigated spatial scales. In contrast, there were significant differences at the scale of 10s of km in ,+. Analyses based on simulations detected significant variations at all spatial scales in ,+. Such findings underline the potential of ,+ in highlighting relevant spatial scales of variation in patterns of hydroid diversity. Our results also suggest that the interplay between natural environmental variations and the complex ecological traits of modular organisms might affect taxonomic distinctness indices. We stress the need for further investigations focusing on modular organisms before any generalizations on the use of taxonomic relatedness measures in examining marine biodiversity can be made. [source] Genome-wide SNP detection in the great tit Parus major using high throughput sequencingMOLECULAR ECOLOGY, Issue 2010NIKKIE E. M. VAN BERS Abstract Identifying genes that underlie ecological traits will open exiting possibilities to study gene,environment interactions in shaping phenotypes and in measuring natural selection on genes. Evolutionary ecology has been pursuing these objectives for decades, but they come into reach now that next generation sequencing technologies have dramatically lowered the costs to obtain the genomic sequence information that is currently lacking for most ecologically important species. Here we describe how we generated over 2 billion basepairs of novel sequence information for an ecological model species, the great tit Parus major. We used over 16 million short sequence reads for the de novo assembly of a reference sequence consisting of 550 000 contigs, covering 2.5% of the genome of the great tit. This reference sequence was used as the scaffold for mapping of the sequence reads, which allowed for the detection of over 20 000 novel single nucleotide polymorphisms. Contigs harbouring 4272 of the single nucleotide polymorphisms could be mapped to a unique location on the recently sequenced zebra finch genome. Of all the great tit contigs, significantly more were mapped to the microchromosomes than to the intermediate and the macrochromosomes of the zebra finch, indicating a higher overall level of sequence conservation on the microchromosomes than on the other types of chromosomes. The large number of great tit contigs that can be aligned to the zebra finch genome shows that this genome provides a valuable framework for large scale genetics, e.g. QTL mapping or whole genome association studies, in passerines. [source] Genetic consequences of habitat fragmentation in plant populations: susceptible signals in plant traits and methodological approachesMOLECULAR ECOLOGY, Issue 24 2008RAMIRO AGUILAR Abstract Conservation of genetic diversity, one of the three main forms of biodiversity, is a fundamental concern in conservation biology as it provides the raw material for evolutionary change and thus the potential to adapt to changing environments. By means of meta-analyses, we tested the generality of the hypotheses that habitat fragmentation affects genetic diversity of plant populations and that certain life history and ecological traits of plants can determine differential susceptibility to genetic erosion in fragmented habitats. Additionally, we assessed whether certain methodological approaches used by authors influence the ability to detect fragmentation effects on plant genetic diversity. We found overall large and negative effects of fragmentation on genetic diversity and outcrossing rates but no effects on inbreeding coefficients. Significant increases in inbreeding coefficient in fragmented habitats were only observed in studies analyzing progenies. The mating system and the rarity status of plants explained the highest proportion of variation in the effect sizes among species. The age of the fragment was also decisive in explaining variability among effect sizes: the larger the number of generations elapsed in fragmentation conditions, the larger the negative magnitude of effect sizes on heterozygosity. Our results also suggest that fragmentation is shifting mating patterns towards increased selfing. We conclude that current conservation efforts in fragmented habitats should be focused on common or recently rare species and mainly outcrossing species and outline important issues that need to be addressed in future research on this area. [source] Integration of DNA barcoding into an ongoing inventory of complex tropical biodiversityMOLECULAR ECOLOGY RESOURCES, Issue 2009DANIEL H. JANZEN Abstract Inventory of the caterpillars, their food plants and parasitoids began in 1978 for today's Area de Conservacion Guanacaste (ACG), in northwestern Costa Rica. This complex mosaic of 120 000 ha of conserved and regenerating dry, cloud and rain forest over 0,2000 m elevation contains at least 10 000 species of non-leaf-mining caterpillars used by more than 5000 species of parasitoids. Several hundred thousand specimens of ACG-reared adult Lepidoptera and parasitoids have been intensively and extensively studied morphologically by many taxonomists, including most of the co-authors. DNA barcoding , the use of a standardized short mitochondrial DNA sequence to identify specimens and flush out undisclosed species , was added to the taxonomic identification process in 2003. Barcoding has been found to be extremely accurate during the identification of about 100 000 specimens of about 3500 morphologically defined species of adult moths, butterflies, tachinid flies, and parasitoid wasps. Less than 1% of the species have such similar barcodes that a molecularly based taxonomic identification is impossible. No specimen with a full barcode was misidentified when its barcode was compared with the barcode library. Also as expected from early trials, barcoding a series from all morphologically defined species, and correlating the morphological, ecological and barcode traits, has revealed many hundreds of overlooked presumptive species. Many but not all of these cryptic species can now be distinguished by subtle morphological and/or ecological traits previously ascribed to ,variation' or thought to be insignificant for species-level recognition. Adding DNA barcoding to the inventory has substantially improved the quality and depth of the inventory, and greatly multiplied the number of situations requiring further taxonomic work for resolution. [source] What makes a species central in a cleaning mutualism network?OIKOS, Issue 8 2010Cristina Sazima Mutualisms often form networks of interacting species, characterized by the existence of a central core of species that potentially drive the ecology and the evolution of the whole community. Centrality measures allow quantification of how central or peripheral a species is within a network, thus informing about the role of each species in network organization, dynamics, and stability. In the present study we addressed the question whether the structural position of species in the network (i.e. their topological importance) relates to their ecological traits. We studied interactions between cleaner and client reef fishes to identify central and peripheral species within a mutualistic network, and investigated five ecological correlates. We used three measures to estimate the level of centrality of a species for distinct structural patterns, such as the number of interactions and the structural proximity to other species. Through the use of a principal component analysis (PCA) we observed that the centrality measures were highly correlated (92.5%) in the studied network, which indicates that the same species plays a similar role for the different structural patterns. Three cleaner and ten client species had positive values of centrality, which suggests that these species are modulating ecological and evolutionary dynamics within the network. Higher centralities were related to higher abundances and feeding habits for client fishes, but not for cleaners. The high correlation between centrality measures in the present study is likely related to the nested structure of the cleaning network. The cleaner species' set, by having central species that are not necessarily the most abundant ones, bears potentially more vulnerable points for network cohesiveness. Additionally, the present study generalizes previous findings for plant,animal mutualisms, as it shows that the structure of marine mutualisms is also related to a complex interplay between abundance and niche-related features. [source] Reproductive interference in two ground-hopper species: testing hypotheses of coexistence in the fieldOIKOS, Issue 9 2007Julia Gröning Similar to resource competition, reproductive interference may hamper the coexistence of closely related species. Species that utilize similar signal channels during mate finding may face substantial fitness costs when they come into contact and demographic displacement of the inferior species (sexual exclusion) is a likely outcome of such interactions. The two ground-hopper species Tetrix ceperoi and Tetrix subulata broadly overlap in their ranges and general habitat requirements, but rarely co-occur on a local scale. Results from laboratory and field experiments suggest that this mosaic pattern of sympatry might be influenced by reproductive interference. Here, we examine the significance of sexual interactions for these species in the field and test hypotheses on mechanisms of coexistence. Our results show that heterospecific sexual interactions also occur under field conditions, but in contrast to the experiments T. ceperoi was not the inferior species. The number of male mating attempts of both species was strongly correlated with encounter frequencies. Males discriminated between the sexes but not between the species, suggesting an incomplete mate recognition system in both species. The analysis of microhabitat preferences and spatial distribution revealed that habitat partitioning is not a suitable mechanism of coexistence in this system. Instead, the costs of reproductive interference are substantially mitigated by different niche breadths leading to different degrees of aggregation. Despite a considerable niche overlap T. ceperoi displayed a stronger preference for bare ground and occurred more aggregated than T. subulata, which had a broader niche. These differences may reduce the frequencies of heterospecific encounters and interactions in the field. Our results demonstrate that coexistence in the presence of reproductive interference is comparable to resource competition, being strongly influenced by ecological traits of the involved species, such as niche breadth and dispersion pattern. [source] Is the historical war against wildlife over in southern Europe?ANIMAL CONSERVATION, Issue 3 2009A. Martínez-Abraín Abstract Most southern European regions have experienced a rapid economical change during the last decades, moving from a historical economy based on agriculture to a society based on industry and technology. We test here whether causes of admission of birds admitted to a large southern European rehabilitation centre, during a 14-year period (1994,2007), reflect these socio-economical changes. Specifically, we estimated the trends in the number of birds admitted to the centre by shooting (S) over the number of birds admitted due to impacts caused by infrastructures (I), for the 10 most commonly admitted species with complete time series available. Species were grouped in three groups following ecological traits: raptors (diurnal and nocturnal) and aquatic birds. Trends were estimated by means of the slope of a linear regression of the log-transformed S/I ratio over time, which provided the finite population growth rate (,) and its 95% confidence intervals. We used the ratio to prevent possible biases caused by changes in wild population densities over the years. We conclude that the overall trend in the S/I ratio, as well as the trends for all three bird groups considered, were negative, and indicated a c. 10% annual reduction in the number of birds admitted by shooting in relation to those admitted by infrastructure-related injuries. Causal relationships were analysed by means of Poisson regressions on absolute numbers. Importantly we show that despite the direct historical war against wildlife seems to be coming to an end in southern Europe, impact to wildlife continues in an indirect way, as collateral damages caused by our post-industrial way of life. So the overall scenario is most likely not one of improved conservation status in southern Europe, but rather one of shifting ways of impacting wildlife in parallel with socio-economic changes. [source] Effects of raised water levels on wet grassland plant communitiesAPPLIED VEGETATION SCIENCE, Issue 3 2009Sarah E. Toogood Abstract Questions: What are the effects of raised water levels on wet grassland plant communities and dynamics? To what extent do time since raised water levels, vegetation management and water regime influence community composition? Location: Pevensey Levels, southeast England, UK. Methods: Plant communities and hydrology were monitored during 2001-03 within 23 wet grassland meadows and pastures where water levels had been raised for nature conservation at different times over 21 years. Community variations were examined using species abundance and ecological traits. Results: Water regime, measured as duration of flooding, groundwater level and soil moisture was significantly related to plant community variation. Communities were divided into grasslands where inundation was shallow (,8 cm) and relatively short (,3 months) and sites where deeper flooding was prolonged (,5 months), supporting a variety of wetland vegetation. With increasing wetness, sites were characterised by more bare ground and wetland plants such as sedges, helophytes and hydrophytes, and species with a stress-tolerating competitive strategy. All sites showed considerable annual dynamics, especially those with substantially raised water levels. There were no significant relationships between time since water levels were raised and plant community composition. Grassland management exerted a limited influence upon vegetation compared to water regime. Conclusions: Grassland plant communities are responsive to raised water levels and have potential for a rapid transition to wetland vegetation, irrespective of grazing or cutting management. Creation or restoration of wet grasslands by (re)wetting is feasible but challenging due to the high dynamism of wetland plant communities and the need for substantially raised water levels and prolonged flooding to produce significant community changes. [source] | |||||||||||||||||||||||||||||||