Dispersal ability rather than ecological tolerance drives differences in range size between lentic and lotic water beetles (Coleoptera: Hydrophilidae)

Aim In aquatic ecosystems, standing (lentic) and running (lotic) waters differ fundamentally in their stability and persistence, shaping the comparative population genetic structure, geographical range size and speciation rates of lentic versus lotic lineages. While the drivers of this pattern remain incompletely understood, the suite of traits making up the ability of a species to establish new populations is instrumental in determining such differences. Here we explore the degree to which the association between habitat type and geographical range size results from differences in dispersal ability or fundamental niche breadth in the members of the Enochrus bicolor complex, an aquatic beetle clade with species across the lentic–lotic divide. Location Western Mediterranean, with a special focus on North Africa, the Iberian Peninsula and Sicily. Methods DNA sequences for four loci were obtained from species of the E. bicolor complex and analysed using phylogenetic inference. Dispersal and establishment abilities were assessed in lentic–lotic species pairs of the complex, using flight wing morphometrics and thermal tolerance ranges as surrogates, respectively. Results There were clear differences in range size between the lotic and lentic taxa of the complex, which appears to have had a lotic origin with two transitions to standing waters. Only small differences were observed in temperature tolerance and acclimation ability between the two lotic–lentic sister species studied. By contrast, wing morphometrics revealed clear, consistent differences between lotic and lentic Enochrus species pairs, the latter having a higher dispersal capacity. Main conclusions We hypothesize that there have been two habitat shifts from lotic to lentic waters, which have allowed marked expansions in geographical range size in western Mediterranean species of the E. bicolor complex. Differences in dispersal rather than in establishment ability appear to underlie differences in geographical range extent, as transitions to lentic waters were associated with changes in wing morphology, but not in thermal tolerance range. In this lineage of water beetles, selection for dispersal in geologically short‐lived lentic systems has driven the evolution of larger range sizes in lentic taxa compared with those of their lotic relatives.     

Not going with the flow: a comprehensive time‐calibrated phylogeny of dragonflies (Anisoptera: Odonata: Insecta) provides evidence for the role of lentic habitats on diversification

Ecological diversification of aquatic insects has long been suspected to have been driven by differences in freshwater habitats, which can be classified into flowing (lotic) waters and standing (lentic) waters. The contrasting characteristics of lotic and lentic freshwater systems imply different ecological constraints on their inhabitants. The ephemeral and discontinuous character of most lentic water bodies may encourage dispersal by lentic species in turn reducing geographical isolation among populations. Hence, speciation probability would be lower in lentic species. Here, we assess the impact of habitat use on diversification patterns in dragonflies (Anisoptera: Odonata). Based on the eight nuclear and mitochondrial genes, we inferred species diversification with a model‐based evolutionary framework, to account for rate variation through time and among lineages and to estimate the impact of larval habitat on the potentially nonrandom diversification among anisopteran groups. Ancestral state reconstruction revealed lotic fresh water systems as their original primary habitat, while lentic waters have been colonized independently in Aeshnidae, Corduliidae and Libellulidae. Furthermore, our results indicate a positive correlation of speciation and lentic habitat colonization by dragonflies: speciation rates increased in lentic Aeshnidae and Libellulidae, whereas they remain mostly uniform among lotic groups. This contradicts the hypothesis of inherently lower speciation in lentic groups and suggests species with larger ranges are more likely to diversify, perhaps due to higher probability of larger areas being dissected by geographical barriers. Furthermore, larger range sizes may comprise more habitat types, which could also promote speciation by providing additional niches, allowing the coexistence of emerging species.     

Habitat availability does not explain the species richness patterns of European lentic and lotic freshwater animals

Aim In Europe, the relationships between species richness and latitude differ for lentic (standing water) and lotic (running water) species. Freshwater animals are highly dependent on suitable habitat, and thus the distribution of available habitat should strongly influence large‐scale patterns of species richness. We tested whether habitat availability can account for the differences in species richness patterns between European lentic and lotic freshwater animals. Location Europe. Methods We compiled occurrence data of 1959 lentic and 2445 lotic species as well as data on the amount of lentic and lotic habitats across 25 pre‐defined biogeographical regions of European freshwaters. We used the range of elevation of each region as a proxy for habitat diversity. We investigated the relationships between species richness, habitat availability and habitat diversity with univariate and multiple regression analyses. Results Species richness increased with habitat availability for lentic species but not for lotic species. Species richness increased with elevational range for lotic species but decreased for lentic species. For both groups, neither habitat availability nor diversity could account for previously reported latitudinal patterns in species richness. For lotic species, richness declined with latitude, whereas there was no relationship between habitat availability and latitude. For lentic species, richness showed a hump‐shaped relationship with latitude, whereas available habitat increased with latitude. Main conclusions Habitat availability and diversity are poor predictors of species richness of the European freshwater fauna across large scales. Our results indicate that the distributions of European freshwater animals are probably not in equilibrium and may still be influenced by history, namely the recurrent European glaciations and possible differences in post‐glacial recolonization. The distributions of lentic species appear to be closer to equilibrium than those of lotic species. This lends further support to the hypothesis that lentic species have a higher propensity for dispersal than lotic species.     

The effect of habitat type on speciation rates and range movements in aquatic beetles: inferences from species-level phylogenies

Most aquatic beetles in the family Dytiscidae are tightly associated either with running (lotic) or stagnant (lentic) water bodies. The range size of lotic species is known to be, on average, much smaller than that of lentic species, presumably as a result of differences in dispersal strategies in each habitat type. We explored possible effects of these differences on clade evolution and speciation rates by comparing species-level phylogenies based on cytochrome oxidase I (COI) and 16S rRNA mitochondrial genes for two genera, the lentic Ilybius and the lotic Deronectes. The expectation that species turnover is higher in lotic lineages due to their lower dispersal propensity compared to lentic species was not strongly supported. Deronectes displays a higher frequency of recent splits than Ilybius, consistent with the hypothesis, but the difference was not significant compared to expected patterns under a constant speciation rate null model. Similarly, when the degree of sympatry was plotted against relative node age, more allopatric splits were evident in the lentic Deronectes, suggesting a slower rate of range movement since speciation, but the differences were not significant. We discuss two explanations for our failure to detect differences between the two clades. First, current methods for analysing species-level phylogenies may be sensitive to taxonomic and sampling artefacts. Second, lentic and lotic clades may indeed display similar levels of species turnover despite occupying very different habitats at different spatial scales. More work is needed to investigate the effects of population level processes and spatial scale on macroevolutionary dynamics.     

Lentic odonates have larger and more northern ranges than lotic species

Aim We analysed latitudinal range, centres of distribution and northern range boundaries of dragonflies and damselflies occurring in Europe and North America with respect to larval habitat (standing water = lentic and running water = lotic). As lentic water bodies are thought to be less predictable in space and time than lotic habitats, species adapted to standing waters depend on effective dispersal ability for long‐term survival. If species occurring in lentic habitats have a higher propensity for dispersal, then larger range sizes in lentic than in lotic species, as well as an increase in the proportion of lentic species with latitude, would be expected. Location Europe, North America. Methods Distributional and habitat data were collected from published sources for all odonates of Europe and North America. Species were assigned to lentic and lotic habitats according to the habitat of the larvae. From distribution maps we estimated the latitudinal range, centre of distribution and northern range boundary of each species. Differences in these distribution variables between lentic and lotic species were evaluated using anova . We related the proportion of lentic species by latitudinal interval in Europe, and by political unit (state, province) in North America, to area, altitudinal range, longitude (only for North America) and latitude by means of generalized linear models. Results Lentic damselflies and dragonflies had larger latitudinal spans, and more northern distribution centres and range boundaries, than lotic species. The proportion of lentic species increased with latitude. These findings were consistent between continents. Main conclusions Our results support previous findings that distribution patterns of freshwater species depend on habitat preference. Evolution of dispersal propensity according to habitat characteristics is the most likely explanation. However, at present, alternative explanations, such as an increase in lentic habitats with latitude, cannot be ruled out.     

Habitat type as a determinant of species range sizes: the example of lotic–lentic differences in aquatic Goleoptera

Species differ in the size of their geographical ranges, but it is unclear how this is affected by the intrinsic properties of various habitat types. Using data on range sizes for 490 species of aquatic Coleoptera from the Iberian Peninsula we show that running-water (lotic) species have much smaller distributional ranges than those occurring in standing water (lentic). This robust association of habitat type and range size has independently arisen in at least four monophyletic coleopteran lineages, in Hydradephaga, Hydrophiloidea, Hydraenidae and Byrrhoidea, and several more times within these main groups. We propose that this pattern is due to different evolutionary dynamics of both habitat types: stagnant water bodies are more likely to completely disappear, requiring frequent migration of resident populations. Rivers and streams, on the contrary, have more temporal and spatial continuity, and therefore permit the long-term persistence of local populations. In less permanent habitats species will require a greater geographical mobility, which indirectly results in a larger size range. The less dispersive populations of running water should also have reduced gene flow, increasing the probability of allopatric speciation, and thus reducing the average range of more widespread ancestral species. These differences in population parameters, and the frequency of transitions between the two habitat types, may have strong macroevolutionary consequences, in particular regarding speciation rates and possible morphological specializations.     

Habitat stability affects dispersal and the ability to track climate change

Habitat persistence should influence dispersal ability, selecting for stronger dispersal in habitats of lower temporal stability. As standing (lentic) freshwater habitats are on average less persistent over time than running (lotic) habitats, lentic species should show higher dispersal abilities than lotic species. Assuming that climate is an important determinant of species distributions, we hypothesize that lentic species should have distributions that are closer to equilibrium with current climate, and should more rapidly track climatic changes. We tested these hypotheses using datasets from 1988 and 2006 containing all European dragon- and damselfly species. Bioclimatic envelope models showed that lentic species were closer to climatic equilibrium than lotic species. Furthermore, the models over-predicted lotic species ranges more strongly than lentic species ranges, indicating that lentic species track climatic changes more rapidly than lotic species. These results are consistent with the proposed hypothesis that habitat persistence affects the evolution of dispersal.     

Habitat type predicts genetic population differentiation in freshwater invertebrates

A basic challenge in evolutionary biology is to establish links between ecology and evolution of species. One important link is the habitat template. It has been hypothesized, that the spatial and temporal settings of a habitat strongly influence the evolution of species dispersal propensity. Here, we evaluate the importance of the habitat type on genetic population differentiation of species using freshwater habitats as a model system. Freshwater habitats are either lentic (standing) or lotic (running). On average, lotic habitats are more stable and predictable over space and time than lentic habitats. Therefore, lentic habitats should favour the evolution of higher dispersal propensity which ensures population survival of lentic species. To test for such a relationship, we used extensive data on species' genetic population differentiation of lentic and lotic freshwater invertebrates retrieved from published allozyme studies. Overall, we analysed more than 150 species from all over the world. Controlling for several experimental, biological and geographical confounding effects, we always found that lentic invertebrates exhibit, on average, lower genetic population differentiation than lotic species. This pattern was consistent across insects, crustaceans and molluscs. Our results imply fundamental differences in genetic population differentiation among species adapted to either lentic or lotic habitats. We propose that such differences should occur in a number of other habitat types that differ in spatio-temporal stability. Furthermore, our results highlight the important role of lotic habitats as reservoirs for evolutionary processes and the potential for rapid speciation.     

Comparative phylogeography of tenebrionid beetles in the Aegean archipelago: the effect of dispersal ability and habitat preference

Comparative phylogeographical studies in island archipelagos can reveal lineage-specific differential responses to the geological and climatic history. We analysed patterns of genetic diversity in six codistributed lineages of darkling beetles (Tenebrionidae) in the central Aegean archipelago which differ in wing development and habitat preferences. A total of 600 specimens from 30 islands and eight adjacent mainland regions were sequenced for mitochondrial cytochrome oxidase I and nuclear Muscular protein 20. Individual gene genealogies were assessed for the presence of groups that obey an independent coalescent process using a mixed Yule coalescent model. The six focal taxa differed greatly in the number of coalescent groups and depth of lineage subdivision, which was closely mirrored by the degree of geographical structuring. The most severe subdivision at both mitochondrial DNA and nuclear DNA level was found in flightless lineages associated with presumed stable compact-soil habitats (phrygana, maquis), in contrast to sand-obligate lineages inhabiting ephemeral coastal areas that displayed greater homogeneity across the archipelago. A winged lineage, although associated with stable habitats, showed no significant phylogenetic or geographical structuring. Patterns of nucleotide diversity and local genetic differentiation, as measured using Φ_ST and hierarchical amova , were consistent with high levels of ongoing gene flow in the winged taxon; frequent local extinction and island recolonisation for flightless sand-obligate taxa; and very low gene flow and geographical structure largely defined by the palaeogeographical history of the region in flightless compact-soil taxa. These results show that differences in dispersal rate, mediated by habitat persistence, greatly influence the levels of phylogeographical subdivision in lineages that are otherwise subjected to the same geological events and palaeoclimatic changes.     

不同生境间龟鳖类体型的差异

体型是动物重要的形态特征,影响动物的生境利用。为揭示龟鳖类体型与生境之间的关系,通过文献收集331种龟鳖(龟鳖目Tesudines总物种数的98.8%)的最大背甲长及其生境信息,将生境分为海洋、淡水、岛屿性陆地和大陆性陆地4种类型,再将淡水生境分为大静水、大流水、小静水、小流水和所有水域5种亚类型,大陆性陆地生境分为高地、平地和荒漠3种亚类型,从而比较不同生境类型或亚类型之间龟鳖类体型的差异。广义线性混合模型分析结果显示:1)海龟体型最大,岛屿性陆龟次之,淡水龟鳖和大陆性陆龟体型最小,且后两者差异无统计学意义。2)淡水龟鳖类的体型在5种亚类型生境间存在差异,大静水和大流水水域的体型均显著大于小静水和小流水水域,而体型在大静水与大流水水域、小静水与小流水水域之间的差异均无统计学意义,表明淡水龟鳖类体型与水域面积有关,而与水域是静水或流水无关。广布所有水域的淡水龟鳖类体型趋于中间型,且与其他4种亚类型生境中的体型之间的差异均无统计学意义。3)大陆性陆龟的体型从高地到平地再到荒漠有逐渐变大的趋势,但差异无统计学意义。本研究揭示龟鳖类的保护对策需要考虑其体型和生境面积的相关性。     

Latitudinal variation of diversity in European freshwater animals is not concordant across habitat types

Aim   We analysed the variation of species richness in the European freshwater fauna across latitude. In particular, we compared latitudinal patterns in species richness and β-diversity among species adapted to different habitat types.
Location   Europe.
Methods   We compiled data on occurrence for 14,020 animal species across 25 pre-defined biogeographical regions of European freshwaters from the Limnofauna Europaea . Furthermore, we extracted information on the habitat preferences of species. We assigned species to three habitat types: species adapted to groundwater, lotic (running water) and lentic (standing water) habitats. We analysed latitudinal patterns of species richness, the proportion of lentic species and β-diversity.
Results   Only lentic species showed a significant species–area relationship. We found a monotonic decline of species richness with latitude for groundwater and lotic habitats, but a hump-shaped relationship for lentic habitats. The proportion of lentic species increased from southern to northern latitudes. β-Diversity declined from groundwater to lentic habitats and from southern to northern latitudes.
Main conclusions   The differences in the latitudinal variation of species richness among species adapted to different habitat types are in part due to differences in the propensity for dispersal. Since lentic habitats are less persistent than lotic or groundwater habitats, lentic species evolved more efficient strategies for dispersal. The dispersal propensity of lentic species facilitated the recolonization of central Europe after the last glaciation. Overall, we stress the importance of considering the history of regions and lineages as well as the ecological traits of species for understanding patterns of biodiversity.     

Habitat type mediates equilibrium with climatic conditions in the distribution of Iberian diving beetles

Aim The contrasting habitat permanence over geological time‐scales of lotic and lentic habitats may impose different constraints on the dispersal ability of their macroinvertebrate populations, and ultimately on the degree of equilibrium with current climate. We aim to test for differences between species typical of either habitat type in their potential versus realized distributions as a surrogate measure of degree of climate equilibrium, both in refuges and more recently deglaciated areas. Location Western Europe. Methods We focus on 99 Iberian diving beetles (family Dytiscidae). A multidimensional envelope procedure was used to estimate their potential distributions, which were projected for different spatial scales. At the continental scale we calculated the percentage of countries with climatically suitable conditions for each species over those actually occupied (range filling). At the regional scale, we estimated realized distributions using: (1) convex hull polygons for Sweden and the Iberian Peninsula; and (2) generalized linear models for the Iberian Peninsula. Results In the Iberian Peninsula, differences in the degree of equilibrium with climatic conditions between lotic and lentic species were few, if any. However, at the continental scale we found significant differences, with lentic species closer to equilibrium than lotic species. In the recently deglaciated area (Sweden) the subset of species with ranges wide enough to encompass Iberia and Scandinavia were mostly lentic, and all were closer to climatic equilibrium without significant differences between habitat types. Main conclusions Our results show that, at continental scales, climate equilibrium is not concordant between the habitat types across western Europe. We hypothesize that: (1) the differences between refuge areas in dispersal ability are erased probably due to long‐term climatic stability, allowing enough time to reach equilibrium, and (2) the species with wide geographical ranges able to recolonize recently deglaciated areas should have the highest dispersal abilities, and are closer to climatic equilibrium.     

Morphological variation between non‐native lake‐ and stream‐dwelling pumpkinseed Lepomis gibbosusin the Iberian Peninsula

The objective of this study was to test if morphological differences in pumpkinseed Lepomis gibbosus found in their native range (eastern North America) that are linked to feeding regime, competition with other species, hydrodynamic forces and habitat were also found among stream‐ and lake‐ or reservoir‐dwelling fish in Iberian systems. The species has been introduced into these systems, expanding its range, and is presumably well adapted to freshwater Iberian Peninsula ecosystems. The results show a consistent pattern for size of lateral fins, with L. gibbosus that inhabit streams in the Iberian Peninsula having longer lateral fins than those inhabiting reservoirs or lakes. Differences in fin placement, body depth and caudal peduncle dimensions do not differentiate populations of L. gibbosus from lentic and lotic water bodies and, therefore, are not consistent with functional expectations. Lepomis gibbosus from lotic and lentic habitats also do not show a consistent pattern of internal morphological differentiation, probably due to the lack of lotic–lentic differences in prey type. Overall, the univariate and multivariate analyses show that most of the external and internal morphological characters that vary among populations do not differentiate lotic from lentic Iberian populations. The lack of expected differences may be a consequence of the high seasonal flow variation in Mediterranean streams, and the resultant low‐ or no‐flow conditions during periods of summer drought.     

An interspecific test of Bergmann's rule reveals inconsistent body size patterns across several lineages of water beetles (Coleoptera: Dytiscidae)

1. Bergmann's rule sensu lato, the ecogeographic pattern relating animals' body size with environmental temperature (or latitude), has been shown to be inconsistent among insect taxa. Body size clines remain largely unexplored in aquatic insects, which may show contrasting patterns to those found in terrestrial groups because of the physiological or mechanical constraints of the aquatic environment. 2. Bergmann's rule was tested using data on body size, phylogeny and distribution for 93 species belonging to four lineages of dytiscid water beetles. The relationship between size and latitude was explored at two taxonomic resolutions – within each independent lineage, and for the whole dataset – employing phylogenetic generalised least‐squares to control for phylogenetic inertia. The potential influence of habitat preference (lotic versus lentic) on body size clines was also considered. 3. Within‐lineage analyses showed negative relationships (i.e. converse Bergmann's rule), but only in two lineages (specifically in those that included both lotic and lentic species). By contrast, no relationship was found between body size and latitude for the whole dataset. 4. These results suggest that there may be no universal interspecific trends in latitudinal variation of body size in aquatic insects, even among closely related groups, and show the need to account for phylogenetic inertia. Furthermore, habitat preferences should be considered when exploring latitudinal clines in body size in aquatic taxa at the interspecific level.     

Dispersal is linked to habitat use in 59 species of water beetles (Coleoptera: Adephaga) on Madagascar

Lentic habitats (standing water, such as ponds and lakes) differ from lotic habitats (running water; streams and rivers) in their spatiotemporal persistence, with lentic habitats being more ephemeral in evolutionary time. This habitat instability is thought to select for dispersal, and several phylogenetic and macroecological studies have suggested that high rates of dispersal are more characteristic of lentic than lotic species. We tested this hypothesis using a comparative population genetic and phylogeographic approach based on mitochondrial DNA for 59 aquatic beetle species, sampled across Madagascar. Species were classified as lotic (n = 25), lentic (n = 25), or lotolentic (associated with both running and standing water; n = 9). Hierarchical population genetic structure (AMOVA), nucleotide diversity (π), and geographic structure were compared among habitat types. Lotic species had significantly greater population structure (Ф_ST = 0.55, hierarchical AMOVA) than lentic (Ф_ST = 0.13) and lotolentic (Ф_ST = 0.19) species using phylogenetic generalized least squares (PGLS) to correct for phylogeny. Body size was independent of habitat preference, and did not explain any of the intraspecific variation. A greater proportion of lotic species were endemic to Madagascar and lotic species had more pronounced geographic structure in their haplotype networks. The results indicate that dispersal is consistently lower among lotic species, independent of phylogenetic relatedness. This has macroevolutionary and biogeographical consequences for the freshwater fauna of this tropical biodiversity hotspot where remaining natural habitats are becoming increasingly isolated from one another.     

Early burst in body size evolution is uncoupled from species diversification in diving beetles (Dytiscidae)

Changes in morphology are often thought to be linked to changes in species diversification, which is expected to leave a signal of early burst (EB) in phenotypic traits. However, such signal is rarely recovered in empirical phylogenies, even for groups with well‐known adaptive radiation. Using a comprehensive phylogenetic approach in Dytiscidae, which harbours ~4,300 species with as much as 50‐fold variation in body size among them, we ask whether pattern of species diversification correlates with morphological evolution. Additionally, we test whether the large variation in body size is linked to habitat preference and whether the latter influences species turnover. We found, in sharp contrast to most animal groups, that Dytiscidae body size evolution follows an early‐burst model with subsequent high phylogenetic conservatism. However, we found no evidence for associated shifts in species diversification, which point to an uncoupled evolution of morphology and species diversification. We recovered the ancestral habitat of Dytiscidae as lentic (standing water), with many transitions to lotic habitat (running water) that are concomitant to a decrease in body size. Finally, we found no evidence for difference in net diversification rates between habitats nor difference in turnover in lentic and lotic species. This result, together with recent findings in dragonflies, contrasts with some theoretical expectations of the habitat stability hypothesis. Thus, a thorough reassessment of the impact of dispersal, gene flow and range size on the speciation process is needed to fully encompass the evolutionary consequences of the lentic–lotic divide for freshwater fauna.     

Stream flow alone does not predict population structure of diving beetles across complex tropical landscapes

Recent theoretical advances have hypothesized a central role of habitat persistence on population genetic structure and resulting biodiversity patterns of freshwater organisms. Here, we address the hypothesis that lotic species, or lineages adapted to comparably geologically stable running water habitats (streams and their marginal habitats), have high levels of endemicity and phylogeographic structure due to the persistent nature of their habitat. We use a nextRAD DNA sequencing approach to investigate the population structure and phylogeography of a putatively widespread New Guinean species of diving beetle, Philaccolilus ameliae (Dytiscidae). We find that P. ameliae is a complex of morphologically cryptic, but geographically and genetically well‐differentiated clades. The pattern of population connectivity is consistent with theoretical predictions associated with stable lotic habitats. However, in two clades, we find a more complex pattern of low population differentiation, revealing dispersal across rugged mountains and watersheds of New Guinea up to 430 km apart. These results, while surprising, were also consistent with the original formulation of the habitat template concept by Southwood, involving lineage‐idiosyncratic evolution in response to abiotic factors. In our system, low population differentiation might reflect a young species in a phase of range expansion utilizing vast available habitat. We suggest that predictions of life history variation resulting from the dichotomy between lotic and lentic organisms require more attention to habitat characterization and microhabitat choice. Our results also underpin the necessity to study fine‐scale processes but at a larger geographical scale, as compared to solely documenting macroecological patterns, to understand ecological drivers of regional biodiversity. Comprehensive sampling especially of tropical lineages in complex and threatened environments such as New Guinea remains a critical challenge.     

On the validity of habitat as a predictor of genetic structure in aquatic systems: a comparative study using California water beetles

Among freshwater organisms, water flow is frequently considered to be one of the most important environmental variables affecting life-history traits such as dispersal abilities and therefore genetic structure. Recent studies have suggested that habitat type alone as defined by water flow is predictive of genetic population differentiation, while others have advocated against broad generalizations in favour of more conservative, species-specific conclusions. If aquatic habitat type is predictive of population differentiation, then one would expect sympatric taxa that occupy the same aquatic habitat to converge on a similar genetic structure. We tested this prediction by examining the haplotype diversity, phylogeographical concordance, population connectivity and population isolation of three lotic water beetle species in southern California: Anacaena signaticollis , Eubrianax edwardsii and Stictotarsus striatellus . In addition to coarse habitat and geography, we also controlled for the potentially confounding factors of range size, method of dispersal and clade independence. Together, the species spanned extremes of genetic and phylogeographical structure in all measures examined, suggesting that a coarse dichotomy of aquatic habitat type is not predictive of genetic structure. While there is little question that water flow plays a major role in shaping the life-history traits of freshwater organisms, it is perilous to confer predictive properties to an artificially simplistic dichotomy or use it as a surrogate for other unmeasured variables.     

Large-scale intraspecific variation in life-history traits of European freshwater fish

Aims To test the magnitude and direction of the effects of large‐scale environmental factors (latitude and habitat type: lotic or lentic) on the intraspecific variations in multiple life‐history traits, across multiple European freshwater fish species. To test the relevance of defining species traits by quantifying the magnitude of interspecific vs. intraspecific variability in traits. Location Europe. Methods We obtained estimates of 11 fish traits from published sources for 1089 populations of 25 European freshwater fish species. Traits were: longevity, maximal length, growth rate, asymptotic length, mortality rate, age and length at maturation, fecundity, egg size, gonadosomatic index, and length of breeding season. We described population habitats by latitude and habitat type (lotic or lentic), when available. For each species we tested the combined effect of latitude and habitat type on the intraspecific variation of each trait using analysis of covariance (ancova ). We compared the intraspecific variation in traits with the variation between species using an analysis of variance (anova ) for each trait, all species pooled. Results We found a consistent effect in direction of latitude on six traits, but we showed that this effect is not always significant across species. Higher‐latitude populations often grew more slowly, matured later, had a longer life span and a higher maximal and asymptotic length, and allocated more energy to reproduction than populations at lower latitudes. By contrast, we noted only a slight effect of habitat type on the intraspecific variation in traits, except for Salmo trutta. All traits varied significantly between species. However, traits such as growth rate, mortality rate and length of breeding season varied more between populations than between species, whereas fecundity and traits associated with body length varied more between species. Main conclusions Latitude, in contrast to habitat type, is an important factor influencing several traits of geographically widely dispersed populations of multiple European freshwater fish species. Species traits that vary more between species than between populations are attractive variables for understanding and predicting the responses of stream fish communities to their environment.     

Multi‐scale effects of impoundments on genetic structure of creek chub (Semotilus atromaculatus) in the Kansas River basin

1. Habitat fragmentation has been implicated as a primary cause for the ongoing erosion of global biodiversity, yet our understanding of the consequences in lotic systems is limited for many species and regions. Because of harsh environmental conditions that select for high colonisation rates, prairie stream fishes may be particularly vulnerable to the effects of fragmentation. Hence, there is urgent need for broader understanding of fragmentation in prairie streams such that meaningful conservation strategies can be developed. Further, examination at large spatial scales, including multiple impoundments and un‐impounded catchments, will help identify the spatial extent of species movement through the landscape. 2. Our study used data from 10 microsatellite loci to describe the genetic structure of creek chub (Semotilus atromaculatus) populations across four catchments (three impounded and one un‐impounded) in the Kansas River basin. We investigated whether genetic diversity was eroded in response to habitat fragmentation imposed by reservoirs and whether intervening lentic habitat increased resistance to dispersal among sites within a catchment. 3. Our analyses revealed that genetic diversity estimates were consistent with large populations regardless of the location of the sampled tributaries, and there was little evidence of recent population reductions. Nevertheless, we found a high degree of spatial genetic structure, suggesting that catchments comprise a set of isolated genetic units and that sample sites within catchments are subdivided into groups largely defined by intervening habitat type. Our data therefore suggest that lentic habitat is a barrier to dispersal among tributaries, thus reducing the opportunity for genetic rescue of populations in tributaries draining into reservoirs. Isolation by a reservoir, however, may not be immediately deleterious if the isolated tributary basin supports a large population.