Patterns Of Variation In Populations Research Articles

Ecological characteristics explain neutral genetic variation of three coastal sparrow species.

Eco-phylogeographic approaches to comparative population genetic analyses allow for the inclusion of intrinsic influences as drivers of intraspecific genetic structure. This insight into microevolutionary processes, including changes within a species or lineage, provides better mechanistic understanding of species-specific interactions and enables predictions of evolutionary responses to environmental change. In this study, we used single nucleotide polymorphisms (SNPs) identified from reduced representation sequencing to compare neutral population structure, isolation by distance (IBD), genetic diversity and effective population size (Ne) across three closely related and co-distributed saltmarsh sparrow species differing along a specialization gradient-Nelson's (Ammospiza nelsoni subvirgata), saltmarsh (A. caudacuta) and seaside sparrows (A. maritima maritima). Using an eco-phylogeographic lens within a conservation management context, we tested predictions about species' degree of evolutionary history and ecological specialization to tidal marshes, habitat, current distribution and population status on population genetic metrics. Population structure differed among the species consistent with their current distribution and habitat factors, rather than degree of ecological specialization: seaside sparrows were panmictic, saltmarsh sparrows showed hierarchical structure and Nelson's sparrows were differentiated into multiple, genetically distinct populations. Neutral population genetic theory and demographic/evolutionary history predicted patterns of genetic diversity and Ne rather than degree of ecological specialization. Patterns of population variation and evolutionary distinctiveness (Shapely metric) suggest different conservation measures for long-term persistence and evolutionary potential in each species. Our findings contribute to a broader understanding of the complex factors influencing genetic variation, beyond specialist-generalist status and support the role of an eco-phylogeographic approach in population and conservation genetics.

Evolutionarily labile dispersal behavior and discontinuous habitats enhance population differentiation in island versus continentally distributed swallows.

The causes of population divergence in vagile groups remain a paradox in evolutionary biology: dispersive species should be able to colonize new areas, a prerequisite for allopatric speciation, but dispersal also facilitates gene flow, which erodes population differentiation. Strong dispersal ability has been suggested to enhance divergence in patchy habitats and inhibit divergence in continuous landscapes, but empirical support for this hypothesis is lacking. Here we compared patterns of population divergence in a dispersive clade of swallows distributed across both patchy and continuous habitats. The Pacific Swallow (Hirundo tahitica) has an insular distribution throughout Southeast Asia and the Pacific, while its sister species, the Welcome Swallow (H. neoxena), has a continental distribution in Australia. We used whole-genome data to demonstrate strong genetic structure and limited introgression among insular populations, but not among continental populations. Demographic models show that historic changes in habitat connectivity have contributed to population structure within the clade. Swallows appear to exhibit evolutionarily labile dispersal behavior in which they reduce dispersal propensity after island colonization despite retaining strong flight ability. Our data support the hypothesis that fragmented habitats enhance population differentiation in vagile groups, and suggest that labile dispersal behavior is a key mechanism underlying this pattern.

Comparative analysis of molecular and morphological diversity in two diploid Paspalum species (Poaceae) with contrasting mating systems.

Interspecific comparison of two Paspalum species has demonstrated that mating systems (selfing and outcrossing) contribute to variation (genetically and morphologically) within species through similar but mutually exclusive processes. Mating systems play a key role in the genetic dynamics of populations. Studies show that populations of selfing plants have less genetic diversity than outcrossing plants. Yet, many such studies have ignored morphological diversity. Here, we compared the morphological and molecular diversity patterns in populations of two phylogenetically-related sexual diploids that differ in their mating system: self-sterile Paspalum indecorum and self-fertile P. pumilum. We assessed the morphological variation using 16 morpho-phenological characters and the molecular diversity using three combinations of AFLPs. We compared the morphological and molecular diversity within and among populations in each mating system. Contrary to expectations, selfers showed higher morphological variation within populations, mainly in vegetative and phenological traits, compared to outcrossers. The high morphological variation within populations of selfers led to a low differentiation among populations. At molecular level, selfing populations showed lower levels of genotypic and genetic diversity than outcrossing populations. As expected, selfers showed higher population structure than outcrossers (PhiST = 0.301 and PhiST = 0.108, respectively). Increased homozygous combinations for the same trait/locus enhance morphological variation and reduce molecular variation within populations in selfing P. pumilum. Thus, selfing outcomes are opposite when comparing morphological and molecular variation in P. pumilum. Meanwhile, pollen flow in obligate outcrossing populations of P. indecorum increases within-population molecular variation, but tends to homogenize phenotypes within-population. Pollen flow in obligate outcrossers tends to merge geographically closer populations; but isolation by distance can lead to a weak differentiation among distant populations of P. indecorum.

Genetic footprints of Quaternary glacial cycles over the patterns of population diversity and structure in three Nacella (Patellogastropoda: Nacellidae) species across the Magellan province in southern South America

Quaternary glaciations severely altered landscape/seascape at high latitudes and had major consequences on species geographical ranges, population sizes, genetic differentiation and speciation rates. The Magellan province in southern South America, constitutes an interesting area to evaluate the effect of glaciations over near-shore marine benthic organisms. Existing data have showed clear signatures of population genetic bottlenecks during glacial maxima followed by recent recolonizations and expansions during the interglacial. Here, we present new population-based analyses in species of the patellogastropod genus Nacella (N. deaurata, N. magellanica, and N. mytilina). The species N. magellanica and N. deaurata inhabit rocky ecosystems while N. mytilina lives closely associated with kelps. The analyzed species exhibit narrow bathymetric ranges and consequently should have been severely affected by recurrent glacial cycles. We performed phylogeographic and demographic analyses in Nacella species including different localities across their respective distributions in the Magellan province including the Falkland/Malvinas Islands (F/M). Genetic analyses showed that all Nacella species exhibited low levels of genetic diversity, the presence of single dominant broadly distributed haplotypes, lack of correlation between geographical and genetic distance, and recent demographic growths, which are evidence supporting rapid postglacial expansions. Such results may have been facilitated by larval and/or rafting-mediated dispersal following the Cape Horn Current System. The three species showed strong and significant differentiation between F/M and southern Pacific margin (SPM) populations including localities across the Strait of Magellan and Cape Horn. Haplotype genealogies and mismatch analyses recognized older and more complex demographic histories in the F/M than in South America. Different glaciological histories between SPM and F/M may be responsible of the marked phylogeographic structure in the analyzed species of Nacella. Alternatively, as previously proposed, the F/M represent a glacial refugium for Nacella species (sink area), as well as a secondary contact zone where endemic haplotypes are found together with recently arrived South American ones. Historical and contemporary processes, contrasting glacial histories between the analyzed areas, as well as life history traits of the analyzed organisms are main factors explaining current phylogeographic patterns of shallow Magellan marine benthic organisms.

A new perspective on the molecular dating of the brown trout complex with an extended phylogeographic information on the species in Serbia

Abstract To elucidate the historical biogeography of a species, the patterns of population divergence must be understood, and the evolutionary history of the species must be accurately known. For brown trout (Salmo trutta complex), estimating divergence times remains a challenge due to the lack of well-defined time calibration points and insufficient phylogeographic coverage in previous studies. The present work aims to improve molecular dating of mitochondrial control region sequences by using a multicalibration framework based on the latest paleogeological evidence for dating the origin of Lake Ohrid and two available Salmo fossils, including the overlooked Salmo immigratus. Our results clearly show that, contrary to common belief, the major divisions within the brown trout occurred in the Late Pliocene, not the Pleistocene. The Pliocene origin suggests that the brown trout lineages did not form because of geo(hydro)morphological changes during glaciation cycles but may be the result of orogeny and drainage evolution. In addition, increased sampling, particularly in Serbia, led to the identification of a new haplogroup (da-int) occupying an intermediate position with respect to da-es and da-bs haplogroups. While the control region can delineate brown trout lineages, its phylogenetic resolution is limited, so even extensive sampling could not further resolve the lineage level polytomies.

Strong selection is poorly aligned with genetic variation in Ipomoea hederacea: implications for divergence and constraint.

The multivariate evolution of populations is the result of the interactions between natural selection, drift, and the underlying genetic structure of the traits involved. Covariances among traits bias responses to selection, and the multivariate axis which describes the greatest genetic variation is expected to be aligned with patterns of divergence across populations. An exception to this expectation is when selection acts on trait combinations lacking genetic variance, which limits evolutionary change. Here we used a common garden field experiment of individuals from 57 populations of Ipomoea hederacea to characterize linear and nonlinear selection on 5 quantitative traits in the field. We then formally compare patterns of selection to previous estimates of within population genetic covariance structure (the G-matrix) and population divergence in these traits. We found that selection is poorly aligned with previous estimates of genetic covariance structure and population divergence. In addition, the trait combinations favored by selection were generally lacking genetic variation, possessing approximately 15%-30% as much genetic variation as the most variable combination of traits. Our results suggest that patterns of population divergence are likely the result of the interplay between adaptive responses, correlated responses, and selection favoring traits lacking genetic variation.

Contrasting patterns of population structure of Bulwer’s petrel (Bulweria bulwerii) between oceans revealed by statistical phylogeography

The patterns of population divergence of mid-latitude marine birds are impacted by only a few biogeographic barriers to dispersal and the effect of intrinsic factors, such as fidelity to natal colonies or wintering grounds, may become more conspicuous. Here we describe, for the first time, the phylogeographic patterns and historical demography of Bulwer’s petrel Bulweria bulwerii and provide new insights regarding the drivers of species diversification in the marine environment. We sampled Bulwer’s petrels from the main breeding colonies and used a statistical phylogeography approach based on surveying nuclear and mitochondrial loci (~ 9100 bp) to study its mechanisms of global diversification. We uncovered three highly differentiated groups including the Western Pacific, the Central Pacific and the Atlantic. The older divergence occurred within the Pacific Ocean, ca. 850,000 ya, and since then the W Pacific group has been evolving in isolation. Conversely, divergence between the Central Pacific and Atlantic populations occurred within the last 200,000 years. While the Isthmus of Panama is important in restricting gene flow between oceans in Bulwer’s petrels, the deepest phylogeographic break is within the Pacific Ocean, where oceanographic barriers are key in driving and maintaining the remarkable structure found in this highly mobile seabird. This is in contrast with the Atlantic, where no structure was detected. Further data will provide insights regarding the extent of lineage divergence of Bulwer’s petrels in the Western Pacific.

Genetic diversity and population structure of two Euglossini bee species in a host-parasite relationship.

In the current study, two euglossine species, Exaerete smaragdina and Eulaema nigrita, a cleptoparasite bee and its host, respectively, were used as models to: (i) access the genetic diversity and population structure of both species, sampled along a wide latitudinal range of Atlantic Forest, where the distribution of El. nigrita and Ex. smaragdina co-occurs; (ii) investigate the evolutionary history of these species through the Atlantic Forest, and in a wider scenario, to examine the evolutionary history of these species across others forest domains. Analyses involved males of El. nigrita and Ex. smaragdina sampled through Brazilian territory, including 19 sites in the Atlantic Forest. Bayesian Skyline Plot (BSP) was used to infer possible climate oscillations on population of both species over time. The BSP revealed stability in effective population size for both species in most of the Plio-Pleistocene period. However, BSP results aligned to the starlike configuration in the haplotype network, neutrality test, and population diversity patterns indicated population expansion of the two species during the late Pleistocene. Our findings suggest areas of potential refugia to the climatic oscillations of the Pleistocene in the Atlantic Forest in the Brazilian states of Espírito Santo for El. nigrita and Pernambuco for Ex. smaragdina.

Within and among population differences in cuticular hydrocarbons in the seabird tick Ixodes uriae

The hydrophobic layer of the arthropod cuticle acts to maintain water balance, but can also serve to transmit chemical signals via cuticular hydrocarbons (CHC), essential mediators of arthropod behavior. CHC signatures typically vary qualitatively among species, but also quantitatively among populations within a species, and have been used as taxonomic tools to differentiate species or populations in a variety of taxa. Most work in this area to date has focused on insects, with little known for other arthropod groups such as ticks. The worldwide distribution and extensive host-range of the seabird tick Ixodes uriae make it a good model to study the factors influencing CHC composition. Genetically differentiated host-races of I. uriae have evolved across the distribution of this species but the factors promoting sympatric population divergence are still unknown. To test for a potential role of host-associated CHC in population isolation, we collected I. uriae specimens from two of its seabird hosts, the Atlantic puffin (Fratercula arctica) and the common guillemot (Uria aalge) in different colonies in Iceland. Using gas-chromatography and mass-spectrometry, we detected a complex cuticular mixture of 22 hydrocarbons, including n-alkanes, methyl-alkanes and alkenes ranging from 17 to 33 carbons in length. We found that each population had a distinct CHC profile. The host group explained the greatest amount of population divergence, with long-chain hydrocarbons being more abundant in puffin tick populations compared to guillemot tick populations. Future work will now be required to test whether the different CHC signals reinforce assortative mating, thereby playing a role in generating I. uriae population divergence patterns, and to evaluate diverse hypotheses on the origin of distinct population signatures.

Leaf Economic and Hydraulic Traits Signal Disparate Climate Adaptation Patterns in Two Co-Occurring Woodland Eucalypts.

With climate change impacting trees worldwide, enhancing adaptation capacity has become an important goal of provenance translocation strategies for forestry, ecological renovation, and biodiversity conservation. Given that not every species can be studied in detail, it is important to understand the extent to which climate adaptation patterns can be generalised across species, in terms of the selective agents and traits involved. We here compare patterns of genetic-based population (co)variation in leaf economic and hydraulic traits, climate–trait associations, and genomic differentiation of two widespread tree species (Eucalyptus pauciflora and E. ovata). We studied 2-year-old trees growing in a common-garden trial established with progeny from populations of both species, pair-sampled from 22 localities across their overlapping native distribution in Tasmania, Australia. Despite originating from the same climatic gradients, the species differed in their levels of population variance and trait covariance, patterns of population variation within each species were uncorrelated, and the species had different climate–trait associations. Further, the pattern of genomic differentiation among populations was uncorrelated between species, and population differentiation in leaf traits was mostly uncorrelated with genomic differentiation. We discuss hypotheses to explain this decoupling of patterns and propose that the choice of seed provenances for climate-based plantings needs to account for multiple dimensions of climate change unless species-specific information is available.

Bottleneck-associated changes in the genomic landscape of genetic diversity in wild lynx populations.

Demographic bottlenecks generally reduce genetic diversity through more intense genetic drift, but their net effect may vary along the genome due to the random nature of genetic drift and to local effects of recombination, mutation, and selection. Here, we analyzed the changes in genetic diversity following a bottleneck by comparing whole‐genome diversity patterns in populations with and without severe recent documented declines of Iberian (Lynx pardinus, n = 31) and Eurasian lynx (Lynx lynx, n = 29). As expected, overall genomic diversity correlated negatively with bottleneck intensity and/or duration. Correlations of genetic diversity with divergence, chromosome size, gene or functional site content, GC content, or recombination were observed in nonbottlenecked populations, but were weaker in bottlenecked populations. Also, functional features under intense purifying selection and the X chromosome showed an increase in the observed density of variants, even resulting in higher θ W diversity than in nonbottlenecked populations. Increased diversity seems to be related to both a higher mutational input in those regions creating a large collection of low‐frequency variants, a few of which increase in frequency during the bottleneck to the point they become detectable with our limited sample, and the reduced efficacy of purifying selection, which affects not only protein structure and function but also the regulation of gene expression. The results of this study alert to the possible reduction of fitness and adaptive potential associated with the genomic erosion in regulatory elements. Further, the detection of a gain of diversity in ultra‐conserved elements can be used as a sensitive and easy‐to‐apply signature of genetic erosion in wild populations.

Integrative assessment of intraspecific diversification in Loggerhead Shrike (Lanius ludovicianus) provides insight on the geographic pattern of phenotypic divergence and process of speciation

Integrated studies of the geographical, ecological, and historical factors that shape intraspecific phenotypic and genetic variation can help us to decipher the processes leading to geographic patterns of population divergence and speciation. We quantify and compare morphological and genetic variation in the Loggerhead Shrike (Lanius ludovicianus Linnaeus, 1766), a broadly distributed passerine in North America with both migratory and non-migratory populations that occupy a diversity of habitats and topographies. The geographic distributions and patterns of differentiation among subspecies suggest that migration has strongly impacted population divergence, including the habit of migrating itself, but also dispersal. Patterns of mitochondrial and nuclear genetic differentiation can be attributed to female-biased dispersal and to increased dispersal rates and distances in migratory populations. Weak phenotypic differentiation among migratory versus migratory and non-migratory populations suggest that migration may more strongly affect morphology than adaptation to local habitats. Our results generally support previous subspecific designations with two notable exceptions. We found little genetic differentiation between two subspecies (Lanius ludovicianus gambeli Ridgway, 1887 and Lanius ludovicianus mexicanus C.L. Brehm, 1854), but identify a new, distinct subspecies, which we refer to as Lanius ludovicianus centralis ssp. nov.

Genetic diversity in global chicken breeds in relation to their genetic distances to wild populations

BackgroundMigration of a population from its founder population is expected to cause a reduction of its genetic diversity and facilitates differentiation between the population and its founder population, as predicted by the theory of genetic isolation by distance. Consistent with that theory, a model of expansion from a single founder predicts that patterns of genetic diversity in populations can be explained well by their geographic expansion from their founders, which is correlated with genetic differentiation.MethodsTo investigate this in chicken, we estimated the relationship between the genetic diversity of 160 domesticated chicken populations and their genetic distances to wild chicken populations.ResultsOur results show a strong inverse relationship, i.e. 88.6% of the variation in the overall genetic diversity of domesticated chicken populations was explained by their genetic distance to the wild populations. We also investigated whether the patterns of genetic diversity of different types of single nucleotide polymorphisms (SNPs) and genes are similar to that of the overall genome. Among the SNP classes, the non-synonymous SNPs deviated most from the overall genome. However, genetic distance to the wild chicken still explained more variation in domesticated chicken diversity across all SNP classes, which ranged from 83.0 to 89.3%.ConclusionsGenetic distance between domesticated chicken populations and their wild relatives can predict the genetic diversity of the domesticated populations. On the one hand, genes with little genetic variation across populations, regardless of the genetic distance to the wild population, are associated with major functions such as brain development. Changes in such genes may be detrimental to the species. On the other hand, genetic diversity seems to change at a faster rate within genes that are associated with e.g. protein transport and protein and lipid metabolic processes. In general, such genes may be flexible to changes according to the populations’ needs. These results contribute to the knowledge of the evolutionary patterns of different functional genomic regions in the chicken.

Contrasting patterns of population divergence on young and old landscapes inBanksia seminuda(Proteaceae), with evidence for recognition of subspecies

AbstractOCBIL theory provides a basis for understanding of the evolution and ecology of biota on old, climatically buffered, infertile landscapes (OCBILs) worldwide. Here, we test a genetic hypothesis presented in OCBIL theory that predicts highly differentiated intraspecific population systems on OCBILs vs. more limited differentiation on young, often disturbed, fertile landscapes (YODFELs). We examined patterns of genomic and morphological divergence in Banksia seminuda across OCBILs and YODFELs in south-western Australia. We also used these data to determine whether these OCBIL and YODFEL populations represent distinct subspecific lineages, a point of previous contention among taxonomists. As hypothesized, genomic analyses based on 3466 SNP loci revealed strong structuring within B. seminuda, with high differentiation across narrow geographic scales among OCBIL populations vs. lower differentiation across much larger geographic scales among YODFEL populations. In addition, genomic and morphological divergence was found between OCBIL and YODFEL populations, providing comprehensive quantitative evidence for two subspecies. These findings have taxonomic implications for the species and provide support for OCBIL theory and its insights into the evolution, ecology and conservation of biota on ancient landscapes.

Self-organizing maps: a powerful tool for capturing genetic diversity patterns of populations

The maintenance of genetic diversity is fundamental to ensure the population’s viability and to perceive how the evolutionary factors act on these. Using self-organizing maps (SOM) may be interesting to organize the genetic diversity and evidence of the effects caused by dispersive and systematic factors. The objective of this work was to verify if the SOM are able to map the genetic drift, selection, migration and inbreeding effects over generations from the allelic (p and q) and genotypic (D, H and R) frequencies. Populations submitted to these factors were simulated by the software Genes. Afterward, the populations submitted to each factor were mapped by the SOM and analyzed. The topological map showed great efficiency in organizing the populations since it was possible to recognize the expected pattern of each effect tested. Thus, SOM have been shown to be efficient in organizing populations that are subject to a process that reduces variability, such as drift, inbreeding, and selection, and to processes that increase genetic variability, such as migration.

Effect of barriers and distance on song, genetic, and morphological divergence in the highland endemic Timberline Wren (Thryorchilus browni, Troglodytidae).

Populations may become isolated by distance, geographic barriers or both. Isolated populations often diverge in behavioral, morphological and genetic traits as a result of reduced inter-population gene flow. Highland species commonly present naturally fragmented distributions that confine populations to the highest mountain peaks, isolated by mountain passes and distance. The endemic Timberline Wren (Thryorchilus browni) inhabits the highlands of the Talamanca mountain range, including western Panama, and the highest peak in the Central Volcanic mountain range of Costa Rica. Using microsatellites and song recordings we studied the effect of a geographic barrier and distance on song, genetic and morphological divergence among four populations in Costa Rica. A lowland mountain pass resulted in the largest genetic, vocal, and morphological (bill length) differences among populations, likely due to reduce the gene flow. Cultural drift and assortative mating by females selecting songs from their own population likely accentuates the effect of isolation and limited gene flow between populations. This pattern of population divergence has been found in other Neotropical highland birds, but over larger geographical scales. We conclude that mountain passes and distance both reduce gene flow between populations in recently-isolated highland species with restricted distributions.

Integrative Population and Physiological Genomics Reveals Mechanisms of Adaptation in Killifish.

Adaptive divergence between marine and freshwater (FW) environments is important in generating phyletic diversity within fishes, but the genetic basis of this process remains poorly understood. Genome selection scans can identify adaptive loci, but incomplete knowledge of genotype-phenotype connections makes interpreting their significance difficult. In contrast, association mapping (genome-wide association mapping [GWAS], random forest [RF] analyses) links genotype to phenotype, but offer limited insight into the evolutionary forces shaping variation. Here, we combined GWAS, RF, and selection scans to identify loci important in adaptation to FW environments. We utilized FW-native and brackish water (BW)-native populations of Atlantic killifish (Fundulus heteroclitus) as well as a naturally admixed population between the two. We measured morphology and multiple physiological traits that differ between populations and may contribute to osmotic adaptation (salinity tolerance, hypoxia tolerance, metabolic rate, body shape) and used a reduced representation approach for genome-wide genotyping. Our results show patterns of population divergence in physiological capabilities that are consistent with local adaptation. Population genomic scans between BW-native and FW-native populations identified genomic regions evolving by natural selection, whereas association mapping revealed loci that contribute to variation for each trait. There was substantial overlap in the genomic regions putatively under selection and loci associated with phenotypic traits, particularly for salinity tolerance, suggesting that these regions and genes are important for adaptive divergence between BW and FW environments. Together, these data provide insight into the mechanisms that enable diversification of fishes across osmotic boundaries.

Patterns of Population Variation in Two Paleopolyploid Eudicot Lineages Suggest That Dosage-Based Selection on Homeologs Is Long-Lived.

Genes that are inherently subject to strong selective constraints tend to be overretained in duplicate after polyploidy. They also continue to experience similar, but somewhat relaxed, constraints after that polyploidy event. We sought to assess for how long the influence of polyploidy is felt on these genes’ selective pressures. We analyzed two nested polyploidy events in Brassicaceae: the At-α genome duplication that is the most recent polyploidy in the model plant Arabidopsis thaliana and a more recent hexaploidy shared by the genus Brassica and its relatives. By comparing the strength and direction of the natural selection acting at the population and at the species level, we find evidence for continued intensified purifying selection acting on retained duplicates from both polyploidies even down to the present. The constraint observed in preferentially retained genes is not a result of the polyploidy event: the orthologs of such genes experience even stronger constraint in nonpolyploid outgroup genomes. In both the Arabidopsis and Brassica lineages, we further find evidence for segregating mildly deleterious variants, confirming that the population-level data uncover patterns not visible with between-species comparisons. Using the A. thaliana metabolic network, we also explored whether network position was correlated with the measured selective constraint. At both the population and species level, nodes/genes tended to show similar constraints to their neighbors. Our results paint a picture of the long-lived effects of polyploidy on plant genomes, suggesting that even yesterday’s polyploids still have distinct evolutionary trajectories.

Erratum to: DNA barcoding of aquatic insects reveals unforeseen diversity and recurrent population divergence patterns through broad-scale sampling in northern Canada

Arctic and subarctic environments are among the most inaccessible regions in the world, making biological surveys difficult to conduct. Thus, the insect fauna of these regions has remained inadequately surveyed. The aquatic insect orders Ephemeroptera, Plecoptera, and Trichoptera (EPTs) are particularly abundant and diverse at high latitudes, playing key roles in trophic chains where nutrients are scarce. However, particular aspects of their life cycle make them difficult to study. Specifically, species-level identification requires last-instar larvae or adults which, because they are short lived, are typically not available for all taxa during a particular collecting event. With the initial goal of surveying the biodiversity of these insect groups, we sampled ca.10,000 EPT specimens from 12 locations across northern Canada over two years. Approximately 800 of these were subsequently selected for COI DNA barcoding. Overall, we identified 155 EPT species (58 Ephemeroptera, 41 Plecoptera, 56 Trichoptera) based on a 2% divergence criterion. Compared to other similar studies on EPTs we found higher (particularly among the Plecoptera and Ephemeroptera) and more even diversity, potentially reflecting environmental differences in sampling localities. We further assessed phylogeographic divergence patterns among seven species, finding that eastern and western populations diverged during the Pleistocene Epoch (<2.5 Ma), with overlapping time frames. This finding highlights the role of potential glacial refugia and subsequent recolonization, as well as the dispersal potential of some EPT species. This study exemplifies how large-scale DNA-based surveys can be combined with phylogeographic inference to better understand the biodiversity and natural history of northern aquatic insect communities.

DNA barcoding of aquatic insects reveals unforeseen diversity and recurrent population divergence patterns through broad-scale sampling in northern Canada

DNA barcoding of aquatic insects reveals unforeseen diversity and recurrent population divergence patterns through broad-scale sampling in northern Canada