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Knowledge of global patterns of genetic diversity is essential for biodiversity conservation as this parameter describes the ability of a species to respond to environmental changes. Ichneumonoids parasitoid wasps are among the few taxa showing an anomalous latitudinal diversity gradient. Using the largest georeferenced molecular dataset for this group, we used a macrogenetics approach to examine latitudinal patterns and predictors of intraspecific genetic diversity. We calculated the mean nucleotide diversity of mitochondrial DNA barcode sequences at three geographic levels: grid cells, latitudinal bands and climatic zones. Nucleotide diversity values were consistently higher at northern temperate latitudes, peaking at 50°. We found a positive but weak relationship between intraspecific diversity and the latitude, between intra‐ and interspecific diversity, and a positive effect of the temperature range. Examining the spatial relationship between different levels of biodiversity and its drivers is particularly relevant considering climate change and its impact on species distribution. Yet, in insects, it has been challenging to integrate ecological, evolutionary and geographical components when analysing the processes leading to species richness gradients. [ABSTRACT FROM AUTHOR]

Myriad environmental and biological traits have been investigated for their roles in influencing the rate of molecular evolution across various taxonomic groups. However, most studies have focused on a single trait, while controlling for additional factors in an informal way, generally by excluding taxa. This study utilized a dataset of cytochrome c oxidase subunit I (COI) barcode sequences from over 7000 ray-finned fish species to test the effects of 27 traits on molecular evolutionary rates. Environmental traits such as temperature were considered, as were traits associated with effective population size including body size and age at maturity. It was hypothesized that these traits would demonstrate significant correlations with substitution rate in a multivariable analysis due to their associations with mutation and fixation rates, respectively. A bioinformatics pipeline was developed to assemble and analyze sequence data retrieved from the Barcode of Life Data System (BOLD) and trait data obtained from FishBase. For use in phylogenetic regression analyses, a maximum likelihood tree was constructed from the COI sequence data using a multi-gene backbone constraint tree covering 71% of the species. A variable selection method that included both single- and multivariable analyses was used to identify traits that contribute to rate heterogeneity estimated from different codon positions. Our analyses revealed that molecular rates associated most significantly with latitude, body size, and habitat type. Overall, this study presents a novel and systematic approach for integrative data assembly and variable selection methodology in a phylogenetic framework. [ABSTRACT FROM AUTHOR]

Abstract: Molecular studies have enlightened our understanding of freshwater zooplankton biogeography, yet questions remain regarding the scale and commonality of geographic speciation. Here, we present a mtDNA-based phylogenetic hypothesis for 92 Daphnia species from all seven continents, with a focus on North and South America, Europe, and Australia, and use it to explore the frequency, scale, and geographical orientation of allopatric divergence events. Allopatric speciation can conservatively account for at least 42% of cladogenetic events among the species included in our study; most of these involve intercontinental splits. Closely related species pairs are concentrated in the circumarctic region and between northern and southern continents, aligned with bird migration routes, suggesting recent dispersal. By contrast, deeper phylogenetic patterns are consistent with vicariance scenarios linked to continental fragmentation. The possible reasons for the puzzling persistence of these ancient patterns in light of the eroding force of dispersal are considered. Our results demonstrate the high frequency and complex pattern of allopatric speciation in this ancient, passively dispersed genus. [Copyright &y& Elsevier]

Recent studies have shown the value of complementing standard taxonomy with genetic analyses to reveal cryptic diversity and to aid in the understanding of patterns of evolution. We surveyed variation in the COI mitochondrial gene in members of the three genera of centropagid copepods from the inland waters in Argentina. In general, we found a close association between molecular and morphological systematics in this group. Similar to findings for marine calanoids, genetic distances within Boeckella species were modest (< 4%), while distances among morphospecies were much larger (> 11%). Parabroteas is currently monotypic, although we detected cryptic genetic diversity, with two lineages showing 5.5% divergence. In contrast, Karukinka was not a valid genus, apparently representing an interesting and atavistic offshoot of B. poppei, a result reinforcing the value of considering both morphological and molecular evidence. Moreover, we used combined genetic and morphological information, analysed with maximum likelihood methods, to evaluate the common assumption that evolution tends to proceed via the loss of structures in crustaceans. Although analysis of other taxa and character types is required to evaluate fully the reduction hypothesis, our results suggest that structures may be gained readily as well as lost. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90, 279–292. [ABSTRACT FROM AUTHOR]

Although the temperate regions of South America are known to have a diverse daphniid fauna, there has been no genetic evaluation of the existing taxonomic system or of the affinities between the North and South American faunas. The present study analyses mitochondrial DNA sequences and allozyme variation to investigate species diversity in 176 Daphnia populations from Argentina. This work established the presence of at least 15 species in Argentina, six of which are either undescribed or are currently misidentified and two of which represent range extensions of North American taxa. Eleven of the Argentine species appear endemic to South America, while the remaining four also occur in North America. In the latter cases, the close genetic similarity between populations from North and South America indicates the recent exchange of propagules between the continents. While biological interactions and habitat availability have undoubtedly contributed to the observed species distributions, chance dispersal has apparently played a dominant role in structuring large-scale biogeographical patterns in this genus and probably in other passively-dispersed organisms. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 140, 171−205. [ABSTRACT FROM AUTHOR]

The loss of flight ability has occurred thousands of times independently during insect evolution. Flight loss may be linked to higher molecular evolutionary rates because of reductions in effective population sizes (N[sub e]) and relaxed selective constraints. Reduced dispersal ability increases population subdivision, may decrease geographical range size and increases (sub)population extinction risk, thus leading to an expected reduction in N[sub e]. Additionally, flight loss in birds has been linked to higher molecular rates of energy-related genes, probably owing to relaxed selective constraints on energy metabolism. We tested for an association between insect flight loss and molecular rates through comparative analysis in 49 phylogenetically independent transitions spanning multiple taxa, including moths, flies, beetles, mayflies, stick insects, stoneflies, scorpionflies and caddisflies, using available nuclear and mitochondrial protein-coding DNA sequences. We estimated the rate of molecular evolution of flightless (FL) and related flight-capable lineages by ratios of non-synonymous-to-synonymous substitutions (dN/dS) and overall substitution rates (OSRs). Across multiple instances of flight loss, we show a significant pattern of higher dN/dS ratios and OSRs in FL lineages in mitochondrial but not nuclear genes. These patterns may be explained by relaxed selective constraints in FL ectotherms relating to energy metabolism, possibly in combination with reduced N[sub e]. [ABSTRACT FROM AUTHOR]

Knowledge of genetic and species-level diversity for freshwater invertebrates in the Canadian Arctic is currently limited. Here, we sampled benthic and planktonic invertebrates from 68 ponds, seven lakes, and six rivers near Cambridge Bay (Iqaluktuuttiaq), Nunavut, between 2018 and 2021 and analysed individuals using mitochondrial cytochrome c oxidase subunit 1 (COI) gene sequences. From the 9336 specimens collected, 7186 provided sequences > 400 base pairs (83% success rate), representing 3358 unique haplotypes and 467 putative species based on Barcode Index Numbers (BINs; as a surrogate for species-level diversity). Chironomidae (non-biting midges) was the most diverse taxon, followed by Trombidiformes mites and Anomopoda (water fleas). Species’ accumulation curves for total diversity as well as the major taxa suggest that taxa we identified represent < 63% of the total diversity likely to be found in this region of the western Canadian Arctic (estimated n = 739) during the ice-free season. Further sampling over a wider geographical range as well as assessments of temporal (seasonal and inter-annual) variability will be required to assess comprehensively the total species richness currently found in the Canadian Arctic. In the interim, the publicly available data we provide here can be used as a baseline for ongoing studies and to track ecological changes occurring in aquatic habitats of the central Canadian Arctic and beyond. [ABSTRACT FROM AUTHOR]