Phylogeography of higher Diptera in glacial and postglacial grasslands in western North America

Abstract

BackgroundPleistocene glaciations have had an important impact on the species distribution and community composition of the North American biota. Species survived these glacial cycles south of the ice sheets and/or in other refugia, such as Beringia. In this study, we assessed, using mitochondrial DNA from three Diptera species, whether flies currently found in Beringian grasslands (1) survived glaciation as disjunct populations in Beringia and in the southern refugium; (2) dispersed northward postglacially from the southern refugium; or (3) arose by a combination of the two. Samples were collected in grasslands in western Canada: Prairies in Alberta and Manitoba; the Peace River region (Alberta); and the southern Yukon Territory. We sequenced two gene regions (658 bp of cytochrome c oxidase subunit I, 510 bp of cytochrome b) from three species of higher Diptera: one with a continuous distribution across grassland regions, and two with disjunct populations between the regions. We used a Bayesian approach to determine population groupings without a priori assumptions and performed analysis of molecular variance (AMOVA) and exact tests of population differentiation (ETPD) to examine their validity. Molecular dating was used to establish divergence times.ResultsTwo geographically structured populations were found for all species: a southern Prairie and Peace River population, and a Yukon population. Although AMOVA did not show significant differentiation between populations, ETPD did. Divergence time between Yukon and southern populations predated the Holocene for two species; the species with an ambiguous divergence time had high haplotype diversity, which could suggest survival in a Beringian refugium.ConclusionsPopulations of Diptera in Yukon grasslands could have persisted in steppe habitats in Beringia through Pleistocene glaciations. Current populations in the region appear to be a mix of Beringian relict populations and, to a lesser extent, postglacial dispersal northward from southern prairie grasslands.

The Himalayan Uplift and the Evolution of Aquatic Biodiversity Across Asia: Snowtrout (Cyprininae: Schizothorax) as a Test Case

“…2). Here, we defined "populations" (= distinct clades) as being haplotypes within groups, per [70]. Probabilities were ascertained using 1,000 permutations, and statistical significance was assigned using a Bonferroni-correction.…”

“…Topologies from ML and BA analyses were statistically compared by assessing each with respect to the original sequence alignment using IQ-TREE2 v2 [70]. To do so, we examined support for each using RELL approximation with 10,000 replicates using: (a) Raw change in loglikelihoods; (b) Bootstrap proportions [77]; (c) Kishino-Hasegawa test [78]; (d) Shimodaira-Hasegawa test [79]; (e) Approximately Unbiased test [80]; and (f) Expected Likelihood weights [81].…”

The Himalayan uplift and evolution of aquatic biodiversity across Asia: Snowtrout (Cyprininae: Schizothorax) as a test case

“…We conducted an analysis of molecular variance (AMOVA: Arlequin v.3.5.1.2; [ 39 ]) to gauge how genetic variation was partitioned statistically among geographic regions (as informed by Geneland ). Here, we defined populations (= distinct gene pools) as being haplotypes within regions [ 40 ]. Probabilities were ascertained using 1,000 permutations, and statistical significance was assigned using a Bonferroni-correction.…”

Weak population‐genetic structure of a widely distributed nematode parasite of frogs in the western Palearctic

“…Population-genetic structure and phylogeography of two known vector species of I. neglecta, a biting midge F. velox and a drain fly S. silacea, were not studied. However, it might be hypothesized that they also survived the Pleistocene glacial periods in climatically favorable regions from which they expanded at the beginning of the Holocene, as was evidenced for other dipteran species occupying temperate zones of Palearctic and Nearctic (Aransay et al, 2003;Porretta et al, 2011;Trájer et al, 2018;Solecki et al, 2019). Contrarily to the definitive hosts (the water frogs), dipteran vectors reveal higher dispersal capacity because they can passively spread long distances and thus might significantly contribute to the spread of the parasites they transmit (Erisoz Kasap et al, 2015;Mignotte et al, 2021).…”