DOI: 10.5061/dryad.sj3tx964b
title: Comparative phylogeography reveals consistently shallow genetic diversity in a mitochondrial marker in Antarctic bdelloid rotifers

description: Aim: The long history of isolation of the Antarctic continent, coupled
 with the harsh ecological conditions of freezing temperatures could affect
 the patterns of genetic diversity in the organisms living there. We aim
 (1) to test whether such pattern can be seen in a mitochondrial marker of
 bdelloid rotifers, a group of microscopic aquatic and limno-terrestrial
 animals, and (2) to speculate on the potential mechanisms driving the
 pattern. Location: focus on Antarctica. Taxon: Rotifera Bdelloidea.
 Methods: We analysed different metrics of genetic diversity, also
 spatially explicit ones, including number of haplotypes, accumulation
 curves, genetic distances, time to the most recent common ancestor, number
 of independently evolving units from DNA taxonomy, strength of the
 correlation between geographic and genetic distances, population genetics
 neutrality and differentiation indices, potential historical processes,
 obtained from an extensive sample of cytochrome oxidase subunit I (COI)
 sequences obtained from bdelloid rotifers. We included 2242 individuals
 from 23 species in a comparison between Antarctic and non-Antarctic taxa,
 correcting for sample size directly in the analyses and then by confirming
 the results also by using only a restricted dataset of nine well-sampled
 species. Results: Antarctic species had consistently lower genetic
 diversity and potential younger relative age than non-Antarctic species,
 even if they were similar in sample size, geographical extent, neutrality
 and differentiation indices, and correlation between genetic and
 geographic distances. Main conclusions: The extensive survey of genetic
 diversity in one mitochondrial marker in Antarctic bdelloids supports
 previous suggestions from other organisms that the origin and maintenance
 of terrestrial Antarctic fauna are different from those of other
 continents. Such differences could be speculated to be due, in the case of
 bdelloid rotifers, to the more recent origin of the species living there
 in comparison to non-Antarctic species.
description: In total, 228 new sequences of 661 base pairs of the
 mitochondrial marker cytochrome c oxidase subunit I (COI) from Antarctic
 bdelloid rotifers were generated from single animals collected in the
 field. Animals were collected across the continent, mostly from Scott and
 Enderby areas and the Antarctic Peninsula. DNA was extracted using Chelex
 or HotShot protocol and the COI Folmer fragment was amplified using the
 HCO2198 and LCO1490 primers. 263 other previously published sequences from
 the same species were gathered from the literature.
 1587 sequences from species of bdelloid rotifers living outside
 Antarctica were gathered from published literature. We kept all the
 species with at least 15 sequences longer than 500 base pairs and that
 passed quality filtering controls, such as not having stop codons within
 the reading frame. In addition, 164 sequences were obtained from Philodina
 megalotrocha in North America. For each Antarctic COI
 sequence, we obtained the WGS84 geographic coordinates of the population
 of origin. For the previously published sequences, such data were obtained
 from the archives of the authors of the sequences. For the non-Antarctic
 species, we gathered detailed geographic coordinates only for a subset of
 well-sampled species with at least 60 sequences.