Contrasting biogeographical patterns in Margarella (Gastropoda: Calliostomatidae: Margarellinae) across the Antarctic Polar Front

Abstract

endemic to South Georgia), M. steineni (South Georgia and Crozet Island) and the morphologically variable M. violacea (=M. expansa , M. porcellana and M. pruinosa) , with populations in southern South America , the Falkland/Malvinas , Crozet and Kerguelen Islands. Margarella violacea and M. achilles are sister species, closely related to M. steineni, with M. antarctica sister to all these. This taxonomy reflects contrasting biogeographic patterns on either side of the APF in the Southern Ocean. Pop-ulations of Margarella north of the APF (M. violacea) showed significant genetic variation but with many shared haplotypes between geographically distant populations. By contrast, populations south of the APF (M. antarctica, M. steineni and M. achilles) exhibited fewer haplotypes and comprised three distinct species, each occurring across a separate geographical range. We hypothesize that the biogeographical differences may be the consequence of the presence north of the APF of buoyant kelpspotential longdistance dispersal vectors for these vetigastro-pods with benthic-protected developmentand their near-absence to the south. Finally, we suggest that the low levels of genetic diversity within higher-latitude Margarella reflect the impact of Quaternary glacial cycles that exterminated local populations during their maxima.

The right tool for the right question: contrasting biogeographic patterns in the notothenioid fish Harpagifer spp. along the Magellan Province

“…Finally, as previously demonstrated in shallow marine benthic organisms including fishes [ 98 ], invertebrates [ 3 , 34 , 40 , 42 , 99 ] and bacteria [ 100 ], the taxonomy of the Southern Ocean biota requires major revisions, including molecular and morphological analyses.…”

“…This pinpoints the necessity to verify the phylogenetic status of each evolutionary unit using different approaches before drawing genealogical conclusions based solely on non-targeted SNPs. In the Southern Ocean, traditional DNA molecular markers have been extensively used for species delimitation analyses (see [ 40 , 41 , 94 , 95 ]). Recently, RRS data has also been successfully applied as a tool for phylogenetic inference [ 50 , 96 , 97 ], but in all those cases, SNP data were complemented with available molecular, morphological or taxonomic evidence.…”

“…Although several near-shore marine species are distributed across the entire Magellan Province, few phylogeographic studies have been conducted across the region [ 34 , 38 , 39 ]. Phylogeographic patterns detected when including the Falkland/Malvinas Islands ranged from the absence of genetic differentiation [ 39 , 40 ] to marked phylogeographic differentiation [ 19 , 33 , 34 ] and the presence of clearly divergent species-level clades [ 41 , 42 ].…”

“…During recent decades, molecular-based analyses using traditional markers (mtDNA and nucDNA sequences) have become the main tool to understand and unravel the role of Quaternary glacial episodes on the distribution and demography of populations, generally improving the understanding of biodiversity and systematics through species delimitation methods [ 2 , 6 , 8 , 40 , 50 ]. Accordingly, the sudden increasing availability of genome-based data in non-model organisms has significantly improved the spatial resolution of genetic structure and potentially allows inferences concerning the historical and contemporary diversification of organisms [ 51 ].…”

Taxonomic re‐appraisal for toothfish (Dissostichus: Notothenioidea) across the Antarctic Polar Front using genomic and morphological studies

“…This occurs when their planktonic eggs and larvae are subject to protracted periods of dispersal along these fronts, with juveniles further migrating to adjacent ecosystems. The Antarctic Convergence or Antarctic Polar Front (APF) delimits the Antarctic and sub‐Antarctic provinces of the Southern Ocean, with their diverse marine fauna shaped by the particular paleoclimatic history, oceanography and ecological determinism of these regions (Dornburg et al ., 2017; Gonzalez‐Wevar et al ., 2017, 2019, 2021; Strugnell et al ., 2008). The APF has been shown to be an important biogeographic feature facilitating connectivity in some groups (Cumming et al ., 2014; Mortimer et al ., 2011) while representing a pronounced barrier to dispersal or gene flow in others (Gonzalez‐Wevar et al ., 2010, 2012; Poulin et al ., 2014).…”