Multilocus DNA analysis supports Didymodon gelidus (Musci, Pottiaceae) as a distinct endemic of the austral polar region

Abstract

The taxonomic position of the Antarctic subendemic species <em>Didymodon gelidus</em> Cardot is controversial, notably because of its notorious sterile condition. Considering the overall appearance and the reddish coloration of the plants, the leaf areolation, reaction of the leaf lamina with KOH, and the presence of multicellular axillary gemmae, this species was considered to be conspecific with the Holarctic <em>D. brachyphyllus</em> (Sull.) R. H. Zander. As a result, the latter was established as a bipolar species. Recent detailed morphological and anatomical studies have revealed a number of features which enable recognition of <em>D. gelidus</em> and <em>D. brachyphyllus</em>, including the shape of leaves, leaf apices and basal leaf cells, as well as costal anatomy. Here, within a larger-scale project focused on the evolution and biogeographical connections of Antarctic endemic mosses, we analyzed the genetic relationships of <em>D. gelidus</em> and <em>D. brachyphyllus</em> to confront the morphology-based conclusions. We selected five geographically distinct collections per species and applied a multilocus DNA analysis based on nuclear (ITS) and plastid (<em>atpIH</em>, <em>trnLF</em>, <em>trnG</em>, <em>rps4</em>) sequences to assess the genetic differentiation of these two taxa. We also placed their lineages in a wider phylogenetic context using an extended sampling of <em>Didymodon</em> taxa and select other representatives of Pottiaceae. Our results showed a clear genetic differentiation of the Southern Hemisphere (<em>D. gelidus</em>) and Northern Hemisphere (<em>D. brachyphyllus</em>) plants. Moreover, the phylogenetic analysis showed that <em>D. gelidus</em> formed a strongly supported clade on its own which was distantly related to <em>D. brachyphyllus</em>. Accordingly, the two taxa do not represent geographical vicariants. <em>Didymodon gelidus</em> must be considered a distinct endemic species of the austral polar region, having its optimal occurrence in the Antarctic and weakly penetrating northward to South Georgia and Îles Kerguelen in the Subantarctic. The relatively isolated phylogenetic position of <em>D. gelidus</em> likely suggests its old age.

The Sinking of Another Tristan da Cunha Moss Endemic and Its Phytogeographical Consequences

“…Didymodon brachyphyllus (Sull.) R. H. Zander was considered to be a bipolar species when its conspecificity with the Antarctic D. gelidus Cardot and Barbula byrdii E. B. Bartram was shown (Ochyra & Zander, 2002;Zander & Ochyra, 2001); however, reexamination of these taxa revealed a definite distinctness of northern and southern species both on morphological (Jiménez & Ochyra, 2017) and molecular grounds (Ronikier et al, 2018). The South American and sub-Antarctic Drepanocladus longifolius (Mitt.)…”

Polar terrestrial ecosystems: ecology, diversity, and biogeography

“…This problem is well illustrated by several Antarctic moss species, whose only gametophytic phase is known, limiting the availability of taxonomically relevant characters. Ronikier et al [24], by applying DNA sequence analysis, provide evidence for distinctness of Didymodon gelidus, an endemic moss of the austral polar region and highlight the importance of molecular tools in polar taxonomy and biogeography.…”

Untitled

“…One extreme example is Antarctic biome, locked-in ice continent with only 0.18% to 0.32% of the area being ice-free. Altogether, 115 species of mosses are known from Antarctica Sollman, 2015;Jiménez & Ochyra, 2017;Ronikier et al, 2018). However, botanical exploration of the Antarctic continent and the maritime Antarctic islands is highly restricted due, among others, to substantial logistic limitations.…”

“…Lavoie (2013) found only three articles that used herbarium specimens from Antarctica for documenting biogeographical patterns or environmental changes. Since then, we have found only a handful of further studies dealt with herbarium moss material from Antarctica including our recent contributions (Pisa et al, 2014;Biersma et al, 2018a;2018b;Ronikier et al, 2018;Saługa et al, 2018). On the other hand, there is a clearly growing interest in research focused on mosses from the high-latitude ecosystems of the Southern Hemisphere and related to their biogeography, evolutionary history and ecology (e.g.…”

“…On the other hand, there is a clearly growing interest in research focused on mosses from the high-latitude ecosystems of the Southern Hemisphere and related to their biogeography, evolutionary history and ecology (e.g. Convey & Lewis Smith, 2006;Peat, Clarke & Convey, 2007;Cannone & Seppelt, 2008;Li et al, 2009;Van der Putten et al, 2009;Hills, Stevens & Gemmill, 2010;Cannone, Convey & Guglielmin, 2013;Kato et al, 2013;Fraser et al, 2014;Pisa et al, 2014;Biersma et al, 2017;Rankin et al, 2017;Waterman et al, 2017;Biersma et al, 2018a;2018b;Fraser et al, 2018;de Freitas et al, 2018;Ronikier et al, 2018;Saługa et al, 2018).…”