Phylogeography of the Anaspides richardsoni species clade (Anaspidacea, Anaspidesidae): glaciation and recolonization of the Tasmanian Central Plateau and the question of paraphyletic species

Abstract

We herein present a phylogenetic and population genetic analysis of a Tasmanian Mountain Shrimp clade, based on ddRAD and cytochrome oxidase subunit-1 data sets. Our data show that the morphologically well-delineated and widespread Anaspides richardsoni Ahyong, 2016 is paraphyletic with respect to four other species (A. eberhardi Ahyong, 2016, A. spinulae Williams, 1965 and two undescribed species). These four species all form discrete (monophyletic) lineages and exhibit clear morphological distinctions in relation to A. richardsoni and to one another. However, we detect signals of introgression between some populations of A. richardsoni, A. spinulae and an undescribed species. We also find two instances of syntopic occurrences without evidence for interbreeding. Also, A. richardsoni is split into several allopatric and comparably old lineages. Anaspides spinulae from Lake St. Clair, however, seems to be a young species that might have differentiated only after the last glacial maximum of central Tasmania (22 000–17 000 years ago). Moreover, we analyse the present population structure and recolonization of the Central Plateau and Western Mountain Ranges in regard to their glacial history. We distinguish several glacial refugia and show that the recolonization most likely occurred only from one or two of these.