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Systematics, phylogeny and biogeography
RESEARCH ARTICLE

Phylogeny of the Echinoderes coulli-group (Kinorhyncha : Cyclorhagida : Echinoderidae) – a cosmopolitan species group trapped in the intertidal

Phillip Vorting Randsø A G , Hiroshi Yamasaki B , Sarah Jane Bownes C , Maria Herranz D , Maikon Di Domenico E , Gan Bin Qii F and Martin Vinther Sørensen A
+ Author Affiliations
- Author Affiliations

A Section for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 2100 Copenhagen, Denmark.

B Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Invalidenstr. 43, D-10115 Berlin, Germany.

C Westville Campus, School of Life Sciences, University of KwaZulu-Natal, University Road, Westville 3629, South Africa.

D Departments of Zoology and Botany, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.

E Laboratório de Modelagem Ecológica, Centro de Estudos do Mar, Universidade Federal do Paraná, 83255-976, PR, Brazil.

F Tropical Marine Science Institute, National University of Singapore, S2S, 18 Kent Ridge Road, 119227 Singapore.

G Corresponding author. Email: pvrandsoe@live.dk

Invertebrate Systematics 33(3) 501-517 https://doi.org/10.1071/IS18069
Submitted: 21 August 2018  Accepted: 29 December 2018   Published: 28 May 2019

Abstract

Kinorhyncha is a phylum of microscopic, benthic marine invertebrates found throughout the world, from the Arctic to Antarctica and from the intertidal zone to the deep sea. Within the most species-rich genus, Echinoderes, we find a putatively monophyletic species group, the so-called Echinoderes coulli-group. The remarkable morphological similarities of the E. coulli-group species and the fact that the group has a global distribution even though most of the species are restricted to intertidal habitats, has led to the hypothesis that dispersal and speciation within the group has been driven by the process of continental drift. However, this has never been confirmed empirically. With morphology and two molecular loci, COI and 18S, we calculated phylogenetic trees by analysing datasets separately and in combination using Maximum Parsimony, Maximum Likelihood and Bayesian Inference. Using different models of evolution in combination with different statistical approaches, we show that two major clade divergences were consistent with historic drifting of continents, suggesting that vicariance has played an important role for the speciation within the E. coulli-group. Furthermore, we found that reconstructions of past tectonic drifting since the Devonian (416–359 million years ago) were able to explain present species distributions, and suggest that the group originated in a supposedly vast shallow marine environment in north-eastern Gondwana by the mid-late Silurian, 426–416 million years ago.

Additional keywords: cosmopolitanism, distribution, Gondwana, meiofauna, phylogeography, vicariance


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