Talitrid amphipods (Crustacea: Amphipoda: Talitridae) and the driftwood ecological niche: a morphological and molecular study

Abstract

Coastal regions of the North East Atlantic and Mediterranean Seas have four known species of driftwood talitrids. Records are extremely scanty, often limited to the type locality and dating to 1950. We were able to study three of them, all belonging to the genus Macarorchestia, using fresh and archived samples including type material. Allometric and molecular analyses support: (1) a close relationship among all the three classically defined Macarorchestia species, (2) Macarorchestia was well separated from non-driftwood taxa, and (3) a putative new driftwood talitrid discovered during this study was not closely related to Macarorchestia. Genetic divergence between the new species and Macarorchestia remyi is as high as the average distance among a number of talitrid species included in the study for comparison. A key is provided to identify all three of the presently known species of Macarorchestia, using morphological characters employed in the allometric study.

Keywords:

• Macarorchestia remyi
• Macarorchestia roffensis
• Macarorchestia martini
• Driftwood habitat
• COI-DNA barcoding
• allometry

Acknowledgements

We thank Ms Miranda Lowe of the Natural History Museum, London for assistance in accessing paratype specimens of M. roffensis and Dr Dirk Platvoet of the Zoologisch Museum, Amsterdam for access to types and paratypes of M. martini. Dr Adriana Radulovici (Département de biologie, Université du Québec, Rimouski, Québec, Canada) is kindly acknowledged for having provided us with some still unpublished COI sequences. We thank Mr John Valentine for improving the English on the first draft of the manuscript. We wish to thank C. Fišer and two anonymous reviewers for useful comments on a first version of the paper.