Pandora’s Box in the Deep Sea –Intraspecific Diversity Patterns and Distribution of Two Congeneric Scavenging Amphipods

Tomasz Mamos,Amy C Driskell,Ed Hendrycks,Pedro Martínez Arbizu,Saskia Brix,Anna M Jażdżewska,Tammy Horton

doi:10.3389/fmars.2021.750180

Abstract

Paralicella tenuipesChevreux, 1908 and Paralicella caperescaShulenberger and Barnard, 1976 are known as widely distributed deep-sea scavenging amphipods. Some recent studies based on genetic data indicated the presence of high intraspecific variation of P. caperesca suggesting it is a species complex. Based on published molecular data from the Pacific and Indian oceans and new material obtained from the North and South Atlantic, we integrated the knowledge on the intraspecific variation and species distribution of the two nominal taxa. The study included analysis of three genes (COI, 16S rRNA, 28S rRNA) and revealed the existence of a single Molecular Operational Taxonomic Unit (MOTU) within P. tenuipes and six different MOTUs forming P. caperesca. The distribution pattern of the recognized lineages varied with three (P. tenuipes, MOTU 1 and MOTU 5 of P. caperesca) being widely distributed. There was evidence of contemporary population connectivity expressed by the share of the same COI haplotypes by individuals from very distant localities. At the same time no signal of recent demographic changes was observed within the studied taxa. The time-calibrated phylogeny suggested the emergence of species to be at the time of Mesozoic/Cenozoic transition that may be associated with global changes of the ocean circulation and deep sea water cooling.

Highlights

The deep sea, the largest ecosystem in the World, has received particular attention in recent decades
A few sequences identified as P. tenuipes that grouped with P. caperesca seem to be associated with identification mistakes and will be discussed later in the text
We have shown that the two studied species have different intraspecific structures, with Paralicella tenuipes constituting a single molecular unit, while P. caperesca is a complex of potentially cryptic species

Summary

Introduction

The deep sea, the largest ecosystem in the World, has received particular attention in recent decades. Recent analyses of abyssal benthic communities have partly challenged the paradigm, reporting very high diversities of several invertebrate groups, especially when applying molecular studies (e.g., Brandt et al, 2007; Janssen et al, 2015; Jazdzewska and Mamos, 2019; Brix et al, 2020). It was observed that underwater physiographic features, not being surmountable barriers for species connectivity, may restrict dispersal, for those taxa lacking a free-living larval stage (Bober et al, 2018; Riehl et al, 2018; Jakiel et al, 2019; Jazdzewska and Mamos, 2019; Brix et al, 2020). Application of molecular methods in studies of some presumed cosmopolitan deep-sea species revealed that they are complexes of taxa with more restricted ranges (Havermans, 2016; Verheye et al, 2016)

Methods

Results

Discussion

Conclusion