Genetic homogeneity, lack of larvae recruitment, and clonality in absence of females across western Mediterranean populations of the starfish Coscinasterias tenuispina

Rocío Pérez-Portela,Marta Campos-Canet,Creu Palacín,Alex Garcia-Cisneros

doi:10.1038/s41598-021-96331-6

Rocío Pérez-Portela, Marta Campos-Canet + Show 2 more

Open Access

https://doi.org/10.1038/s41598-021-96331-6

Copy DOI

Abstract

We here analysed the populations’ genetic structure of Coscinasterias tenuispina, an Atlantic-Mediterranean fissiparous starfish, focusing on the western Mediterranean, to investigate: the distribution and prevalence of genetic variants, the relative importance of asexual reproduction, connectivity across the Atlantic-Mediterranean transition, and the potential recent colonisation of the Mediterranean Sea. Individuals from 11 Atlantic-Mediterranean populations of a previous study added to 172 new samples from five new W Mediterranean sites. Individuals were genotyped at 12 microsatellite loci and their gonads histologically analysed for sex determination. Additionally, four populations were genotyped at two-time points. Results demonstrated genetic homogeneity and low clonal richness within the W Mediterranean, due to the dominance of a superclone, but large genetic divergence with adjacent areas. The lack of new genotypes recruitment over time, and the absence of females, confirmed that W Mediterranean populations were exclusively maintained by fission and reinforced the idea of its recent colonization. The existence of different environmental conditions among basins and/or density-depend processes could explain this lack of recruitment from distant areas. The positive correlation between clonal richness and heterozygote excess suggests that most genetic diversity is retained within individuals in the form of heterozygosity in clonal populations, which might increase their resilience.

Highlights

Genetic diversity, needed for populations to adapt to environmental changes, has a profound influence on evolutionary and ecological processes of the species, and is one of the key components of ecosystems b iodiversity[1,2,3]
Our study explores in detail the distribution and frequency of C. tenuispina genetic variants within a part of the W Mediterranean sub-basin, over space and time, and includes samples from the Alboran Sea, an important marine transition between the Atlantic Ocean and the Mediterranean Sea (e.g.25,26)
The general genetic structure of C. tenuispina was characterised by large genetic distances between major oceanographic areas, NE Atlantic, W Mediterranean, and E Mediterranean, and across marine fronts, including the Gibraltar Strait, the Almeria-Oran front, and the Siculo-Tunisian front, as demonstrated by genetic distances, Bayesian clustering, and Discriminant analyses of principal components (DAPC) analyses

Summary

Introduction

Genetic diversity, needed for populations to adapt to environmental changes, has a profound influence on evolutionary and ecological processes of the species, and is one of the key components of ecosystems b iodiversity[1,2,3]. In many benthic invertebrate groups, such as bryozoans, ascidians, or corals, among others, asexual reproduction during adulthood is mostly linked to colonial growing, generating colonies composed of immobile ramets (single individuals generated by clonal propagation)[8]. In others, such as some echinoderms, adults and/or larvae can divide into two new freeliving individuals, yielding mobile ramets with considerable dispersal capability when the splitting happens at the larval stages[9,10]. The same data suggested a relatively recent colonisation of the Mediterranean Sea from the Atlantic Ocean during one of the last interglacial periods of the P leistocene[23], but more data are required to confirm this hypothesis, including the role of the Atlantic-Mediterranean transition in the connectivity patterns between both basins

Methods

Results

Conclusion