Thursday, June 23, 2016

New paper published: Spatio-temporal patterns of genetic diversity of Styela plicata in harbour populations

by Xavier Turon

We add another paper to the Styela plicata history: “Stochasticity in space, persistence in time: genetic heterogeneity in harbour populations of the introduced ascidian Styela plicata”, by Mari-Carmen Pineda, Beatriz Lorente, Susanna López-Legentil, Creu Palacín and Xavier Turon, which has been published today (23rd June) in PeerJ.

In this study, we analysed genetic structure of the populations of Styela plicata in 9 harbours along the Iberian Mediterranean coast and adjacent Atlantic waters (>1,200 km range) at two time points 5 years apart (2009 and 2014). Using COI sequence data of ca. 400 specimens, we found strong spatial genetic structure, with significant differences among many populations, but no significant differences among years. Our results revealed spatial genetic heterogeneity and temporal homogeneity in S. plicata, suggesting a limited role of recurrent, vessel-mediated transport of organisms among small to medium-size harbours. Our study area is representative of many highly urbanized coasts with dense harbour networks. In these environments, the episodic chance arrival of colonisers appears to determine the genetic structure of populations and the genetic composition of these early colonising individuals persists in the respective harbours, at least over moderate time frames (five years) that encompass ca. 20 generations of S. plicata.

This article is yet another instance of the importance of the temporal component in studies of introduced species to unravel processes occurring during secondary dispersal of non-indigenous species.
Map of the Iberian Peninsula (NW Mediterranean) showing the sampling sites of Styela plicata. Pie charts represent haplotype frequencies for the COI gene in each population analysed in 2009 and 2014.