New paper published: Genetic diversity and demography of the red starfish

A beautiful specimen of the red starfish Echinaster sepositus.

by Alex Garcia-Cisneros

One of the most wonderful starfish of the Mediterranean suffered a large demographic expansion since the last maximum glacial period. However, its demographic expansion does not prevent it to have a weakness point: a low genetic diversity that might indicate the vulnerability of the species. These and more results were recently published by the ChallenGen team in a manuscript entitled “Low genetic diversity and demographic expansion in the red starfish Echinaster sepositus (Retzius 1816)” at the Scientific Reports.

The authors used both mitochondrial and nuclear markers to resolve the phylogeography and population genetics of the commonly named “red starfish” (Echinaster sepositus). The authors analysed samples from most of the distribution range of the species, with 15 localities distributed between both Mediterranean basins and the Atlantic Ocean.

Besides to demonstrate the low genetic diversity of the species compared with other echinoderms, the species showed a weak genetic structure within marine basins despite the a priori low dispersal potential of its lecithotrophic larva. The lecithotrophic larva in this species does not live more than few days before the settlement and therefore, it makes it difficult to connect distant or isolated populations. Furthermore, we found sharp differences in two Mediterranean localities, Cartagena and Livorno, that are located close to large marine harbours and coastal areas affected by industry, although our experimental design does not allow us to assess the effects of pollutants on the genetic structure.

Bar plots of the Bayesian clustering analysis obtained using STRUCTURE for different K values and based on the combination of both mitochondrial sequences (COI) and microsatellite loci.

Temporal genetic structure in the introduced ascidian Styela plicata

by M.Carmen Pineda

It’s been almost three years since the last paper on Styela plicata was published by our group, but the saga is not over yet!! The article entitled “Stable populations in unstable habitats: temporal genetic structure of the introduced ascidian Styela plicata in North Carolina”, by M.Carmen Pineda, Xavier Turon, Rocio Perez-Portela and Susanna Lopez-Legentil, has been just published online in the journal Marine Biology.

The solitary ascidian Styela plicata.

Styela plicata is a solitary ascidian, which has been introduced by ship fouling to harbours and marinas around the globe. This species has been extensively studied during the last years, based on its potential to become a plague. However, this is the first time that its genetic composition is studied on a temporal scale. On this recent study, a combination of nuclear and mitochondrial markers (7 microsatellites and a fragment of the gene Cytochrome Oxidase subunit I, COI) were used to analyse the genetic composition of one population subjected to environmental fluctuations and periodical die-offs, every 2 months and over 2.5 years. Overall, our results indicate that the investigated population is stable over time and relies on a periodic arrival of larvae from other populations, maintaining high genetic diversity and a complex interplay of allele gains and losses.

Temporal analyses exploring genetic trends over time are a great tool to predict the likelihood of long time survival of an introduced population in a new habitat and its invasive potential. This kind of information is particularly relevant when deciding which introduced species are more detrimental, and should help resource managers to focus their control and eradication efforts.