Phylogeography of the Atlanto‐Mediterranean sea cucumber Holothuria (Holothuria) mammata: the combined effects of historical processes and current oceanographical pattern

Abstract

We assessed the genetic structure of populations of the widely distributed sea cucumber Holothuria (Holothuria) mammata Grube, 1840, and investigated the effects of marine barriers to gene flow and historical processes. Several potential genetic breaks were considered, which would separate the Atlantic and Mediterranean basins, the isolated Macaronesian Islands from the other locations analysed, and the Western Mediterranean and Aegean Sea (Eastern Mediterranean). We analysed mitochondrial 16S and COI gene sequences from 177 individuals from four Atlantic locations and four Mediterranean locations. Haplotype diversity was high (H=0.9307 for 16S and 0.9203 for COI), and the haplotypes were closely related (π=0.0058 for 16S and 0.0071 for COI). The lowest genetic diversities were found in the Aegean Sea population. Our results showed that the COI gene was more variable and more useful for the detection of population structure than the 16S gene. The distribution of mtDNA haplotypes, the pairwise F(ST) values and the results of exact tests and amova revealed: (i) a significant genetic break between the population in the Aegean Sea and those in the other locations, as supported by both mitochondrial genes, and (ii) weak differentiation of the Canary and Azores Islands from the other populations; however, the populations from the Macaronesian Islands, Algarve and West Mediterranean could be considered to be a panmictic metapopulation. Isolation by distance was not identified in H. (H.) mammata. Historical events behind the observed findings, together with the current oceanographic patterns, were proposed and discussed as the main factors that determine the population structure and genetic signature of H. (H.) mammata.

Genetic differentiation among Parastichopus regalis populations from Western Mediterranean Sea: potential effects of its fishery and current connectivity.

“…This pattern of genetic diversity can be attributed to a recent population expansion after a period of low population size, thereby enhancing the retention of new mutations (Grant & Bowen, 1998). Previous studies carried out on other Atlantic-Mediterranean holothurians, such as Holothuria mammata and H. arguinensis, or Mediterranean species, such as H. polii, showed a similar genetic pattern (Borrero-Pérez et al, 2010;Vergara-Chen et al, 2010;Borrero-Pérez et al, 2011;Valente et al, 2015;Rodrigues et al, 2015). Both markers, i.e., COI and 16S genes, have also been used to clarify taxonomic uncertainties, species relationships, biogeography and evolution of the family Stichopodidae (Byrne et al, 2010) and have showed high diversity, especially for the COI gene.…”

“…Therefore, sea cucumbers could have high genetic connectivity and show low population differentiation over large geographical scales (Vergara-Chen et al, 2010;Valente et al, 2015). Nev- ertheless, genetic differentiation among marine populations is also possible even in species with pelagic larvae, when geographical barriers or biological factors cause some restrictions in gene flow (Riginos & Nachman, 2001;González-Wangüemert et al, 2004;De Croos & Pálsson, 2010;González-Wangüemert et al, 2010;Borrero-Pérez et al, 2011;González-Wangüemert & VergaraChen, 2014). Thus, our data demonstrated the existence of gene flow barriers among the studied locations, which could be represented by hydrological (eddies and currents), bathymetrical (different depths and slopes influencing the continuity of the habitat for our target species) or environmental factors (temperature, salinity, and chlorophyll).…”

Effects of fishery protection on biometry and genetic structure of two target sea cucumber species from the Mediterranean Sea

“…Turkish localities under fishery pressure such as Foça (H. mammata) and Ayvalik (H. tubulosa), showed very low genetic diversity compared with other localities sampled in the Atlantic Ocean (only H. mammata) and Mediterranean Sea (H. mammata and H. tubulosa) (BorreroPérez, 2010;Borrero-Pérez et al, 2011). A recent genetic study on H. polii established the highest genetic diversity of this species in Kusadasi (Valente et al, 2014).…”

“…According previous genetic studies carried out on sea cucumbers (Vergara-Chen et al, 2010;Borrero-Pérez et al, 2011;González-Wangüemert & Borrero-Pérez, 2012;Valente et al, 2014), a representative number of individuals from each locality were analyzed. DNA extractions were done based on Sambrook et al (1989) protocol.…”

Filogeografía de Holothuria (Halodeima) inornata Semper, 1868 (Echinodermata: Holothuroidea)

“…Para algunas especies de holoturias se han realizado trabajos en regiones del Océano Pacífico e Índico y el Atlántico oriental y el Mediterráneo (Uthicke et al 1998, Arndt y Smith 1998, Uthicke y Benzie 2000, Uthicke y Benzie 2003, Chang et al 2009, Borrero-Pérez et al 2011. Sin embargo, no se han registrado estudios en la región del POT entre México y Perú, para ninguna especie de pepino de mar.…”