Multi-Genetic Marker Approach and Spatio-Temporal Analysis Suggest There Is a Single Panmictic Population of Swordfish Xiphias gladius in the Indian Ocean

Abstract

Genetic population structure of swordfish Xiphias gladius was examined based on 2231 individual samples, collected mainly between 2009 and 2010, among three major sampling areas within the Indian Ocean (IO; twelve distinct sites), Atlantic (two sites) and Pacific (one site) Oceans using analysis of nineteen microsatellite loci (n = 2146) and mitochondrial ND2 sequences (n = 2001) data. Sample collection was stratified in time and space in order to investigate the stability of the genetic structure observed with a special focus on the South West Indian Ocean. Significant AMOVA variance was observed for both markers indicating genetic population subdivision was present between oceans. Overall value of F-statistics for ND2 sequences confirmed that Atlantic and Indian Oceans swordfish represent two distinct genetic stocks. Indo-Pacific differentiation was also significant but lower than that observed between Atlantic and Indian Oceans. However, microsatellite F-statistics failed to reveal structure even at the inter-oceanic scale, indicating that resolving power of our microsatellite loci was insufficient for detecting population subdivision. At the scale of the Indian Ocean, results obtained from both markers are consistent with swordfish belonging to a single unique panmictic population. Analyses partitioned by sampling area, season, or sex also failed to identify any clear structure within this ocean. Such large spatial and temporal homogeneity of genetic structure, observed for such a large highly mobile pelagic species, suggests as satisfactory to consider swordfish as a single panmictic population in the Indian Ocean.

Highly restricted gene flow between disjunct populations of the skunk clownfish (Amphiprion akallopisos) in the Indian Ocean

“…The absence of shared haplotypes and the results of the AMOVAs and pairwise comparisons indicate highly restricted gene flow between the disjunct populations of Amphiprion akallopisos in the EIO and WIO. Although some species are able to disperse across the Indian Ocean (Craig et al 2007;Horne et al 2008;Vogler et al 2012;Muths et al 2013), the findings of this study provide new evidence for the existence of a barrier to gene flow between the EIO and the WIO (Ridgway & Sampayo 2005). These empirical results also support the predictions from dispersal models stating that larvae generally do not drift over distances of thousands of kilometres and predominantly settle close to their home reef (Cowen et al 2006).…”

“…; Muths et al . ), the findings of this study provide new evidence for the existence of a barrier to gene flow between the EIO and the WIO (Ridgway & Sampayo ). These empirical results also support the predictions from dispersal models stating that larvae generally do not drift over distances of thousands of kilometres and predominantly settle close to their home reef (Cowen et al .…”

“…; Muths et al . ). On the contrary, significant differentiation among populations from the East African coast and from Indian Ocean islands has been discovered, indicating a genetic break (Gopal et al .…”

“…Significant population structure was detected in the WIO, but no genetic break associated with a particular geographical location or oceanographical feature could be found. Several studies in the WIO have indicated low levels of genetic differentiation and the absence of genetic breaks in invertebrates (Duda & Palumbi 1999;Gopurenko et al 1999;Fratini et al 2010;Silva et al 2010b;He et al 2011;Vogler et al 2012) and fish (Dorenbosch et al 2006;Hoareau et al 2007;Muths et al 2013). On the contrary, significant differentiation among populations from the East African coast and from Indian Ocean islands has been discovered, indicating a genetic break (Gopal et al 2006;Ragionieri et al 2010;Muths et al 2012).…”

Lack of genetic population structure of slimy sculpin in a large, fragmented lake

“…Low genetic structure is usually a feature of highly connected populations with high mobility and capacity for dispersal (Muths, Le Couls, Evano, Grewe, & Bourjea, 2013;Thompson, Patel, Baker, Constantine, & Millar, 2015). However, adult slimy sculpin are not considered highly mobile.…”