Panmixia in a fragmented and unstable environment: the hydrothermal shrimp Rimicaris exoculata disperses extensively along the Mid-Atlantic Ridge

Abstract

Dispersal plays a fundamental role in the evolution and persistence of species, and especially for species inhabiting extreme, ephemeral and highly fragmented habitats as hydrothermal vents. The Mid-Atlantic Ridge endemic shrimp species Rimicaris exoculata was studied using microsatellite markers to infer connectivity along the 7100-Km range encompassing the sampled sites. Astonishingly, no genetic differentiation was found between individuals from the different geographic origins, supporting a scenario of widespread large-scale dispersal despite the habitat distance and fragmentation. We hypothesize that delayed metamorphosis associated to temperature differences or even active directed migration dependent on physical and/or chemical stimuli could explain these results and warrant further studies on adaptation and dispersal mechanisms.

Figure 1. Allele distributions.

Distribution of the alleles found for each locus at the different hydrothermal vent sites sampled along the Mid-Atlantic Ridge and for all sampling dates. For locus Rim 9 and Rim 26 not all alleles are represented numerically underneath the respective graph, however, the allelic distribution is represented in the graphs for all alleles found. Population codes: RBW- Rainbow; LOG- Logatchev.

Figure 2. FCA plot.

Three dimensional plot (presented from three different angles) of the factorial correspondence analysis for all sampled sites along the Mid-Atlantic Ridge and all sampling dates. Based on 11 microsatellite loci.

Figure 3. Bayesian skyline plot.

Graph depicting changes in effective population size over time based on mitochondrial COI sequence data of Rimicaris exoculata, and based on a mutation rate of 0.7% (this mutation rate may be overestimated for a deep-sea vent species when compared to coastal ones). On the y-axis N _e represents effective population size and T is generation time; on the x-axis time is represented in thousands of years (Kyr). The thick black line represents the median and the blue lines the 95% highest posterior density of the N _eT estimates.