Testing the consistency of connectivity patterns for a widely dispersing marine species

Abstract

Connectivity is widely recognized as an important component in developing effective management and conservation strategies. Although managers are generally most interested in demographic, rather than genetic connectivity, new analytic approaches are able to provide estimates of both demographic and genetic connectivity measures from genetic data. Combining such genetic data with mathematical models represents a powerful approach for accurately determining patterns of population connectivity. Here, we use microsatellite markers to investigate the genetic population structure of the New Zealand Rock Lobster, Jasus edwardsii, which has one of the longest known larval durations of all marine species (42 years), a very large geographic range (45500 km), and has been the subject of extensive dispersal modeling. Despite earlier mitochondrial DNA studies finding homogeneous genetic structure, the mathematical model suggests that there are source-sink dynamics for this species. We found evidence of genetic structure in J. edwardsii populations with three distinct genetic groups across New Zealand and a further Australian group; these groups and patterns of gene flow were generally congruent with the earlier mathematical model. Of particular interest was the consistent identification of a self-recruiting population/region from both modeling and genetic approaches. Although there is the potential for selection and harvesting to influence the patterns we observed, we believe oceanographic processes are most likely responsible for the genetic structure observed in J. edwardsii. Our results, using a species at the extreme end of the dispersal spectrum, demonstrate that source-sink population dynamics may still exist for such species.

Linking basin‐scale connectivity, oceanography and population dynamics for the conservation and management of marine ecosystems

“…As shown by Thomas & Bell (), the persistent larval sources/sinks that we identified have the potential to impact upon the genetic connectivity of local subpopulations. For instance, the genetic homogeneity found among the sea bream ( Diplodus sargus ) populations of the Italian, French and Spanish coasts (Lenfant & Planes, ) could be related to the efficient gene flows occurring among those source areas.…”

“…Our results, and more generally the tunable modelling framework proposed here, should allow (1) formal testing of the effects of specific oceanographic processes on population genetics by integrating the most relevant biological traits for a group of species into this general framework, and (2) targeting of sub-regions with dissimilar connectivity behaviours as predicted here, whose effects on connectivity in relation to species distributions and life-history traits could be evaluated. As shown by Thomas & Bell (2013), the persistent larval sources/sinks that we identified have the potential to impact upon the genetic connectivity of local subpopulations. For instance, the genetic homogeneity found among the sea bream (Diplodus sargus) populations of the Italian, French and Spanish coasts (Lenfant & Planes, 1996) could be related to the efficient gene flows occurring among those source areas.…”

Isolation by resistance across a complex coral reef seascape

“…Currents have been well documented to be a major force influencing gene flow in the marine environment [20,24,30,80,81]. Variable ocean currents and bathymetric complexities can work synergistically to produce fine-scale source-sink dynamics that isolate local populations and produce high levels of genetic divergence, particularly across island archipelagos that are made up of a mosaic of reefs [37].…”

Outlier SNPs detect weak regional structure against a background of genetic homogeneity in the Eastern Rock Lobster, Sagmariasus verreauxi

“…While S. verreauxi are yet to be assessed with high resolution genetic markers, SNPs recently confirmed a trans-Tasman genetic break in the co-distributed, closely related, commercially important Southern Rock Lobster, Jasus edwardsii (Villacorta-Rath et al 2016). Oceanographic models indicate that trans-Tasman gene flow for both species of lobster is possible due to their long PLDs (Chiswell et al 2003); microsatellite studies have indicated that for J. edwardsii, trans-Tasman gene flow occurs at levels low enough to maintain genetic structure (Thomas and Bell 2013). As S. verreauxi and J. edwardsii have many similar life-history characteristics, such as long pelagic larval durations, high fecundity and restricted breeding times (Table 1), we could expect the subdivision detected for J. edwardsii to be mirrored in S. verreauxi populations.…”