Matching oceanography and genetics at the basin scale. Seascape connectivity of the Mediterranean shore crab in the Adriatic Sea

Abstract

Investigating the interactions between the physical environment and early life history is crucial to understand the mechanisms that shape the genetic structure of marine populations. Here, we assessed the genetic differentiation in a species with larval dispersal, the Mediterranean shore crab (Carcinus aestuarii) in the Adriatic Sea (central Mediterranean), and we investigated the role of oceanic circulation in shaping population structure. To this end, we screened 11 polymorphic microsatellite loci from 431 individuals collected at eight different sites. We found a weak, yet significant, genetic structure into three major clusters: a northern Adriatic group, a central Adriatic group and one group including samples from southern Adriatic and Ionian seas. Genetic analyses were compared, under a seascape genetics approach, with estimates of potential larval connectivity obtained with a coupled physical-biological model that integrates a water circulation model and a description of biological traits affecting dispersal. The cross-validation of the results of the two approaches supported the view that genetic differentiation reflects an oceanographic subdivision of the Adriatic Sea into three subbasins, with circulation patterns allowing the exchange of larvae through permanent connections linking north Adriatic sites and ephemeral connections like those linking the central Adriatic with northern and southern locations.

Population genomics of an endemic Mediterranean fish: differentiation by fine scale dispersal and adaptation

“…These findings agree with the hydrodynamic provinces suggested in the Mediterranean from Lagrangian simulations and network reconstruction identifying different regions in the Adriatic Sea according to different PLDs48. Similarly, Lagrangian simulations assuming larval movement of Carcinus aestuarii support the oceanographic subdivision of the Adriatic Sea into three sub-basins matching currents from north to south49. However, only weak genetic differentiation was observed in C. aestuarii mostly differentiating northern and southern locations along the western coast.…”

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].…”

“…The majority of seascape approaches to date have been applied along essentially linear coastlines or at large spatial scales (more than 250 km) [23][24][25][26][27][28][29][30], with very few applied to complex systems (like island archipelagos) at smaller spatial scales (less than 100 km) [18,20,31]. These smaller spatial scales are generally more relevant to management, so linking gene flow with the physical environment at this spatial scale should be a priority, particularly for habitat-forming species such as reef-building corals, which are in decline globally [32].…”

One species for one island? Unexpected diversity and weak connectivity in a widely distributed tropical hydrozoan

“…Nevertheless, Shanks (2009) observed that the relationship between direct or indirect development, pelagic larval duration, swimming capacity and dispersal capacity is not always straightforward, as a large body of literature exists, detailing examples of lecithotrophs, brooders and direct developers, with biogeographic ranges spanning oceans (Ayre and Hughes, 2000;Kyle and Boulding, 2000;Boissin et al, 2008). Thus, other aspects, for example, larval behaviour and species ecology, must be considered to explain the patterns of marine population connectivity (Shanks, 2009), as well as oceanic circulation and historical sea-level variations (Treml et al, 2007;Ayre et al, 2009;Schiavina et al, 2014). In order to achieve a more comprehensive understanding of the maintenance of natural populations over time, it is necessary to multiply the number of biological models studied.…”