Abstract
Effective predictive and management approaches for species occurring in a metapopulation structure require good understanding of interpopulation connectivity. In this study, we ask whether population genetic structure of marine species with fragmented distributions can be predicted by stepping-stone oceanographic transport and habitat continuity, using as model an ecosystem-structuring brown alga, Cystoseira amentacea var. stricta. To answer this question, we analysed the genetic structure and estimated the connectivity of populations along discontinuous rocky habitat patches in southern Italy, using microsatellite markers at multiple scales. In addition, we modelled the effect of rocky habitat continuity and ocean circulation on gene flow by simulating Lagrangian particle dispersal based on ocean surface currents allowing multigenerational stepping-stone dynamics. Populations were highly differentiated, at scales from few metres up to thousands of kilometres. The best possible model fit to explain the genetic results combined current direction, rocky habitat extension and distance along the coast among rocky sites. We conclude that a combination of variable suitable habitat and oceanographic transport is a useful predictor of genetic structure. This relationship provides insight into the mechanisms of dispersal and the role of life-history traits. Our results highlight the importance of spatially explicit modelling of stepping-stone dynamics and oceanographic directional transport coupled with habitat suitability, to better describe and predict marine population structure and differentiation. This study also suggests the appropriate spatial scales for the conservation, restoration and management of species that are increasingly affected by habitat modifications.
Highlights
The application of landscape genetics in the marine environment, known as ‘seascape genetics’, focuses mainly on the comparison of expected dispersal with observedThis study addresses two challenges in seascape genetics research, asymmetrical dispersal and multigeneration dispersal effects linking sites by steppingstone movements
Population connectivity is increasingly affected by a variety of human modifications to the environment (Jones 2007), leading to habitat fragmentation and loss and genetic disjunction even at small spatial scales (Fraser et al 2010; Alberto et al 2011) or alternatively introducing novel artificial urban habitats that can act as a conduit for some species across the seascape (Airoldi et al 2015)
The effects of these processes should be considered in coastal management and restoration (McKay et al 2005). This goal can be achieved by modelling the stepping-stone dynamics of species among fragmented patches of suitable habitats
Summary
The application of landscape genetics in the marine environment, known as ‘seascape genetics’, focuses mainly on the comparison of expected dispersal with observedThis study addresses two challenges in seascape genetics research, asymmetrical dispersal and multigeneration dispersal effects linking sites by steppingstone movements. Population connectivity is increasingly affected by a variety of human modifications to the environment (Jones 2007), leading to habitat fragmentation and loss and genetic disjunction even at small spatial scales (Fraser et al 2010; Alberto et al 2011) or alternatively introducing novel artificial urban habitats that can act as a conduit for some species across the seascape (Airoldi et al 2015) Any of these effects would be relevant for species with low dispersal ability, affecting their capability to recover from disturbances, colonize new habitats or migrate, as response to future climate changes (Opdam & Wascher 2004; Thrush et al 2013). Potential limitations to dispersal in a marine metapopulation system can be caused by the species’ dispersal biology, oceanographic transport and the spatial distribution of suitable habitat These can in turn affect population genetic diversity and connectivity. This goal can be achieved by modelling the stepping-stone dynamics of species among fragmented patches of suitable habitats
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