Resistance of an Edaphic-Island Specialist to Anthropogenic-Driven Fragmentation

Fragmentation is one of the most important human-induced threats to biodiversity. Linear infrastructures, together with agriculture intensification, alter migration patterns, inducing isolation and/or affecting the connectivity between populations. The combined effect of these drivers has, as far as we know, never been explored. A population genetics approach was proposed to assess the effects of both drivers in an edaphic specialist. We selected a fragmented scenario of gypsum soil habitats, within an agricultural matrix divided by a highway to assess the impact of fragmentation on the genetic structure of the edaphic specialist, Helianthemum squamatum. For each patch, connectivity values, soil composition and plant densities were estimated. Microsatellite markers were used to evaluate the genetic diversity of each fragment, gene flow between patches and global genetic structure. Sampled patches showed similar values for the genetic parameters, suggesting the absence of a defined genetic structure and scarce influence of these two fragmentation drivers on gene flow. No association between ecological characteristics of the fragments and genetic features was found, although population density was correlated with inbreeding coefficient. Species biology and population dynamics are essential factors to understand the effects of fragmentation. Since the studied species is an edaphic specialist, its evolutionary history has taken place in an island-like scenario and, thus, human-driven fragmentation may have only marginal effects on its genetic structure. The results also outline the importance of maintaining a moderate population size within each fragment to avoid the potential genetic pernicious effects.