Fragmentation and comparative genetic structure of four mediterranean woody species: complex interactions between life history traits and the landscape context

Aim The effect of habitat fragmentation on population genetic structure results from the interaction between species’ life history traits and the particular landscape context, and both components are inherently difficult to tease apart. Here, we compare the genetic (allozyme) structure of four co-occurring woody species with contrasting life histories to explore how well their response to the same fragmentation process can be predicted from their functional traits. Location A highly fragmented forest landscape located in the lower Guadalquivir catchment, south-western Spain. Methods We sampled four species (Cistus salviifolius, Myrtus communis, Pistacia lentiscus and Quercus coccifera) from the same 23 forest fragments known to form a representative array of habitat characteristics in the region. We assessed genetic diversity (A, He and Ng) and differentiation (FIS and FST) for each species and explored their potential drivers using a model-selection approach with four fragment features (size, historical and current connectivity, and stability) as predictor variables. Results Regional-scale genetic diversity increased from the shortest-lived to the longest-lived species, while population differentiation of the self-compatible species was roughly double that of the three self-incompatible species. Fragment size was the only feature that did not consistently affect the genetic diversity of local populations across all species. Three species showed signs of being affected by fragmentation, yet each responded differently to the set of fragment features considered. We observed several trends that were at odds with simple life history- based predictions but could arise from patterns of gene flow and/or local-scale demographic processes. Main conclusions Our comparative study of various landscape features and species underscores that the same fragmentation process can have very different, and complex, consequences for the population genetic structure of plants. This idiosyncrasy renders generalizations across natural systems very difficult and highlights the need of context-oriented guidelines for an efficient conservation management of species-rich landscapesPeer reviewe