Population density influences genetic connectivity in the Canary Islands endemics Viola cheiranthifolia and Viola guaxarensis

Abstract

Background and Aims

Island-endemic plants with narrow geographic ranges are highly vulnerable to invasive herbivores and climate change, which can reduce reproductive success and shift their distributions. To understand how these pressures shape population connectivity, we studied two endemic violets (Viola cheiranthifolia and V. guaxarensis) from El Teide, Canary Islands. Methods

We examined genetic diversity and related it to climatic and topographic variables using linear models. To assess how landscape features affect gene flow, we applied gravity models at the population level in V. cheiranthifolia (163 individuals) and in 48 V. guaxarensis individuals (one population). Key Results

We found no significant correlation between genetic diversity and environmental variables in V. cheiranthifolia. While greater herbivore densities did not appear to decrease connectivity, larger violet populations, including those protected from herbivory, showed greater connectivity. Geographic distance limited genetic exchange in V. cheiranthifolia, whereas diurnal temperature changes, precipitation, and slope were key factors explaining connectivity in V. guaxarensis. Future projections indicated minimal changes in gene flow patterns for both species. Conclusions

Conservation measures that increase population density enhance genetic connectivity in these endangered endemic violets. Furthermore, understanding how specific landscape variables shape connectivity can directly inform restoration efforts in targeted areas. By identifying key connectivity hubs and zones most in need of intervention, our research offers practical strategies for enhancing the resilience of this unique island flora.