Effects of microhabitat on population performance and genetic diversity in Primula elatior

Abstract

Understanding what influences population performance is essential for effective conservation of species and populations. Plant populations are increasingly threatened by declining habitat quality, typically defined as a shift away from the species' environmental optimum. Common examples include soil eutrophication and acidification, which can impair plant performance. Another important but often overlooked aspect of habitat quality is microhabitat heterogeneity. Heterogeneous habitats may support both short-term and long-term resilience of populations, for example by offering wetter or cooler conditions that are beneficial during dry and warm periods and supporting genetic diversity by facilitating natural selection. However, the importance of microhabitat heterogeneity for specific effects on variation within a species (intraspecific variation) remains poorly understood. In this study, we investigated the effect of habitat quality on population performance in the perennial herb Primula elatior . We studied 33 populations located in forest and grassland habitats in the Netherlands, measuring microhabitat parameters (e.g., soil nutrient concentrations, pH, organic matter, bryophyte and litter cover) alongside plant performance (e.g., adult densities, flowering, seedling presence) and population genetic diversity using genotyping by sequencing. Forest and grassland habitats showed substantial overlap in microhabitat conditions and plant performance. Adult density and the proportion of young individuals declined with increasing soil phosphate concentration. A thicker litter layer negatively affected seedling presence, while higher bryophyte cover was linked to greater seedling presence and higher adult and flower density. Importantly, populations in more heterogeneous habitats showed greater genetic diversity, emphasizing the importance of microhabitat heterogeneity in maintaining genetic diversity within populations.