Abstract
Plants are one of the most vulnerable groups to fragmentation and habitat loss, that may affect community richness, abundance, functional traits, and genetic diversity. Here, we address the effects of landscape features on adaptive quantitative traits and evolutionary potential, and on neutral genetic diversity in populations of the Neotropical savanna tree Caryocar brasiliense. We sampled adults and juveniles in 10 savanna remnants within five landscapes. To obtain neutral genetic variation, we genotyped all individuals from each site using nine microsatellite loci. For adaptive traits we measured seed size and mass and grown seeds in nursery in completely randomized experimental design. We obtained mean, additive genetic variance (Va) and coefficient of variation (CVa%), which measures evolvability, for 17 traits in seedlings. We found that landscapes with higher compositional heterogeneity (SHDI) had lower evolutionary potential (CVa%) in leaf length (LL) and lower aboveground dry mass (ADM) genetic differentiation (QST). We also found that landscapes with higher SHDI had higher genetic diversity (He) and allelic richness (AR) in adults, and lower genetic differentiation (FST). In juveniles, SHDI was also positively related to AR. These results are most likely due to longer dispersal distance of pollen in landscapes with lower density of flowering individuals. Agricultural landscapes with low quality mosaic may be more stressful for plant species, due to the lower habitat cover (%), higher cover of monocropping (%) and other land covers, and edge effects. However, in landscapes with higher SHDI with high quality mosaic, forest nearby savanna habitat and the other environments may facilitate the movement or provide additional habitat and resources for seed disperses and pollinators, increasing gene flow and genetic diversity. Finally, despite the very recent agriculture expansion in Central Brazil, we found no time lag in response to habitat loss, because both adults and juveniles were affected by landscape changes.
Highlights
Impacts of fragmentation and habitat loss on plant genetic diversity are still poorly understood, despite the increase in the number of studies in recent years (Storfer et al, 2010; Manel and Holderegger, 2013)
The variation in fragmentation and habitat loss effects on genetic diversity may be due to differences in life history because each species respond to landscape changes according to their dispersal capacity and ecological requirements (Prevedello and Vieira, 2010; Eycott et al, 2012)
Plants depend on animals for pollen and seed dispersal, the response to landscape changes will relies on how pollinators and seed disperses perceive environmental modifications (García et al, 2007; Carvalho et al, 2015; Auffret et al, 2017; Uroy et al, 2019), which may hinder the detection of habitat loss and fragmentation effects on plant genetic diversity
Summary
Impacts of fragmentation and habitat loss on plant genetic diversity are still poorly understood, despite the increase in the number of studies in recent years (Storfer et al, 2010; Manel and Holderegger, 2013). Genetic diversity and differentiation in adult trees may be the outcome of past environmental changes and not recent or ongoing changes in landscape (Collevatti et al, 2001; Kramer et al, 2008). Some studies have shown significant effects of fragmentation process, decreasing genetic diversity in seedlings, but not in adult trees (Sebbenn et al, 2011; Quesada et al, 2013; Martins et al, 2016), suggesting a time lag for ongoing habitat fragmentation be detected in adults (e.g., Aguilar et al, 2008). Comparing the effects of landscape changes in genetic diversity of seedlings and adults may give clues on the different roles of ongoing habitat loss and fragmentation and past demographic history
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