Disentangling the Environmental Factors That Shape Genetic and Phenotypic Leaf Trait Variation in the Tree Qualea grandiflora Across the Brazilian Savanna

Abstract

Identifying the environmental factors that shape intraspecific genetic and phenotypic diversity of species can provide insights into the processes that generate and maintain divergence in highly diverse biomes such as the savannas of the Neotropics. Here, we sampled Qualea grandiflora, the most widely distributed tree species in the Cerrado, a large Neotropical savanna. We analyzed genetic variation with microsatellite markers in 23 populations (418 individuals) and phenotypic variation of 10 metamer traits (internode, petiole and corresponding leaf lamina) in 36 populations (744 individuals). To evaluate the role of geography, soil, climate, and wind speed in shaping the divergence of genetic and phenotypic traits among populations, we used Generalized Dissimilarity Modelling. We also used multiple regressions to further investigate the contributions of those environmental factors on leaf trait diversity. We found high genetic diversity, which was geographically structured. Geographic distance was the main factor shaping genetic divergence in Qualea grandiflora, reflecting isolation by distance. Genetic structure was more related to past climatic changes than to the current climate. We also found high metamer trait variation, which seemed largely influenced by precipitation, soil bulk density and wind speed during the period of metamer development. The high degree of metamer trait variation seems to be due to both, phenotypic plasticity and local adaptation to different environmental conditions, and may explain the success of the species in occupying all the Cerrado biome.

Genetic and functional leaf trait diversity throughout the distribution of two Cerrado tree species: Testing the centre‐periphery hypothesis

“…However, we did not detect a decrease of genetic diversity from the historical centre for both species. Nevertheless, phylogeographical and genetic studies in Q. grandiflora and A. crassiflora indicated that genetic diversity and structure were shaped by Quaternary climatic changes in both species (Buzatti et al, 2018(Buzatti et al, , 2019Ribeiro, Souza, et al, (2016). This apparent contradiction between results obtained here and phylogeographical studies indicating effects of past events on genetic diversity, and structure of these species, can be explained by several factors.…”

“…org/10.5061/dryad.n7dv6. For complete information about DNA extraction and amplification, and genotyping methods, please refer Buzatti et al, (2019) and Ribeiro, Souza, et al, (2016).…”

“…To test for genetic patterns across species' range, we used two distinct diversity indexes estimated by Buzatti et al, (2019) and Ribeiro, Souza, et al, (2016): expected heterozygosity (H E ) and allele richness (A R ) estimated using a rarefaction method to correct for disparities among sample sizes. These indexes were estimated in ARLEQUIN version 3.5.1.2 (Excoffier & Lischer, 2010).…”

“…located within the large central stable areas and small peripheral ones, compared to the ones located outside these refugia. Another probable explanation is the presence of a strong genetic structure shaped by Quaternary climatic fluctuations in both species, with the formation of several genetic groups along the species distribution (Buzatti et al, 2018(Buzatti et al, , 2019Ribeiro, Souza, et al, 2016), shuffling centre-marginal signs.…”

“…Studies investigating the Cerrado flora have found relationships between diversity and distribution of species and environmental conditions (as climate and soil) (Assis et al, 2011;Bueno et al, 2018;Ratter et al, 2003). Environmental drivers of the geographical distribution of intraspecific functional traits and genetic neutral markers diversity in Cerrado have also been studied in some species (Buzatti et al, 2019;Ribeiro, Souza et al 2016;Souza et al, 2019). In addition, phylogeographical studies have shown that Quaternary climatic changes have influenced the genetic diversity and structure of Cerrado plant species, with higher genetic diversity in climatically stable areas, known as refugia (Buzatti et al, 2017(Buzatti et al, , 2018Collevatti et al, 2013Collevatti et al, , 2014Ribeiro, Lemos-Filho, Buzatti, Lovato & Heuertz, 2016;Souza et al, 2017).…”