Influência dos fatores ambientais nos padrões de diversidade evolutiva de Myrtaceae

Abstract

The Atlantic Forest domain is considered an ecological hotspot because of its high number of endemic species and increasing degree of threat. Its high biodiversity is not homogeneously distributed in the domain, which presents high environmental heterogeneity, sheltering ancient forests and newly formed forests. To understand the distribution and analyze the patterns of diversity in this domain it is necessary to combine historical and ecological biogeography. In this sense, we used as a model group the Myrtaceae plant family, which stands out as the most diverse woody plant family in the domain. Our goal was to analyze how environmental factors influence patterns of evolutionary diversity in Myrtaceae. Specifically, we tested whether warmer and wetter areas favor speciation and whether more climatically stable areas will have accumulated more species due to lower extinction rates. We used four indices of evolutionary diversity: the phylogenetic species variability index (PSV), relative phylogenetic diversity (rPD), phylogenetic endemism (PE), and mean root distance between species (MRD) for each community studied. Each community studied here consists of floristic records available in the literature and compiled by the authors of the Caaporan and NeotropTree databases, 1282 plant communities were analyzed in the domain that altogether harbor 39,044 records and 492 species of Myrtaceae. Based on 31 environmental variables, 19 bioclimatic (WorldClim), 11 soil (Soil Grids) and 1 referring to climate stability, we investigated which factors influenced the evolution of the group. After selecting the variables through statistical criteria, we used 9 of them to build the regression models, namely precipitation in the wettest month and the coldest quarter, mean diurnal thermal interval, isothermality and maximum temperature in the warmest month, volume fraction of coarse fragments (> 2 mm), clay and silt, and climatic stability. The predictor maximum temperature in the warmest month was significant for all indices. The selected variables explained MRD (R²: 0.508) and PSV (R²: 0.429), whereas PE (R²: 0.364) and rPD (R²: 0.249) showed the lowest fit. Lineages that derived more species and more recently (MRD) and species that are more closely related to each other (PSV) occurr in regions with high rainfall in the wet season and warmer areas. Communities with lower phylogenetic endemism (PE) occurs in warmer areas with high monthly temperature variation, sites with higher PE have large volume fraction of coarse fragments (> 2 mm) and silt. The amount of energy/heat and precipitation are factors that increase primary productivity and can accelerate and increase rates of species evolution. Higher temperatures increase energy availability, enabling population increase and generating lower extinction rates. By analyzing the influence of environmental predictors in the evolutionary metrics of Myrtaceae in the Atlantic Forest, we can better understand how the evolution of the flora in this domain occurred.