Ecological genomics of local adaptation in altitudinal gradient in Atlantic Forest Mountains

• Grant number: 24/13843-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2024
• End date: August 31, 2026
• Field of knowledge: Biological Sciences - Botany
• Principal Investigator: Clarisse Palma da Silva
• Grantee: Maria Eduarda Visentini
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 21/10639-5 - Center for Research on Biodiversity Dynamics and Climate Change, AP.CEPID

Abstract

Local adaptation has become a crucial research area given the ongoing climate challenge and the necessity to conserve genetic resources. Populations often contain adaptations to local environments. It happens because several environmental and biotic factors yield different selective pressures and the strength of each factor varies across habitats. The geographical distribution of species is related to physiological tolerances along environmental gradients. Temperature, in particular, is the abiotic variable that most affects the performance of organisms along altitudinal gradients. Therefore, organisms located at higher and lower elevations may present higher tolerance to cold and heat, respectively. Such stratification may also result in a limitation of dispersion along the elevation gradient and lead to divergence between populations and, eventually, speciation. Therefore, climatic oscillations responsible for expansions or contractions in species' distribution according to their physiological tolerances can lead populations to isolation in refuges. In this case, physically and ecologically heterogeneous regions, such as tropical mountains, can promote rapid divergence among populations and promote speciation.In this project, we will apply population genomics based on thousands SNPs obtained from Rad-seq approach of Pitcairnia flammea (Bromeliaceae) populations adapted to an elevational gradient (> 2000 meters) in the Serra do Mar and Mantiqueira Mountains in the Brazilian Atlantic Forest. Atlantic rainforest is the second largest wet forest in Neotropics, with impressive high levels of species and endemic species. This biome consists of a range of diverse and complex ecosystems and communities greatly influenced by topography and micro-habitats. Vegetation endemic to low and high-elevation rock outcrops and inselbergs are important part of the Atlantic rainforest domain. Such naturally fragmented habitats are considered terrestrial islands due to their spatial and ecological isolation, which offers a barrier against dispersal and migration, potentially promoting speciation and local adaptation. The wide yet patchy distribution in the Neotropics makes P. flammea a particularly interesting model to investigate how ecological processes affect local adaptation in mountain systems. Our previous studies with this species demonstrate low-to-moderate genetic diversity within populations, and deep population structuring caused by limited gene flow, low connectivity, genetic drift and inbreeding of long-term isolation and persistence of rock outcrop populations. Moreover, the variable responses of demographic changes in the populations were observed all over the species' range, suggesting that the effects might be due to uneven ecological and local adaptation responses in each population. High-elevation rock outcrops may have acted as refugia for xerophilic and/or cold-adapted species during glacial-interglacial periods implying that climatically stable microhabitats could have contributed to the maintenance of these rock-outcrop population (Mota et al 2020). The objectives of this study are: 1) To prepare and sequence RAD libraries for individuals from 8 populations of the Pitcairnia flammea covering species altitudinal range (sea level to >2000 meter high), 2) To use the reducedgenomic data generated with the RAD method to estimate demographic scenarios and to detect selection signatures and footprints of local adaption, 3) To investigate whether high genetic drift linked to low levels of gene flow and high endogamy may preclude local adaptation in this species; 4) To draw conclusions regarding the evolution of P. flammea, describing the processes responsible for diversification of these plants.