Abordagem eco-evolutiva para entender a influência das mudanças do clima e da paisagem em lagartos de formações abertas amazônicas

Abstract

Environmental change has affected the ecological and evolutionary patterns of several species throughout history. Climatic fluctuations during dynamic geological periods such as the Pleistocene (~2.6 Ma) shaped species distributions, diversity, and their demographic histories in neotropical forests, for example. In the current scenario, the consequences of the anthropic intensification of climate and landscape change on biodiversity are already observed. The main responses from biodiversity indicate range shifts to track favorable climates and occupation of new habitats, altering entire ecosystems. Genetic variation suggesting possible adaptations to local environmental conditions are also expected, however adaptive processes are slower than the current environmental changes, increasing extinction risks. Particularly for reptiles, climatic conditions directly affect the organism’s physiology, foraging, reproductive success, and, consequently, their survival. Such risks can be even more alarming in areas more susceptible to climate fluctuations, with high fragmentation and threat from land use, such as the Amazonian open ecosystems. Environments with such specific characteristics as open habitats may harbor species that are not found in adjacent forests, as the lizards from the Cnemidophorus lemniscatus species group, which includes three Amazonian species: two bisexual, C. lemniscatus and C. gramivagus, and one parthenogenetic, C. cryptus. However, they are cryptic species and their evolutionary histories are not well known. In this context, in my thesis I investigated the impacts of climate and landscape variation at different time scales on the ecology, distribution, and diversification of the C. lemniscatus group. First, based on systematics and molecular biogeography, I delimited the main lineages, estimated divergence times, and investigated the association between demographic history and the emergence of Amazonian open areas. I also investigated the association between lineage’s thermal traits linked with sensitivity or resilience to environmental changes and the environment. I recovered six lineages, three of them corresponding to the recognized species, and three others yet unnamed. I found that Pleistocene climate change affected the demographic history of the group in the same way that influenced the establishment of open Amazonian areas. I identified conservatism of thermal traits between lineages, which possibly facilitates niche tracking and population establishment in open ecosystems as they became available. From the phylogenetic relationships recovered in the first chapter, in the second chapter I investigated the association between genomic variation and climatic and landscape features, in addition to looking for genomic regions that indicated possible selection and local environmental adaptation. I identified association between neutral and adaptive genetic composition and vegetation in at least one species (C. lemniscatus). For the other two species, geographic distances between sites explained better the genetic variation, suggesting that the environment is not as important in structuring populations. Finally, in the third chapter, through hybrid species distribution modeling, I estimated habitat suitability and local extinction risks induced by global climate change, by incorporating physiological information into species occurrence data. Unlike what expected based on the conservatism of thermal tolerances found in the first chapter, I estimated different responses between lineages, with an increase in the suitable areas for C. lemniscatus occurrence, but a decrease for C. cryptus under moderate and severe carbon emission scenarios for 2060 and 2100. I conclude that environmental fluctuations affect the ecology and evolution of the C. lemniscatus group at all time scales and that even closely related taxonomic groups can be affected differently by environmental changes. The innovative eco-evolutionary approach of this thesis brings important results to foster priority actions for the conservation of natural open ecosystems in Amazonia and their associated biodiversity.