Genômica evolutiva do gênero Leopardus (Mammalia, felidae) com ênfase no processo de hibridação entre L. Guttulus e L. Geoffroyi

Abstract

Leopardus is a genus of small Neotropical felids showing rapid and recent diversification in eight currently recognized species. In addition, it comprises cases of both ancient and recent hybridization involving different species pairs, which compound with other factor to create challenges for its complete taxonomic resolution. One of the main questions pertains to the tigrina complex, currently composed by L. tigrinus and L. guttulus. These two cryptic species have only recently been identified as independent species, and likely will be further split based on current morphological, molecular, and niche modeling analyses. Hybridization with other Leopardus species is also present in the complex: L. tigrinus with L. colocola, and L. guttulus with L. geoffroyi. The former is an example of an ancient admixture episode, with complete introgression of the L. colocola mitochondrial genome into L. tigrinus, with so far unobserved nuclear vestiges of such process. On the other hand, the second pair presents a current and active hybrid zone at the center of Rio Grande do Sul/Brazil state, which is still poorly known with respect to its geographic extension, causes and consequences for the parental populations. In this thesis, genomic data was employed to better understand the taxonomic relationships within Leopardus, focusing on the tigrina complex species and its hybridization processes – especially on the L. guttulus vs. L. geoffroyi hybrid zone. Based on phylogenetic and demographic inferences using genomic markers, it was verified that the tigrina complex is paraphyletic. The data support the split of L. tigrinus into at least two species that diverged 2.45 million years ago, one including the northeastern Brazilian population and the other one including the Central American population. Additionally, no genomic signatures of hybridization between L. tigrinus and L. colocola were observed. On the other hand, aiming to deeply characterize the hybrid zone between L. guttulus and L. geoffroyi, complete genomes at low depth of 306 individuals, sampled in a transect including both parental populations and their hybrids, were used. This process was shown to be asymmetric and bidirectional, spanning ca. 300 km, with hybrids occurring mainly south of the contact zone, predominance of L. geoffroyi ancestry, and contribution of both males and females from both parental species. Moreover, the results showed that both species present low differentiation, with spikes of higher differentiation in different genomic regions, one of which contains a gene associated with coat pattern – an important characteristic that distinguishes these species. Such overall differentiation was especially low for the L. guttulus population closer to the hybrid zone, suggesting an impact of this process on apparently non-admixed populations. Further, the time since admixture is very recent, happening for no longer than 200 years at the contact zone in Rio Grande do Sul state. This result support a role of human disturbances in the Atlantic Forest and Pampas biomes, such as habitat fragmentation and modification, as potential causes, or at least intensifiers, of such process. This is particularly relevant within the Pampas, where a study showed higher suitability of hybrids in altered regions compared to the parentals. Knowing that hybridization can present strong consequences in species evolution, that both species from tigrina complex are considered to be Vulnerable by the IUCN, and that knowledge on genetic structure and taxonomic delimitation are essential to better guide risk assessment and management actions, the results presented here have the potential to enable improved conservations strategies on behalf of these felids.