Comparative Assessment of Genetic and Morphological Variation at an Extensive Hybrid Zone between Two Wild Cats in Southern Brazil

Abstract

Increased attention towards the Neotropical cats Leopardus guttulus and L. geoffroyi was prompted after genetic studies identified the occurrence of extensive hybridization between them at their geographic contact zone in southern Brazil. This is a region where two biomes intersect, each of which is associated with one of the hybridizing species (Atlantic Forest with L. guttulus and Pampas with L. geoffroyi). In this study, we conducted in-depth analyses of multiple molecular markers aiming to characterize the magnitude and spatial structure of this hybrid zone. We also performed a morphological assessment of these species, aiming to test their phenotypic differentiation at the contact zone, as well as the correlation between morphological features and the admixture status of the individuals. We found strong evidence for extensive and complex hybridization, with at least 40% of the individuals sampled in Rio Grande do Sul state (southernmost Brazil) identified as hybrids resulting from post-F1 generations. Despite such a high level of hybridization, samples collected in this state still comprised two recognizable clusters (genetically and morphologically). Genetically pure individuals were sampled mainly in regions farther from the contact zone, while hybrids concentrated in a central region (exactly at the interface between the two biomes). The morphological data set also revealed a strong spatial structure, which was correlated with the molecular results but displayed an even more marked separation between the clusters. Hybrids often did not present intermediate body sizes and could not be clearly distinguished morphologically from the parental forms. This observation suggests that some selective pressure may be acting on the hybrids, limiting their dispersal away from the hybrid zone and perhaps favoring genomic combinations that maintain adaptive phenotypic features of one or the other parental species.

Hybridization and genetic introgression patterns between two South American catfish along their sympatric distribution range

“…This outcome demonstrates the high genetic divergence between parental species and highlights the value of tested markers in analyzing hybridization between P. corruscans and P. reticulatum. This threshold is in accordance with previous studies using the same program to distinguish between species and hybrids (Sanz et al, 2009;Aboim et al, 2010;Trigo et al, 2014).…”

“…Final classification of individuals was performed using Bayesian analyses considering the most efficient set of markers and the appropriate q range and Q threshold for STRUCTURE and NEWHYBRIDS obtained from simulated data, respectively (see results), and by considering previous works on the field (Sanz et al, 2009;Trigo et al, 2014). The maternal species origin for each individual obtained using the mitochondrial SNP marker was finally added to the nuclear data to identify the maternal origin of F1 or further hybridization events.…”

Phylogenomic evidence for ancient hybridization in the genomes of living cats (Felidae)

“…Recent genetic analyses demonstrated complex speciation/hybridization affecting at least four species within this group: two tigrina species, one from northeastern Brazil (Leopardus tigrinus) that possesses pampas cat (L. colocolo) mitochondria within a tigrina-like nuclear background, and a recently proposed sister species from southeastern Brazil (L. guttulus, not sampled here) which hybridizes with the Geoffroy's cat (L. geoffroyi) in a narrow hybrid zone in southern Brazil (Trigo et al 2008(Trigo et al , 2013(Trigo et al , 2014. As predicted, the northeastern tigrina we genotyped possessed pampas cat mtDNA within a tigrina nuclear DNA background (Supplemental Fig.…”

Refined assessment of the geographic distribution of Geoffroy's cat (Leopardus geoffroyi) (Mammalia: Felidae) in the Neotropics

“…Nevertheless, on a local scale, new surveys seem to slightly expanded northward the distribution limit of this species in Rio Grande do Sul state. But also in this case, this pattern might be attributed to the occurrence of hybridization events between Leopardus geoffroyi and L. guttulus that could be hampering the accurate identification of pure individuals and leading to a misperception of a geographic expansion (Trigo et al ., ). In this case, additional studies focusing on the geographic and ecological patterns of pure and hybrid specimens distribution are still needed to specifically characterize the exact limits of this species occurrence in southern Brazil.…”