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Inter-species hybridization among Neotropical cats of the genus Leopardus, and evidence for an introgressive hybrid zone between L. geoffroyi and L. tigrinus in southern Brazil - PubMed

Inter-species hybridization among Neotropical cats of the genus Leopardus, and evidence for an introgressive hybrid zone between L. geoffroyi and L. tigrinus in southern Brazil

T C Trigo et al. Mol Ecol. 2008 Oct.

Abstract

Natural hybrid zones between distinct species have been reported for many taxa, but so far, few examples involve carnivores or Neotropical mammals in general. In this study, we employed mitochondrial DNA (mtDNA) sequences and nine microsatellite loci to identify and characterize a hybrid zone between two Neotropical felids, Leopardus geoffroyi and L. tigrinus, both of which are well-established species having diverged from each other c. 1 million years ago. These two felids are mostly allopatric throughout their ranges in South America, with a narrow contact zone that includes southern Brazil. We present strong evidence for the occurrence of hybridization between these species and identify at least 14 individuals (most of them originating from the geographical contact zone) exhibiting signs of interspecific genomic introgression. The genetic structure of Brazilian L. tigrinus populations seems to be affected by this introgression process, showing a gradient of differentiation from L. geoffroyi correlated with distance from the contact zone. We also corroborate and extend previous findings of hybridization between L. tigrinus and a third related felid, L. colocolo, leading to an unusual situation for a mammal, in which the former species contains introgressed mtDNA lineages from two distinct taxa in addition to its own.

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Figures

Fig. 1
Fig. 1

(A) Geographical distribution of Leopardus tigrinus (grey-shaded area), L. geoffroyi (area defined by the grey broken Line) and L. colocolo (area defined by the black dotted line) in South America (modified from Oliveira 1994; Nowell & Jackson 1996; Eisenberg & Redford 1999). (B) Map of the study area showing approximate sample collection sites for L. tigrinus (grey circles), L. geoffroyi (black circles) and L. colocolo (white circles). Each symbol represents one sampling locale and may include one or more individuals (only individuals with known collection locales are included). The Central American sample of L. tigrinus (Lti13) and the samples from other felid species (L. guigna, L. pardalis, L. wiedii) are not shown in the figure. White triangles indicate the sampling sites of hybrids between L. tigrinus and L. geoffroyi, while black triangles indicate collection locales for hybrids between L. tigrinus and L. colocolo. Abbreviations of Brazilian states: RS (Rio Grande do Sul), SC (Santa Catarina), Paraná (PR), MS (Mato Grosso do Sul), SP (Sao Paulo), RJ (Rio de Janeiro), ES (Espírito Santo), GO (Goiás).

Fig. 2
Fig. 2

Maximum likelihood (ML) phylogeny of mitochondrial DNA haplotypes (concatenated control region, ND5 and ATP8 segments, totaling 1024 bp) sampled in multiple individuals of Leopardus tigrinus (bLti), L. geoffroyi (bLge), L. colocolo (Lco), L. guigna (bLgu), L. wiedii (Lwi) and L. pardalis (Lpa) (see Supplementary material for details on sample ID and collection data). Individuals shown in bold italic fonts are inferred to be interspecific hybrids carrying an introgressed mtDNA haplotype from a different species. Values above or below branches indicate support for the subsequent node based on ML/MP/NJ/BI (Bayesian posterior probabilities are indicated as percentages); support is depicted only for nodes defining major clades relevant for our analyses.

Fig. 3
Fig. 3

Median-joining network of mtDNA haplotypes sampled in Leopardus tigrinus (grey) and L. geoffroyi (black) individuals. Only control region (CR) and ND5 sequences were used in this analysis (totaling 795 bp), and all sites containing missing information or gaps were excluded. The area of each circle is roughly proportional to the haplotype frequency. Haplotypes shared between the two species are represented by circles with mixed colours, in which the relative frequency is indicated by the proportion of black and grey. Bars placed on connecting lines indicate the exact number of nucleotide differences between haplotypes. The branch connecting the two main clades contains 48 nucleotide differences and a synapomorphic deletion of 13 nucleotides in the CR defining the L. geoffroyi clade.

Fig. 4
Fig. 4

Graph depicting the results of the Bayesian admixture analysis focusing on the hybridization between Leopardus geoffroyi and L. tigrinus (performed with STRUCTURE, with K = 2, employing the correlated frequencies model and no use of prior population information, i.e. only the genetic data were used to infer population assignment). All L. colocolo individuals and the five identified hybrids with that species were excluded from this data set. Diamonds represent the mean q1 value for each individual (averaged over five independent runs). Vertical lines represent a conservative estimate of the credibility interval (CI) for each individual, i.e. the range between the lower and upper bounds of the CIs observed across the five runs. Thicker black lines correspond to individuals morphologically identified as L. geoffroyi, while thinner gray lines indicate individuals identified as L. tigrinus. Individuals are sorted according to their mean q1 value (see Supplementary material for a complete list of q-values and their CIs for all individuals).

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