Neotropical Cats: The Margay & the Ocelot

7 of the 10 wild cat species found in the Neotropical Region belong to the monophyletic ocelot lineage, radiating most likely from a common ancestor during the formation of the Panamanian isthmus 3-5 million years ago (Eizirik et.al. 1998). The sister species Leopardus pardalis and L. wiedii, or the ocelot and the margay, evolved from the ocelot lineage that migrated into Central and South America via the newly formed Panamanian land bridge. After colonising the South American tropics, the ocelot and the margay have become sympatric species, also occurring in southern USA and northern Argentina (see figure 1.). An investigation by Eizirik et.al. (1998) studied the patterns of population genetic divergence in the margay and the ocelot by conducting phylogenetic analyses of mitochondrial DNA (mtDNA) control region sequences in individuals sampled across the Americas.


Figure 1. Map showing the distribution of ocelots and margays. The shaded areas represent current distribution, the plotted points represent collection areas and the solid lines encompass major phylogenetic groups for each species (Eizirik et.al. 1998).



It was discovered that the two lineages diverged approximately 3 million years ago, and that ocelots and margays possess some of the highest levels of mtDNA control region diversity known to modern science (Eizirik et.al. 1998). Thus, the two species either have very fast substitution rates in the selected mtDNA segment or they both have very long evolutionary histories with no major population bottlenecks in the recent past. The latter proposal is the most likely cause (Eizirik et.al. 1998). Between the two species the margays possessed higher levels of control region diversity, at both species and population levels, this may suggest that the evolutionary rate of the hypervariable mtDNA segment analysed is faster in margays than in ocelots, due to different molecular and demographic processes. Alternatively, the rate of sequence evolution is similar between the two, but the margay lineage may be older (Eizirik et.al. 1998). 

It was also found that margays and ocelots have similar phylogeographic patterns with a clear division present between Central and South American lineages (see figure 1.). The genetic divergence observed between the northern most populations and the populations found south of the Amazon River furthermore suggests that the Amazon River is a significant geographic barrier that has isolated the populations in the past and continues to isolate the populations by restricting gene flow (Eizirik et.al. 1998). Therefore, the phylogeographic patterns and mtDNA evolution of the two Leopardus species indicate that speciation is a likely possibility.

References:
  • Eizirik E, Bonatto SL, Johnson WE, Crawshaw PG, Vié JC, Brousset DM, O'Brien SJ & Salzano FM 1998, 'Phylogeographic Patterns and Evolution of the Mitochondrial DNA Control Region in Two Neotropical Cats (Mammalia, Felidae)', Journal of Molecular Evolution, vol. 47, pp. 613-624.

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