Tzuultaq’a: defensa territorial y diferencia radical entre los mayas q’eqchi’

Abstract

Effective programs for conserving biodiversity require the integration of both ecological and molecular data. Maintenance of genetic diversity and the identification of management units that reflect specific evolutionarily lineages are primary objectives in management of threatened species. Consequently the Crocodile Specialist Group of the IUCN has emphasized the need for information on population status and population genetic studies of threatened crocodilian species. The goals of this research were to explore the use of mitochondrial DNA sequences as molecular markers to infer genetic diversity, population genetic structure and gene flow of the American crocodile (Crocodylus acutus) and Morelets crocodile (C. moreletii) in southeastern Mexico, with emphasis in the Yucatan Peninsula populations, as well as interspecific hybridization between these species along the sympatric area in the Mexican Caribbean. Both species are listed on the IUCN Red List and in Appendix I of CITES. Analysis of 477 base pairs of the mitochondrial tRNAPro-tRNAPhe-Dloop region from 116 individuals (52 C. acutus; 64 C. moreletii) revealed the presence of pure Crocodylus acutus (n = 43) and C. moreletii (n = 56), as well as a high proportion of interspecific hybrids (n = 17, 14.6%). Although all individuals could be assigned to one species or other based on phenotypic characters, 18 crocodiles had been characterized as potential hybrids in the field by anomalous scale counts. After removing hybrid crocodiles, population statistics were calculated for the remaining individuals. Only three haplotypes were present in C. acutus, and four in C. moreletii. Haplotypic diversity (h) was higher in C. acutus (0.6722 0.0229 SD) than in C. moreletii (0.3617 0.0728 SD). Low nucleotide diversity was found in both species (π = 0.0017 in C. acutus; π = 0.0020 in C. moreletii), few polymorphic sites (two in C. acutus; four in C. moreletii), and low levels of nucleotide substitution. AMOVA tests resulted in a major partitioning between sampling localities of C. moreletii (ФST = 0.86273, P < 0.05) than those of C. acutus (ФST = 0.32246, P < 0.05), but populations of the later are more diverse internally. Overall our findings of pairwise comparisons of FST values suggest some population subdivision and moderate to high migration rates among populations of both species, which are consistent with the isolation by distance model of gene flow. Hybridization between Crocodylus acutus and C. moreletii is bidirectional, and the hybridization zone lies along the area of sympatry between these species in this study, but extend further inland if previous hybrid localities from Belize are included. In addition, the occurrence of hybridization in two ways indicates considerably more genetic contact between these species than previously recognized, and is probably more detrimental to the genetic integrity of smaller C. acutus populations. In this concern, a more intensive study of the pattern of hybridization and population genetics using multiple molecular markers is warranted and supports continued classification of C. acutus as a critically threatened species in the Yucatan Peninsula.