Genetic variation and recent population history of the tropical gar Atractosteus tropicus Gill (Pisces: Lepisosteidae)

• Published in: Journal of fish biology 2008-12, Vol.73 (8), p.1919-1936
• Main Authors: Barrientos-Villalobos, J., Espinosa de los Monteros, A.
• Format: Article
• Language: English
• Subjects: Atractosteus tropicus; gene flow; genetic variation; Lepisosteidae; mtDNA; phylogeography; Pisces; population structure; tropical gar
• ISSN: 0022-1112; 1095-8649
• DOI: 10.1111/j.1095-8649.2008.01993.x

The tropical gar Atractosteus tropicus belongs to one of the few extant lineages of early bony fishes. The genetic variation detected both within and among 11 natural populations of A. tropicus in Mesoamerica along with the implications for their recent history are presented. Sequences from cytochrome b (307 bp) and cytochrome oxidase subunit II (607 bp) were used as data sources. Apparently, the populations of this fish have decreased in size because of anthropogenic pressures, such as habitat degradation and destruction. The observed values for nucleotide diversity (0·0016 ± 0·0018) and haplotype diversity (0·477 ± 0·302) suggest low levels of genetic variation. Nonetheless, most of the populations studied are currently in a period of genetic stasis. Recent isolation by distance, reduced gene flow and translocation were inferred as the processes maintaining this stasis. Phylogenetic analyses showed reciprocal monophyly between the haplotypes from Guatemala and the other populations. This, together with the observed genetic variation, suggests that the Guatemalan haplotypes might represent a new species. The haplotypes, other than those from Guatemala, exhibited a geographic pattern consistent with two main reproductive populations, one from the Pacific and the other from the Gulf of Mexico–Caribbean slope of Mesoamerica. Pleistocene glacial and interglacial periods might be responsible for moulding the heterogeneity in the genetic structure observed during this study.