Mesoamerica is considered a biodiversity hot spot with levels of endemism and species diversity likely underestimated. For mammals, the patterns of diversification of Mesoamerican taxa still are controversial. Reasons for this include the region's complex geologic history, and the relatively recent timing of such geological events. Previous studies, however, support the view that substantial migration between North (NA) and South America (SA) occurred prior or/and during the Great American Biotic Interchange (GABI) ~3.5 Ma. This was followed by repeated periods of isolation during Pleistocene climatic oscillations, which produced most of the diversification in the region. From a North American origin, the subfamily Sigmodontinae migrated to SA, where most of its present day diversity exists. The taxonomic history of this subfamily, and of Oryzomynii, its largest tribe, has been exceptionally complex. Recently, extensive studies have helped to clarify genealogical relationships among major clades, but have left the evolutionary histories of several groups unresolved. Such is the case for the genus Handleyomys that includes nine species; seven of which are endemic to Mesoamerica; and of its phylogenetic position among closely related genera Euryoryzomys, Hylaeamys, Oecomys, Nephelomys and Transandinomys. The results supported the monophyly of Handleyomys, and four clades with inter-generic levels of divergence within the genus, three of these clades restricted to Mesoamerica (the alfaroi, chapmani and melanotis species groups). Furthermore, the estimated time for the split of the Mesoamerican Handleyomys is on average, 2.0 Myr older than the proposed migrations to NA during the GABI. In addition, the position of Handleyomys as the sister clade to Euryoryzomys, Hylaeamys, Oecomys, Nephelomys and Transandinomys was well supported, as it was a biogeographic hypotheses that depicted a polyphyletic origin for these genera and Handleyomys 5.5-6.0 Ma. The integrative approach implemented in this dissertation allowed the development of more biologically realistic hypothesis than has previously been conducted in Mesoamerica, where half of the endemic mammals are listed under the IUCN Red list; and where mammals with small ranges, which are the most vulnerable to extinction, are found largely outside reserves. The continued decline of the ecosystems health in this region calls for a more precise account of its biodiversity for its proper conservation; and for rigorous biogeographic studies for its management, since the region also serves as a biological corridor for intercontinental connectivity.
College and Department
Life Sciences; Biology
BYU ScholarsArchive Citation
Villalba Almendra, Ana, "Evolution and Biogeography of Mesoamerican Small Mammals: With Focus on the Genus Handleyomys and Related Taxa" (2015). Theses and Dissertations. 5812.
Mesoamerica, rodents, biogeography, molecular phylogenetics, ecological niche models, Pliocene-Pleistocene