Diversification in the northern neotropics: mitochondrial and nuclear DNA phylogeography of the iguana Ctenosaura pectinata and related species

Abstract

While Quaternary climatic changes are considered by some to have been a major factor promoting speciation within the neotropics, others suggest that much of the neotropical species diversity originated before the Pleistocene. Using mitochondrial and nuclear sequence data, we evaluate the relative importance of Pleistocene and pre-Pleistocene events within the evolutionary history of the Mexican iguana Ctenosaura pectinata, and related species. Results support the existence of cryptic lineages with strong mitochondrial divergence (> 4%) among them. Some of these lineages form zones of secondary contact, with one of them hybridizing with C. hemilopha. Evolutionary network analyses reveal the oldest populations of C. pectinata to be those of the northern and southern Mexican coastal regions. Inland and mid-latitudinal coastal populations are younger in age as a consequence of a history of local extinction within these regions followed by re-colonization. Estimated divergence times suggest that C. pectinata originated during the Pliocene, whereas geographically distinct mitochondrial DNA lineages first started to diverge during the Pliocene, with subsequent divergence continuing through the Pleistocene. Our results highlight the influence of both Pliocene and Pleistocene events in shaping the geographical distribution of genetic variation within neotropical lowland organisms. Areas of high genetic diversity in southern Mexico were detected, this finding plus the high levels of genetic diversity within C. pectinata, have implications for the conservation of this threatened species.

Molecular phylogenetics and species delimitation of leaf-toed geckos (Phyllodactylidae: Phyllodactylus) throughout the Mexican tropical dry forest

“…Recent empirical analyses conflict as to the role played by Pleistocene climatic shifts in shaping diversification patterns in lowland Neotropical species (Klicka and Zink, 1997;Weir, 2006;Weir and Schluter, 2004;Zarza et al, 2008;Zink et al, 2004). Some alternative perspectives may be due to the employment of different statistical methods.…”

Phylogeny, phylogeography, phylobetadiversity and the molecular analysis of biological communities

“…Within species that deviate from panmixia, such as those having a history involving geographical structure chequered by regional population extinction and recolonization, there may no longer be an obvious ancestral sequence [33] (figure 1). However, lower order ancestral sequences (ancestral sequences within a subsection of a network or gene tree) may be identifiable if the root location of a network can be identified [33][34][35] (figure 1). The spatial relationships among ancestral and descendant haplotypes may then be used to infer the geographical origin of a particular lineage of sequences [33][34][35].…”

“…However, lower order ancestral sequences (ancestral sequences within a subsection of a network or gene tree) may be identifiable if the root location of a network can be identified [33][34][35] (figure 1). The spatial relationships among ancestral and descendant haplotypes may then be used to infer the geographical origin of a particular lineage of sequences [33][34][35]. Although this has not been done within a rigorous statistical framework, such a development would seem like a plausible future possibility.…”

Gene trees, species and species trees in the Ctenosaura palearis clade

“…There are no published fossil records corresponding to the focal species in this study, thus, following Zarza et al (2008) we incorporated paleontological data from other iguana species as external calibration points. One calibration point corresponds to the oldest record of an iguanid lizard, Pristiguana, dated at 93 MYA (Estes and Price 1973).…”

“…In these analyses our calibration points constrained the Iguaninae to have originated no more than 93 MYA but not more recently than 24 MYA. From the BEAST analysis the mrca of the C. palearis clade is estimated at 3.55 MYA (95% CI: Zarza et al (2008) and Malone et al (2000). When 93 and 24 MYA were used as a fixed calibration points the mrca for the C. palearis clade were 10.417 MYA (95% CI: 4.38-21.99 MYA) and 2.73 MYA (95% CI: 1.13-5.89 MYA) respectively.…”