Two main hypotheses have been proposed to explain the diversification of the Caatinga biota. The riverine barrier hypothesis (RBH) claims that the São Francisco River (SFR) is a major biogeographic barrier to gene flow. The Pleistocene climatic fluctuation hypothesis (PCH) states that gene flow, geographic genetic structure and demographic signatures on endemic Caatinga taxa were influenced by Quaternary climate fluctuation cycles. Herein, we analyse genetic diversity and structure, phylogeographic history, and diversification of a widespread Caatinga lizard (Cnemidophorus ocellifer) based on large geographical sampling for multiple loci to test the predictions derived from the RBH and PCH. We inferred two well-delimited lineages (Northeast and Southwest) that have diverged along the Cerrado-Caatinga border during the Mid-Late Miocene (6-14 Ma) despite the presence of gene flow. We reject both major hypotheses proposed to explain diversification in the Caatinga. Surprisingly, our results revealed a striking complex diversification pattern where the Northeast lineage originated as a founder effect from a few individuals located along the edge of the Southwest lineage that eventually expanded throughout the Caatinga. The Southwest lineage is more diverse, older and associated with the Cerrado-Caatinga boundaries. Finally, we suggest that C. ocellifer from the Caatinga is composed of two distinct species. Our data support speciation in the presence of gene flow and highlight the role of environmental gradients in the diversification process.
Two syntopic species of Cnemidophorus are described from the Caatingas of the Parque Nacional da Serra das Confusões (PNSC), located in the Southwestern region of the state of Piauí in Brazil. Both species are assigned to the ocellifer group, differing from all other members of the group by their distinct color pattern and lepidosis. Besides these differences, both new species share a number of particular features with other members of the group. One of them, C. venetacaudus, shares with C. abaetensis and C. littoralis the presence of spurs in the heels of males, six supraciliar scales, a high number of femoral pores (from 21–45), a row of enlarged scales in the dorsal region of the arm, 8–10 rows of ventral scales, and a bright bluish-green tail, while the other species, C. confusionibus, shares with C. ocellifer, C. mumbuca, and C. jalapensis a low number of femoral pores, enlarged scales in the temporal region (posterior to third subocular), 5 supraciliar scales, and 6–8 rows of ventral scales. Based on these comparisons, we suggest that the ocellifer group is more complex than previously admitted, being composed by at least two morphologically recognizable species subgroups.
Lizards of the family Teiidae (infraorder Scincomorpha) were formerly known as Macroteiidae. There are 13 species of such lizards in the Amazon, in the genera Ameiva (Meyer, 1795), Cnemidophorus (Wagler, 1830), Crocodilurus (Spix, 1825), Dracaena (Daudin, 1801), Kentropyx (Spix, 1825) and Tupinambis (Daudin, 1802). Cytogenetic studies of this group are restricted to karyotype macrostructure. Here we give a compilation of cytogenetic data of the family Teiidae, including classic and molecular cytogenetic analysis of Ameiva ameiva (Linnaeus, 1758), Cnemidophorus sp.1, Kentropyx calcarata (Spix, 1825), Kentropyx pelviceps (Cope, 1868) and Tupinambis teguixin (Linnaeus, 1758) collected in the state of Amazonas, Brazil. Ameiva ameiva, Kentropyx calcarata and Kentropyx pelviceps have 2n=50 chromosomes classified by a gradual series of acrocentric chromosomes. Cnemidophorus sp.1 has 2n=48 chromosomes with 2 biarmed chromosomes, 24 uniarmed chromosomes and 22 microchromosomes. Tupinambis teguixin has 2n=36 chromosomes, including 12 macrochromosomes and 24 microchromosomes. Constitutive heterochromatin was distributed in the centromeric and terminal regions in most chromosomes. The nucleolus organizer region was simple, varying in its position among the species, as evidenced both by AgNO3 impregnation and by hybridization with 18S rDNA probes. The data reveal a karyotype variation with respect to the diploid number, fundamental number and karyotype formula, which reinforces the importance of increasing chromosomal analyses in the Teiidae.
We provide the description for a new species from Catamarca province, Argentina that belongs to the Liolaemus darwinii group. The new species was previously considered as a population of L. ornatus, but it can be distinguished from that species mainly because of differences on coloration pattern, and its geographic distribution, which is disjunct from the populations of L. ornatus. The new species is characterized for having males with a dorsal background coloration of light brown to ferrous red, the head darker than the rest of the body, paravertebral markings rounded and never in contact, dorsolateral strips lightly marked, small dark brown spots on the throat, and a belly that is white or light red.
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