Robert L. Bezy

Testing species boundaries in an ancient species complex with deep phylogeographic history: Genus Xantusia(Squamata: Xantusiidae)

Identification of species in natural populations has recently received increased attention with a number of investigators proposing rigorous methods for species delimitation. Morphologically conservative species (or species complexes) with deep phylogenetic histories (and limited gene flow) are likely to pose particular problems when attempting to delimit species, yet this is crucial to comparative studies of the geography of speciation. We apply two methods of species delimitation to an ancient group of lizards (genus Xantusia) that occur throughout southwestern North America. Mitochondrial cytochrome b and nicotinamide adenine dinucleotide dehydrogenase subunit 4 gene sequences were generated from samples taken throughout the geographic range of Xantusia. Maximum likelihood, Bayesian, and nested cladogram analyses were used to estimate relationships among haplotypes and to infer evolutionary processes. We found multiple well‐supported independent lineages within Xantusia, for which there is considerable discordance with the currently recognized taxonomy. High levels of sequence divergence (21.3%) suggest that the pattern in Xantusia may predate the vicariant events usually hypothesized for the fauna of the Baja California peninsula, and the existence of deeply divergent clades (18.8%–26.9%) elsewhere in the complex indicates the occurrence of ancient sundering events whose genetic signatures were not erased by the late Wisconsin vegetation changes. We present a revised taxonomic arrangement for this genus consistent with the distinct mtDNA lineages and discuss the phylogeographic history of this genus as a model system for studies of speciation in North American deserts.

Multi‐locus DNA sequence data reveal a history of deep cryptic vicariance and habitat‐driven convergence in the desert night lizard Xantusia vigilis species complex (Squamata: Xantusiidae)

The lizard genus Xantusia of southwestern North America has received recent attention in relation to delimiting species. Using more than 500 lizards from 156 localities, we further test hypothesized species boundaries and clarify phylogeographical patterns, particularly in regions of potential secondary contact. We sequenced the entire mitochondrial cytochrome b gene for every lizard in the study, plus a second mitochondrial DNA (mtDNA) region and two nuclear introns for subsets of the total sample. Phylogenetic analyses of the mtDNA recover a well‐resolved, novel hypothesis for species in the Xantusia vigilis complex. The nuclear DNA (nDNA) data provide independent support for the recognition of X. arizonae, X. bezyi and X. wigginsi. Differences between the respective mtDNA and nDNA topologies result from either the effects of lineage sorting or ancient introgression. Nuclear data confirm the inference that some populations of X. vigilis in northwestern Arizona converged on rock‐crevice‐dwelling morphology and are not X. arizonae with an introgressed X. vigilis mtDNA genome. The historical independence of ancient cryptic lineages of Xantusia in southern California is also corroborated, though limited introgression is detected. Our proposed biogeographical scenario indicates that diversification of this group was driven by vicariance beginning in the late Miocene. Additionally, Pleistocene climatical changes influenced Xantusia distribution, and the now inhospitable Colorado Desert previously supported night lizard presence. The current taxonomy of the group likely underestimates species diversity within the group, and our results collectively show that while convergence on the rock‐crevice‐dwelling morphology is one hallmark of Xantusia evolution, morphological stasis is paradoxically another.

DNA EVIDENCE FOR NONHYBRID ORIGINS OF PARTHENOGENESIS IN NATURAL POPULATIONS OF VERTEBRATES

Naturally occurring unisexual reproduction has been documented in less than 0.1% of all vertebrate species. Among vertebrates, true parthenogenesis is known only in squamate reptiles. In all vertebrate cases that have been carefully studied, the clonal or hemiclonal taxa have originated through hybridization between closely related sexual species. In contrast, parthenogenetic reproduction has arisen in invertebrates by a variety of mechanisms, including likely cases of “spontaneous” (nonhybrid) origin, a situation not currently documented in natural populations of vertebrates. Here, we present molecular data from the Neotropical night lizard genus Lepidophyma that provides evidence of independent nonhybrid origins for diploid unisexual populations of two species from Costa Rica and Panama. Our mitochondrial and nuclear phylogenies are congruent with respect to the unisexual taxa. Based on 14 microsatellite loci, heterozygosity (expected from a hybrid origin) is low in Lepidophyma reticulatum and completely absent in unisexual L. flavimaculatum. The unique value of this system will allow direct comparative studies between parthenogenetic and sexual lineages in vertebrates, with an enormous potential for this species to be a model system for understanding the mechanisms of nonhybrid parthenogenesis.

Phylogenetic relationships within the lizard clade Xantusiidae: Using trees and divergence times to address evolutionary questions at multiple levels

Xantusiidae (night lizards) is a clade of small-bodied, cryptic lizards endemic to the New World. The clade is characterized by several features that would benefit from interpretation in a phylogenetic context, including: (1) monophyletic status of extant taxa Cricosaura, Lepidophyma, and Xantusia; (2) a species endemic to Cuba (Cricosaura typica) of disputed age; (3) origins of the parthenogenetic species of Lepidophyma; (4) pronounced micro-habitat differences accompanied by distinct morphologies in both Xantusia and Lepidophyma; and (5) placement of Xantusia riversiana, the only vertebrate species endemic to the California Channel Islands, which is highly divergent from its mainland relatives. This study incorporates extensive new character data from multiple gene regions to investigate the phylogeny of Xantusiidae using the most comprehensive taxonomic sampling available to date. Parsimony and partitioned Bayesian analyses of more than 7 kb of mitochondrial and nuclear sequence data from 11 loci all confirm that Xantusiidae is monophyletic, and comprises three well-supported clades: Cricosaura, Xantusia, and Lepidophyma. The Cuban endemic Cricosaura typica is well supported as the sister to all other xantusiids. Estimates of divergence time indicate that Cricosaura diverged from the (Lepidophyma+Xantusia) clade ≈ 81 million years ago (Ma), a time frame consistent with the separation of the Antilles from North America. Our results also confirm and extend an earlier study suggesting that parthenogenesis has arisen at least twice within Lepidophyma without hybridization, that rock-crevice ecomorphs evolved numerous times (>9) within Xantusia and Lepidophyma, and that the large-bodied Channel Island endemic X. riversiana is a distinct, early lineage that may form the sister group to the small-bodied congeners of the mainland.

Nonrandom expression of lactate dehydrogenase isozymes in the lizard family xantusiidae

Abstract A preliminary study of allozyme evolution in the lizard family Xantusiidae revealed the complete absence of expression of the A 1 B 3 lactate dehydrogenase heterotetramer isozyme in both muscle and liver tissue in 17 taxa surveyed. The four-banded LDH pattern resulting from this loss is postulated te be a derived (synapomorphic) character state for the entire family, perhaps shared with the Scincidae. Additional derived character states were observed to have evolved in parallel in several lineages within the Xantusiidae. Loss of the A 3 B 1 asymmetrical heterotetramer appears to have occurred a minimum of four times, and one species, Lepidophyma tuxtlae , also appears to have lost the B 4 homotetramer, having only a two-banded LDH isozyme pattern (A 4 and A 2 B 2 ).

Amphibians and reptiles of Yécora, Sonora and the Madrean Tropical Zone of the Sierra Madre Occidental in northwestern Mexico

The Municipio de Yecora is located in the Madrean Tropical Zone of the Sierra Madre Occidental in eastern Sonora, Mexico. The herpetofauna of the region is very diverse with 93 species in 59 genera and 27 families known from the Rio Yaqui to the Chihuahua border. This includes 20 species of amphibians and 73 species of reptiles. Thirty-six species in the Yecora area fauna have protection in NOM-059-SEMARNAT-2010 law. There are no non-native species in the fauna. The Yecora area herpetofauna is representative of the Madrean Tropical Zone and serves as a baseline to evaluate faunas of the Madrean Archipelago in northeastern Sonora and southeastern Arizona, USA as well as those to the south along the axis of the range.

Two New Species of Night Lizards (Xantusia) from Mexico

Abstract Two lineages of Xantusia occurring in northwestern Mexico are each deeply divergent in mitochondrial and nuclear DNA, mutually exclusive relative to other members of the genus, and morphologically diagnosable. They are formally described here as new species. The new species from Sonora resembles its nearest relative, Xantusia arizonae, in that females lack well-developed femoral pores, but it differs in numbers of dorsal scales around midbody and in color pattern. It is found near the Sea of Cortez in a unique microhabitat, fallen Pachycereus pringlei (cardon), whereas X. arizonae occurs in rock crevices in central Arizona. The new species from Baja California Sur differs from its nearest relative, Xantusia gilberti, in color pattern and in having small scales bordering the labium behind the fifth infralabial. It is found in Yucca valida (datilillo) on the Magdalena Plains near the Pacific Coast, whereas X. gilberti occurs in pine-oak woodland of the Sierra La Laguna, 350 km to the south.

Distribution, Species Status, and Reproductive Mode of the Xantusiid Lizard Lepidophyma pajapanensis

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