Uri Omar García-Vázquez

Relative roles of Neogene vicariance and Quaternary climate change on the historical diversification of bunchgrass lizards (Sceloporus scalaris group) in Mexico.

Neogene vicariance during the Miocene and Pliocene and Quaternary climate change have synergistically driven diversification in Mexican highland taxa. We investigated the impacts of these processes on genetic diversification in the widely distributed bunchgrass lizards in the Sceloporus scalaris group. We searched for correlations between timing in diversification and timing of (1) a period of marked volcanism across the Trans-Mexican Volcanic Belt in central Mexico 3-7.5million years ago (Ma) and (2) a transition to larger glacial-interglacial cycles during the mid-Pleistocene. From our phylogenetic analyses of mitochondrial DNA we identified two major clades that contained 13 strongly supported lineages. One clade contained lineages from the two northern sierras of Mexico, and the other clade included lineages associated with the Trans-Mexican Volcanic Belt and Central Mexican Plateau. Results provided support for Neogene divergences within the S. scalaris group in response to uplift of the Trans-Mexican Volcanic Belt, a pattern observed in several co-distributed taxa, and suggested that Quaternary climate change likely had little effect on diversification between lineages. Uplift of the Trans-Mexican Volcanic Belt during specific time periods appears to have strongly impacted diversification in Mexican highland taxa.

Diversification in the Mexican horned lizard Phrynosoma orbiculare across a dynamic landscape

The widespread montane Mexican horned lizard Phrynosoma orbiculare (Squamata: Phrynosomatidae) represents an ideal species to investigate the relative impacts of Neogene vicariance and Quaternary climate change on lineage diversification across the Mexican highlands. We used mitochondrial DNA to examine the maternal history of P. orbiculare and estimate the timing and tempo of lineage diversification. Based on our results, we inferred 11 geographically structured, well supported mitochondrial lineages within this species, suggesting P. orbiculare represents a species complex. Six divergences between lineages likely occurred during the Late Miocene and Pliocene, and four splits probably happened during the Pleistocene. Diversification rate appeared relatively constant through time. Spatial and temporal divergences between lineages of P. orbiculare and co-distributed taxa suggest that a distinct period of uplifting of the Transvolcanic Belt around 7.5-3 million years ago broadly impacted diversification in taxa associated with this mountain range. To the north, several river drainages acting as filter barriers differentially subdivided co-distributed highland taxa through time. Diversification patterns observed in P. orbiculare provide additional insight into the mechanisms that impacted differentiation of highland taxa across the complex Mexican highlands.

Phylogenomics and species delimitation in the knob-scaled lizards of the genus Xenosaurus (Squamata: Xenosauridae) using ddRADseq data reveal a substantial underestimation of diversity

Middle American knob-scaled lizards of the genus Xenosaurus are a unique radiation of viviparous species that are generally characterized by a flattened body shape and a crevice-dwelling ecology. Only eight species of Xenosaurus, one of them with five subspecies (X. grandis), have been formally described. However, species limits within Xenosaurus have never been examined using molecular data, and no complete phylogeny of the genus has been published. Here, we used ddRADseq data from all of the described and potentially undescribed taxa of Xenosaurus to investigate species limits, and to obtain a phylogenetic hypothesis for the genus. We analyzed the data using a variety of phylogenetic models, and were able to reconstruct a well-resolved and generally well-supported phylogeny for this group. We found Xenosaurus to be composed of four major, allopatric clades concordant with geography. The first and second clades that branch off the tree are distributed on the Atlantic slopes of the Sierra Madre Oriental and are composed of X. mendozai, X. platyceps, and X. newmanorum, and X. tzacualtipantecus and an undescribed species from Puebla, respectively. The third clade is distributed from the Atlantic slopes of the Mexican Transvolcanic Belt in west-central Veracruz south to the Pacific slopes of the Sierra Madre del Sur in Guerrero and Oaxaca, and is composed of X. g. grandis, X. rectocollaris, X. phalaroanthereon, X. g. agrenon, X. penai, and four undescribed species from Oaxaca. The last clade is composed of the four taxa that are geographically closest to the Isthmus of Tehuantepec (X. g. arboreus, X. g. rackhami, X. g. sanmartinensis, and an undescribed species from Oaxaca). We also utilized a variety of molecular species delimitation approaches, including analyses with GMYC, PTP, BPP, and BFD∗, which suggested that species diversity in Xenosaurus is at least 30% higher than currently estimated.

Evolutionary relationships amongst polymorphic direct-developing frogs in the Craugastor rhodopis Species Group (Anura: Craugastoridae)

The Craugastor rhodopis Species Group includes two leaf-litter frog species (C. loki and C. rhodopis). These direct-developing frogs inhabit tropical regions of Mexico and northern Central America. Characterizing diversity within the group has been difficult due to high levels of phenotypic polymorphism within and between species. Because of these polymorphisms, each taxon has junior synonyms. Using a fragment of mitochondrial DNA (mtDNA), we investigated genetic diversity in the C. rhodopis Species Group. We then examined type specimens (including types of junior synonyms) to match nomenclature to geographically circumscribed genetic clusters. Our molecular analyses revealed four major lineages within the C. rhodopis Species Group: (1) a widely distributed clade in western Mexico, (2) a highland clade in eastern Mexico, (3) a widely distributed lowland clade occurring in eastern Mexico, Guatemala and El Salvador, and (4) a haplotype from Volcán San Martín in Veracruz, Mexico. We identified the first clade as C. occidentalis, a taxon currently placed in the ecologically similar but phylogenetically distant C. mexicanus Species Series. In light of this we place C. occidentalis in the C. rhodopis Species Group and designate a lectotype and paralectotype for the species. The second and third clades inhabiting eastern Mexico and northern Central America correspond to C. rhodopis and C. loki, respectively. Additionally, we examined the taxonomic distribution of certain colour pattern traits and compensatory mutations in Domain III of the mtDNA 12S ribosomal RNA gene. Our recovery of the divergent Veracruz haplotype and extensive mtDNA structure within species indicates that additional taxonomic revision will be necessary.

A new species of Plestiodon (Squamata: Scincidae) from Sierra Madre del Sur of Guerrero, México

We describe a new species of lizard of the genus Plestiodon from the Sierra Madre del Sur of Guerrero, Mexico. Plestiodon nietoi sp. nov. shares a characteristic with all members of the P. brevirostris group in that the scale that medially borders the postgenial is wider than long. This species is most similar to P. brevirostris and P. indubitus from which it differs by having the following combination of characters: large adult size, interparietal enclosed posteriorly by parietals, and a pale lateral line on the neck.

Thermoregulation by a Population of Sceloporus palaciosi from Sierra del Ajusco, Distrito Federal, Mexico

Abstract We evaluated the influence of environmental temperature and phenotype on thermoregulation by Sceloporus palaciosi, a diurnal iguanid lizard from high elevations in central Mexico. Range of body temperature was 13–36°C with a mean of 27.82 ± 5.31°C. Active lizards had a higher body temperature than inactive ones. After removal of state of activity from analysis, sexes did not differ in body temperature. Body temperature was significantly correlated with temperature of air and substrate in both active and inactive lizards.

A New Species of Scincella (Squamata: Scincidae) from the Cuatro Ciénegas Basin, Coahuila, Mexico

Abstract A new species of Scincella, previously confused with S. lateralis, is described from the Cuatro Ciénegas Basin, Coahuila, Mexico. The new species differs from all congeners in North and Middle America by possessing two dark, narrow ventrolateral stripes on each side (vs. dark, narrow ventrolateral stripes on each side absent in the other species); from all congeners in North and Middle America, except S. lateralis, by having three or more pairs of nuchal scales (vs. fewer than three pairs of nuchals in the other species) and the first nuchal in contact with the tertiary temporal row (vs. first nuchal usually in contact with the upper secondary temporal in the other species); and from S. lateralis by having longer limbs (limbs overlapping by 1–15 scales when adpressed against body, hindlimb length/SVL ratio 0.30–0.42,  =  0.36; vs. limbs separated by 2–23 scales when adpressed against body, hindlimb length/SVL ratio 0.24–0.37,  =  0.30, in S. lateralis) and usually more scales around midbody (28–30,  =  29.0, n  =  15; vs. 24–29,  =  26.4, n  =  28, in S. lateralis). The new species is geographically closest, and morphologically most similar, to S. lateralis.

A New Species of the Geophis sieboldi Group (Squamata: Colubridae) Exhibiting Color Pattern Polymorphism from Guerrero, Mexico

Abstract A new species of the colubrid genus Geophis is described from the Sierra Madre del Sur of Guerrero, Mexico. The new species possesses all of the diagnostic characters of the sieboldi group, but differs from all of the other species in the group by having dorsal scales arranged in 17 rows, 133–139 ventrals in females and 130–137 in males, 24–31 subcaudals in females and 34–39 in males, keeled dorsal scales on at least the posterior three-fourths of the body, apparently no apical pits, and a light nuchal collar in juveniles. The new species fills a gap in the distribution of the sieboldi group between Michoacán and Oaxaca, and is the first Mexican species of the genus reported to exhibit both a unicolor (uniformly dark) and a bicolor (with dark markings on a red background color) body and tail dorsal patterns, a polymorphism similar to that previously documented in few lower Central American species.

Present and future ecological niche modeling of garter snake species from the Trans-Mexican Volcanic Belt

Land use and climate change are affecting the abundance and distribution of species. The Trans-Mexican Volcanic Belt (TMVB) is a very diverse region due to geological history, geographic position, and climate. It is also one of the most disturbed regions in Mexico. Reptiles are particularly sensitive to environmental changes due to their low dispersal capacity and thermal ecology. In this study, we define the important environmental variables (considering climate, topography, and land use) and potential distribution (present and future) of the five Thamnophis species present in TMVB. To do so, we used the maximum entropy modeling software (MAXENT). First, we modeled to select the most important variables to explain the distribution of each species, then we modeled again using only the most important variables and projected these models to the future considering a middle-moderate climate change scenario (rcp45), and land use and vegetation variables for the year 2050 (generated according to land use changes that occurred between years 2002 and 2011). Arid vegetation had an important negative effect on habitat suitability for all species, and minimum temperature of the coldest month was important for four of the five species. Thamnophis cyrtopsis was the species with the lowest tolerance to minimum temperatures. The maximum temperature of the warmest month was important for T. scalaris and T. cyrtopsis. Low percentages of agriculture were positive for T. eques and T. melanogaster but, at higher values, agriculture had a negative effect on habitat suitability for both species. Elevation was the most important variable to explain T. eques and T. melanogaster potential distribution while distance to Abies forests was the most important variable for T. scalaris and T. scaliger. All species had a high proportion of their potential distribution in the TMVB. However, according to our models, all Thamnophis species will experience reductions in their potential distribution in this region. T. scalaris will suffer the biggest reduction because this species is limited by high temperatures and will not be able to shift its distribution upward, as it is already present in the highest elevations of the TMVB.

New records of bee flies (Diptera, Bombyliidae) from Cuatro Ciénegas, Coahuila, Mexico

Abstract Forty one new records of species of Bombyliidae are reported for Coahuila in northeastern Mexico. Nine of these species are reported for the first time for the country. The specimens were collected in the Cuatro Ciénegas Basin and Sierra La Madera mountains during 2007–2013. The modified distributions of species are discussed. The gaps in the distribution of many species suggest an undersampling of this group of insects in the north of Mexico.