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1.
J Morphol ; 280(1): 35-49, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30478960

RESUMO

The evolution of viviparity alters the physical relationship between mothers and offspring and the prevalence of viviparity among squamate reptiles presents an opportunity to uncover patterns in the evolution of placental structure. Understanding the breadth of this diversity is limited because studies of placental structure and function have emphasized a limited number of lineages. We studied placental ontogeny using light microscopy for an embryological series of the Mexican gerrhonotine lizard, Mesaspis viridiflava. This species develops an elaborate yolk sac placenta, an omphaloplacenta, which receives vascular support arising in a structure known only from other gerrhonotine lizards. A prominent feature of the omphaloplacenta is a zone of uterine and embryonic epithelial cell hyperplasia located at the upper shoulder of the yolk mass, often extending above the yolk mass. The omphaloplacenta covers more than one-half of the surface area of maternal-embryonic contact. The chorioallantoic placenta has a more restricted distribution because the allantois remains in the embryonic hemisphere of the egg throughout development and lies internal to the vascular support for the omphaloplacenta in areas where they overlap. The structural profile of the chorioallantoic placenta indicates a potential for respiratory exchange and/or hemotrophic nutritive transport, while that of the omphaloplacenta suggests that nutritive transfer is primarily via histotrophy. An eggshell is present in the earliest embryonic stages examined but regresses relatively early in development. Placental specializations of this species are consistent with a pattern of matrotrophic embryonic nutrition and have evolved in a unique lineage specific developmental pattern.

2.
Mol Ecol Resour ; 19(4): 818-837, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30506631

RESUMO

Introgression is now commonly reported in studies across the Tree of Life, aided by recent advancements in data collection and analysis. Nevertheless, researchers working with nonmodel species lacking reference genomes may be stymied by a mismatch between available resources and methodological demands. In this study, we demonstrate a fast and simple approach for inferring introgression using RADseq data, and apply it to a case study involving spiny lizards (Sceloporus) from northeastern México. First, we find evidence for recurrent mtDNA introgression between the two focal species based on patterns of mito-nuclear discordance. We then test for nuclear introgression by exhaustively applying the "five-taxon" D-statistic (DFOIL ) to all relevant individuals sampled for RADseq data. In our case, this exhaustive approach (dubbed "ExDFOIL ") entails testing up to ~250,000 unique four-taxon combinations of individuals across species. To facilitate use of this ExDFOIL approach, we provide scripts for many relevant tasks, including the selection of appropriate four-taxon combinations, execution of DFOIL tests in parallel and visualization of introgression results in phylogenetic and geographic space. Using ExDFOIL , we find evidence for ancient introgression between the focal species. Furthermore, we reveal geographic variation in patterns of introgression that is consistent with patterns of mito-nuclear discordance and with recurrent introgression. Overall, our study demonstrates that the combination of DFOIL and RADseq data can effectively detect introgression under a variety of sampling conditions (for individuals, populations and loci). Importantly, we also find evidence that batch-specific error and linkage in RADseq data may mislead inferences of introgression under certain conditions.


Assuntos
Biologia Computacional/métodos , Evolução Molecular , Fluxo Gênico , Lagartos/genética , Análise de Sequência de DNA/métodos , Animais , Bioestatística/métodos , DNA Mitocondrial/genética , México
3.
Integr Zool ; 13(4): 450-470, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29436768

RESUMO

Determining the susceptibility of species to changing thermal niches is a major goal for biologists. In this paper we develop an eco-physiological model of extinction risk under climate change premised on behavioral thermoregulation. Our method downscales operative environmental temperatures, which restrict hours of activity of lizards, hr , for present-day climate (1975) and future climate scenarios (2070). We apply our model using occurrence records of 20 Phrynocephalus lizards (or taxa in species complexes) drawn from literature and museum records. Our analysis is phylogenetically informed, because some clades may be more sensitive to rising temperatures. The limits for computed hr predict local extirpations among Phrynocephalus lizards at continental scales and delineate upper boundaries of thermal niches as defined by Extreme Value Distributions. Under the 8.5 Representative Concentration Pathway scenario, we predict extirpation of 64% of local populations by 2070 across 20 Phrynocephalus species, and 12 are at high risk of total extinction due to thermal limits being exceeded. In tandem with global strategies of lower CO2 emissions, we propose regional strategies for establishing new national parks to protect extinction-prone taxa by preserving high-elevation climate refugia within existing sites of species occurrence. We propose that evolved acclimatization - maternal plasticity - may ameliorate risk, but is poorly studied. Previous studies revealed that adaptive maternal plasticity by thermoregulating gravid females alter progeny thermal preferences by ±1 °C. We describe plasticity studies for extinction-prone species that could assess whether they might be buffered from climate warming - a self-rescue. We discuss an epigenetic framework for studying such maternal-effect evolution.


Assuntos
Extinção Biológica , Lagartos/fisiologia , Temperatura Ambiente , Aclimatação , Altitude , Animais , Regulação da Temperatura Corporal , Mudança Climática , Feminino , Geografia , Masculino , Óvulo , Filogenia
4.
Artigo em Inglês | MEDLINE | ID: mdl-29189909

RESUMO

Integrative behavioral studies show that the interplay between individual physiology and social behavior influences the ecology of the species, ultimately affecting individual fitness. Particularly in lizards, color polymorphism is associated with differential behaviors and reproductive strategies, which are evident in mature males during the mating season. Dominant males generally have greater endurance, higher body temperature, and larger bodies than submissive males, so they can acquire and defend larger territories and have greater access to females for mating. We studied whether the color morphs observed in males of one of the world's southernmost reptiles, Liolaemus sarmientoi, are related to behavioral variation during agonistic interactions, thermal physiology, morphology, and/or locomotor stamina. Liolaemus sarmientoi males exhibit three color morphs: red (RR), red-yellow (RY), and yellow (YY). These lizards exhibit subtle behavioral displays and we did not observe stamina differences among morphs. However, we found that RR males are more aggressive than YY males during agonistic encounters. In addition, greater body temperature change during trials, higher field body temperatures, and greater head sizes of RR males compared to RY or YY indicate that RR is a dominant morph, which may influence their ability to acquire and defend territory and tactics for achieving reproductive success.


Assuntos
Comportamento Animal , Lagartos/fisiologia , Pigmentação , Agressão , Animais , Temperatura Corporal , Cabeça/anatomia & histologia , Lagartos/anatomia & histologia , Masculino , Movimento , Tamanho do Órgão , Resistência Física
5.
J Therm Biol ; 48: 1-10, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25660624

RESUMO

Thermoregulatory studies of ectothermic organisms are an important tool for ecological physiology, evolutionary ecology and behavior, and recently have become central for evaluating and predicting global climate change impacts. Here, we present a novel combination of field, laboratory, and modeling approaches to examine body temperature regulation, habitat thermal quality, and hours of thermal restriction on the activity of two sympatric, aridlands horned lizards (Phrynosoma cornutum and Phrynosoma modestum) at three contrasting Chihuahuan Desert sites in Mexico. Using these physiological data, we estimate local extinction risk under predicted climate change within their current geographical distribution. We followed the Hertz et al. (1993, Am. Nat., 142, 796-818) protocol for evaluating thermoregulation and the Sinervo et al. (2010, Science, 328, 894-899) eco-physiological model of extinction under climatic warming. Thermoregulatory indices suggest that both species thermoregulate effectively despite living in habitats of low thermal quality, although high environmental temperatures restrict the activity period of both species. Based on our measurements, if air temperature rises as predicted by climate models, the extinction model projects that P. cornutum will become locally extinct at 6% of sites by 2050 and 18% by 2080 and P. modestum will become extinct at 32% of sites by 2050 and 60% by 2080. The method we apply, using widely available or readily acquired thermal data, along with the modeling, appeared to identify several unique ecological traits that seemingly exacerbate climate sensitivity of P. modestum.


Assuntos
Regulação da Temperatura Corporal , Extinção Biológica , Lagartos/fisiologia , Modelos Teóricos , Animais , Clima Desértico , Feminino , Masculino , México , Risco , Simpatria
7.
Mol Ecol ; 24(7): 1523-42, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25712551

RESUMO

Interspecific gene flow is pervasive throughout the tree of life. Although detecting gene flow between populations has been facilitated by new analytical approaches, determining the timing and geography of hybridization has remained difficult, particularly for historical gene flow. A geographically explicit phylogenetic approach is needed to determine the overlap of ancestral populations. In this study, we performed population genetic analyses, species delimitation, simulations and a recently developed approach of species tree diffusion to infer the phylogeographic history, timing and geographic extent of gene flow in lizards of the Sceloporus spinosus group. The two species in this group, S. spinosus and S. horridus, are distributed in eastern and western portions of Mexico, respectively, but populations of these species are sympatric in the southern Mexican highlands. We generated data consisting of three mitochondrial genes and eight nuclear loci for 148 and 68 individuals, respectively. We delimited six lineages in this group, but found strong evidence of mito-nuclear discordance in sympatric populations of S. spinosus and S. horridus owing to mitochondrial introgression. We used coalescent simulations to differentiate ancestral gene flow from secondary contact, but found mixed support for these two models. Bayesian phylogeography indicated more than 60% range overlap between ancestral S. spinosus and S. horridus populations since the time of their divergence. Isolation-migration analyses, however, revealed near-zero levels of gene flow between these ancestral populations. Interpreting results from both simulations and empirical data indicate that despite a long history of sympatry among these two species, gene flow in this group has only recently occurred.


Assuntos
Fluxo Gênico , Genética Populacional , Lagartos/genética , Filogenia , Simpatria , Animais , Teorema de Bayes , Núcleo Celular/genética , DNA Mitocondrial/genética , Funções Verossimilhança , México , Modelos Genéticos , Modelos Estatísticos , Dados de Sequência Molecular , Filogeografia , Análise de Sequência de DNA
8.
Mol Phylogenet Evol ; 84: 254-65, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25620603

RESUMO

Methods and approaches for accurate species delimitation continue to be a highly controversial subject in the systematics community. Inaccurate assessment of species' limits precludes accurate inference of historical evolutionary processes. Recent evidence suggests that multilocus coalescent methods show promise in delimiting species in cryptic clades. We combine multilocus sequence data with coalescence-based phylogenetics in a hypothesis-testing framework to assess species limits and elucidate the timing of diversification in leaf-toed geckos (Phyllodactylus) of Mexico's dry forests. Tropical deciduous forests (TDF) of the Neotropics are among the planet's most diverse ecosystems. However, in comparison to moist tropical forests, little is known about the mode and tempo of biotic evolution throughout this threatened biome. We find increased speciation and substantial, cryptic molecular diversity originating following the formation of Mexican TDF 30-20million years ago due to orogenesis of the Sierra Madre Occidental and Mexican Volcanic Belt. Phylogenetic results suggest that the Mexican Volcanic Belt, the Rio Fuerte, and Isthmus of Tehuantepec may be important biogeographic barriers. Single- and multilocus coalescent analyses suggest that nearly every sampling locality may be a distinct species. These results suggest unprecedented levels of diversity, a complex evolutionary history, and that the formation and expansion of TDF vegetation in the Miocene may have influenced subsequent cladogenesis of leaf-toed geckos throughout western Mexico.


Assuntos
Florestas , Especiação Genética , Lagartos/classificação , Filogenia , Animais , Teorema de Bayes , México , Modelos Genéticos , Análise de Sequência de DNA
9.
PLoS One ; 8(2): e57433, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23451230

RESUMO

Habitat fragmentation due to both natural and anthropogenic forces continues to threaten the evolution and maintenance of biological diversity. This is of particular concern in tropical regions that are experiencing elevated rates of habitat loss. Although less well-studied than tropical rain forests, tropical dry forests (TDF) contain an enormous diversity of species and continue to be threatened by anthropogenic activities including grazing and agriculture. However, little is known about the processes that shape genetic connectivity in species inhabiting TDF ecosystems. We adopt a landscape genetic approach to understanding functional connectivity for leaf-toed geckos (Phyllodactylus tuberculosus) at multiple sites near the northernmost limit of this ecosystem at Alamos, Sonora, Mexico. Traditional analyses of population genetics are combined with multivariate GIS-based landscape analyses to test hypotheses on the potential drivers of spatial genetic variation. Moderate levels of within-population diversity and substantial levels of population differentiation are revealed by FST and Dest. Analyses using structure suggest the occurrence of from 2 to 9 genetic clusters depending on the model used. Landscape genetic analysis suggests that forest cover, stream connectivity, undisturbed habitat, slope, and minimum temperature of the coldest period explain more genetic variation than do simple Euclidean distances. Additional landscape genetic studies throughout TDF habitat are required to understand species-specific responses to landscape and climate change and to identify common drivers. We urge researchers interested in using multivariate distance methods to test for, and report, significant correlations among predictor matrices that can impact results, particularly when adopting least-cost path approaches. Further investigation into the use of information theoretic approaches for model selection is also warranted.


Assuntos
Lagartos/genética , Animais , Mudança Climática , Ecossistema , Meio Ambiente , Variação Genética , Genética Populacional , Geografia/métodos , México , Dinâmica Populacional , Especificidade da Espécie , Árvores
10.
Rev. biol. trop ; 56(4): 1871-1881, Dec. 2008. graf, tab
Artigo em Espanhol | LILACS | ID: lil-637784

RESUMO

Morphologic variation of the parthenogenetic lizard Aspidoscelis rodecki (Squamata: Teiidae): evolutionary and conservation implications. Post-formational divergence has been used for the recognition of new parthenogenetic species. Currently, the parthenogenetic lizard Aspidoscelis rodecki McCoy and Maslin 1962 is recognized as a single taxon that was derived from a single, parthenogenetically capable, hybrid. This lizard had been derived via hybridization between individuals of two gonochoristic species, Aspidoscelis angusticeps Cope 1878 and Aspidoscelis deppii Wiegmann 1834. The distribution of A. rodecki includes Isla Contoy and Isla Mujeres and the adjacent mainland of Quintana Roo, México. Previous studies have found post-formational divergence in genetic, chromatic and life-history characteristics among a continental population (Puerto Juárez) and an insular population (Isla Contoy). A meristic analysis was carried out to evaluate the morphological divergence among both populations of A. rodecki. We used 38 individuals from Puerto Juárez and 23 individuals from Isla Contoy. Nine meristic characters with discrimination value among species of the genus Aspidoscelis were used in both univariate (t-Student) and multivariate analyses (principal components and canonical variate analysis). According to both analyses, Puerto Juárez is meristically distinguishable from Isla Contoy. Both populations differ in five meristic characters and were a high correct classification in the canonical variate analysis: 97% of Puerto Juárez and 100% of Isla Contoy. A small sample from Isla Mujeres and a single specimen from Punta Sam (mainland) may represent different morphological groups. Due to the patterns of phenotypic variation, A. rodecki is considered as a single variable parthenogenetic species with high priority to conservation. The populations of A. rodecki have been extremely affected by the tourism developers. If the habitat of the parthenogenetic lizard (beach grasses) is allowed to stay, the expansion by the developers will not affect the survivorship of these populations. Nevertheless, the first sign of development is the total destruction of natural grasses that occurs on the beach, leaving only sand. There is a last chance to save the parthenogenetic lizard A. rodecki, but any effort will be useless without the support from the environmental authority of Mexico and cooperation from the developers. We suggest that Puerto Juárez and Isla Contoy receive separate management because they have unique portions of phenotypic variation of A. rodecki. The two lizard populations can be considered separate "Evolutionary Significant Units" (ESU). Rev. Biol. Trop. 56 (4): 1871-1881. Epub 2008 December 12.


La divergencia post-formación se ha utilizado para el reconocimiento de nuevas especies partenogenéticas. Actualmente, la lagartija partenogenética Aspidoscelis rodecki McCoy y Maslin 1962 es reconocida como una sola especie, que se originó de un híbrido partenogenético. Estudios previos han encontrado divergencia genética, en coloración y en características de historia de vida entre una población continental (Puerto Juárez) y una insular (Isla Contoy) en Quintana Roo, México. Se llevó a cabo un análisis merístico para evaluar la divergencia entre ambas poblaciones de A. rodecki. Se utilizaron 38 individuos de Puerto Juárez y 23 individuos de Isla Contoy. Se usaron nueve características merísticas y se realizaron análisis univariados (t de Student) y multivariados (análisis de componentes principales y análisis de variación canónica). De acuerdo a ambos análisis, Puerto Juárez es merísticamente distinguible de Isla Contoy. Ambas poblaciones difieren en cinco características merísticas y presentaron un alto porcentaje de clasificación en el análisis de variación canónica: 97% para Puerto Juárez y 100% para Isla Contoy. Una pequeña muestra de Isla Mujeres y un solo individuo de Punta Sam (continente) pueden representar otros grupos morfológicos. Con base en los patrones de variación fenotípica, A. rodecki es considerada como una sola especie partenogenética variable y prioritaria para la conservación. Debido a que cada población contiene una porción única de la variación de A. rodecki, Puerto Juárez e Isla Contoy merecen un manejo separado y se sugiere que cada una constituya una "Unidad Evolutiva Significativa" (ESU).


Assuntos
Animais , Feminino , Lagartos/genética , Partenogênese/genética , Evolução Molecular , Lagartos/anatomia & histologia , Lagartos/classificação , México , Fenótipo
11.
Rev Biol Trop ; 56(4): 1871-81, 2008 Dec.
Artigo em Espanhol | MEDLINE | ID: mdl-19419088

RESUMO

Post-formational divergence has been used for the recognition of new parthenogenetic species. Currently, the parthenogenetic lizard Aspidoscelis rodecki McCoy and Maslin 1962 is recognized as a single taxon that was derived from a single, parthenogenetically capable, hybrid. This lizard had been derived via hybridization between individuals of two gonochoristic species, Aspidoscelis ungusticeps Cope 1878 and Aspidoscelis deppii Wiegmann 1834. The distribution of A. rodecki includes Isla Contoy and Isla Mujeres and the adjacent mainland of Quintana Roo, México. Previous studies have found post-formational divergence in genetic, chromatic and life-history characteristics among a continental population (Puerto Juárez) and an insular population (Isla Contoy). A meristic analysis was carried out to evaluate the morphological divergence among both populations of A. rodecki. We used 38 individuals from Puerto Juárez and 23 individuals from Isla Contoy. Nine meristic characters with discrimination value among species of the genus Aspidoscelis were used in both univariate (t-Student) and multivariate analyses (principal components and canonical variate analysis). According to both analyses, Puerto Juárez is meristically distinguishable from Isla Contoy. Both populations differ in five meristic characters and were a high correct classification in the canonical variate analysis: 97% of Puerto Juárez and 100% of Isla Contoy. A small sample from Isla Mujeres and a single specimen from Punta Sam (mainland) may represent different morphological groups. Due to the patterns of phenotypic variation, A. rodecki is considered as a single variable parthenogenetic species with high priority to conservation. The populations of A. rodecki have been extremely affected by the tourism developers. If the habitat of the parthenogenetic lizard (beach grasses) is allowed to stay, the expansion by the developers will not affect the survivorship of these populations. Nevertheless, the first sign of development is the total destruction of natural grasses that occurs on the beach, leaving only sand. There is a last chance to save the parthenogenetic lizard A. rodecki, but any effort will be useless without the support from the environmental authority of Mexico and cooperation from the developers. We suggest that Puerto Juárez and Isla Contoy receive separate management because they have unique portions of phenotypic variation of A. rodecki. The two lizard populations can be considered separate "Evolutionary Significant Units" (ESU).


Assuntos
Lagartos/genética , Partenogênese/genética , Animais , Evolução Molecular , Feminino , Lagartos/anatomia & histologia , Lagartos/classificação , México , Fenótipo
12.
Mol Phylogenet Evol ; 36(3): 682-94, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15964216

RESUMO

The peninsula of Baja California has a complex geological history that has strongly affected the regional biota. Genealogical histories of many species have revealed congruent patterns, which suggest that the peninsula was temporarily submerged at two locations. We sequenced a total of 1953 base pairs (bp) of the mitochondrial genome for 42 specimens of the zebra-tailed lizard (Callisaurus draconoides). The resulting maternal genealogy supports the former existence of a mid-peninsular seaway and a Plio-Quaternary seaway across the Isthmus of La Paz. In addition, a genealogical break is revealed in the vicinity of Loreto. This genealogical break may have resulted from prolonged submergence of the Loreto Basin during Pliocene. The mid-peninsular seaway may have occurred as early as late Miocene, at a time significantly earlier than previously hypothesized. Comparison with other genealogies and geological evidence suggests that current models on the evolution of Baja California's fauna are temporally shallow. The deep genealogical patterns of C. draconoides also disagree with the very limited population differentiation previously reported for allozyme markers, suggesting that maternal history may not be an appropriate approximation for population differentiation.


Assuntos
DNA Mitocondrial/genética , Enzimas/genética , Variação Genética/genética , Lagartos/classificação , Lagartos/genética , Filogenia , Animais , Sequência de Bases , México
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