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The opposing forces of gene flow and isolation are two major processes shaping genetic diversity. Understanding how these vary across space and time is necessary to identify the environmental features that promote diversification. The detection of considerable geographic structure in taxa from the arid Nearctic has prompted research into the drivers of isolation in the region. Several geographic features have been proposed as barriers to gene flow, including the Colorado River, Western Continental Divide (WCD), and a hypothetical Mid-Peninsular Seaway in Baja California. However, recent studies suggest that the role of barriers in genetic differentiation may have been overestimated when compared to other mechanisms of divergence. In this study, we infer historical and spatial patterns of connectivity and isolation in Desert Spiny Lizards (Sceloporus magister) and Baja Spiny Lizards (Sceloporus zosteromus), which together form a species complex composed of parapatric lineages with wide distributions in arid western North America. Our analyses incorporate mitochondrial sequences, genomic-scale data, and past and present climatic data to evaluate the nature and strength of barriers to gene flow in the region. Our approach relies on estimates of migration under the multispecies coalescent to understand the history of lineage divergence in the face of gene flow. Results show that the S. magister complex is geographically structured, but we also detect instances of gene flow. The WCD is a strong barrier to gene flow, while the Colorado River is more permeable. Analyses yield conflicting results for the catalyst of differentiation of peninsular lineages in S. zosteromus. Our study shows how large-scale genomic data for thoroughly sampled species can shed new light on biogeography. Furthermore, our approach highlights the need for the combined analysis of multiple sources of evidence to adequately characterize the drivers of divergence. [ABSTRACT FROM AUTHOR]

We describe Geophis berillus sp. nov., a new species of the Geophis sieboldi group based on three specimens from the Valle de Bravo region in the Trans-Mexican Volcanic Belt, Estado de México, Mexico. The new species differs from all other members of this group by having 17 dorsal scale rows without apical pits, 149 and 151–152 ventrals (in males and females, respectively), and the lower portion of each scale in the first dorsal scale row pale. The new species is allopatric respective to other Geophis species. A phylogenetic analysis based on mitochondrial DNA (cyt-b) supports the inclusion of G. berillus sp. nov. in the G. sieboldi group and a sister relationship with G. sieboldi, a finding corroborated by morphological evidence. Describimos a Geophis berillus sp. nov una nueva especie del grupo Geophis sieboldi con base en tres especímenes de la región de Valle de Bravo en la Faja Volcánica Transmexicana. La nueva especie se diferencia de otros miembros del grupo por poseer 17 hileras de escamas dorsales sin fosas apicales, 149 y 152–153 ventrales (en machos y hembras, respectivamente) y la porción inferior de cada escama en la primera hilera de escamas dorsales clara. La nueva especie es alopátrica con respecto a otras especies de Geophis. Un análisis filogenético basado en DNA mitocondrial (cyt-b) respalda la inclusión de Geophis berillus sp. nov en el grupo G. sieboldi y su relación como grupo hermano de G. sieboldi, lo cual se corrobora con la evidencia morfológica. [ABSTRACT FROM AUTHOR]

How biotic and abiotic factors act together to shape biological diversity is a major question in evolutionary biology. The recent availability of large datasets and development of new methodological approaches provide new tools to evaluate the predicted effects of ecological interactions and geography on lineage diversification and phenotypic evolution. Here, we use a near complete phylogenomic‐scale phylogeny and a comprehensive morphological dataset comprising more than a thousand specimens to assess the role of biotic and abiotic processes in the diversification of monitor lizards (Varanidae). This charismatic group of lizards shows striking variation in species richness among its clades and multiple instances of endemic radiation in Indo‐Australasia (i.e., the Indo‐Australian Archipelago and Australia), one of Earth's most biogeographically complex regions. We found heterogeneity in diversification dynamics across the family. Idiosyncratic biotic and geographic conditions appear to have driven diversification and morphological evolution in three endemic Indo‐Australasian radiations. Furthermore, incumbency effects partially explain patterns in the biotic exchange between Australia and New Guinea. Our results offer insight into the dynamic history of Indo‐Australasia, the evolutionary significance of competition, and the long‐term consequences of incumbency effects. [ABSTRACT FROM AUTHOR]

Hybridization between species occurs more frequently in vertebrates than traditionally thought, but distinguishing ancient hybridization from other phenomena that generate similar evolutionary patterns remains challenging. Here, we used a comprehensive workflow to discover evidence of ancient hybridization between the Komodo dragon (Varanus komodoensis) from Indonesia and a common ancestor of an Australian group of monitor lizards known colloquially as sand monitors. Our data comprise |$>$| 300 nuclear loci, mitochondrial genomes, phenotypic data, fossil and contemporary records, and past/present climatic data. We show that the four sand monitor species share more nuclear alleles with |$V$|⁠. komodoensis than expected given a bifurcating phylogeny, likely as a result of hybridization between the latter species and a common ancestor of sand monitors. Sand monitors display phenotypes that are intermediate between their closest relatives and |$V$|⁠. komodoensis. Biogeographic analyses suggest that |$V$|⁠. komodoensis and ancestral sand monitors co-occurred in northern Australia. In agreement with the fossil record, this provides further evidence that the Komodo dragon once inhabited the Australian continent. Our study shows how different sources of evidence can be used to thoroughly characterize evolutionary histories that deviate from a treelike pattern, that hybridization can have long-lasting effects on phenotypes, and that detecting hybridization can improve our understanding of evolutionary and biogeographic patterns.[Biogeography; introgression; Komodo dragon; phylogenetic networks; phylogenomics; reticulation; Varanus. ] [ABSTRACT FROM AUTHOR]

Recent studies on the systematics and phylogeny of the blue-tailed skinks in the Plestiodon brevirostris group identified a population from the Sierra Madre del Sur of eastern Guerrero, Mexico, that appeared to represent an undescribed species. Here, we formally describe this lineage as a new species, compare it with the other species in the P. brevirostris group, identify a specimen from western Oaxaca that belongs to the new species, and provide an updated key to the group. The new species is morphologically similar and closely related to P. ochoterenae, but molecular and morphological data support its evolutionary independence. The new species is distinguished from the other species in the P. brevirostris group, except for P. ochoterenae, by the presence of a primary temporal, a well-defined lateral pale line on the neck, and a well-defined dorsolateral pale line that extends posteriorly to the level of the hind limbs. It differs from P. ochoterenae by having longer limbs and a well-defined lateral pale line on the neck. The present study further highlights the relevance of the Sierra Madre del Sur as a hotspot of endemism and undescribed diversity. [ABSTRACT FROM AUTHOR]

Sexually selected traits can be expected to increase in importance when the period of sexual behavior is constrained, such as in seasonally restricted breeders. Anolis lizard male dewlaps are classic examples of multifaceted signaling traits, with demonstrated intraspecific reproductive function reflected in courtship behavior. Fitch and Hillis found a correlation between dewlap size and seasonality in mainland Anolis using traditional statistical methods and suggested that seasonally restricted breeding seasons enhanced the differentiation of this signaling trait. Here, we present two tests of the Fitch–Hillis Hypothesis using new phylogenetic and morphological data sets for 44 species of Mexican Anolis. A significant relationship between dewlap size and seasonality is evident in phylogenetically uncorrected analyses but erodes once phylogeny is accounted for. This loss of strong statistical support for a relationship between a key aspect of dewlap morphology and seasonality also occurs within a species complex (A. sericeus group) that inhabits seasonal and aseasonal environments. Our results fail to support seasonality as a strong driver of evolution of Anolis dewlap size. We discuss the implications of our results and the difficulty of disentangling the strength of single mechanisms on trait evolution when multiple selection pressures are likely at play. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Environmental, molecular, and morphological data were used in a unified framework. • Integrative delimitation allowed to discern between competing hypotheses. • Plestiodon brevirostris is composed of four distinct lineages. • Some of the discovered species are cryptic, microendemic, and/or parapatric. Abstract Integrative taxonomy has been generally considered as a goal in systematics for more than a decade. Here, we employed environmental, molecular, and morphological data to evaluate the species boundaries within the short-nosed skink Plestiodon brevirostris from south-central Mexico, one member of the morphologically conservative P. brevirostris group. Our molecular dataset includes one mitochondrial and two nuclear loci. The mitochondrial fragment includes the full length of the gene coding for the NADH dehydrogenase subunit 1 protein, a segment of the gene coding for 16S ribosomal RNA, and flanking tRNAs. The nuclear dataset includes fragments of the genes coding for the megakaryoblastic leukemia 1 and RNA fingerprint 35 proteins. We employed phylogenetic reconstruction, analyses of population structure and morphological variation, and species delimitation methods (including the integration of the three kinds of data in a unified probabilistic framework) to evaluate species limits. Our results suggest that P. brevirostris represents four distinct species. The information provided by each kind of data allowed us to discern between alternative explanations for the observed patterns of geographic structure. Two of the newly recognized lineages are poorly differentiated morphologically but apparently differ in environmental preferences and are allopatric. Additionally, one lineage is microendemic and parapatric with respect to another one. Moreover, our phylogenetic analyses suggest that other taxa within the P. brevirostris group may represent species complexes. We discuss our results in the context of integrative species delimitation. [ABSTRACT FROM AUTHOR]

A new species of the Rhadinaea decorata group is described based on two specimens from the Sierra Madre del Sur, Guerrero, Mexico. The new species differs from all other members of the genus Rhadinaea by having: eight supralabials; 149-151 (male) ventrals; 63-77 (male) subcaudals; two large pale nuchal blotches, forming an incomplete collar that occupies two scales laterally and is bissected along the dorsal midline; a postocular pale marking consisting of a well-defined, narrow line beginning behind the upper posterior margin of the eye and extending posteriorly nearly horizontally until connecting with the nuchal blotches; and the dark ground color of the flanks extending to the lateral portion of the ventrals. The large nuchal blotches distinguish the new species from the other members of the R. decorata group, except for R. cuneata and some individuals of R. hesperia (pale nuchal marking one-scale wide in R. marcellae, absent in the other species). The condition of the postocular pale marking distinguishes it from R. cuneata and R. hesperia (postocular pale marking wedge-shaped in R. cuneata, not connected with the pale post-cephalic markings in R. hesperia). Furthermore, the number of subcaudals and the coloration of the lateral portion of the ventrals distinguish it from R. omiltemana and R. taeniata, the remaining congeners found in Guerrero (85-90 in males of R. omiltemana and 91-121 in R. taeniata; dark color of the flanks not reaching ventrals in the former species, occasionally and faintly in R. taeniata). Additionally, a new combination for R. stadelmani is proposed. The new species is the first described in the genus Rhadinaea in more than 40 years. [ABSTRACT FROM AUTHOR]

A new species of the Geophis dubius group is described from the mountains of the Sierra Zongolica in west-central Veracruz and the Sierra de Quimixtlán in central-east Puebla. The new species is most similar to G. duellmani and G. turbidus, which are endemic to the mountains of northern Oaxaca and the Sierra Madre Oriental of Puebla and Hidalgo, respectively. However, the new species differs from G. duellmani by the presence of postocular and supraocular scales and from G. turbidus by having a bicolor dorsum. With the description of the new species, the species number in the genus increases to 50 and to 12 in the G. dubius group. Additionally, a key to the species of the G. dubius group is provided. [ABSTRACT FROM AUTHOR]

The article provides information on Cacophis squamulosus (golden-crowned snake) in New South Wales, which was found active on dirt road surrounded by coastal dry shrub forest.

The article discusses the defensive behavior of the Western Ribbonsnake. Topics include the documentation of tail pseudoautotomy in T. proximus, a defensive mechanism where the snake loses its tail to escape predators, the first recorded instance of this behavior in the species, and the specific circumstances under which the behavior was observed, including the snake's habitat and capture details.

The article focuses on the first record of Barisia ciliaris in Santa Bárbara, Chihuahua, Mexico, marking a new municipality and second state record, extending its known range by 90.4 kilometers.

The article details the discovery of Lampropeltis mexicana (San Luis Potosí Kingsnake) in San Luis Potosí, Mexico.

Rhadinaea marcellae Taylor, 1949 is known from only 12 specimens. Based on recent fieldwork and research in scientific collections and databases, we report 14 new records of R. marcellae, bringing the total number of verified occurrences up to 26, updating our understanding of this secretive species' distribution in the tropical and cloud forests of the Sierra Madre Oriental in Mexico. The new records come from the Mexican states of Hidalgo, Puebla, San Luis Potosí and Veracruz. All the newly reported specimens are morphologically concordant with R. marcellae, but exhibit noteworthy variation. [ABSTRACT FROM AUTHOR]

[Display omitted] • We produce detailed phylogenetic analyses for a comprehensive sampling of the Antaresia genus of dwarfed pythons. • Population structure and species delimitation analyses show extensive admixture. • Historical demography analyses show the importance of biodiversity hotspots in the Pilbara, Kimberley and Cape York. • Our molecular results, combined with linear and geometric morphometric analyses highlight the importance of integrative approaches. • Our results lead us to lump the widespread species A. childreni and A. stimsoni, and to describe a new species of Antaresia for Torres Strait and New Guinea as well as two subspecies of A. maculosa in northeast Australia. Advances from empirical studies in phylogeography, systematics and species delimitation highlight the importance of integrative approaches for quantifying taxonomic diversity. Genomic data have greatly improved our ability to discern both systematic diversity and evolutionary history. Here we combine analyses of mitochondrial DNA sequences, thousands of genome-wide SNPs and linear and geometric morphometrics on Antaresia, a clade of four currently recognised dwarf pythons from Australia and New Guinea (Antaresia childreni, A. stimsoni, A. maculosa and A. perthensis). Our integrative analyses of phylogenetics, population structure, species delimitation, historical demography and morphometrics revealed that the true evolutionary diversity is not well reflected in the current appraisal of the diversity of the group. We find that Antaresia childreni and A. stimsoni comprise a widespread network of populations connected by gene flow and without evidence of species-level divergence among them. However, A. maculosa shows considerable genetic structuring which leads us to recognise two subspecies in northeastern Australia and a new species in Torres Strait and New Guinea. These two contrasting cases of over and under estimation of diversity, respectively, illustrate the power of thorough integrative approaches into understanding evolution of biodiversity. Furthermore, our analyses of historical demographic patterns highlight the importance of the Kimberley, Pilbara and Cape York as origins of biodiversity in Australia. [ABSTRACT FROM AUTHOR]

• We found important mito-nuclear discordance in the evolution of the Liolaemus leopardinus group. • Species delimitation using mtDNA under-estimates diversity. • SNP-based delimitation uncovers more accurate and complex diversity. • These patterns are likely due to introgression between taxa in the same mountain chain. • We sink one species and describe a new one for Liolaemus. Organisms rapidly diversifying across unstable environments such as mountain tops provide substantial challenges for resolving evolutionary histories and delimiting species. The Liolaemus leopardinus clade is a group of five species of lizards adapted to high altitudes in central Chile, with most species found in the Andes, but one species, L. frassinettii is found in the independent Costa Cordillera. Despite their allopatric distributions, they display shallow mitochondrial divergences, making phylogenetics and species delimitation of this clade hard to resolve. We use an integrative approach to delimit species by considering morphological data (linear and landmark-based), mitochondrial DNA (mtDNA), and nuclear DNA (Sequences and SNPs collected with ddRADseq). We find strong conflicting signals between phylogenetic analyses of the nuclear and mtDNA data. While mtDNA places L. frassinettii as sister to the rest of the clade, the SNPs support a south to north order of divergences, with southernmost species (new taxon described here) as sister to the rest of the clade. Moreover, species delimitation using mtDNA only supports two species (one in the Costa and one in the Andes), whereas combined analyses using the nuclear data and morphology support multiple Andean taxa, including a new one we describe here. Based on these results, population structure analyses and our knowledge of the geological and climatic history of the Andes, we argue that this mito-nuclear discordance is explained by past introgression among the Andean taxa, likely during glacial periods that forced these lizards to lower altitudes where they would hybridize. The complete isolation between the Costa and Andes cordilleras has prevented any further contact between taxa on either mountain chain. Our study highlights the importance of using multiple lines of evidence to resolve evolutionary histories, and the potential misleading results from relying solely on mtDNA. [ABSTRACT FROM AUTHOR]