Species delimitation, biogeography, and natural history of dwarf funnel web spiders (Mygalomorphae, Hexurellidae, Hexurella) from the United States / Mexico borderlands.

The rarely encountered spider genus Hexurella Gertsch & Platnick, 1979 includes some of the smallest mygalomorph spiders in the world, with four poorly known taxa from central and southeastern montane Arizona, southern California, and northern Baja California Norte. At time of description the genus was known from fewer than 20 individuals, with sparse natural history information suggesting a vagrant, web-building, litter-dwelling natural history. Here the first published taxonomic and natural history information for this taxon is provided in more than 50 years, working from extensive new geographic sampling, consideration of male and female morphology, and sequence capture-based nuclear phylogenomics and mitogenomics. Several new species are easily diagnosed based on distinctive male morphologies, while a complex of populations from central and northern Arizona required an integrative combination of genomic algorithmic species delimitation analyses and morphological study. Four new species are described, including H.ephedrasp. nov., H.uwiiltilsp. nov., H.xericasp. nov., and H.zassp. nov. Females of H.encina Gertsch & Platnick, 1979 are also described for the first time. It is predicted that additional new species will ultimately be found in the mountains of central and northwestern Arizona, northern mainland Mexico, and the Mojave Desert of California.

Geographic isolation alone does not explain divergence of a group of orchid species across Brazil's campos rupestres sky-islandsIsolamento geográfico por si só não explica a divergência de um grupo de espécies de orquídeas nos campos rupestres do Brasil.

Mountains play a crucial role in the origin and maintenance of Neotropical biodiversity, but there are still unanswered questions about the diversification of the campos rupestres (CR), an herbaceous-shrubby sky-island vegetation in eastern South America. For orchids distributed across this disjunct rock habitat, difficulties with distinguishing morphological taxa add an additional challenge to disentangling the history of divergence. Here, we combined the power of ddRAD genomic data with broad sampling of Bulbophyllum sect. Didactyle (Orchidaceae), across the CR and other Neotropical outcrops, to estimate evolutionary relationships and evaluate the biogeography of the group's diversification. Although genetic lineages generally align with geographic disjunctions, we also observe distantly related lineages within some previously recognized species. For such taxa, their lack of monophyly and a shared regional divergence pattern suggests a complex history that may include unrecognized diversity. When viewed through the lens of morphological variability, our study raises intriguing questions about the persistence and permeability of species barriers among orchid populations. These results, in addition to the recency of the divergence history of B. sect. Didactyle, provide insights about hypothesized community level vs. species-specific paths of diversification across the Neotropical sky-islands of the CR.

Rugged relief and climate promote isolation and divergence between two neotropical cold-associated birds.

The role of historical factors in establishing patterns of diversity in tropical mountains is of interest to understand the buildup of megadiverse biotas. In these regions, the historical processes of range fragmentation and contraction followed by dispersal are thought to be mediated by the interplay between rugged relief (complex topography) and climate fluctuations and likely explain most of the dynamics of diversification in plants and animals. Although empirical studies addressing the interaction between climate and topography have provided invaluable insights into population divergence and speciation patterns in tropical montane organisms, a more detailed and robust test of such processes in an explicit spatio-temporal framework is still lacking. Consequently, our ability to gain insights into historical range shifts over time and the genomic footprint left by them is limited. Here, we used niche modeling and subgenomic population-level datasets to explore the evolution of two species of warbling finches (genus Microspingus) disjunctly distributed across the Montane Atlantic Forest, a Neotropical region with complex geological and environmental histories. Population structure inferences suggest a scenario of three genetically differentiated populations, which are congruent with both geography and phenotypic variation. Demographic simulations support asynchronous isolation of these populations as recently as ∼40,000 years ago, relatively stable population sizes over recent time, and past gene flow subsequent to divergence. Throughout the last 800,000 years, niche models predicted extensive expansion into lowland areas with increasing overlap of species distributions during glacial periods, with prominent retractions and isolation into higher altitudes during interglacials, which are in line with signs of introgression of currently isolated populations. These results support a dual role of cyclical climatic changes: population divergence and persistence in mountain tops during warm periods followed by periods of expansion and admixture in lower elevations during cold periods. Our results underscore the role of the interplay between landscape and climate as an important mechanism in the evolution of the Neotropical montane biota.

A new species of Aphonopelma (Araneae: Mygalomorphae: Theraphosidae) from the Madrean pine-oak woodlands of northeastern Sonora, Mexico.

The tarantula spider genus Aphonopelma Pocock, 1901 has received considerable attention in recent years but the group's diversity remains poorly understood in Mexico, particularly in the pine-oak woodlands of the Sierra Madre Occidental and associated Madrean "Sky Islands". A pair of tarantulas discovered from an unsampled region in the Sierra de Bacadéhuachi (the westernmost range of the Sierra Madre Occidental) in northeastern Sonora was found to be closely related to four species from the Madrean "Sky Islands" in Arizona and New Mexico. An integrative approach for delimiting species (incorporating data from molecular phylogenetics, morphology, distributions, and breeding periods) suggests that the specimens from Sierra de Bacadéhuachi belong to an undescribed species that is herein named Aphonopelma bacadehuachi sp. nov. This new species adds to our knowledge of an increasingly diverse assemblage of Aphonopelma from the Madrean Pine-Oak Woodlands Hotspot. Collaborations between Mexican and American researchers are needed to accelerate discovery and description of the group's remaining diversity, particularly in light of the many threats facing the ecoregion including habitat degradation and climate change.

Predator-prey interactions and venom composition in a high elevation lizard specialist, Crotalus pricei (Twin-spotted Rattlesnake).

The Twin-spotted Rattlesnake (Crotalus pricei) is a small lizard specialist restricted to higher montane habitat in the Sky Islands of Arizona and México. Though this species is restricted to high elevations and dispersal between mountaintops is impossible, few studies have investigated venom composition or the predator-prey relationship between C. p. pricei and its primary prey source, Yarrow's Spiny Lizard (Sceloporus jarrovii). Because of current isolation of populations in disjunct mountain ranges, it is possible that populations show local adaptation to prey and/or environmental conditions, as reflected by distinct venom phenotypes. Here we characterize venom composition of C. pricei from several different Sky Island mountain ranges and its relationship with S. jarrovii by using various analytical techniques and comparative toxicity tests. Results of venom analyses indicate that there is limited geographic variation in venom composition, occurring primarily in venoms of C. pricei from Durango, México, which had unusual PLA2 isoforms that are lacking from venoms of U.S. populations. Toxicity assays reveal that S. jarrovii has not developed resistance specific to C. p. pricei venom but does display a general tolerance to venom of several snakes in the genus Crotalus. These results provide insight into the evolutionary relationship between a lizard specialist and its natural prey, in addition to novel information on the venom composition of a little-studied species with a narrow range in the United States.

Dung beetle vicariant speciation in the mountains of Oaxaca, Mexico, with a description of a new species of Phanaeus (Coleoptera, Geotrupidae, Scarabaeidae).

An analysis of vicariant speciation of Geotrupes and Phanaeus (Coleoptera, Geotrupidae, Scarabaeidae) from the mountains of Oaxaca, Mexico is undertaken. The new species of dung beetle (Coleoptera: Scarabaeidae) from Oaxaca, Mexico, Phanaeus dionysiussp. n. is described. Photos of the habitus and a distribution map are provided. Phanaeus malyi Arnaud is revalidated. An updated key for the Phanaeus endymion species group and new localities are also presented. An updated key for the Geotrupes of Oaxaca and new locality records are also submitted.

ResumenSe realiza un análisis de especiación vicariante de Geotrupes y Phanaeus (Coleoptera, Geotrupidae, Scarabaeidae) de las montañas de Oaxaca, México. La siguiente especie nueva de escarabajo estercolero (Coleoptera: Scarabaeidae) se describe de Oaxaca: Phanaeus dionysiussp. n. Se incluyen fotografías, así como el respectivo mapa de distribución. Se revalida a la especie Phanaeus malyi Arnaud. Se presenta una clave puesta al día del grupo de especies de Phanaeus endymion, así como nuevos registros de distribución. Se incluye también una clave puesta al día para los Geotrupes de Oaxaca.