Microgeographic population structuring in a genus of California trapdoor spiders and discovery of an enigmatic new species (Euctenizidae: Promyrmekiaphila korematsui sp. nov.)

The recognition and delineation of cryptic species remains a perplexing problem in systematics, evolution, and species delimitation. Once recognized as such, cryptic species complexes provide fertile ground for studying genetic divergence within the context of phenotypic and ecological divergence (or lack thereof). Herein we document the discovery of a new cryptic species of trapdoor spider, Promyrmekiaphila korematsui sp. nov. Using subgenomic data obtained via target enrichment, we document the phylogeography of the California endemic genus Promyrmekiaphila and its constituent species, which also includes P. clathrata and P. winnemem. Based on these data we show a pattern of strong geographic structuring among populations but cannot entirely discount recent gene flow among populations that are parapatric, particularly for deeply diverged lineages within P. clathrata. The genetic data, in addition to revealing a new undescribed species, also allude to a pattern of potential phenotypic differentiation where species likely come into close contact. Alternatively, phenotypic cohesion among genetically divergent P. clathrata lineages suggests that some level of gene flow is ongoing or occurred in the recent past. Despite considerable field collection efforts over many years, additional sampling in potential zones of contact for both species and lineages is needed to completely resolve the dynamics of divergence in Promyrmekiaphila at the population-species interface.

But wait, there’s more! Descriptions of new species and undescribed sexes of flattie spiders (Araneae, Selenopidae, Karaops) from Australia

Nineteen new species of Karaops are described: K. durrantorumsp. nov. (♂), K. morganoconnellisp. nov. (♀♂), K. joehaenerisp. nov. (♀), K. dalmanyisp. nov. (♀♂), K. garyodwyerisp. nov. (♂), K. dejongisp. nov. (♀♂), K. malumbusp. nov. (♀♂), K. conilurussp. nov. (♂), K. yumbubaarnjisp. nov. (♀♂), K. markharveyisp. nov. (♀♂), K. nitmiluksp. nov. (♀), K. kennerleyorumsp. nov. (♂), K. jawaywaysp. nov. (♀), K. mparntwesp. nov. (♀), K. larapintasp. nov. (♀), K. kwartatumasp. nov. (♂), K. madhawundusp. nov. (♀), and K. mareebasp. nov. (♀). The male of K. umiida Crews, 2013 was found to be misidentified and is now K. conilurussp. nov.Karaops yindjibarndisyn. nov. is a new synonym of K. nyiyaparli. Selenops australiensis L. Koch, 1875 is considered a nomen dubium because the holotype is an immature male, and the species previously referred to as K. australiensis (L. Koch, 1875) is here described as K. strayamatesp. nov. (♀♂). The males of K. marrayagong Crews & Harvey, 2011 and K. banyjima Crews, 2013 are described for the first time. To manage the growing diversity of the genus, most of the species have been placed in species groups, which are diagnosed. They are the Central Desert group, the strayamate group, the raveni group, the dawara group, the francesae group, the Kimberley group, and the Pilbara-Gascoyne group. New keys are provided to accommodate the new species, and new distribution maps and new records are provided for all species. Diagnoses and descriptions are emended where required. Images of live spiders, many not previously seen alive, and natural history information are also provided.

Trapped indoors? Long-distance dispersal in mygalomorph spiders and its effect on species ranges

The Mygalomorphae includes tarantulas, trapdoor, funnel-web, purse-web and sheet-web spiders, species known for poor dispersal abilities. Here, we attempted to compile all the information available on their long-distance dispersal mechanisms from observations that are often spread throughout the taxonomic literature. Mygalomorphs can disperse terrestrially, and in some tarantulas, for example, spiderlings walk together in single files away from their maternal burrow, a mechanism limited in distance covered. Conversely, at least eight species disperse aerially, via dropping on drag lines from elevated positions and being passively blown off ('suspended ballooning'). The first record of this behaviour is 135 years old, but we still know very little about it. Phylogeographic studies suggest several occurrences of transcontinental dispersal in the evolutionary history of mygalomorphs, but these might result from contingent rafting events, rather than regular dispersal mechanisms. We use occurrence data to show that suspended ballooning increases the species ranges in Australian mygalomorph families where this behaviour has been recorded. We also identified Anamidae, Idiopidae, and especially Atracidae, as families that might employ suspended ballooning or another efficient but undiscovered dispersal mechanism. Finally, we suggest that molecular studies with mitochondrial genes will help disentangle behavioural limitations of dispersal from ecological or physical ones.

Integrative species delimitation reveals cryptic diversity in the southern Appalachian Antrodiaetus unicolor (Araneae: Antrodiaetidae) species complex

Although species delimitation can be highly contentious, the development of reliable methods to accurately ascertain species boundaries is an imperative step in cataloguing and describing Earth's quickly disappearing biodiversity. Spider species delimitation remains largely based on morphological characters; however, many mygalomorph spider populations are morphologically indistinguishable from each other yet have considerable molecular divergence. The focus of our study, the Antrodiaetus unicolor species complex containing two sympatric species, exhibits this pattern of relative morphological stasis with considerable genetic divergence across its distribution. A past study using two molecular markers, COI and 28S, revealed that A. unicolor is paraphyletic with respect to A. microunicolor. To better investigate species boundaries in the complex, we implement the cohesion species concept and use multiple lines of evidence for testing genetic exchangeability and ecological interchangeability. Our integrative approach includes extensively sampling homologous loci across the genome using a RADseq approach (3RAD), assessing population structure across their geographic range using multiple genetic clustering analyses that include structure, principal components analysis and a recently developed unsupervised machine learning approach (Variational Autoencoder). We evaluate ecological similarity by using large-scale ecological data for niche-based distribution modelling. Based on our analyses, we conclude that this complex has at least one additional species as well as confirm species delimitations based on previous less comprehensive approaches. Our study demonstrates the efficacy of genomic-scale data for recognizing cryptic species, suggesting that species delimitation with one data type, whether one mitochondrial gene or morphology, may underestimate true species diversity in morphologically homogenous taxa with low vagility.