ABSTRACT Aim In west‐central California, the landscapes west of the San Andreas fault include the arc plutons of the Salinian block which form the geologic backbone of several South Coast mountain ranges. In the early Miocene Salinia was adjacent to the southern Sierra Nevada, but was subsequently captured by the Pacific Plate, with right‐lateral slip migration displacing terranes northwestwards since the formation of the San Andreas fault. We hypothesise that a migrating Salinia has played an important role in the biogeographic history of dispersal‐limited Megahexura mygalomorph spiders. Location Central and southern California Floristic Province, including Salinia (Santa Lucia, Sierra de Salinas, Gabilan, and Santa Cruz mountains), southern Sierra Nevada, and Transverse Ranges. Taxon Megahexura , Family Megahexuridae, Infraorder Mygalomorphae, Order Araneae. Methods Analyses of ultraconserved element (UCE) nuclear loci and single nucleotide polymorphism (SNP) data are used to estimate ingroup relationships and genetic population structuring, root placement and divergence timing, and a Bayesian‐estimated biogeographic history of Megahexura . Results Phylogenomics strongly supports three primary phylogenetic lineages in Megahexura , with a common ancestor that diverged in the early to mid‐Miocene, depending upon calibration parameters. The southern Sierra Nevada is reconstructed as the centre of origin for Megahexura , and one Megahexura lineage now resides mostly on ranges that include Salinian basement rocks. In the Santa Lucia Range, phylogenetic directionality is structured from north to south. The southern Sierra Nevada is also a more recent ancestral area for Megahexura populations currently occupying the western and southern Transverse Ranges, some of which have expanded northwestwards to secondarily contact Salinian populations. Main Conclusions We uncover a unique biogeographic history where instead of animal populations dispersing recently over an old landscape, phylogenomic patterns are best explained by the landscape itself moving, carrying animal populations. Our results are consistent with a compelling Salinian biogeography and represent a possible case of Neogene divergence driven principally by plate tectonics.

We present a morphological description of a recently discovered species of spider in the family Trogloraptoridae from the Columbia River Gorge in northwestern Oregon. The family was previously monotypic (Trogloraptor marchingtoni) and only known from populations near the southwestern Oregon-northern California border. Trogloraptor tulishpunsp. nov. retains the key family synapomorphy, distinctive subsegmented raptorial tarsi, and an oblique membranous division of the basal segment of the anterior lateral spinnerets. Trogloraptor tulishpun is distinguished from T. marchingtoni by its color pattern, clypeal height, vulvar and palp structure. We have found T. tulishpun in four localities in the Columbia River Gorge, which show little mitochondrial sequence divergence from one another, but are highly genetically distinct from T. marchingtoni. Trogloraptor tulishpun is found in basalt features, including lava tubes and shallow talus caves, and has been observed to eat arachnids and moths, making them top predators in these environments.

Many people are afraid of spiders and consider them to be both dangerous and disgusting, which can negatively impact their mental well-being as well as their relationship with nature. Very few studies have examined what characteristics draw visual attention toward or away from spiders, or have assessed the impact of arachnophobia and sex on attentional biases. Here, 118 undergraduate students freely viewed single and paired images of spiders and other arthropods in their natural environments while having their eye movements monitored. Participants also completed a survey measuring spider phobia and attitudes toward spiders. Multiple eyetracking metrics (total dwell time, first run dwell time, first fixation time, and run count) were used as indicators of attentional bias. Findings suggest a general avoidance of spider images in the presence of other non-spider arthropod images as well as avoidance of scorpion images in the presence of non-scorpion arachnid images. Presentation of image pairs with two kinds of spiders elicit attention toward spider-specific features. These effects were occasionally, though not often, moderated by sex and phobia levels. Across all metrics, there was a tendency to record longer first fixation times, shorter dwell times, and lesser run counts toward images of spiders. Images of jumping spiders and insects received considerably more and faster attentional allocation relative to other spiders. Understanding how general body form versus specific spider features influence visual attention provides insight into visual factors that may motivate spider phobia, providing evidence-based knowledge that could be useful in treatments. Additionally, knowledge of potentially appealing features of spiders may provide useful perspectives for communicating the usefulness of spiders in our ecosystem.

The systematics of humble-in-appearance brown spiders (“marronoids”), within a larger group of spiders with a modified retrolateral tibial apophysis (the RTA Clade), has long vexed arachnologists. Although not yet fully settled, recent phylogenomics has allowed the delimitation and phylogenetic relationships of families within marronoids to come into focus. Understanding relationships within these families still awaits more comprehensive generic-level sampling, as the majority of described marronoid genera remain unsampled for phylogenomic data. Here we conduct such an analysis in the family Cybaeidae Banks, 1892. We greatly increase generic-level sampling, assembling ultraconserved element (UCE) data for 18 of 22 described cybaeid genera, including all North American genera, and rigorously test family monophyly using a comprehensive outgroup taxon sample. We also conduct analyses of traditional Sanger loci, allowing curation of some previously published data. Our UCE phylogenomic results support the monophyly of recognized cybaeids, with strongly supported internal relationships, and evidence for five primary molecular subclades. We hypothesize potential morphological synapomorphies for most of these subclades, bringing a robust phylogenomic underpinning to cybaeid classification. A new cybaeid genus Siskiyu gen. nov. and species Siskiyu armilla sp. nov. is discovered and described from far northern California and adjacent southern Oregon and a new species in the elusive genus Cybaeozyga, C. furtiva sp. nov., is described from far northern California.

Heterospecific interactions between nascent species offer insights into how sexual selection shapes novel traits, illuminating patterns in species interactions and diversification. We tested female preferences between two recently diverged, allopatric species of jumping spiders: Habronattus americanus PLC, with red-coloured males performing short multimodal displays, and Habronattus sansoni CC, with brown-coloured males performing long multimodal displays. Mate choice experiments showed that females of both species preferred H. americanus PLC males. To examine the role of red coloration, we manipulated male coloration in both species. Results indicated that red-painted H. sansoni CC males experienced an increase in mating success, whereas brown-painted H. americanus PLC males did not show reduced success. Our study suggests that (i) strong latent female preferences can drive unidirectional introgression across species boundaries, potentially leading to genomic homogenization; (ii) latent preferences may override preferences for existing traits; and (iii) the geographical distribution of colour morphs is consistent with a hypothesis of strong latent preferences across populations. Overall, our study demonstrates the role that mating interactions can play in speciation dynamics.

We use ultraconserved elements (UCE) and Sanger data to study the phylogeny, age, and biogeographical history of harmochirine jumping spiders, a group that includes the species-rich genus Habronattus, whose remarkable courtship has made it the focus of studies of behaviour, sexual selection, and diversification. We recovered 1947 UCE loci from 43 harmochirine taxa and 4 outgroups, yielding a core dataset of 193 UCEs with at least 50 % occupancy. Concatenated likelihood and ASTRAL analyses confirmed the separation of harmochirines into two major clades, here designated the infratribes Harmochirita and Pellenita. Most are African or Eurasian with the notable exception of a clade of pellenites containing Habronattus and Pellenattus of the Americas and Havaika and Hivanua of the Pacific Islands. Biogeographical analysis using the DEC model favours a dispersal of the clade's ancestor from Eurasia to the Americas, from which Havaika's ancestor dispersed to Hawaii and Hivanua's ancestor to the Marquesas Islands. Divergence time analysis on 32 loci with 85 % occupancy, calibrated by fossils and island age, dates the dispersal to the Americas at approximately 4 to 6 million years ago. The explosive radiation of Habronattus perhaps began only about 4 mya. The phylogeny clarifies both the evolution of sexual traits (e.g., the terminal apophyses was enlarged in Pellenes and not subsequently lost) and the taxonomy. Habronattus is confirmed as monophyletic. Pellenattus is raised to the status of genus, and 13 species moved into it as new combinations. Bianor stepposus Logunov, 1991 is transferred to Sibianor, and Pellenes bulawayoensis Wesołowska, 1999 is transferred to Neaetha. A molecular clock rate estimate for spider UCEs is presented and its utility to inform prior distributions is discussed.

Idealized ring species, with approximately continuous gene flow around a geographic barrier but singular reproductive isolation at a ring terminus, are rare in nature. A broken ring species model preserves the geographic setting and fundamental features of an idealized model but accommodates varying degrees of gene flow restriction over complex landscapes through evolutionary time. Here we examine broken ring species dynamics in Calisoga spiders, which, like the classic ring species Ensatina salamanders, are distributed around the Central Valley of California. Using nuclear and mitogenomic data, we test key predictions of common ancestry, ringlike biogeography, biogeographic timing, population connectivity, and terminal overlap. We show that a ring complex of populations shares a single common ancestor, and from an ancestral area in the Sierra Nevada mountains, two distributional and phylogenomic arms encircle the Central Valley. Isolation by distance occurs along these distributional arms, although gene flow restriction is also evident. Where divergent lineages meet in the South Coast Ranges, we find rare lineage sympatry, without evidence for nuclear gene flow and with clear evidence for morphological and ecological divergence. We discuss general insights provided by broken ring species and how such a model could be explored and extended in other systems and future studies.

Genetic introgression, allele exchange across species boundaries, is a commonly recognized feature of animal evolution. Under such a paradigm, contemporary contact zones provide first-hand insight into the geographic, phenotypic, and genetic details of introgression. Also, when mate choice phenotypes are conspicuous and variable in hybrids, contact zones provide potential insight into how sexual selection interacts with species boundary maintenance, particularly when postzygotic reproductive isolation is weak. The Habronattus americanus subgroup includes several recently evolved jumping spider species, with an estimated age of about 200,000 yr, and substantial evidence for hybridization and introgression. We explored a contact zone involving H. americanus (Keyserling, 1885) and H. kubai (Griswold, 1979) on Mount Shasta, CA, in alpine habitats that would have been unavailable (under ice) at the Last Glacial Maximum. We characterized morphological diversity within the contact zone, including the fine-scale geographic distribution of hybrid and parental individuals, and assessed genetic variation using ddRADseq data. Combined results indicate a lack of measured genomic differentiation between specimens with distinct morphologies, including individuals with phenotypes of the parental species. We identified a diverse array of hybrid morphologies, with phenotypic evidence for backcrossing, essentially forming a phenotypic bridge between parental taxa. The study area is characterized by more hybrid than parental individuals, with a significantly larger number of red-palped morphologies than white- and/or yellow-palped morphologies; the novel, white-palped phenotype is perhaps transgressive. Overall, these results contribute to a better understanding of the expected ebb and flow of lineage interactions during the early stages of speciation. Graphical Abstract

Antrodiaetus is a lineage of mygalomorph spider (Mygalomorphae: Antrodiaetidae) that has persisted since the late Cretaceous and has a disjunct Holarctic distribution and strong morphological conservatism. These folding-door spiders possess a life history (i.e., limited dispersal, conserved environmental niche) that closely ties their evolution to geology. This study produces a robust, well-supported phylogenomic inference of all currently recognized Antrodiaetus species using UCEs (Ultraconserved Elements), corroborates previous biogeographical hypotheses, and proposes new hypotheses about diversification patterns. We also confirm that previously suspected cryptic diversity within A. pacificus is underestimated, as this nominal species comprises multiple divergent and cryptic lineages. Our phylogeny now serves as a foundation for understanding Antrodiaetus species relationships, biogeography, and speciation.

Although patterns of population genomic variation are well-studied in animals, there remains room for studies that focus on non-model taxa with unique biologies. Here we characterise and attempt to explain such patterns in mygalomorph spiders, which are generally sedentary, often occur as spatially clustered demes and show remarkable longevity. Genome-wide single nucleotide polymorphism (SNP) data were collected for 500 individuals across a phylogenetically representative sample of taxa. We inferred genetic populations within focal taxa using a phylogenetically informed clustering approach, and characterised patterns of diversity and differentiation within- and among these genetic populations, respectively. Using phylogenetic comparative methods we asked whether geographical range sizes and ecomorphological variables (behavioural niche and body size) significantly explain patterns of diversity and differentiation. Specifically, we predicted higher genetic diversity in genetic populations with larger geographical ranges, and in small-bodied taxa. We also predicted greater genetic differentiation in small-bodied taxa, and in burrowing taxa. We recovered several significant predictors of genetic diversity, but not genetic differentiation. However, we found generally high differentiation across genetic populations for all focal taxa, and a consistent signal for isolation-by-distance irrespective of behavioural niche or body size. We hypothesise that high population genetic structuring, likely reflecting combined dispersal limitation and microhabitat specificity, is a shared trait for all mygalomorphs. Few studies have found ubiquitous genetic structuring for an entire ancient and species-rich animal clade.