Research Article |
Corresponding author: Marshal Hedin ( mhedin@sdsu.edu ) Academic editor: Chris Hamilton
© 2023 Rodrigo Monjaraz-Ruedas, Raymond Wyatt Mendez, Marshal Hedin.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Monjaraz-Ruedas R, Mendez RW, Hedin M (2023) Species delimitation, biogeography, and natural history of dwarf funnel web spiders (Mygalomorphae, Hexurellidae, Hexurella) from the United States / Mexico borderlands. ZooKeys 1167: 109-157. https://doi.org/10.3897/zookeys.1167.103463
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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. ephedra sp. nov., H. uwiiltil sp. nov., H. xerica sp. nov., and H. zas sp. 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.
Biogeography, micro-endemism, Mojave Desert, sky islands, taxonomy, ultraconserved elements
Dwarf funnel web spiders in the genus Hexurella Gertsch & Platnick, 1979 are infrequently encountered and poorly known. In the first and only revision of this taxon
Ingroup-only UCE concatenated ML tree. Specimen numbers correspond to those in Suppl. material
In a phylogenomic analysis of all atypoid mygalomorph genera,
The biogeographic histories of animal taxa that include disjunct representatives in upland habitats of southern California / Baja California Norte and central and southeastern Arizona are mostly unstudied. One emphasis has been on the disjunct habitats in which such animals occur, which are dominated by sclerophyllous woody plant taxa. One hypothesis is that these plant communities, and perhaps the animals dependent upon them, are part of an Oligocene-Miocene Madro-Tertiary Geoflora (
The Sky Islands of southern Arizona and northern Mexico are a biologically diverse region where mountain ranges, isolated by arid lowland basins, act as refugia for various montane lineages (summarized in
The revisionary research presented here is based on original and recent collections of Hexurella populations from Arizona, southwestern California, and northwestern Baja California Norte. This sampling has greatly increased the number of known populations for the genus and includes detailed natural history information. New distributional records extend further south into Baja California Norte, further north into the Mojave Desert of California, into the mountains of northwest Arizona, and include extensive records for the montane sky islands of southeastern Arizona. For these new specimens we have studied male and female morphology, and for a representative sample have gathered ultraconserved element (UCE) nuclear phylogenomic data, and mitogenomic data as UCE by-catch. We also conduct formal genetic species delimitation analyses, using the newly developed methods SPEEDEMON (
We collected specimens from Arizona, southern California, and Baja California Norte, on the traditional and ancestral lands of the Yuhaaviatam/Maarenga’yam (Serrano), Kumeyaay, Paipai (Akwa’ala), Ko’lew (Kiliwa), Hualapai, Tohono O’odham, Yavapai, Western Apache, and Chiricahua Apache peoples. We searched appropriate microhabitats for spiders and collected specimens by hand or using an aspirator. Most spiders were preserved in the field in either 80% EtOH for morphological study, or 100% EtOH for DNA analysis. Specimens preserved for DNA analysis were later stored in a -80 °C freezer. Geographic location data were taken in the field using a cell phone and later verified using ACME Mapper (https://mapper.acme.com/).
If immatures (imm) were collected in association with adults from the same geographic location and in the same microhabitats, these specimens were attributed to the species found at that location (Suppl. material
We gathered UCE data for 51 specimens, including 47 Hexurella, and a handful of distant atypoid outgroups (two Megahexura fulva (Chamberlin, 1919), Aliatypus gulosus Coyle, 1975, and Aliatypus isolatus Coyle, 1975; Suppl. material
Bioinformatic analyses were carried out on the Mesxuuyan HPC at SDSU. Raw demultiplexed reads were quality-filtered and cleaned of adapter contamination with Trimmomatic (
We created two datasets for phylogenomic analyses, including ingroup + outgroup (51 samples, 588 loci), and ingroup only (47 samples, 608 loci) (Suppl. material
An ingroup-only species tree was estimated under a multispecies coalescent model using ASTRAL v. 5.7.7 (
For SNP-based analyses (see below) we extracted SNPs from ingroup-only UCE alignments using the script ’snps_from_uce_alignments’ (
Because no mitochondrial reference is available for Hexurella we followed a two-step workflow for gathering approximately full mitogenome UCE by-catch data for ingroup samples. This workflow included mitochondrial contig identification and genes recovery. We first mapped assembled UCE contigs to a reference mitogenome of Megahexura fulva (unpublished data) using MitoFinder v. 1.4.1 (
Phylogenetic analysis of a concatenated mitochondrial matrix was conducted using IQ–TREE ML searches. This matrix was partitioned by gene with a best–fitting partition scheme found by possibly merging partitions; support was measured using 1000 replicates of ultrafast bootstrap.
Divergence times were estimated using BEAST v. 2.4.8 (
We used MEGA v. 11 (
We approached the species delimitation problem in two different ways. First, we used an integrative, morphology-first approach, where a priori morphological species were “validated” via phylogenomic analyses. Here we defined species as “single populations (= collection localities) or sets of populations that share diagnostic male morphologies, strongly supported (using multiple measures) by nuclear phylogenomic monophyly.”
For most Hexurella taxa this integrative approach appeared to perform well, with clear morphological groupings with minimal intraspecific morphological variation, strongly supported by nuclear phylogenomics (see Results). One exception involved the H. pinea “complex” in central and northwestern Arizona. Here, five separate sample locations included males that differed to various degrees from each other. These five populations together formed a phylogenomic clade, itself with divergent internal branches (see Results). Here, the distinction between intraspecific variation vs. interspecific divergence (i.e., species boundaries) was less clear.
To address this uncertainty, we used formal genomic algorithmic species delimitation analyses. We used two alternative approaches, SPEEDEMON (
SPEEDEMON (
SPEEDEMON analyses were performed in BEAST v. 2.6.7 (
In addition to SPEEDEMON we also used DELINEATE (
Our descriptions of somatic and genitalic morphology paralleled the characters also emphasized by
Specimens were digitally imaged using a Visionary Digital BK plus system including a Canon 40D digital camera and Infinity Optics Long Distance Microscope. Individual images were combined into a composite image using Helicon Focus v. 6.6.2 software, then edited using Adobe Photoshop. Images were taken with specimens immersed in filtered 70% EtOH, using KY jelly to secure samples.
Female spermathecae were dissected from specimens using fine forceps, immersed in BioQuip specimen clearing fluid on a depression slide, then imaged directly in this fluid on slides. We imaged spermathecal organs for most taxa for sake of completeness but did not emphasize these characters in our taxonomic diagnoses. Although
Holotype and paratype specimens from California and Arizona have been deposited at the Bohart Museum of Entomology (BME) at UC Davis. Holotype and paratype specimens from Baja California Norte have been deposited at the Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California, Mexico (
The total morphological and molecular sample considered is summarized in Suppl. material
Raw UCE read data have been submitted to the Sequence Read Archive (BioProject ID: PRJNA95350). Final alignments were available for 51 samples and 588 loci (ingroup + outgroup), or for 47 samples and 608 loci (ingroup only). The ingroup-only matrix included a concatenated length of 364,758 base pairs. All input matrices, analysis log files, and output tree files can be found in Suppl. material
Concatenated ML analyses including distant atypoid outgroups recovered a monophyletic Hexurella, with internal eastern (AZ) versus western (CA + Baja) clades (Fig.
Mitochondrial data for 47 Hexurella specimens were gathered as UCE by-catch (Suppl. material
Presuming an eastern versus western root placement, the mitochondrial topology is very similar to nuclear topologies (Fig.
Between-group mean K2–P COI distances range from 10.5–12.7% in the western clade, 7.8–10.5% in the H. pinea complex, and 8.5–9.6% among geographic subclades within H. apachea (Table
COI between-group mean K2–P distances. “pinea_south” and “pinea_farSouth” correspond to H. zas sp. nov.
Mules | apachea_western | apachea_eastern | ||
---|---|---|---|---|
apachea_western | 0.096 | |||
apachea_eastern | 0.0947 | 0.0908 | ||
apachea_central | 0.0902 | 0.0886 | 0.0849 | |
pinea_north | pinea_central | pinea_south | ||
pinea_central | 0.0783 | |||
pinea_south | 0.0922 | 0.0795 | ||
pinea_farSouth | 0.1051 | 0.1022 | 0.078 | |
xerica | ephedra | rupicola | uwiiltil | |
ephedra | 0.1095 | |||
rupicola | 0.1133 | 0.1100 | ||
uwiiltil | 0.1115 | 0.1052 | 0.1104 | |
encina | 0.1269 | 0.1186 | 0.1160 | 0.1077 |
Nuclear and mitogenomic analyses recover well-supported eastern versus western clades (Figs
The Colorado River barrier hypothesis is a general paradigm found in the literature, although as noted above, this pattern does not apply in phalangodid harvesters (
Biogeographic patterns and estimated divergence times within H. apachea are discussed below in the Taxonomy section for this species.
We recognized six morphological species a priori, including the previously described H. apachea, H. rupicola, and H. encina, and three newly discovered morphologically distinctive species. These six morphological species are all also recovered with high support with nuclear phylogenomic data (as measured by ML bootstrap, concordance factors, ASTRAL local posterior probabilities; Figs
SPEEDEMON ε = 0.02 recovers a seven species hypothesis with a support of 99.54%, with the H. pinea complex subdivided into two species (Table
Results of species delimitation analyses, showing support for each species across different methods and parameters. Fixed = Lineage constrained as “known” in DELINEATE analyses. Merged cells denote lineages recovered as a single species. “pinea complex S” and “pinea complex FS” correspond to H. zas sp. nov.
Lineage | SPEEDEMON | DELINEATE | ||
---|---|---|---|---|
ε = 0.02 | ε = 0.0185 | ε = 0.02 | ε = 0.0185 | |
H. apachea | 100 | 100 | Fixed | Fixed |
H. encina | 100 | 100 | Fixed | Fixed |
H. rupicola | 100 | 100 | Fixed | Fixed |
H. uwiiltil | 99.64 | 100 | Fixed | Fixed |
H. ephedra | 99.60 | 100 | Fixed | Fixed |
H. xerica | 100 | 100 | 100 | |
H. pinea complex C | 99.99 | 99.98 | 100 | 100 |
H. pinea complex N | 99.98 | 100 | 100 | |
H. pinea complex FS | 99.94 | 100 | 100 | 100 |
H. pinea complex S | 100 | 100 | 100 | |
Total species | 7 | 10 | 10 | 10 |
DELINEATE recovers a 10 species hypothesis regardless of the different input SPEEDEMON trees used (from different ε values). Within the H. pinea complex, North, Central, South and FarSouth lineages are recovered as independent species each with a posterior support of 1 (Table
The taxonomy presented below is organized to follow phylogenomic results, including separate sections for eastern versus western lineages, and following sister taxon relationships within lineages. Fig.
We follow the generic diagnosis provided by Hedin and Bond in
Well-supported phylogenomic clade, currently known from east of the Colorado River in the uplands of northwestern, central, and southeastern Arizona.
Included species. Hexurella apachea Gertsch & Platnick, 1979, Hexurella pinea Gertsch & Platnick, 1979, Hexurella zas sp. nov.
Hexurella apachea
Near-type locality material: USA – Arizona, Cochise Co. • 1♂, 1 imm; Chiricahua Mtns., Cave Creek Canyon, 31.8815, -109.1978; 15 Mar. 2021; R.W. Mendez leg. – Cochise Co. • 1♂; Chiricahua Mtns., Cave Creek Canyon, 1 mi. E Southwest Research Station, FR 42, 31.8809, -109.1890; 12 Oct. 2021; R.W. Mendez leg.; RWM 21_050. – Cochise Co. • 5♂, 1♀, 2 imm; Chiricahua Mtns., Cave Creek Canyon, FR-42, Snowshed Trailhead, 31.8811, -109.1968; 20 Oct. 2021; R.W. Mendez, R.A. Mendez leg; RWM 21_057.
H. apachea Eastern Lineage – Arizona, Cochise Co. • 3♂, 4♀, 7 imm; Chiricahua Mtns., Price Canyon,31.7266, -109.2387; 16 Mar. 2021; R.W. Mendez leg. – Cochise Co. • 3♂, 6♀; Dragoon Mtns, 1 mi E West Stronghold trailhead, Cochise Trail 279, 31.9223, -109.9899; 30 Oct. 2021; R.W. Mendez, K. Silvestre-Bringas, E. Ciaccio leg.; RWM 21_061. – Cochise Co. • 5 imm; Dragoon Mtns, 2.8 mi up NF-345A, 0.4 mi down ravine, 31.9036, -109.9830; 21 Aug. 2021; R.W. Mendez, M.A. Leimroth leg.; RWM 21_027. – Cochise Co. • 3♂, 3♀, 2 imm; Dragoon Mtns, 2.8 mi up NF-345A, 31.8997, -109.9835; 17 Nov. 2021; R.W. Mendez, C.A. Hamilton leg.; RWM 21_076. – Cochise Co. • 1♀, 4 imm; Dragoon Mtns., Middlemarch Canyon, E of Middlemarch Pass, W of Pearce, 31.8729, -109.9399; 23–24 Jul. 2021; M. Hedin, R.W. Mendez leg.; MCH 21_084. – Cochise Co. • 1♂, 2♀, 4 imm; Pedregosa Mtns., Prune Canyon, 31.5668, -109.3800; 17 Apr. 2021; R.W. Mendez leg.
H. apachea Central Lineage – Cochise Co. • 1♂, 1♀, 1 imm; SW of Winchester Mtns, Johnny Lyon Hills, W of Keith Peak, 32.1154, -110.2237; 17 Jan. 2022; R.W. Mendez, M.A. Leimroth leg.; RWM 22_009. – Cochise Co. • 3♀; Whetstone Mtns, French Joe Canyon, 31.8092, -110.3976; 23 Aug. 2021; R.W. Mendez leg. – Cochise Co. • 6♂, 3♀, 4 imm; Whetstone Mtns, French Joe Canyon, E French Joe Spring, 31.8107, -110.3945; 14 Nov. 2021; R.W. Mendez, C.A. Hamilton, M.A. Leimroth leg.; RWM 21_075. – Pima Co. • 4♀, 3 imm; Whetstone Mtns, 0.5 mi SE Willow Spring, Apache Canyon, 31.8193, -110.4571; 22 Aug. 2021; R.W. Mendez leg; RWM 21_030. – Pima Co. • 3♀, 3 imm; Whetstone Mtns, 0.75 mi E Willow Spring, Apache Canyon, 31.8252, -110.4487; 22 Aug. 2021; R.W. Mendez leg; RWM 21_029. – Santa Cruz Co. • 4♂, 8♀, 2 imm; Mustang Mtns, NW Mustang Peak, 31.6852, -110.4709; 14 Nov. 2021; R.W. Mendez, C.A. Hamilton, M.A. Leimroth leg.; RWM 21_074.
H. apachea Western Lineage – Pima Co. • 2♂, 2♀, 8 imm; Santa Catalina Mtns, Redington Pass, 1 mi W Youtey Pasture Tank., Redington Road, 32.3107, -110.5508; 2 Oct. 2021; R.W. Mendez, D. Roth leg.; RWM 21_044. – Pima Co. • 1♀; Santa Catalina Mtns, Nugget Cyn., E Peppersauce Cave, 32.5249, -110.7106; 11 Jul. 2021; R.W. Mendez leg. – Santa Cruz Co. • 4♂, 7♀, 1 imm; Patagonia Mtns, 0.5 mi N Harshaw/Duquesne Road jnct, 31.3917, -110.6885; 6 Nov. 2021; R.W. Mendez, M.A. Leimroth leg.; RWM 21_062. – Santa Cruz Co. • 1 imm; Patagonia Mtns, 1 mi E Harshaw Road, 31.4659, -110.7099; 5 Sep. 2021; R.W. Mendez, M.A. Leimroth leg.; RWM 21_035. – Santa Cruz Co. • 3♂, 3♀, 1 imm; Patagonia Mtns, 1.5 mi W Harshaw/Duquesne jct., Duquesne Wash, 31.3856, -110.7114; 18 Nov. 2021; R.W. Mendez, C.A. Hamilton leg.; RWM 21_078. – Santa Cruz Co. • 1♀, 3 imm; Santa Rita Mtns, Adobe Canyon, 0.5 mi S Bathtub Tank, 31.6730, -110.7601; 16 Sep. 2021; R.W. Mendez leg.; RWM 21_040. – Santa Cruz Co. • 1 imm; Santa Rita Mtns, Madera Canyon; date unknown; M. Hedin leg.; MCH 99_010. – Santa Cruz Co. • 2♂, 3 imm; Santa Rita Mtns., Aliso Springs, 31.7355, -110.8040; 6 Mar. 2021; R.W. Mendez leg.
H. apachea Mule Lineage – Cochise Co. • ♂, 1 imm; Mule Mtns, 0.5 mi S Mule Pass, Bisbee, 31.4528, -109.9403; 13 Nov. 2021; R.W. Mendez, C.A. Hamilton, M.A. Leimroth leg., RWM 21_073. – Cochise Co. • 2♂, 3♀, 3 imm; Mule Mtns, drainage off Escabrosa Ridge, 31.4530, -109.9634; 9 Mar. 2021; R.W. Mendez leg. – Cochise Co. • ♂; Mule Mtns, Fissure Peak, 31.4473, -109.9631; 9 Mar. 2021; R.W. Mendez leg.
This species differs from all other congeners in possessing a diagnostic comb of robust spines distally on the prolateral surface of the male I patella, with a dorsal-most spine that is long and distinctively curved (Fig.
H. apachea A ♂ leg I, prolateral view, Mule Mtns (SDSU_TAC000684) B ♂ leg I, prolateral view, Cave Creek Canyon (SDSU_TAC000685) C ♂ leg I, prolateral view, Mustang Mtns (SDSU_TAC000686) D ♂ leg I, prolateral view, Redington Pass (SDSU_TAC000687) E ♀ spermathecae (Mustang Mtns, SDSU_TAC000688) F live ♀, Johnny Lyon Hills (RWM 22_009).
Representative variation in male leg I patella/tibia spine counts (including some spines tending towards the ventral surface on the patella) is as follows: Mule Lineage – Mule Pass (7, 10), Fissure Peak (6, 10); Western Lineage – Redington Pass (5, 8), Duquesne Wash (6, 11), Aliso Springs (5, 7); Central Lineage – Johnny Lyon Hills (3, 15), French Joe Canyon (6, 12), Mustang Mtns (7, 12); Eastern Lineage – Cave Creek Canyon (5, 10), Price Canyon (4, 12), Cochise Trail (5, 9).
Hexurella apachea is represented by a series of four phylogeographic lineages distributed north-south through the Cordilleran Gap of southeastern Arizona. COI suggests divergence times between the four clades spanning from the late Miocene to the early Pliocene (Fig.
Vaejovis vorhiesi and Pseudouroctonus apacheanus group scorpions, often collected with H. apachea, were diverging in this area throughout the Miocene (with occasional Pleistocene divergences between geographically adjacent ranges) and were dispersing from south to north and east to west, respectively (Bryson et al. 2013a, b). Vaejovis Koch, 1836 exhibits a similar pattern to H. apachea; a series of lineages oriented north south, but most extending much further north in Vaejovis. The biogeographic origin for H. apachea remains unclear, and material from northern Sonora and the gap between H. apachea and H. zas sp. nov. (Fig.
A comparison can be made with Yarrow’s Spiny Lizard, Sceloporus jarrovii jarrovii Cope, 1875 regarding the Central and Eastern Clades in H. apachea. Hexurella apachea often live at lower elevations than S. j. jarrovii, but both utilize rock outcrops and canyons in Madrean Oak Woodlands.
The Santa Rita and Patagonia Mountains are closely adjacent, divided by the headwaters of Sonoita Creek. Oak forest comes very low here, connecting the ranges with suitable or near-suitable Hexurella habitat. As a result, it is not surprising that H. apachea populations may have had contact between these ranges, although the divergences in the Western Clade are not recent (Fig.
Hexurella apachea is primarily found in low elevation Madrean oak communities between 1400–2075 meters. Nearly all collections have come from flipping small to medium-sized rocks in oak litter (Fig.
H. apachea A ♂ palp, retrolateral view, Mule Mtns (SDSU_TAC000684) B ♂ palp, retrolateral view, Cave Creek Canyon (SDSU_TAC000685) C ♂ palp, retrolateral view, Mustang Mtns (SDSU_TAC000686) D ♂ palp, retrolateral view, Redington Pass (SDSU_TAC000687) E habitat, Whetstone Mtns (RWM 21_029) F web, French Joe Canyon (RWM 21_075).
The litter utilized by H. apachea is generally compacted and dense, yet well-draining and without much active fungal activity. Webs are constructed at the transition between litter and soil, consisting of numerous short and interconnected branching tunnels that open into small, space-filling funnel webs wherever voids are present in the leaf matrix (Fig.
Despite their small size, H. apachea are typically found in fairly dry microhabitats, especially when compared to the commonly syntopic funnel-web spider Euagrus chisoseus Gertsch, 1939. In captivity, H. apachea has proven to be remarkably desiccation tolerant, requiring no substrate moisture as long as the temperatures remain stable between 20–25 °C and the room has some ambient humidity (10–20%). Like western taxa, H. apachea must survive high temperatures and low humidity in the dry season. Egg sacs (laid in late March) have invariably molded when enclosures are kept moist, and the sacs observed in the field are usually placed above the webs, away from the soil in cracks under rocks. In captivity and in the wild, egg sacs are coated with debris, behavior like E. chisoseus (RWM, personal observation). Adults likely take two years to mature based on the two overlapping size classes of juveniles usually seen in the wild and captive growth rates, with mature females living for at least two years after maturing.
While patchily distributed throughout their range, H. apachea can be dense in appropriate habitats, with 8 males and >75 immatures and females observed (not all collected) in 2 m2 in one collection (RWM 21_057) from the type locality in Cave Creek Canyon, Chiricahua Mountains. Small rocks will often have at least one adult female and three or four subadults under them. Despite their proximity in the wild, H. apachea (and Hexurella in general) do not tolerate cohabitation and readily cannibalize. Mature males have been collected in the field from early October through April; it is unknown if these are overwintering or a different set of males. Males are found running through litter, in 4–5 cm temporary retreats that may function as sperm webs, and the webs of females. Males and juveniles will descend via draglines, permitted by their small size.
Because of an overall shared male palpal (Fig.
Widely distributed and sometimes common in mostly mid-elevation habitats, viewed as secure.
Hexurella pinea Gertsch & Platnick (1979): 28, figs 70–72, 74, 76–80 (Dmf).
Near-type locality material: USA – Arizona, Yavapai Co. • 1♂, 1 imm; Brushy Mtn., W of Skull Valley, SW Grasshopper Spring, 34.5555, -112.7475; 13 Apr. 2022; R.W. Mendez leg.; RWM 22_099.
USA – Arizona, Mohave Co. • 1♂, 3 imm; Cerbat Mtns, SW Antelope Springs, Antelope Canyon, NE Mt. Tipton, 35.5962, -114.2039; 6 Apr. 2022; R.W. Mendez leg.; RWM 22_087. – Mohave Co. • 4♂, 1♀, 3 imm; Music Mtns, NW Garnet Mtn., Fox Canyon, 35.8196, -114.0491; 7 Apr. 2022; R.W. Mendez leg.; RWM 22_088.
The femur I prolateral surface of male H. pinea includes 6–10 larger spines (with a single exception), differing from populations of H. zas sp. nov. which possess 11 or more long spines.
H. pinea A ♂ leg I, prolateral view (SDSU_TAC000691, Brushy Mtn) B ♂ palp, retrolateral view (SDSU_TAC000691, Brushy Mtn) C ♂ leg I, prolateral view (SDSU_TAC000689, Music Mtns) D ♂ palp, retrolateral view (SDSU_TAC000689, Music Mtns) E ♂ leg I, prolateral view (SDSU_TAC000690, Cerbat Mtns) F ♂ palp, retrolateral view (SDSU_TAC000690, Cerbat Mtns).
The northernmost known Hexurella species, distributed from the Music Mountains on the Colorado River to the Sierra Prieta near Prescott, at elevations between 1400–1575m (Fig.
Hexurella pinea males have been the most difficult to collect of the three eastern species. This is likely in part due to the gritty soils seemingly preferred by this species, allowing males not attached to a web to quickly escape into the rapidly collapsing substrate when flipping rocks. At a second locale in the Music Mountains a male was lost because of this; no other individuals were found. Additionally, population densities seem low in H. pinea, comparable to the Mojave species H. ephedra sp. nov. and H. xerica sp. nov. The reduced monsoonal rainfall and cooler winter temperatures throughout the distribution of this species may play a role in keeping populations smaller in this species.
DELINEATE and SPEEDEMON ε = 0.0185 analyses (Table
The type locality for H. pinea, “5 mi. west of Prescott” (
Suitable habitat sampled west of the Colorado River in southern Nevada and the Virgin Mountains failed to produce Hexurella. However, due to the often-patchy distribution of this genus and the local scarcity of H. pinea (or perhaps other undescribed Hexurella species), more collecting is needed in this area.
Likely secure in appropriate habitats, although uncommon.
Hexurella pinea
Type material: Holotype: – Maricopa Co. • ♂ holotype; Mt. Ord, 0.5 mi NW Mt. Ord summit, FDR-1688, 33.9125, -111.4145; 15 Apr. 2022; R.W. Mendez leg.; RWM 22_102; SDSU_TAC000693; Paratype: • ♀ paratype; data as for holotype; SDSU_TAC000694.
USA – Arizona, Maricopa Co. • 6♀, 5 imm; Mt. Ord, 0.5 mi NW Mt. Ord summit, FDR-1688, 33.9119, -111.4146; 11 Dec. 2021; R.W. Mendez, M.A. Leimroth leg.; RWM 21_082. – Maricopa Co. • 9♂; Mt. Ord, 0.5 mi NW Mt. Ord summit, FDR-1688, 33.9125, -111.4145; 15 Apr. 2022; R.W. Mendez leg.; RWM 22_102. – Yavapai Co. • 5♂, 3♀, 2 imm; Bradshaw Mtns, 2.15 mi S The Cements, off W Wagoner Road, 34.1374, -112.4475; 14 Apr. 2022; R.W. Mendez leg.; RWM 22_100. – Yavapai Co. • 1♀, 1 imm; Bradshaw Mtns, Crown King Road, near Perkins Tunnel Spring, 34.2263, -112.3092; 24 Mar. 2012; M. Hedin, A. Schönhofer, C. Richart, A. DiDomenico, E. Stiner, K. Emata, E. Garcia, D. Sitzmann leg.; MCH 12_009.
Differs from H. pinea in the condition of prolateral male femur I, with H. zas sp. nov. possessing 11 or more long spines, totaling a larger number than found in H. pinea males (single exception noted above).
(SDSU_TAC000693; Fig.
H. zas sp. nov. A ♂ holotype leg I, prolateral view (SDSU_TAC000693, Mt Ord) B ♂ holotype palp, retrolateral view (SDSU_TAC000693, Mt Ord) C ♂ leg I, prolateral view (SDSU_TAC000692, Bradshaw Mtns) D ♂ palp, retrolateral view (SDSU_TAC000692, Bradshaw Mtns) E live ♂, Mt. Ord (RWM 22_102) F ♀ paratype (SDSU_TAC000694, Mt Ord).
(SDSU_TAC000694; Fig.
Important male variation exists in both populations considered. A randomly chosen subset of three non-type males from the type locality (Mt. Ord) reveals a variable number of prolateral femoral spines (11–13), although not arranged in distinct diagonal rows as in the holotype specimen. These males also reveal variation in leg I metatarsus ventral spination, with up to 3 or 4 total spines. Consideration of a randomly chosen subset of four males from the Bradshaw Mtns (RWM 22_100) also reveals a variable number of prolateral femur I spines (from 11–16 long spines, Fig.
Known from three locations in low to mid-elevation (1325–1850m) habitats in the Arizona transition zone north of Phoenix. Collections in the Bradshaw Mountains are from sclerophyllous oak litter like that preferred by H. apachea, while Mt. Ord specimens were taken from nearly pure Rhamnus ilicifolia Kellogg (Hollyleaf Redberry). The lower elevation collections in the Bradshaws have been in sheltered canyons and rock outcrops, where they are protected from the sun though remain mostly dry, while the higher elevation Mt. Ord locale was on an open, north-facing slope.
Like H. apachea, webs consist of a convoluted structure of reticulate tunnels and void-filling sheets. Seemingly less reliant on organic substrates, however they have been collected in crumbly soils and gravel mixtures a short distance away from the main patches of litter. Mature males have been collected in April and May. Dedicated searching at Mt. Ord in mid-December 2021 produced numerous females and immatures, but no males. Pockets of snow were present on the ground, but spiders were still active in their webs. When revisiting the Mt. Ord location the following spring, densities in H. zas were similar to H. apachea, with multiple individuals sharing small rocks and eleven males seen (two escaping) in an area of approximately 3 m2.
A noun in apposition which means “snow” in the Western Apache language (Bray, 1998), referencing the colder temperatures and increased snowfall faced by this species in winter. The Western Apache, along with the Yavapai, are the original occupants of the land H. zas sp. nov. is found on and their language is undergoing important revitalization efforts.
DELINEATE and SPEEDEMON ε = 0.0185 analyses (Table
Likely secure in appropriate habitats.
Well-supported phylogenomic clade of five species (Figs
Included species. Hexurella ephedra sp. nov., Hexurella xerica sp. nov., Hexurella rupicola Gertsch & Platnick, 1979, Hexurella encina Gertsch & Platnick, 1979, Hexurella uwiiltil sp. nov.
Type material: Holotype: USA – California, San Bernardino Co. • ♂ holotype; Granite Mountains, Deadman’s Hills, 0.5 mi behind Amaral Spring, 34.5148, -117.0640; 17 Feb. 2022; R.W. Mendez leg.; RWM 22_018. Paratype: – San Bernardino Co. • ♀ paratype; Granite Mountains, Deadman’s Hills, above Quail Spring, 34.5367, -117.0821; 4 Apr. 2023; R.W. Mendez leg.; RWM 23_032. Non-type material: – San Bernardino Co. • 3 imm; Granite Mountains, Deadman’s Hills, 0.5 mi behind Amaral Spring, 34.5148, -117.0640; 17 Feb. 2022; R.W. Mendez leg.; RWM 22_018. • 2♂, 1♀, 6 imm; Granite Mountains, Deadman’s Hills, above Quail Spring, 34.5367, -117.0821; 4 Apr. 2023; R.W. Mendez leg.; RWM 23_032.
Easily distinguished from sister taxon H. xerica sp. nov. in that the male palpal tibia possesses a comb of 9 thick distal, retromarginal spines (Fig.
H. ephedra sp. nov. A live ♂ holotype (SDSU_TAC000680) B ♂ holotype (SDSU_TAC000680), dorsal view C ♂ palp, retrolateral view, holotype (SDSU_TAC000680) D ♂ leg I, prolateral view, holotype (SDSU_TAC000680) E ♂ palp, retrolateral view (Quail Spring, RWM 23_032) F ♂ leg I, prolateral view (Quail Spring, RWM 23_032) G live ♀ (Quail Spring, RWM 23_032) H ♀ paratype spermathecae (pencil outline included to show boundaries of medial and lateral receptacles).
(TAC_000680; Fig.
(SDSU_TAC000695; Fig.
Males from Quail Spring have more femur I spines than topotypic males (Fig.
Known only from the Deadman Hills in the Mojave Desert of southern San Bernardino County, California (Fig.
The name is a noun in apposition referring to the gymnosperm genus Ephedra L. which was found in close association with the species at the two known localities.
Based on shared palpal morphology, seemingly contiguous habitat, and close geographic proximity (~ 2.5 km distant, Fig.
Currently known only from a single small mountain range, and therefore of conservation concern. Further surveys are needed to understand the full distribution of this species, including from other canyons and springs in the Granite Mountains.
Type material: Holotype: USA – California, San Bernardino Co. • ♂ holotype; Ord Mountains, Ord Mountain, Sweetwater Spring, 34.6918, -116.8235; 14 Feb. 2022; R.W. Mendez leg.; RWM 22_014. Paratype: –San Bernardino Co. • ♀ paratype; Stoddard Ridge, Traer Agua Canyon, 34.6716, -116.9962; 7 Apr. 2023; R.W. Mendez leg.; RWM 23_034. Non-type material: – San Bernardino Co. • 2 imm; Ord Mountains, Ord Mountain, Sweetwater Spring, 34.6918, -116.8235; 14 Feb. 2022; R.W. Mendez leg.; RWM 22_014. – San Bernardino Co. • 3♂, 1 imm; Ord Mountains, Ord Mountain, Sweetwater Spring, 34.6918, -116.8235; 8 Apr. 2023; R.W. Mendez leg.; RWM 23_035. –San Bernardino Co. • 3♂, 3♀, 1 imm; Stoddard Ridge, Traer Agua Canyon, 34.6716, -116.9962; 7 Apr. 2023; R.W. Mendez leg.; RWM 23_034. –San Bernardino Co. • 4♂, 4♀, 4 imm; Stoddard Mtn, below summit, 34.7003, -117.1236; 6 Apr. 2023; R.W. Mendez leg.; RWM 23_033.
Easily distinguished from sister taxon H. ephedra in that the male palpal tibia includes only three thick, distal retromarginal spines (Fig.
H. xerica sp. nov. A ♂ leg I, prolateral view, holotype (SDSU_TAC000679) B ♂ palp, retrolateral view, holotype (SDSU_TAC000679) C ♂ leg I, prolateral view (Stoddard Ridge, RWM 23_034) D ♂ palp, retrolateral view (Stoddard Ridge, RWM 23_034) E ♂ leg I, prolateral view (Stoddard Mtn, RWM 23_033) F ♂ palp, retrolateral view (Stoddard Ridge, RWM 23_033).
(SDSU_TAC000679; Fig.
(SDSU_TAC000696; Fig.
Males from Stoddard Ridge and Stoddard Mountain locations have more femur I spines than topotypic males (Fig.
Known only from three adjacent locations in the Mojave Desert of southern San Bernardino County (Fig.
Named to reflect the harsh, xeric conditions in which this species persists, from the Greek xeros meaning “dry, withered.”
Males from Stoddard Ridge and Stoddard Mountain, which lie ~ 10–15 km west of the type locality, respectively (Fig.
Hexurella xerica sp. nov. populations (Ord Mtn., Stoddard Mtns) are found approximately 50 km north of Hexurella ephedra sp. nov. populations (Granite Mtns), possibly separated by low elevation desert habitats of the northern Lucerne Valley (Fig.
Currently known only from three adjacent desert locations and therefore of potential conservation concern.
Hexurella rupicola Gertsch & Platnick (1979): 31, figs 4, 32, 82, 89–91 (Dmf).
Hexurella rupicola Platnick & Forster (1982): 8, fig. 22.
Hexurella rupicola
Near-type locality material: USA – California, Riverside Co. • ♂, 1 imm; west of Temecula, Rancho California Rd, 33.4973, -117.1694; 22 Dec. 2021; M. Hedin, R. Monjaraz-Ruedas, G. Azevedo leg.; MCH 21_107; Non-type material: – California, San Diego Co. • ♂; 1.3 mi W of Guatay, Old Hwy 80, N side Guatay Mtn, 32.8541, -116.5754; 26 Jan. 2002; M. Hedin leg.; MCH 02_029; – San Diego Co. • ♀, 1 imm; 1.3 mi W of Guatay, Old Hwy 80, N side Guatay Mtn, 32.8541, -116.5754; 24 Mar. 2002; M. Hedin leg.; MCH 02_045; • ♂, 1 imm; 1.3 mi W of Guatay, Old Hwy 80, N side Guatay Mountain, 32.8541, -116.5754; 29 Feb. 2004; M. Hedin leg.; MCH 04_002; • ♀; 1.3 mi W of Guatay, Old Hwy 80, N side Guatay Mountain, 32.8541, -116.5754; 28 Jan. 2006; M. Hedin leg.; MCH 06_010; – San Diego Co. • ♂, 2 imm; south side of Viejas Mtn, off I-8 at Williams Rd, 32.8357, -116.7319; 19 Dec. 2021; M. Hedin leg.; MCH 21_105; – San Diego Co. • 2♀, 1 imm; near Viejas Mountain trailhead, off Boundary Truck Trail, 32.8550, -116.7400; 11 Mar. 2022; R.W. Mendez leg.; RWM 22_061.– San Diego Co. • 2♂, 6♀, 5 imm; San Ysidro Mtns, NW Lupe Spring, off Cottonwood Creek road, 32.5906, -116.7738; 10 Mar. 2022; R.W. Mendez leg.; RWM 22_058.
Following the original diagnosis of
H. rupicola A ♂ leg I, prolateral view (SDSU_TAC000682, San Ysidro Mtns) B ♂ palp, retrolateral view (SDSU_TAC000682, San Ysidro Mtns) C live ♂ in web (San Ysidro Mtns, RWM 22_058) D live ♂ in situ (Viejas Mtn, MCH 21_105), E ♀ spermathecae (SDSU_TAC000683, San Ysidro Mtns) F Viejas Mtn (MCH 21_105) microhabitat.
We have examined adult males from three locations in San Diego County (near Guatay, Viejas Mtn, San Ysidro Mtns), south of the type locality in Riverside County. Males from all locations are similar in condition, lacking spines on the prolateral surface of femur I (Fig.
Known from inland chaparral in Riverside and San Diego Counties. Temecula specimens were uncommonly found under stones in north facing Adenostoma fasciculatum Hook & Arn. (Chamise) chaparral, while Viejas Mountain specimens were found to be common under well-set intrusive igneous rocks in more exposed, south-facing Chamise chaparral (Fig.
The gap between H. rupicola and the Mojave species requires further sampling. We however note that many devoted mygalomorph biologists have sampled for decades in this region (e.g., Wendell Icenogle in Riverside County) without detecting Hexurella.
Likely secure, and likely with a slightly larger distribution than is currently known.
Hexurella encina Gertsch & Platnick (1979): 30, figs 73, 75, 86–88 (Dm).
Near-type locality material: MEXICO – Baja California Norte • 5♀, 1 imm; Hwy 3, just N Ejido Zapate, N end Guadalupe Valley, 32.1692, -116.5056; 25 Mar. 2022; M. Hedin, R. Monjarez Ruedas, R.W. Mendez leg.; MCH 22_024 • 5♀, 8 imm; Hwy 3, just N Ejido Zapate, N end Guadalupe Valley, 32.1692, -116.5056; 15–16 Jan. 2023; M. Hedin, D. Leavitt leg.; MCH 23_001. Non-type material: – Baja California Norte • 5♀, 1 imm; road to Cerro Bolla, southeast of Valle de Las Palmas, 32.3300, -116.6454; 25 Mar. 2022; M. Hedin, R. Monjarez Ruedas, R.W. Mendez leg.; MCH 22_023.– Baja California Norte • 7♀, 4 imm; road to Sierra San Pedro Martir, W of Hacienda Sinaloa, 30.9815, -116.0960; 28 Mar. 2022; M. Hedin, R. Monjarez Ruedas, R.W. Mendez leg.; MCH 22_037.
Easily distinguished from sister taxon H. uwiiltil sp. nov. in that the H. encina male femur I lacks spines on the prolateral surface (
♀ (SDSU_TAC000681; Fig.
H. encina A ♀ live (NE end Guadalupe Valley, MCH 23_001) B ♀ dorsal view (SDSU_TAC000681, NE end Guadalupe Valley) C ♀ spermathecae (SDSU_TAC000681, NE end Guadalupe Valley) D near type locality habitat (NE end Guadalupe Valley, MCH 23_001), spiders common under rocks along bank E web (road to Sierra San Pedro Martir, MCH 22_037).
Females conspicuously large, with specimens from west of Hacienda Sinaloa (MCH 22_037) the largest females we have seen for this genus.
Spiders at the Ejido Zapate locale were found to be exceedingly common under rubble and small stones in very exposed situations in coastal sage scrub (Fig.
The Cerro Bolla and Hacienda Sinaloa collections were from north-facing situations with richer plant communities, and webs were frequently made in a matrix of both leaf litter and millipede frass at the later collection (Fig.
The larger sizes seen in H. encina and H. uwiiltil sp. nov. may be an adaptation for the exposed microhabitats they inhabit and the increasingly arid conditions moving south into Baja California Norte. The larger size could help with water loss as the surface area/volume ratio shrinks.
The southernmost record for this species (west of Hacienda Sinaloa, MCH 22_037) is south of the type locality of Hexurella uwiiltil sp. nov. (Fig.
Likely secure, and likely with a larger distribution than currently known.
Type material: Holotype: Mexico – Baja California Norte • ♂ holotype; Arroyo Salado, E of Hwy 1, 31.2603, -116.0654; 28 Mar. 2022; M. Hedin, R. Monjarez Ruedas, R.W. Mendez leg.; SDSU_TAC000677. Paratype: • ♀ paratype; data as for holotype; SDSU_TAC000678; Non-type material: • 7♀; data as for holotype; MCH 22_041.
This species differs from all other members of the western clade in that the male femur I includes a patch of 10 prolateral spines (Fig.
(SDSU_TAC000677; Fig.
(SDSU_TAC000678; Fig.
Only a single male is known. We did not dissect and compare spermathecae from other topotypic females, but these non-paratype specimens are like the paratype in body size and markings (e.g., dark abdomens, dark carapace edges, etc.).
Only known from the type locality, a north-facing ravine in low coastal desert (Fig.
A noun in apposition which means spider in the Kiliwa language. The Kiliwa are indigenous peoples of northern Baja California, originally inhabiting an area surrounding the Sierra de San Pedro Mártir. The Kiliwa language is in danger of extinction, with fewer than 50 speakers in a recent census. We honor them and their language by naming this species in the same way they named these spiders centuries ago.
Both mitogenomic and nuclear phylogenomic data support Hexurella uwiiltil sp. nov. as sister to H. encina (Figs
This species is currently known only from a single locality, with bounding locations for H. encina to the north and south (Fig.
Many people helped to collect specimens, including Karina Silvestre-Bringas, Erik Ciaccio, Chris Hamilton, Dean Leavitt, D Roth, Axel Schönhofer, Casey Richart, Angela DiDomenico, Kristen Emata, Erica Garcia, Daniel Sitzmann, and Guilherme Azevedo. Special thanks go to Mason Adler Leimroth for his tireless efforts sampling in southern Arizona. Mike Simpson, Tom Chester, and Jim André helped with plant identifications. Specimens from Baja California Norte were collected under permit SEMARNAT S271/19. Comments of Guilherme Azevedo, Chris Hamilton, Jim Starrett, and two anonymous reviewers helped to improve the manuscript.
No conflict of interest was declared.
No ethical statement was reported.
A grant from the National Science Foundation (DEB 1937725 to MH and Jason Bond) funded this research. RMR was supported by the NSF and a CONACYT postdoctoral grant (# 770665/800981).
Fieldwork - all authors; Data Collection - all authors; Data Analysis - RMR, MH; Writing - all authors.
Rodrigo Monjaraz-Ruedas https://orcid.org/0000-0002-6462-3739
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Molecular and morphological voucher information
Data type: occurences, morphological, phylogenetic
Explanation note: Voucher specimen and genomic data information.
Custom scripts for bioinformatic analyses
Data type: scripts
Input matrices, analysis log files, and output tree files for nuclear and mitochondrial analyses
Data type: data matrices, etc.
Ingroup + outgroup UCE concatenated ML tree. Specimen numbers correspond to those in Suppl. material
Data type: phylogenetic tree
Ingroup-only mitochondrial ML gene tree. Specimen numbers correspond to those in Suppl. material
Data type: mitochondrial ML gene tree