Four new species of the spider genus Physocyclus Simon, 1893 (Araneae: Pholcidae) from Mexico, with updated taxonomic identification keys

. Four new species of the spider genus Physocyclus Simon, 1893 are described from Mexico. Two species are described based on male and female adult specimens: Physocyclus mariachi sp. nov. and P. sikuapu sp. nov. Two species are described only with female adult specimens: P . lyncis sp. nov. and P . pocamadre sp. nov. The biogeographical province with the highest diversity of species is the Balsas Depression, located in the Mexican Neotropic, with 12 species. Physocyclus lyncis sp. nov. belongs to the dugesi species group, whereas the other three new species belong to the globosus species group. The total number of species of Physocyclus is increased to 37, distributed in North America (mainly Mexico) and Central America, with one cosmopolitan species: P . globosus . Updated taxonomic identification keys for males and females are provided.


Introduction
The spider family Pholcidae C.L. Koch, 1850 is the ninth largest family in the order Araneae, currently composed by 96 genera and 1854 species, including the species herein described (WSC 2022). The family is subdivided into five subfamilies: Arteminae Simon, 1893 Modisiminae Simon, 1893, Ninetinae Simon, Autónoma de Mexico, Mexico City. The additional examined material is deposited at the Laboratory of Arachnology (LATLAX), Laboratorio Regional de Biodiversidad y Cultivo de Tejidos Vegetales (LBCTV), IBUNAM, Tlaxcala City, Mexico; and the American Museum of Natural History (AMNH), New York City, United States. The specimens were measured and examined with a Zeiss Discovery Stereoscope V.8, and the photographs were done using a Zeiss Axio Zoom V.16 microscope and Axio Zoom Zen and Zen Pro digital software. The map was made with QGIS ver. 3.10. The photographs and map were edited in Photoshop CS6 ver. 130x32. The measurements of all specimens are in millimeters (mm). The male palps and female epigyna were dissected and observed in ethanol (80%). Photography was conducted with specimens and structures submerged in commercial-use gel alcohol (to hold them in the appropriate position), and the preparation completely covered with 80% ethanol. A dissecting microscope (Zeiss Discovery Stereoscope V.8) fitted with a camera lucida was used to make the drawings. The female genitalia were cleaned in potassium hydroxide (KOH 10%) for 10 minutes, to clean the soft tissues around the pore plates. Morphological terminology and descriptions follow Valdez-Mondragón & Francke (2015) and Nolasco & Valdez-Mondragón (2020).

Etymology
The species name is a noun in apposition, and it refers to a genre of regional and popular Mexican music commonly known as "Mariachi", from the state of Jalisco where the type locality of the species is located.  Other material MEXICO • 1 ♂, 1 ♀; Nayarit, Municipality of El Nayar, Arroyo Santiago; AMNH • 1 immature; same collection data as for holotype; LATLAX • 1 immature; same collection data as for second paratype; LATLAX.
PaLP. DAP wide and dark (Fig. 21). PR entirely dark, with notch in middle part, ending in long thin spine 26). ES small and short, with oval shape in prolateral and retrolateral views 26), wide, long and sinuous in dorsal view 27). E small and short in retrolateral view, ending in a small tip. SO positioned in distal part of E (Fig. 26).
oPisthosoMa. With dorsal patch in anterior part (Fig. 28, red arrow). This structure might be a functional complex (with the protuberance of prosoma).

Variation Females
Female collected in Plan de Barrancas is bigger than female collected at type locality. With an ocher coloration. The coloration of the dorsal pattern of the carapace and chelicerae is darker in this female. (N=1): Tibia I: 5.7; tibia II: 3.9; tibia III: 2.9; tibia IV: 4.4; tibia I L/d: 26.2.

Remarks
This new species was previously recorded by W. J. Gertsch from Arroyo Santiago, Nayarit, Mexico, who tentatively named the species as Physocyclus "nayaritus". The species was never described, however, Gertsch drew some sketches consulted by A. Valdez-Mondragón at the American Museum of Natural History (AMNH) (year 2008). Those sketches are shown herein (Figs 34-37).

Natural history
The specimens were collected among boulders on the ground. The male type and one female were collected close together during copulation. The vegetation of the type locality was disturbed deciduous forest (Figs 70-71
Legs. All segments with light beige coloration. Trochanters light brown, darker than in female. Femora and tibiae with barely visible ring-shaped marks distally.
ePigynuM. Wider than long, bell-shaped, VAE small and slightly curved in lateral view (Figs 55-56). Anterior part of epigynum has a central gray spot, between the VAE (Fig. 55). Posterior part of epigynum darker than anterior part and seems to have stretch marks transversally (Figs 55-56). PP oval, with a pair of bag-shaped structures below them, which have an oval shape (Fig. 57).

Males
Male paratype collected at the same locality as male holotype is smaller, with a light beige coloration. Sternum with same color as carapace, with irregular darker marks in the periphery. The marks in the opisthosoma are slightly darker. (N=1): tibia I: missing; tibia II: 7.6; tibia III: 5.4; tibia IV: 7.6.

Natural history
The specimens were collected among big boulders in a disturbed tropical deciduous forest, and inside of a small karstic cave on walls and in the ground (Figs 72-73).

Natural History
The specimens were collected on the walls of a small cave. The wall of the cave is of clay material that came off on contact (Fig. 75). This cave is located in perturbed oak forest, but the predominant vegetation of the Ejido La Primavera is oak-pine forest (Fig. 74). This type of vegetation is somewhat unusual for the genus Physocyclus, which commonly inhabits deciduous tropical forest and xerophytic scrub, but rarely temperate forest.

Etymology
The species name is a noun in apposition, from the Mexican slang words "poca madre", which mean something cool or something nice.
oPisthosoMa. Longer than wide, with a dorsal patch located in anterior part (blue arrow on Fig. 64). This structure might be functional, together with dorsal protuberance of carapace (Fig. 64).

Male
Unknown.

Females
Females paratypes smaller than female holotype. One of them has a pale beige coloration and the pattern of the body has a light gray coloration, whereas the other female has a similar color as the female holotype. (N=2): female 1: tibia I: 5.3; tibia II: 3.9; tibia III: 2.9; tibia IV: 3.9. Female 2: tibia I: missing; tibia II: 3.6; tibia III: 2.7; tibia IV: 3.8. The ring coloration of tibiae and femora are light beige, barely visible. The pattern on carapace is slightly dark. (N=1): tibia I: 7.8; tibia II: 5.6; tibia III: 3.8; tibia IV: 5.4.

Natural history
The specimens were collected on their sheet webs among and under large boulders on the ground at both localities, close to the beaches "El Tecolote" and "Punta San Francisquito" (Figs 76-77). The vegetation type of both localities is dry xerophilous scrub, with cacti and scrubby vegetation (Figs 76-77). The specimens collected close to the beach "El Tecolote" were collected on their sheet webs among and under large boulders on the ground, and on walls of the cave, which is a concavity on a big wall.

Discussion
The distribution pattern of the species groups is the Mesoamerican and Mexican Mountain biotic components for the globosus group, and the Mesoamerican and Continental Neartic biotic components for the dugesi group (Valdez-Mondragón 2013, 2014. Recent molecular phylogenetic studies under mitochondrial and nuclear markers support the monophyly of both species groups (in prep.).
Mexico is by far the richest country in terms of troglomorphic species of pholcid spiders, although the apparent dominance of species richness may be partly due to collectors' and taxonomists' biases (Huber 2018). Although the species of the genus Physocyclus are commonly found in caves and grottos in Mexico, no troglomorphic species has been collected so far, and all the species of the genus are considered troglophilic.
The total number of species of Physocyclus increases to 37, with 36 distributed along the Mexican territory. However, despite the growing knowledge of the genus Physocyclus since previous revisions by Valdez-Mondragón (2010) and the morphological phylogeny by Valdez-Mondragón (2013, 2014, the diversity of this genus in Mexico is still poorly known. The biogeography of Mexico is extremely complex; there were several dispersal and vicariance events because the Nearctic and Neotropical biotic elements, known as the Mexican Transition Zone, overlap in Mexico (Morrone 2005). Provinces such as the Pacific Coast, Baja California, the Southern Altiplano, the Sonorense Province and long regions of tropical deciduous forest in the Pacific region (Valdez-Mondragón & Francke 2015: figs 22-23) are poorly sampled. The province of the Balsas Depression (BD), which has the highest diversity of species of Physocyclus, is the one that exhibits a greater influence of the Tropical Mesoamerican element. The vicariant events associated with the biotic evolution of the Transitional component would be related to the development of the Sierras Madre and the volcanism of the Trans-Mexican Volcanic Belt, which explain why the BD is one of the most biodiverse regions in the country (Morrone 2005).
Intensive sampling is needed to uncover the diversity of these spiders mainly in such semiarid ecosystems, xeric shrub zones, deserts, and tropical deciduous forest. Additionally, caves from tropical deciduous forest, a typical ambient for some genera of pholcids from Mexico, could be a significant source of new species (Valdez-Mondragón 2010).