Salticidae (Arachnida, Araneae) of Thailand: new species and records of Epeus Peckham & Peckham, 1886 and Ptocasius Simon, 1885

The study is based on new material from the collections of the Naturalis Biodiversity Centre in Leiden (RNHM) and the Hungarian Natural History Museum (HNHM) and addresses issues in two genera: Epeus Peckham & Peckham, 1886 and Ptocasius Simon, 1885 from Thailand. Both genera are of Asian/Indomalayan origin, the latter with a diversity hotspot in the subtropical valleys of the Himalayas. Based on morphological data, we propose three new species of Epeus (Epeus daiqini sp. nov. (♂♀), Epeus pallidus sp. nov. (♀), Epeus szirakii sp. nov. (♀)) and two new species of Ptacasius (Ptocasius metzneri sp. nov. (♂♀) and Ptocasius sakaerat sp. nov. (♀)). Additionally, we redescribed E. tener (Simon, 1877) and added photographs of morphological characters. The genus Ptocasius is redefined due to the inclusion of 37 species, previously included in Yaginumaella Prószyński, 1979. Relationships and distribution of both genera are discussed in reference to molecular, morphological and distributional data, published by other authors in recent years.


INTRODUCTION
The list of jumping spiders from Thailand comprises 29 genera and 46 species (WSC, 2020), seven genera and 13 species being poorly documented and in need of verification (Żabka & Gardzińska, 2017). The comparison of Thailand salticid checklist with other countries of the region (126 species in Vietnam, 511 in China, 386 in Indonesia; Metzner, 2020) illustrates that the real numbers for Thailand are seriously underestimated and could reach several hundred species as is found in Vietnam (Żabka, 1985). In this study we describe five new species from two genera: Epeus (Peckham & Peckham, 1886) and Ptocasius (Simon, 1885), the latter being recorded in Thailand for the first time. Both genera are of Asiatic origin (Bodner & Maddison, 2012;Maddison, 2015), and are found in SE Asia, China and subtropical Himalayas (Jastrzębski, 2010). The Himalayas have become a biodiversity hotspot for Ptocasius, with a large
Diagnosis. In comparison with related Telamonia (Thorell, 1887), males with crest of carapace setae arranged in mohawk manner, and cymbium with an apophysis instead of strong bristles. Unlike Plexippoides, the body is very elongate and the cymbium much narrower. Female genitalic structures in the three mentioned genera rather similar and of limited diagnostic value. In the genus Epeus, the epigynal plate with large atrium, membranous copulatory ducts running posteriorly and multi-looped spermathecae. Accessory glands present, but not always clearly visible.
Description. Spiders 4-8 mm long, alive individuals lush green, yellow to orange (Fig. 1). Carapace height about 80% of length, in some species eye field in males with fringe/crest of hairs upright in a mohawk style (Figs. 1B and 3C). Thoracic slope distinctive. AME much larger than ALE, the latter slightly behind AME. Abdomen elongate, pale or green with  Relationships. According to Prószyński & Deeleman-Reinhold (2012) the genus is closely related to Plexippoides (Prószyński, 1984), sharing morphological similarities in male genitalia, especially in the form of the cymbial apophysis, tegular lobe and embolus. On the basis of molecular quantitative analyses, Maddison (2015) proposed close relationships between Epeus and Plexippoides, Ptocasius, Telamonia and Yaginumaella. We basically agree with both hypotheses and, on the basis of genitalic structure, we consider Epeus, Plexippoides and Telamonia to be the close relatives. Distribution and biology. The genus Epeus is a vegetation dweller, distributed from subtropical Himalayan valleys, through India, Indochina, southern China, Philippines and Sunda Archipelago (Fig. 11). The map of the predicted distribution ( Fig. 11) suggests the presence of the genus in other areas, including New Guinea, however, despite the review of major collections from New Guinea (MŻ) no evidence was found to support such a prediction.   Simon, 1903: 743, 752;Merian, 1911: 315. Epeus tener Prószyński, 1984Żabka, 1985: 216;Prószyński & Deeleman-Reinhold, 2012: 38, Prószyński, 2017 33. Diagnosis. Epeus tener can be distinguished from all other species by having an embolus serrated at the base and a tegular apophysis base fixed at 4.30 o'clock, with an additional outgrowth set at 7 o'clock. Cymbial apophysis pointed, its edges serrated. Epigynal plate widening posteriorly. Internal genitalia similar in structure to E. pallidus, but copulatory openings strongly sclerotized, oriented more anteriorly, proximal spermathecal loop different in course.
Material: 1♂, Prov. Prachin Buri, Sakaerat Environmental Research Station, Thailand, [14 •   Remark. The species has already been recorded in Thailand (as Viciria cristata, (Thorell, 1887). Here we give new locality and complete the description with habitus and palp images, drawing and a distribution map.
Epeus daiqini sp. nov.  Etymology. The specific epithet is a patronym in honour of Prof. Daiqin Li (National University of Singapore) in recognition of his research on the behaviour of Salticidae.
Diagnosis. Males differ from similar/related species E. tener, E. furcatus (Zhang, Song & Li, 2003), and E. bicuspidatus (Song, Gu and Chen, 1988) as missing embolic serration, and the presence of a small outgrowth on the retrolateral cymbial apophysis. Female copulatory openings more widely separated from each other than in E. alboguttatus, but less distant than in E. pallidus and E. szirakii. Females differ from E. tener by the orientation of copulatory openings (more diagonal in E. daiqini). Copulatory ducts do not reach epigastric fold, and proximal spermathecal loop (psl) less distinctive than in other species, accessory glands clearly visible. Description. Male holotype (Figs. 3A-3G). Carapace orange with cephalic crest (Fig. 3C), covered with scale-like light hairs. Surroundings of AME brown, other eye surroundings black. Abdomen yellowish, spinnerets orange. Clypeus and chelicerae dark brown. Endites and labium orange, with paler tips, the former with no protuberance. Sternum yellow, with darker margin. Ventral abdomen yellowish. Legs light brown, the first pair darker and stronger than the others, with a fringe of brown setae on ventral patella, tibia and metatarsus. Spines numerous on all legs. Spination of leg I: tibia ventral 2-2-2-2, retrolateral 1-1-0-1, metatarsus ventral 2-2, pro-and retrolateral 1-1. Cymbium apically slightly curved, its apophysis with a short outgrowth (Fig. 3G). Tegulum with a small bump and with a distinctive, posterior finger-like tegular lobe. Retrolateral tibial apophysis single (Fig. 3G) (Figs. 4F-4H), copulatory openings with joined posterior margins, oriented anterodiagonally. The area between openings strongly sclerotized (Fig. 4F) Etymology. The specific epithet, ''pallidus'', refers to the spider's pale coloration. Diagnosis. Can be distinguished from all other species by rather rectangular epigynal plate, and large and wide atrium. Copulatory openings widely spaced, more distant than in E. albus (Prószyński, 1992), but similar to E. szirakii. In comparison with the latter species proximal spermathecal loops (psl) different in shape.

Genus Ptocasius (Simon, 1885)
Diagnosis. Unlike related Epeus, Plexippoides and Telamonia the body is not elongate, and abdominal pattern with chevrons or transverse dark and light stripes. Cymbium rather wide, neither with apophysis nor with strong bristles. In some species a cymbial bump present. Tegulum either round or elongate. Tegulum shape, embolus and tibial apophysis similar to related Epeus, Telamonia and Plexippoides.
Relationships. On the basis of a molecular analysis, Maddison (2015) placed Ptocasius in the Plexippini tribe, together with Epeus, Plexippoides, Telamonia, Yaginumaella and 42 other genera. Prószyński (2017), using morphological characters, agrees that there is a close relationship between Ptocasius and Yaginumaella. We support both views, and, after the comparison of our material with Ptocasius weyersi-the type species of the genus, we have transferred 37 species of Yaginumaella (most of them described by MŻ) to the genus Ptocasius. Our decision is based on homologies/similarities in genitalic structures and priority of the generic name Ptocasius. At this stage we do not discuss the validity of Yaginumaella as such. Indeed, the genus presents some differences in genitalia, however its status remains an open issue.
Distribution and biology. Newly formulated, the genus Ptocasius includes 52 species distributed in two major diversity centres. The richest diversity is located in Nepal-Buthan Himalayas (from 700 to 3,400 m) and comprises 27 species characterised by small morphological gaps in the genitalic structures and found in narrow altitudinal vegetation zones. Prószyński (1980) suggested that such a case is the result of high speciation rate in unique ecological, historical and bioclimatic conditions. Such a phenomenon is widely known in tropical and subtropical mountains for many groups of animals and plants (Mani, 1974;Nice et al., 2013;Ebersbach, Schnitzler & Favre, 2017).
The second major diversity centre includes 23 species found in SE China, Hong Kong, Vietnam, Myanmar, Thailand and Malay Peninsula. A map of the predicted distribution ( Fig. 13), generated for all species and all available localities (72 records), suggests that the number for the latter area is seriously underestimated.
There are two hypotheses about possible relationships between these two groups: 1. The Himalayan lineage is derived from tropical (SE Asian) ancestors and speciated in great numbers on the spot. The isolation in various Himalayan valleys and the changing bioclimatic conditions found in different altitudinal zones certainly created ideal conditions for such an intense radiation. 2. The SE Asian group of species is derived from Himalayan ancestors.
The relationships of the genus Ptocasius to related genera suggest the first hypotheses to be more likely, but to verify the case it will be necessary to perform molecular analyses to estimate relationships and dates of divergence within the genus.
Species of the genus Ptocasius can be found in evergreen forests of Quercus, Rubus, Castanopsis, and different types of Rhododendron and bamboo forests at higher altitudes (Fig. 14).
Etymology. The specific epithet is patronym in honour of Dr. Heiko Metzner, prominent German salticid researcher.
Diagnosis. In comparison with P. stemmleri tegular bump at 1 o'clock vs 2 o'clock position. In related P. weyersi the tegular bump is missing. External epigyne similar in structure to P. simoni, P. supina, P. tenella, P. stemmleri, and P. helvetorum. From P. helvetorum and P. simoni it differs by smaller copulatory openings, much longer and narrower copulatory ducts. Unlike in P. stemmleri and P. supina spermathecae much longer and multi-coiled. In opposition to P. tenella copulatory opening crevices shorter and not wavy.

Data Availability
The following information was supplied regarding data availability: Distribution records of Epeus and Ptocasius are available in File S1. Described specimens with accession numbers are available in File S2; the specimens are located at the Hungarian Natural History Museum, Budapest, Hungary; RMNH Naturalis biodiversity centre in Leiden, Nederlands.

New Species Registration
The following information was supplied regarding the registration of a newly described species: Publication

Supplemental Information
Supplemental information for this article can be found online at http://dx.doi.org/10.7717/ peerj.9352#supplemental-information.