Gasteracantha doriae Simon, 1877

Macharoenboon, Kongkit, Siriwut, Warut & Jeratthitikul, Ekgachai, 2021, A review of the taxonomy of spiny-backed orb-weaving spiders of the subfamily Gasteracanthinae (Araneae, Araneidae) in Thailand, ZooKeys 1032, pp. 17-62 : 17

Gasteracantha doriae Simon, 1877 Figures 7 , 11G-I

Gasteracantha doriae Simon, 1877: 232, pl.3, fig. 3. Type locality: Sarawak, Borneo Island.

Gasteracantha doriae Full list of synonyms and usage of the name available in World Spider Catalog (2020).

Material.

Thailand • 3 ♀ juvenile; Trat Province, Laem Ngop District ; 12°10.39'N, 102°24.33'E; MUMNH-ARA-GAS053 • 1 ♀ juvenile; Surat Thani Province, Khiri Rat Nikhom District, Wang Badarn Cave ; 08°54.52'N, 98°57.08'E; MUMNH-ARA-GAS068 • 5 ♀; Rayong Province, Wang Chan District, Pa Yup Nai ; 13°01.27'N, 101°26.83'E; MUMNH-ARA-GAS130, MUMNH-ARA-GAS131 .

Diagnosis.

Sternum brownish black with large yellow spot at the center. Abdomen much wider than long. Dorsal side of abdomen with two black and three white horizontal bands. Two black abdominal horizontal bands arched with sinuous margins. First black horizontal band slightly hollow at the anterior middle. Edge of abdomen with serrated spikes, obvious on spines. Anterior spines smallest, directed obliquely. Posterior spines conical, pointed backward. Median spines longest, less conical, and slightly arched backward. One large median spot between the bases of posterior spines, and one lateral spot on each side. Ventral side of abdomen blackish with chalk-white spots and small black granules. Sigilla reddish brown. Anterior edge with ten sigilla: four sigilla in the middle smaller, forming a straight line, three sigilla on each side larger, trapezoid-shaped. Four median sigilla arranged in trapezoid shape. Posterior edge with ten sigilla: six sigilla in the middle smaller, forming a straight line, with the pair in the middle close together; two sigilla on each side larger, trapezoid. Outer posterior edge with five sigilla near posterior spines. Epigynum with a pair of hook-shaped sclerotized structures between spermathecae, visible in posterior view (Fig. 11I ). Spermathecae round (Fig. 11G ), ventrally partially overlapped by wing-shaped sclerotized structure (Fig. 11H ). Scape long, pointed posteriorly, flanked by lateral sclerotized plates (Fig. 11I ). Copulatory ducts encapsulated by sclerotized structure (Fig. 11G ). Fertilization duct emerging posteriorly from spermathecae (Fig. 11G ).

Variation.

Two color morphs are observed consisting of the black-white banded morph (Fig. 7A ) and the black-yellow banded morph (Fig. 7B ). The black bands in the B&Y morph are less sinuous than in the B&W morph.

Remarks.

This species resembles G. frontata , G. diadesmia , and G. sturi . These species can be distinguished from each other by abdominal spines and abdominal color pattern. The median spines of G. doriae are longer and less conical than G. frontata . The median spines of G. diadesmia are thicker and wider than G. doriae . Gasteracantha doriae differs from G. sturi in having longer and pointed median spines and wider black horizontal bands. Additionally, the angle between anterior and median spines of G. doriae is more obtuse than other species. Although the type specimen of G. frontata is without horizontal bands ( Blackwall 1864; Pickard-Cambridge 1879), there are some reports stating that G. frontata contains abdominal horizontal bands ( Pickard-Cambridge 1879; Pocock 1900). Pocock (1900) reported that the first horizontal band of G. frontata reaches the base of the anterior spine, whereas the first horizontal band of G. doriae terminates before the base of the anterior spine.

Two Gasteracantha species with abdominal horizontal bands that were previously recognized as G. diardi by Tan et al. (2019) are grouped separately from other Thai G. diardi with high nodal support. In addition, these two individuals are morphologically different from other G. diardi specimens from Thailand by having smaller size of median spines, as well as different color pattern (horizontal bands morph). By comparing photographs in Tan et al. (2019) and previous taxonomic publications ( Simon 1877; Workman and Workman 1892), we propose that these two individuals were Gasteracantha doriae . Unfortunately, our specimens (Fig. 7C ) in D1 clade that were placed in the same clade with G. doriae s.s. Tan et al. (2019) were still juvenile, and therefore we were unable to examine the genitalia.

Interestingly, the phylogenetic tree and species delimitation results suggest another distinct clade in G. doriae (clade D2 in Figs 3 and 4 ). These two clades of G. doriae show a distant relationship and potentially are cryptic species. Only a couple of morphological differences can be detected. Morphological characters of G. doriae D1, which we observed via photographs in Tan et al. (2019), is similar to the original description ( Simon 1877), while G. doriae D2 shows morphological variation. The horizontal black bands of G. doriae D1 are rather straight with smooth margin, whereas the horizontal black bands of G. doriae D2 are curved and with apparently sinuous margin (Figs 7A, B ). In addition, G. doriae D1 possesses three horizontal black bands, while G. doriae D2 presents only two horizontal black bands. The angle between anterior and median spines of G. doriae D2 is more obtuse than in G. doriae D1. All molecular analyses (i.e., phylogenetic analyses, species delimitation, and genetic distance) in this study strongly suggest that the two lineages are distinct species. However, due to unavailability of adult specimens of G. doriae D1, we were unable to compare the female genitalia structure between G. doriae D1 and D2, which is usually used as a reliable and distinguishable character in Gasteracantha species. Further investigation of adult female specimens from the type locality is necessary to resolve this taxonomic problem.

Distribution and habitat.

Indonesia (Borneo), Malaysia, and Thailand ( World Spider Catalog 2020). Adult spiders were collected from shrubs and trees. The female spider builds a vertical web between shrubs or trees in open areas. They sit at the center of the web with head directed downward.

Figures

Figure 3. Maximum Likelihood phylogenetic tree reconstructed from COI + 16 S + H 3 genes of Gasteracanthinae and outgroups. Nodal support values are labeled as Jackknife support / ML bootstrap values / Bayesian posterior probability.

Figure 4. Ultrametric tree generated by BEAST from 675 bp of COI gene showing clusters of OTUs as suggested by morphological identification, and three molecular species delimitation algorithms, ABGD, bPTP, and GMYC. Nodal support values are labeled as MP Jackknife support / ML bootstrap values / Bayesian posterior probability. Gene tree from MP and ML analyses are available as Suppl. material 1 (Suppl. material 1: Figs S 3, S 4).

Figure 7. Females of Gasteracantha doriae A black-white bands morph, specimen from Rayong (MUMNH-ARA-GAS 131) B black-yellow bands morph, specimen from Rayong (MUMNH-ARA-GAS 130 - 1) C juvenile, specimen from Trat (MUMNH-ARA-GAS 053) A, B belong to clade D 2 and C from clade D 1 in Fig. 3.

Figure 11. Female genitalia of A-C Gasteracantha diadesmia D-F G. diardi G-I G. doriae J-L G. kuhli. Genitalia are shown in dorsal view (A, D, G, J), ventral view from external (B, E, H, K), and posterior view (C, F, I, L).