Tuesday, July 3, 2018

[Entomology • 2018] Lepidotrigona satun • A New Species of Lepidotrigona (Hymenoptera: Apidae) from Thailand with the Description of Males of L. flavibasis and L. doipaensis and Comments on Asymmetrical Genitalia in Bees

Lepidotrigona satun Attasopa & Bänziger, 2018

in Attasopa, Bänziger, Disayathanoowat & Packer, 2018.

We describe Lepidotrigona satun Attasopa and Bänziger new species from southern Thailand based upon associated males and females (workers). The new species is a member of the L. ventralis species group, which is otherwise represented in Thailand only by L. flavibasis and L. doipaensis. We also describe the males of the latter two species, associated with nests from close to their type localities in northern Thailand. Lepidotrigona doipaensis Schwarz and L. flavibasis (Cockerell) had previously often been misidentified as L. ventralis (Smith), a species confirmed only from Borneo. Based upon differences in male morphology, especially of the metasomal sterna, we conclude that the male described from Vietnam by Sakagami (1975) as belonging to L. flavibasis represents an undescribed species. Our findings support previous taxonomic studies that highlight the importance of including males in the differentiation of closely related species of meliponines and their association with workers. The three species whose males we describe have asymmetric penis valves with the asymmetry differentially developed among the three. We compare this genitalic asymmetry with that known from a different apid genus, Tarsalia.

Keywords: Hymenoptera, Asymmetry, Lepidotrigona satun n. sp., L. ventralis, stingless bees, taxonomy, Trigona

FIGURE 4. Lepidotrigona satun n. sp., dorsal habitus. (A) male holotype and (B) worker paratype.

Lepidotrigona satun Attasopa and Bänziger n. sp. 

Etymology. The specific epithet refers to the province in Thailand where the species was collected; it is a noun in apposition.

 Diagnosis. Lepidotrigona satun is a member of the “ventralis” species group based primarily on size: body and forewing length each less than 5 mm. It is the only species in the group known from the lower peninsula of Thailand. Males can be differentiated from those of the other two species of the “ventralis” group confirmed as occurring in Thailand (L. flavibasis and L. doipaensis) based upon external morphology as follows: margin of mesoscutum of L. satun with plumose, scale-like, yellow hairs (Fig. 4: A) (no such hairs in the other two species). S4 of L. satun is angularly emarginate apicomedially (Fig. 2: A1) (convex medially and bisinuate laterally in L. flavibasis, slightly concave in L. doipaensis). The apicosubmedial lobes of S5 in L. satun are apically rounded each with 4–7 thick, long setae (Fig. 2: A2) (the lobes are pointed in the other two species and bear only 1–2 setae which are very short in L. flavibasis (Fig. 2: B2) or with one very long and, if present, a second much shorter in L. doipaensis (Fig. 2: C2)). S5 gradulus does not touch the antecosta in L. satun (Fig. 2: A2) whereas it does touch it in the other two species, briefly in L. flavibasis (Fig. 2: B2) and extensively in L. doipaensis (Fig. 2: C2).

FIGURE 5. Lepidotrigona satun n. sp., lateral habitus. (A) male holotype and (B) worker paratype. 

 FIGURE 6. Lepidotrigona satun n. sp., head, frontal view. (A) male holotype and (B) worker paratype.


Final Comments on the Lepidotrigona ventralis species group. 
Our data clearly demonstrate that what has been considered by some to be a single (Ascher & Pickering 2017), albeit perhaps variable (Sakagami 1975), species termed L. ventralis, is a complex of species (as recognized by Rasmussen 2008) whose members are readily differentiable using pubescence coloration characteristics, morphological measurements and, where males are available, details of male metasomal sterna and genitalia. The male external metasomal sterna and the genital capsules of L. satun n. sp. provide excellent characters for species delimitation, and also permit the differentiation of other species in the L. ventralis group: L. flavibasis and L. doipaensis and the undescribed species thought to belong to the former by Sakagami (1975). We encourage others to make the, often considerable, effort required to find males of Meliponini from nests, as our data suggest they may often have more diagnostic species level characters than do the workers, as has been noted by others (Schwarz 1939; Sakagami 1975, 1978; Sakagami & Inoue 1978; Camargo & Moure 1994; Camargo et al. 2000; Gonzalez & Griswold 2011, 2012; Dollin et al. 2015; Halcroft et al. 2016; Engel et al. 2017b). However, we would argue against nest destruction in order to find them: all the males we describe here were collected as they left the nest entrance associated with conspecific nestmate workers. Lepidotrigona ventralis differs from the new species not only by morphology of the holotype as indicated in the original description by Smith (1857), Schwarz’s (1939) identification key (as L. ventralis s.s.), and the holotype examined by Rasmussen (2016, pers. comm. with H.B.), but also our examined museum specimens from the type locality and nearby areas, in which all the hairs on the dorsal surface of the metatibia are white. 

There are biogeographic differences between the new species and the others in the L. ventralis species group in Thailand. The new species’ nests were discovered from a low altitude area, 100 m a.s.l. in Satun province, which is around 480 km away from the Isthmus of Kra to the South. Kra is a biogeographically important region; it is an ecotone between the evergreen forests south of it and the forests with a marked dry season north of it (van Steenis 1950; Woodruff 2003). In contrast, L. doipaensis and L. flavibasis, for which type material and our own specimens agree, come from higher altitudes, of at least 500–1100 and 925–1700 m a.s.l. respectively in northern Thailand, some 1,300 km north of Satun. Moreover, L. ventralis itself is known only from the island of Borneo which is at least 1,200 km across the South China Sea from the type locality of the new species. Although L. ventralis s.s. has been recorded from several other countries, including Thailand (as listed in Rasmussen 2008), Schwarz (1939) never verified this species from anywhere except the type locality. All supposed L. ventralis s.s. H.B. has seen from Thailand were misidentified.

Korrawat Attasopa, Hans Bänziger, Terd Disayathanoowat and Laurence Packer. 2018. A New Species of Lepidotrigona (Hymenoptera: Apidae) from Thailand with the Description of Males of L. flavibasis and L. doipaensis and Comments on Asymmetrical Genitalia in Bees. Zootaxa. 4442(1); 63–82. DOI:  10.11646/zootaxa.4442.1.3

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