Ooceraea quadridentata Yamada, Luong et Eguchi, 2018

Ooceraea quadridentata Yamada, Luong et Eguchi, 2018 View in CoL

Fig. 1 View Fig

MATERIAL EXAMINED. Indonesia: West Sumatra: Padang: Kota Padang, Gunung Pangilun , 0°54'59.7"S, 100°22'4.7"E, ca 70 m asl., 2023, worker (Colony code: GP-30v23- 01) GoogleMaps .

DIAGNOSIS. Worker ( Fig. 1 View Fig ). This specimen is similar to Ooceraea quadridentata but it has morphological variations seen from the lateral view, the propodeum denticles shorter than the holotype. The diagnosis of the worker agree well with original description of this species as follows: in the full face view, the cranium is subrectangular with weakly convex lateral margins and a medially concave posterior margin; the antennal scape is folded back to almost reach the midlength of the cranium; region surrounding the antennal socket, which is strongly depressed and bounded by the torulo-posttorular complex and parafrontal ridge. A row of tiny, barely noticeable teeth can be seen on the mandibular masticatory margin; in dorsal view, the parafrontal ridge clearly produced the anteriad; complete absence of ocelli and compound eye; with an enlarged apical segment XI that is nearly as long as segments V – X combined, antenna 11-segmented .

MEASUREMENTS AND INDICES. Worker: HL – 0.68; HW – 0.63; SL – 0.4, ML – 0.92; PL – 0.32; PH – 0.41; PW – 0.3; PPL – 0.38; PPH – 0.36; PPW – 0.35; CI – 92.65; SI – 63.49; PI1 – 78.05; PI2– 93.75; PPI1 – 105.55; PPI2 – 92.1; WI – 116.67.

DISTRIBUTION. Indonesia: Sumatra (new record); Vietnam: Dak Lak; Thailand: Udom Sab Subdist.

REMARKS. The denticles of propodeum of specimens from Sumatra are shorter and body smaller than the same of holotype and specimens from Thailand . We assumed that the O. quadridentata has intraspecific morphological variations in the worker caste. The variations of these characters not prevent the identification process of this species, due to the unique characteristics of this species, i.e. the two pair of denticles in propodeum. Moreover, Jaitrong et al. (2021) recognized the morphological variation between the population from Thailand and Vietnam.

We collected the Ooceraea quadrendata in the lowland disturbed forest in West Sumatra, while Yamada et al. (2018) collected the colony of this species in a disturbed and bamboomixed evergreen forest in the highland of Vietnam. The habitat of the colony found in Sumatra is a relatively unique which is a fragmented disturbed forest in the middle of the city and surround by residential areas. The vegetation of this area is completely different from the habitat where the holotype collected. In Sumatra, the colony of O. quadrendata was collected in the leaf-litter on hillsides at the edge of hiking trails.

The DNA barcoding system that uses the mitochondrial gene cytochrome C oxidase subunit 1 (cox 1 or COI) is very efficient for distinguishing vertebrate and invertebrate species (Rodrigues, 2017). In this study we used COI to determine the genetic variation of the same species but have a geographic range. The diversity in this study was collected from areas several hundred kilometers apart, which may have contributed to their morphological and genetic differentiation (Mary, 2016). Even though they are the same species, Ooceraea quadridentata from the two regions has a genetic distance of ±0.16 and the average genetic distance of the outgroup is ±0.2 ( Table 1).

In this study we found that genetic variation occurs in ant Ooceraea quadentata populations with geographic ranges. New branches were formed in O. quadridentata sp. 1 and sp. 2 from Sumatra, this indicates genetic variation with the O. quadridentata from Vietnam ( Fig. 2 View Fig ). This condition is actually affected by the biotic and abiotic factors caused the individualism ability to survive and procreate. In different populations of the same species, this leads to genetic variation. Population adaptation to different geographic ranges results in genetic variation ( Eckert, 2008).