Crematogaster subcircularis, Smith, 1857, Smith

Hosoishi, Shingo, Maruyama, Munetoshi, Yamane, Seiki, Jaitrong, Weeyawat, Hashim, Rosli, Syaukani, Syaukani, Sokh, Heng, Itioka, Takao, Meleng, Paulus & Pham, Thai Hong, 2023, Multilocus phylogeny and historical biogeography of the Crematogaster inflata-group (Hymenoptera: Formicidae) in South-East Asia, Zoological Journal of the Linnean Society 198 (3), pp. 901-922 : 917-918

IS CREMATOGASTER SUBCIRCULARIS A RELICT SPECIES?

Crematogaster subcircularis was revealed to have an interesting distribution pattern. This species is found in mountainous areas (600–1250 m elevation) of the Sundaic region: the Malay Peninsula (Fraser’s Hill, 1000 m), Borneo (Poring, 600–700 m; Crocker Range, 1100 m) and Java (Cikaniki, 1000–1250 m). This distribution suggests that the ancestor retreated to high-altitude forests during the ice age, whereas the other related species ( C. modiglianii ) remained in lowaltitude forests (0–600 m elevation). Despite a postulated savannah corridor through central Sundaland ( Bird et al., 2005) that might have restricted the west– east dispersal of forest species, gallery forests in the Sunda Shelf could have served as corridors for forest species and facilitated the dispersal of C. subcircularis ( Fig. 4 ). Rising sea-levels in the Late Pleistocene may have isolated the three populations.

Molecular dating estimates and restricted highland distribution imply that C. subcircularis is a relict species. Several studies have hypothesized that continuous mountain ranges, which span Myanmar, Thailand, Laos, south China and Vietnam, acted as glacial refugia ( Brandon-Jones, 1996; Gorog et al., 2004; Iyengar et al., 2005). Assuming that C. subcircularis is a relict with a wide distribution range in the glacial periods, those populations were fragmented into several geographical ones when the sea level was higher, then closely related or sister-species might have retreated to the high-elevation refugia of mainland South-East Asia ( Surridge et al., 1999).

Figures

Figure 4. A, historical biogeography of the Crematogaster inflata-group based on BEAST2 and BioGeoBEARS analyses using the dispersal multiplier [Scheme (ii)] and two time slices. Blue horizontal bars depict the 95% highest posterior probability (HPD). Node labels N1–N11 correspond with denotations in Table 2. Biogeographical analysis employed a DEC model, with eight regions. The left-bottom map represents the Indo-Australian Archipelago delimited into eight areas. Colours of squares correspond to the coloured area on the map. Coloured squares indicate the most likely ancestral area recovered at each node. The present distribution of each species is given by coloured squares. B–D, palaeogeographic maps were redrawn and modified from Hall (2013): B, 15 Mya. C, 10 Mya. D, 5 Mya.