Crematogaster inflata-subgroup, F. Smith, 1857

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 : 916

The Crematogaster inflata-subgroup

Crematogaster aurita is distributed in Indochina, and does not extend southward beyond the Isthmus of Kra. The phylogenetic position of the species was sister to C. onusta within the C. inflata -subgroup. Biogeographic analyses based on the distribution pattern and phylogenetic position of the species suggests that C. aurita appeared as a result of a dispersal event ( Fig. 4 ). During the Pliocene to Pleistocene, terrestrial Indochinese animals might have had many opportunities to disperse to the Sundaic regions and vice versa, since these land areas were connected in the Sunda Shelf during glacial periods. The absence of C. aurita to the south of the Isthmus of Kra presumably resulted from limited dispersal capability and could also be a consequence of competition between related species. The distribution in the Indochinese Peninsula is possibly related to the preference of C. aurita for open, dry habitats. This preference could be explained by savannah corridors that are thought to have spanned Sundaland during glacial periods ( Bird et al., 2005) and drier and seasonal habitats are currently present in the Indochinese Peninsula and Java.

However, Crematogaster inflata and C. physothorax are sympatric in the Malay Peninsula. Our molecular dating analyses revealed that C. inflata and C. physothorax diverged approximately 6 Mya ( Fig. 4 ; Table 2 ). This high divergence implies an old split of these populations. It is unclear whether this divergence resulted from a vicariant event or dispersal of the ancestor of both species. The sympatric distribution of these two species in the peninsula might be due to secondary contact after their speciation ( Fig. 4 ). The estimated divergence suggests that the present geographic overlap of the two species is the result of independent colonization events from different geographic centres of origin.

Hosoishi & Ogata (2009: figs 25, 28) represented the distribution records of Crematogaster inflata and C. physothorax based on the original descriptions and literature, but the allocations in the figures seem controversial. A record of C. inflata from Myanmar was based on misidentification. Yet extensive field surveys in the Indochinese Peninsula were not able to find C. physothorax (e.g. Khachonpisitsak et al., 2020), whose type locality is Thagata, Tenasserim, Myanmar and presumably this species is not distributed in the Indochinese Peninsula.

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.