Mitochondrial sequencing and geometric morphometrics suggest two clades in the Tetragonilla collina (Apidae: Meliponini) population of Thailand

The stingless bee Tetragonilla collina Smith, 1857, is broadly distributed across Indochina. In this study, we use a combination of molecular and geometric morphometric analyses to quantify the genetic structure and diversity of the T. collina population of Thailand. We found striking regional differences in both mitochondrial haplotype frequencies and morphology. A Bayesian analyses of molecular diversity of the mitochondrial COI region revealed two clades, roughly divided into the population northeast of the Thai-Malay Peninsula (clade A) and the western and Thai-Malay Peninsula population (clade B). In addition, morphometric analysis showed that bees in clade A have significantly larger wings than bees from clade B. These results suggest that the T. collina population of Thailand is divided into two distinct populations. The spatial distributions seem to reflect contemporary ecological features such as annual flooding (bees of clade B are absent from areas subject to inundation), rather than past biogeography. Thus, T. collina differs from the honey bees Apis dorsata and A. cerana that show genetic differentiation north and south of the Isthmus of Kra, perhaps reflective of past separation during the Pleistocene when sea levels were much higher.