Abstract
Two distinct new species of the ant genus Crematogaster, C. khmerensis sp. nov. and C. pfeifferi sp. nov., are described from Cambodia and Malaysia, respectively. The two species are unique among Asian Crematogaster in that they have vertically directed propodeal spines, but their systematic positions have not been determined based on morphological characters alone. Molecular phylogenetic analysis of 89 Crematogaster taxon matrices previously published plus C. khmerensis sp. nov., using nuclear genes, reveals that C. khmerensis sp. nov. is nested within the Australo-Asian Crematogaster clade. Morphological assignment of the developed pronotal shoulders implies a close relationship between C. khmerensis sp. nov. and the C. tetracantha-group. Based on molecular and morphological evidence, we erect a new species group, C. khmerensis-group, to contain C. khmerensis sp. nov. and C. pfeifferi sp. nov. Divergence time estimates using MCMCTree shows that the root node of the C. khmerensis sp. nov. terminal is estimated to be of middle Miocene age at 15 million years old. The position of the C. khmerensis-group well supports the Oriental- to Australian-region dispersal history that has been proposed for the Australo-Asian Crematogaster clade.
Highlights
Ants (Formicidae) are one of the most familiar insect groups and they play important ecological roles in the ecosystems they inhabit (Hölldobler & Wilson 1990)
No parsimony informative characters (PIC) 74 67 93 142 44 420 topologies for the position of C. khmerensis sp. nov., but the Bayesian inference (BI) analysis differed in topology from the maximum parsimony (MP) and maximum likelihood (ML) analyses
The MP analysis recovered that C. khmerensis sp. nov. was nested within node A with high bootstrap support (100%) (Fig. 2)
Summary
Ants (Formicidae) are one of the most familiar insect groups and they play important ecological roles in the ecosystems they inhabit (Hölldobler & Wilson 1990). They are abundant in terms of biomass, are distributed worldwide and form a diverse family, in the tropics. Studies of distinct morphological characteristics are important contributions to ant taxonomy While these distinct morphological forms (autapomorphies) can be distinguished from other more typical forms, and can be described as new taxa, it can be difficult to determine their phylogenetic position. While uniqueness makes it easy to distinguish one taxon from others, elucidating the systematics of such taxa can be difficult
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