Another banner day for myrmecology! My friend and former labmate Andrea Lucky has just published her dissertation on the evolutionary history of Australasian Leptomyrmex spider ants. At first glance it seems very good research: a thoughtfully cautious phylogenetic analysis reveals a compelling story about a charismatic group of insects. Here’s an excerpt:
This molecular phylogenetic study significantly reframes our understanding of the deep history of the ant genus Leptomyrmex, painting a picture of a lineage that originated in the Neotropics approximately 48 Ma and dispersed to Australia where it diversified, today surviving only in relictual wet forest habitat on the edge of the Australian continent and on two Pacific islands, New Guinea and New Caledonia. The relatively recent diversification of these island taxa as a result of dispersal is especially notable, considering the low motility of the flightless queens in this genus. The future of this lineage of ants is now threatened by climate change, habitat loss and invasive species.
Spider ants are Gee-Whiz insects, the sort of creatures that evoke involuntary exclamations of wonder on first sighting. “Whoa- what’s that!?” was my response on encountering for the first time Leptomyrmex foragers bouncing along in the leaf-litter of a forest near Brisbane.
Leptomyrmex are what we’d get if the arachnid gods took control of the ant factory for a day. These are large, colorful, perky insects that teeter about like daddy-longlegs on spindley appendages, their gasters held high.
What I find most striking about Lucky’s results is how tightly the phylogeny tracks geography: closely-related species occur near each other on the Australian continent. This pattern may have emerged from a quirk of spider ant biology. Unlike queens of most ant species, Leptomyrmex queens are permanently wingless and disperse on foot. Thus, spider ant distributions may be more correlated with evolutionary descent than in ants with the more typical airborne dispersal.
I’d like to see more of this sort of study. Our planet is home to some 300 genera of ants, but fewer than a dozen have received the level of phylogentic scrutiny as Lucky as given Leptomyrmex. Evolutionary myrmecology is still in its infancy.
Lucky, A. 2011. Molecular phylogeny and biogeography of the spider ants, genus Leptomyrmex Mayr (Hymenoptera: Formicidae). Molecular Phylogenetics and Evolution, online early, doi:10.1016/j.ympev.2011.03.004.
Leptomyrmex virtual museum at Antweb
Live Leptomyrmex photos at alexanderwild.com