New Research: A History of the Amazing Spider Ants

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.

Leptomyrmex darlingtoni

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.

Leptomyrmex unicolor

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.


Sources:
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

9 thoughts on “New Research: A History of the Amazing Spider Ants”

  1. > “I’d like to see more of this sort of study”

    ;D We all would, and not only in ants, but also in some of the more important insect taxa, lol. They will come and after all, this capability was only a gleam in some taxonomists eyes not all that long ago.

    I am just happy to see them at all. Great work !

  2. Airborne ant dispersal vs. ground travel got me thinking – I wonder if ant species with alate queens disperse with patterns similar to plants species with airborne seeds? Has such a study been done before?

    1. Workin’ on that right now. Look for a paper or two in a year or two. Short answer so far: ant queens that fly are highly selective of the habitats they choose to land in.

  3. This is very cool. Nice job Andrea!
    I’m beginning to think the phylogeny of North American Polyergus will turn out tracking its geography something like this, though perhaps not as tightly. Though the they can fly, Polyergus queens are limited in dispersal by the apparent patchiness of susceptible host populations. Further, many of them only search for host colonies to parasitize near their parent nest or at least within its neighborhood, even following pupa-robbing raids to help them encounter a colonizable host nest.

  4. You can find all the treatments in Lucky & Ward’s paper (Zootaxa 2688: 1–67 (2010)):
    Abstract
    The ants of the genus Leptomyrmex (Hymenoptera: Formicidae), commonly called ‘spider ants’, are distinctive members of the ant subfamily Dolichoderinae and prominent residents of intact wet forest and sclerophyll habitats in eastern Australia, New Caledonia and New Guinea. This revision redresses pervasive taxonomic problems in this genus by using a combination of morphology and molecular data to define species boundaries and clarify nomenclature. Twenty-seven Leptomyrmex species are recognized and are informally split into two groups: the macro-Leptomyrmex (21 species), and its sister group, the micro-Leptomyrmex (six species). Nine subspecies are elevated to species status: L. cnemidatus Wheeler 1915, L. geniculatus Emery 1914, L. melanoticus Wheeler 1934, L. nigriceps Emery 1914, L. rothneyi Forel 1902, L. ruficeps Emery 1895, L. rufipes Emery 1895, L. rufithorax Forel 1915 and L. tibialis Emery 1895. Nineteen new synonymies are proposed (senior synonyms listed first): L. cnemidatus Wheeler 1915 = L. erythrocephalus venustus Wheeler 1934 = L. erythrocephalus brunneiceps Wheeler 1934; L. darlingtoni Wheeler 1934 = L. darlingtoni fascigasterWheeler 1934 = L. darlingtoni jucundus Wheeler 1934; L. erythrocephalus (Fabricius 1775) = L. froggatti Forel 1910 =
    L. erythrocephalus mandibularis Wheeler 1915 = L. erythrocephalus unctus Wheeler 1934 = L. erythrocephalus clarki Wheeler 1934; L. fragilis (F. Smith 1859) = L. fragilis femoratus Santschi 1932 = L. fragilis maculatus Stitz 1938 = L. wheeleri Donisthorpe 1948; L. melanoticus Wheeler 1934 = L. contractus Donisthorpe 1947; L. niger Emery 1900 = L. lugubris Wheeler 1934; L. rufipes Emery 1895 = L. quadricolor Wheeler 1934; L. rufithorax Forel 1915 = L. erythrocephalus basirufus Wheeler 1934; L. tibialis Emery 1895 = L. nigriventris hackeri Wheeler 1934; L. varians Emery 1895 = L. erythrocephalus decipiens Wheeler 1915 = L. varians angusticeps Santschi 1929; L. wiburdi Wheeler 1915 = L. wiburdi pictus Wheeler 1915. Tools for identification of the macro-Leptomyrmex species include a revised species-level key based on the worker caste, keys to males in Australia and New Guinea, full descriptions of workers, images of known workers, males and queens, and illustration of male genitalia. Phylogenetic relationships among the macro- and micro- Leptomyrmex species are discussed, as is the status of a putative fossil relative.

    It is available on antbase.

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