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Archive for April, 2009

Asexuality in ants

Eukaryotic organisms mostly reproduce sexually. Since no males were collected in the Neotropical ant fungus growing ant Mycocepurus smithii, Himler and colleagues tested if M. smithii is asexual using different strategies: genetic tools, morphological measures and experimental analyses. Read this paper and check out the neat images of the reproductive tracts.

Abstract: Asexual reproduction imposes evolutionary handicaps on asexual species, rendering them prone to extinction, because asexual reproduction generates novel genotypes and purges deleterious mutations at lower rates than sexual reproduction. Here, we report the first case of complete asexuality in ants, the fungus-growing ant Mycocepurus smithii, where queens reproduce asexually but workers are sterile, which is doublyenigmatic because the clonal colonies of M. smithii also depend on clonal fungi for food. Degenerate female mating anatomy, extensive field and laboratory surveys, and DNA fingerprinting implicate complete asexuality in this widespread ant species. Maternally inherited bacteria (e.g. Wolbachia, Cardinium) and the fungal cultivars can be ruled out as agents inducing asexuality. M. smithii societies of clonal females provide a unique system to test theories of parent–offspring conflict and reproductive policing in social insects. Asexuality of both ant farmer and fungal crop challenges traditional views proposing that sexual farmer ants outpace coevolving sexual crop pathogens, and thus compensate for vulnerabilities of their asexual crops. Either the double asexuality of both farmer and crop may permit the host to fully exploit advantages of asexuality for unknown reasons or frequent switching between crops (symbiont reassociation) generates novel ant–fungus combinations, which may compensate for any evolutionary handicaps of asexuality in M. smithii.

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Cane toad, Bufo marinus, are large toxic animals that are native to Central and South America and were introduced to Australia in 1935 to eradicate sugarcane beetles. These toads however have had detrimental effects on native Australian fauna – including marsupials, snakes & lizards. Checking the spread of these toads has been a task next to impossible. Recent work from Rick Shine’s lab shows that the diurnal toads somehow fail to detect approaching Iridomyrmex reburrus ants, and the ants kill and feed on the toads. Read more about this latest research where the authors report their findings and discuss the possibility of using these ants to control cane toad spread.

Reference: Ward-Fear G et al., 2009. Maladaptive traits in invasive species: in Australia cane toads are more vulnerable to predatory ants than are native frogs. Functional Ecology: DOI 10.1111/j.1365-2435.2009.01556.x

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