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A recent paper I found interesting (and I am sure was interesting to Dr Logsdon) about Multiple losses of sex within a single genus of Microsporidia. In the paper Joseph Ironside describes multiple instances of loss of sex within the Nosema/Vairimorpha group testing the hypothesis that the ancestral lineage was asexual. The group of species are undergoing rapid evolution where changes in lifestyle/lifecycle can occur even among very closely related lineages. In order to do test a formal hypothesis about whether the ancestor was asexual or sexual this the author had to improve the resolution of the phylogenetic relationships of these species and deal with some technical problems due to mutational biases in the rDNA sequences. The result he found was that the ancestral lineage was sexual and that asexuality arose multiple times among these species. He also provides a caution:
“The rapid evolution of microsporidian life cycles indicated by this study also suggests that even closely related microsporidia cannot be assumed to have similar life cycles and the life cycle of each newly discovered species must therefore be completely described.”
Something one has to be careful about in comparative studies of these species.
I don’t know if you’ve heard, but bee colonies are disappearing! Colony collapse disorder, as this phenomenon is better known, worries bee-keepers, agriculturalists and insect admirers all over: over 25% of the commerical bee colonies have disappeared since last fall. Normally, when a commerical hive collapses, honey is left behind in the box and wild bees set up shop on top of this free resource. But it seems that wild bees are also suffering, as honey filled boxes remain bee-less.
Researchers are scrambling to determine the cause of this bee die-off. Given the agricultural implications of losing one of nature’s best pollinators, time is of the essence. All sorts of hypotheses have been suggested, from pesticides or pathogens to solar flares and cell phones, but little evidence has been accumulated (mostly due to the fact that bee bodies are rarely found).
Fortunately, a recent breakthrough occured at UCSF. Joe DiRisi’s group found, in collaboration with other researchers, that Nosema ceranae (a microsporidian) had invaded several dead bees that had been found in the wild. There are several bee pathogens in the fungi (e.g. Ascosphera apis, whose genome was recently sequenced), but the discovery of Nosema infection is notable given that Nosema apis was the cause of widespread colony collapse disorder in Spain during the mid-nineties.
So is this pathogen the cause of the widespread colony die off? The jury is still out. But this represents some of the best evidence to date that fungi may be playing a role in this unfortunate event.