Guest essay by Eric Worrall

A study published in the Journal of Hymenoptera finds that Australian bee populations expanded with the end of the last ice age, then plateaued around 6000 years ago.

The small carpenter bees, genus Ceratina, are highly diverse, globally distributed, and comprise the sole genus in the tribe Ceratinini. Despite the diversity of the subgenus Neoceratina in the Oriental and Indo-Malayan region, Ceratina (Neoceratina) australensis is the only ceratinine species in Australia. We examine the biogeography and demography of C. australensis using haplotype variation at 677 bp of the barcoding region of COI for specimens sampled from four populations within Australia, across Queensland, New South Wales, Victoria and South Australia. There is geographic population structure in haplotypes, suggesting an origin in the northeastern populations, spreading to southern Australia. Bayesian Skyline Plot analyses indicate that population size began to increase approximately 18,000 years ago, roughly corresponding to the end of the last glacial maximum. Population expansion then began to plateau approximately 6,000 years ago, which may correspond to a slowing or plateauing in global temperatures for the current interglacial period. The distribution of C. australensis covers a surprisingly wide range of habitats, ranging from wet subtropical forests though semi-arid scrub to southern temperate coastal dunes. The ability of small carpenter bees to occupy diverse habitats in ever changing climates makes them a key species for understanding native bee diversity and response to climate change.

Read more: http://jhr.pensoft.net/articles.php?id=8066

Given frequent model based predictions that climate will cause bee populations to crash, I admire the daring of an evidence based study which suggests that bee populations expand in response to increased availability of food.

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