Recent and rapid diversification of the small carpenter bees in eastern North America

Abstract

Bees fulfil a critical ecological role as pollinators, significantly contributing to the reproductive success of myriad angiosperm species. Although increasingly appreciated for their agricultural contributions, relatively little is yet known about the natural history of the vast majority of the more than 20 000 wild bee species worldwide. The small carpenter bee genus Ceratina occurs globally, and is represented in North America by its most recently diverged subgenera, Ceratinula and Zadontomerus. Recent genetic analysis of eastern Ceratina (Zadontomerus) supports the existence of five closely related, yet genetically distinct species living in sympatry. This phylogeographical study employs molecular barcoding of the most comprehensive specimen collection yet assembled to confirm the identities of these recently diverged eastern North American Ceratina (Zadontomerus) species. Delineation of extant population structure, evolutionary history and known range of this emerging model native pollinator are greatly improved by this study. We consider ecological and behavioural factors potentially contributing to the maintenance of genetic identity among these sympatric species.

Biogeography and demography of an Australian native bee Ceratina australensis (Hymenoptera, Apidae) since the last glacial maximum

“…We note that the mitochondrial mutation rate for Caenorhabditis elegans (Maupas) is estimated as 9.7 × 10 -8 mutations per site per generation, close to the rate for D. melanogaster, and that they have mitochondrial AT biases of 76% and 82% respectively. Previous studies have reported an AT bias of 74% for the same barcoding region as in our study (Groom et al 2014a;Shell and Rehan 2016), and our Ceratina haplotypes had an AT bias of 78%. The number of generations was determined as two per year based on nest contents data from the Victorian and South Australian sites (Dew and Rehan, unpublished data), which also corresponds to detailed studies on the Queensland population (Rehan et al 2010b(Rehan et al , 2011(Rehan et al , 2014.…”

“…6.2 x 10 -8 mutations per site per generation as an estimate of the mutation rate for Ceratina australensis (Haag-Liautard et al 2008). This method follows a previous study on demographic history in Fijian halictine bees in the genus Lasioglossum (Groom et al 2014a) and North American Ceratina species (Shell and Rehan 2016). We note that the mitochondrial mutation rate for Caenorhabditis elegans (Maupas) is estimated as 9.7 × 10 -8 mutations per site per generation, close to the rate for D. melanogaster, and that they have mitochondrial AT biases of 76% and 82% respectively.…”

“…Assuming a mutation rate of 6.2 × 10 -8 and two generations per year (Shell and Rehan 2016), these values correspond approximately to 20 kya and 6.5 kya respectively.…”

“…Both studies found a strong response to Pleistocene climates, suggesting that these two faunal groups have been impacted by glacial cycles despite their tropical distribution. Small carpenter bees, Ceratina (Apidae: Ceratinini), of the subgenus Zadontomerus in eastern North America also showed a rapid population expansion approximately 20 kya, linked to post-glacial cycles (Shell and Rehan 2016). However, no studies have examined possible impacts of historical climates on bee species spanning temperate to xeric zones, beyond those using museum records.…”

Transcriptional profiling of overwintering gene expression in the small carpenter bee, Ceratina calcarata

“…This species ranges from Georgia north to Ontario and east to Nova Scotia (Rehan and Sheffield 2011;Shell and Rehan 2015). Unlike many temperate insects (Danks 1991;Denlinger 2002), C. calcarata overwinters as an adult (Rehan and Richards 2010a).…”