Phylogeography and population genetics of the Australian small carpenter bee, Ceratina australensis

Abstract

The Australian small carpenter bee, Ceratina australensis, is the sole member of the small carpenter bees, genus Ceratina, in Australia. Ceratina australensis is found throughout eastern Australia in dead, broken stems of weedy plant species, where it makes its nests. Here we developed eight microsatellite loci and used these markers to characterize the genetic structure of three populations across three distinct ecoregions that are connected by the Murray-Darling River basin. We genotyped 57 female bees and found significant and geographically consistent variation in allelic diversity and heterozygosity between populations. Through comparisons with the results of mitochondrial DNA screening from a previous study, we infer the possibilities of male-biased dispersal and limited interpopulation migration. Based on available distribution data, the expansion of C. australensis into arid regions appears to follow the Murray-Darling River basin and associated waterways. This basin has undergone severe anthropogenic disturbance since European settlement of Australia, with large-scale changes to native vegetation communities. Although it is unknown how these changes have affected local insect communities, C. australensis does not rely on a single plant species for nesting habitat. We provide evidence for the hypothesis that expansion of C. australensis into Australia might have been aided by the introduction of non-native pithy stemmed plants.

Comparative metagenomics reveals expanded insights into intra- and interspecific variation among wild bee microbiomes

“…In our study, Queensland not only featured the most unique and significantly overrepresented taxa but also the most distinct metagenomic profile across all analyses. Our metagenomic data are thus broadly consistent with former amplicon, microsatellite, and genome-wide datasets used in previous C. australensis studies (e.g., 40 , 41 , 43 .) which found similar dimensions of structure among these populations.…”

“…(2) Does local environment drive metagenomic composition among populations of C. australensis across its distribution? We hypothesize that variation among C. australensis metagenomes is directly tied to environmental distinction among populations, as has been seen in previous amplicon sequencing microbiome studies within the species 40 , 41 . (3) Does the C. australensis metagenome reveal signals of sociality?…”

“…which found similar dimensions of structure among these populations. Gradually dispersing from an origin population in Queensland 49 , C. australensis is thought to have spread south and west following the Murray River to reach its current distribution 40 . This trajectory suggests that any substantial variation in metagenomic profiles between Queensland and either South Australia or Victoria should reveal relatively novel elements associated with those environments.…”