DOI: 10.5061/dryad.vm11c
title: Data from: Phenological, but not social, variation associated with climate differences in a eusocial sweat bee, Halictus ligatus, nesting in southern Ontario

description: Studies of annual and geographic variation in eusocial bee populations
 suggest that more stringent environmental conditions result in stronger
 reproductive skew favouring queens, while moderate conditions favour
 increasing worker reproduction. To test these predictions, we compared the
 phenology and colony development of H. ligatus nesting in St. Catharines,
 Ontario, Canada to a previously studied aggregation 90 km north of St.
 Catharines, in Victoria, Ontario. Despite the close proximity of these two
 locations, St. Catharines has markedly shorter winters and longer summers.
 Comparisons between St. Catharines in 2006 and Victoria in the 1980s and
 1990s incorporate both geographic differences in climate and temporal
 differences due to climate change. We predicted that St. Catharines
 foundress queens should emerge from hibernation and initiate nests earlier
 in spring, giving them time to produce more workers. Since earlier studies
 indicated that queens have difficulty suppressing worker reproduction in
 larger colonies, we also predicted higher rates of worker ovarian
 development in St. Catharines. In spring and summer 2006, we excavated 65
 H. ligatus nests, comparing their contents to 713 specimens collected in
 pan traps. As predicted, nests were initiated about a month earlier in St.
 Catharines than in Victoria, but contrary to prediction, fewer workers
 were produced in St. Catharines. St. Catharines workers were just as
 likely to have developed ovaries as Victoria workers. About 40% of St.
 Catharines workers were classified as reproductive, and larger
 reproductive workers tended to have higher ovarian scores. Early queen
 mortality in the longer nest cycle of St. Catharines bees may have
 enhanced opportunities for worker reproduction despite their smaller
 numbers. Novel features of H. ligatus sociobiology in St. Catharines
 included evidence that queens can initiate new nests following the loss of
 their first brood, overlap between worker and gyne production within some
 nests, and high rates of independent nest founding by worker-sized
 females, suggesting that many worker-brood females overwinter. Overall,
 the distinctly warmer climate of St. Catharines compared to Victoria led
 to earlier nest initiation and lengthening of the flight season, but not
 to the predicted differences in colony social organisation or queen-worker
 reproductive skew. A second objective of our study was to assess how well
 pan trap collections capture important information about demographic and
 social parameters important in assessing social variability in sweat bees.
 Nest excavations and pan traps produced similar results, suggesting that
 pan traps are a good alternative when nest excavations are impossible.
description: Dryad Nest bee
 dissection dataAll measurement and
 dissection observations for females collected during nest
 excavationsHalictus ligatus 2006
 nest excavation recordsRecords of Halictus
 ligatus nest contents excavated in St. Catharines in
 2006Dryad
 Nest excavation records.csv