The phenology and social biology of four sweat bees in a marginal environment: Cape Breton Island

Abstract

Augochlorella striata, Lasioglossum (Evylaeus) cinctipes, Lasioglossum (Evylaeus) comagenense, and Lasioglossum (Dialictus) laevissimum were studied on Cape Breton Island, Nova Scotia, throughout their flight season in 1987. The weather during the summer was unusually good, with above-average temperatures and hours of sunshine but very low rainfall. Conversely, the previous summer had been very poor for bees, with comparatively few days suitable for foraging, particularly in July. Augochlorella striata was basically solitary but some nests produced one or, at most, two workers, thereby becoming eusocial. In other localities, L. cinctipes is known to be eusocial with well-developed morphological and physiological caste differentiation. However, most foundresses observed in 1987 were extremely small, smaller than usual for workers elsewhere, and none of the more than 100 nests produced adult workers or a reproductive brood. Most foundresses were either survivors of the worker brood from the previous year or unusually small reproductive brood females produced as a result of the bad weather in 1986. Lasioglossum comagenense was solitary or semisocial with one to four females occupying a nest. Lasioglossum laevissimum exhibited significant levels of pleometrosis and an extended period of worker foraging in summer. A comparison of the productivities of these four species indicates the importance of a flexible social system in a marginal climate.

Allozyme variation, linkage disequilibrium and diploid male production in a primitively social bee Augochlorella striata (Hymenoptera; Halictidae)

“…This is because the bees nested in small patches of earth amongst stones and rocks directly exposed to incident sunlight. The temperatures and humidities experienced by developing immatures and adults within nests fluctuated markedly (Packer et a!., 1989a The finding of highly significant linkage disequilibrium, even between only two of the loci, is interesting because values of D for allozyme loci are typically close to zero in outbred populations unless the loci are tightly linked (Hedrick, 1985).…”

“…This population is of particular interest because of its extremely low level of sociality (Packer et aL, 1989a;Packer, submitted). A. striata is a member of the bee family Halictidae, a group well known for its wide range of social organisation and multiple origins of eusociality (Michener, 1974).…”

Phylogeny of Halictidae with an emphasis on endemic African Halictinae

“…Halictids are important bees for studies of social evolution because they show enormous intra- (Sakagami and Munakata, 1972;Yanega, 1988;Eickwort et al, 1996;Richards, 2000;Soucy, 2002) and inter-specific variation in social behavior. Variation in social behavior within species is often linked with altitude and latitude such that populations at high elevation and latitude tend to be solitary, while populations at lower elevation and latitude tend to be eusocial (Sakagami and Munakata, 1972;Packer et al, 1989;Eickwort et al, 1996;Soucy, 2002;Soucy and Danforth, 2002). Diversity in social behavior among species was often thought to be due to frequent independent origins of eusociality in halictids (Eickwort, 1986) but recent molecular studies within and among genera of Halictinae have suggested that reversals from eusociality to solitary nesting may be common (Packer, 1997;Danforth, 1999;Danforth et al, 1999Danforth et al, , 2003Brady et al, 2006).…”

Solitary and eusocial nests in a population of Augochlorella striata (Provancher) (Hymenoptera; Halictidae) at the northern edge of its range

“…1) suggests a low frequency of multiple foundress association. For discussion of the limited evidence for multiple foundress nests see Packer et al (1989a).…”