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Dive into the research topics where Sandra M. Rehan is active.

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Featured researches published by Sandra M. Rehan.


Canadian Entomologist | 2010

Nesting biology and subsociality in Ceratina calcarata (Hymenoptera: Apidae)

Sandra M. Rehan; Miriam H. Richards

Abstract To evaluate sociality in small carpenter bees (Ceratina Latreille), we studied the life history and nesting biology of a common eastern North American species, Ceratina (Zadontomerus) calcarata Robertson. Pan-trap and nest collections throughout the active season (May to September 2006) were used to assess seasonal phenology and nesting biology of C. calcarata in southern Ontario. Adults overwintered in their natal nests. Males emerged in early May and occupied preexisting hollows in twigs and stems. Females emerged from hibernacula 2 weeks later, founding new nests. Nest founding and provisioning occurred throughout the spring; females remained with developing brood through the summer. Complete nests contained, on average, 6.9 offspring, with egg-to-adult development averaging 46 days. Ceratina calcarata is subsocial rather than solitary: mothers are long-lived and nest-loyal, and care for offspring from egg to adulthood. Subsociality is found in all behaviourally classified small carpenter bees, while some species cross the boundary into social life, making Ceratina an important genus for the study of the transition between solitary and social life.


Biology Letters | 2011

The evolution of eusociality in allodapine bees: workers began by waiting.

Michael P. Schwarz; Simon M. Tierney; Sandra M. Rehan; Luke B. Chenoweth; Steven J.B. Cooper

Understanding how sterile worker castes in social insects first evolved is one of the supreme puzzles in social evolution. Here, we show that in the bee tribe Allodapini, the earliest societies did not entail a foraging worker caste, but instead comprised females sharing a nest with supersedure of dominance. Subordinates delayed foraging until they became reproductively active, whereupon they provided food for their own brood as well as for those of previously dominant females. The earliest allodapine societies are, therefore, not consistent with an ‘evo-devo’ paradigm, where decoupling of foraging and reproductive tasks is proposed as a key early step in social evolution. Important features of these ancestral societies were insurance benefits for dominants, headstart benefits for subordinates and direct reproduction for both. The two lineages where morphologically distinct foraging worker castes evolved both occur in ecosystems with severe constraints on independent nesting and where brood rearing periods are very seasonally restricted. These conditions would have strongly curtailed dispersal options and increased the likelihood that dominance supersedure occurred after brood rearing opportunities were largely degraded. The origins of foraging castes, therefore, represented a shift towards assured fitness gains by subordinates, mediated by the dual constraints of social hierarchies and environmental harshness.


Molecular Phylogenetics and Evolution | 2010

Molecular phylogeny of the small carpenter bees (Hymenoptera: Apidae: Ceratinini) indicates early and rapid global dispersal

Sandra M. Rehan; Thomas William Chapman; Andrew Ian Craigie; Miriam H. Richards; Steven J.B. Cooper; Michael P. Schwarz

The small carpenter bees (tribe Ceratinini, family Apidae) are recorded from all continents except Antarctica. The Ceratinini have a near-global distribution which contrasts strongly with their sister tribe, the Allodapini which has a largely southern Old World distribution. The Ceratinini therefore provides an excellent group to understand the factors that help determine the biogeography and radiation of the bees. This is the first molecular study of ceratinine bees covering representatives from both northern and southern hemisphere Old and New World regions. We use two mitochondrial and one nuclear marker (totalling 2807 nucleotides) to examine the age, cladogenesis and historical biogeography of this tribe. Tree topology and molecular dating support an African origin at about 47 Mya with subsequent dispersal into Eurasia 44 Mya, and followed by an American invasion 32 Mya. Concentrated African and Malagasy sampling revealed there were two or three dispersals events into Madagascar ranging from 25 to 9 Mya. Lineage through time analyses suggest higher rates of cladogenesis close to the origin of the tribe, and this corresponds to both major dispersal events and divergences of lineages leading to extant subgenera. Ceratinini have potentially great importance for future studies to understand the relative roles of dispersal ability and time of origin in determining bee biogeography.


PLOS ONE | 2012

A Mid-Cretaceous Origin of Sociality in Xylocopine Bees with Only Two Origins of True Worker Castes Indicates Severe Barriers to Eusociality

Sandra M. Rehan; Remko Leys; Michael P. Schwarz

The origin of sterile worker castes, resulting in eusociality, represents one of the major evolutionary transitions in the history of life. Understanding how eusociality has evolved is therefore an important issue for understanding life on earth. Here we show that in the large bee subfamily Xylocopinae, a simple form of sociality was present in the ancestral lineage and there have been at least four reversions to purely solitary nesting. The ancestral form of sociality did not involve morphological worker castes and maximum colony sizes were very small. True worker castes, entailing a life-time commitment to non-reproductive roles, have evolved only twice, and only one of these resulted in discrete queen-worker morphologies. Our results indicate extremely high barriers to the evolution of eusociality. Its origins are likely to have required very unusual life-history and ecological circumstances, rather than the amount of time that selection can operate on more simple forms of sociality.


BMC Evolutionary Biology | 2014

At the brink of eusociality: transcriptomic correlates of worker behaviour in a small carpenter bee

Sandra M. Rehan; Ali J. Berens; Amy L. Toth

BackgroundThere is great interest in understanding the genomic underpinnings of social evolution, in particular, the evolution of eusociality (caste-containing societies with non-reproductives that care for siblings). Subsociality is a key precursor for the evolution of eusociality and characterized by prolonged parental care and parent-offspring interaction. Here, we provide the first transcriptomic data for the small carpenter bee, Ceratina calcarata. This species is of special interest because it is subsocial and in the same family as the highly eusocial honey bee, Apis mellifera. In addition, some C. calcarata females demonstrate alloparental care without reproduction, which provides a unique opportunity to study worker behaviour in a non-eusocial species.ResultsWe uncovered similar gene expression patterns related to maternal care and sibling care in different groups of females. This agrees with the maternal heterochrony hypothesis, specifically, that changes in timing of offspring care gene expression are related to worker behaviour in incipient insect societies. In addition, we also detected some similarity to caste-related gene expression patterns in highly eusocial honey bees, and uncovered large lifetime changes in gene expression that accompany shifts in reproductive and maternal care behaviour.ConclusionsFor Ceratina calcarata, we found that transcript expression profiles were most similar between sibling care and maternal care females. The maternal care behaviour exhibited post-reproductively by Ceratina mothers is concordant in terms of transcript expression with the alloparental care exhibited by workers. In line with theoretical predictions, our data are consistent with the maternal heterochrony hypothesis for the evolutionary development of worker behaviour in subsocial bees.


Canadian Entomologist | 2011

Bee diversity in naturalizing patches of Carolinian grasslands in southern Ontario, Canada

Miriam H. Richards; A. Rutgers-Kelly; Jason Gibbs; J.L. Vickruck; Sandra M. Rehan; Cory S. Sheffield

Abstract The bee fauna (Hymenoptera: Apoidea) of the Niagara Peninsula, at the eastern end of the Carolinian Zone in Ontario, Canada, is poorly known. From April to October 2003, we studied bee abundance and diversity in set-aside grasslands at Brock University and the Glenridge Quarry Naturalization Site in southern St. Catharines, Ontario. Using three sampling methods (pan traps, sweep nets, and aerial nets), we collected and identified 15 733 specimens of 124 species and morphospecies representing all bee families, except Melittidae, found in North America. Abundance-based diversity estimators suggested bee species richness to be as high as 148 species. There were three seasonal peaks in bee abundance (early spring, late spring, and midsummer) with a lull in activity shortly after the summer solstice. Several indicators suggested substantial impacts of disturbance on the Niagara bee community, including evidence of high dominance by the most abundant species. Comparison of the sampling methods indicated considerable catch variation among taxa; Halictidae and Apidae were dominant in pan trap samples and in sweep—aerial net samples, respectively. However, bee abundances in pan traps and sweep nets were highly correlated, suggesting that both methods fairly sample local bee abundances.


Insectes Sociaux | 2010

Social polymorphism in the Australian small carpenter bee, Ceratina (Neoceratina) australensis

Sandra M. Rehan; Miriam H. Richards; Michael P. Schwarz

The bee tribe Ceratinini provides important insights into the early stages of sociality. Many arthropods exhibit behaviours precursory to social life, including adult longevity, parental care, nest loyalty and mutual tolerance, yet the origins of social behaviour are few. Here we describe the biology of a facultatively social bee, Ceratina (Neoceratina) australensis, which exhibits all of the preadaptations for successful group living, yet presents ecological and behavioural characteristics that seemingly disfavour frequent colony formation. This species is socially polymorphic with both solitary and social nests collected in sympatry. Social colonies consist of two foundresses, one contributing both foraging and reproductive effort and the second which remains at the nest as a passive guard. Cooperative nesting provides no overt reproductive benefits over solitary nesting in this population, although brood survival tends to be greater in social colonies. Maternal longevity, subsociality and bivoltine nesting phenology in this species favour colony formation, while dispersal habits and offspring longevity may inhibit more frequent social nesting in this and other ceratinines.


Journal of the Kansas Entomological Society | 2009

Evidence of social nesting in the Ceratina of Borneo (Hymenoptera: Apidae).

Sandra M. Rehan; Miriam H. Richards; Michael P. Schwarz

Abstract The bee tribe Ceratinini is important for understanding early stages in social evolution. Their extant sister tribe Allodapini contains no strictly solitary species, and while some Ceratinini are commonly regarded as solitary, little behavioural data exist to substantiate this. Studies on Asian congeners have shown recurrent sociality in temperate and subtropical ranges while behavioural data are lacking in tropical regions. Field work along the west coast of Borneo in Sarawak, Malaysia, has provided some insight into these tropical taxa. Here we describe the nesting biology and social behaviour of four taxonomically described yet behaviourally unclassified Ceratina species. These four species are from three subgenera, namely Ceratina (Ceratinidia) accusator Cockerell, C. (Ceratinidia) nigrolateralis Cockerell, C. (Neoceratina) dentipes Friese, C. (Pithitis) smaragdula Fabricius. Nests of all species were typically attended by an adult female while all species except C. accusator had a low frequency of multi-female nesting assemblages. The four tropical ceratinines described here and all other behaviourally classified species exhibit recurrent patterns of maternal care, maternal longevity, and nest protection. Prolonged parental care found across the genus and occasional transitions into sociality make Ceratina of future interest for the study of life history and social evolution.


Annual Review of Entomology | 2017

Molecular Evolution of Insect Sociality: An Eco-Evo-Devo Perspective

Amy L. Toth; Sandra M. Rehan

The evolution of eusociality is a perennial issue in evolutionary biology, and genomic advances have fueled steadily growing interest in the genetic changes underlying social evolution. Along with a recent flurry of research on comparative and evolutionary genomics in different eusocial insect groups (bees, ants, wasps, and termites), several mechanistic explanations have emerged to describe the molecular evolution of eusociality from solitary behavior. These include solitary physiological ground plans, genetic toolkits of deeply conserved genes, evolutionary changes in protein-coding genes, cis regulation, and the structure of gene networks, epigenetics, and novel genes. Despite this proliferation of ideas, there has been little synthesis, even though these ideas are not mutually exclusive and may in fact be complementary. We review available data on molecular evolution of insect sociality and highlight key biotic and abiotic factors influencing social insect genomes. We then suggest both phylogenetic and ecological evolutionary developmental biology (eco-evo-devo) perspectives for a more synthetic view of molecular evolution in insect societies.


Molecular Ecology | 2016

Characterization of pollen and bacterial community composition in brood provisions of a small carpenter bee

Quinn S. McFrederick; Sandra M. Rehan

Many insects obtain gut microbes from their diet, but how a mothers foraging patterns influence the microbes found in her offsprings food remains an open question. To address this gap, we studied a bee that forages for pollen from multiple species of plants and may therefore acquire diverse bacteria from different plants. We tested the hypothesis that pollen diversity correlates with bacterial diversity by simultaneously characterizing these two communities in bee brood provisions for the first time. We used deep sequencing of the plant RBCL gene and the bacterial 16S rRNA gene to characterize pollen and bacterial diversity. We then tested for associations between pollen and bacterial species richness and community composition, as well as co‐occurrence of specific bacteria and pollen types. We found that both pollen and bacterial communities were extremely diverse, indicating that mother bees visit a wide variety of flowers for pollen and nectar and subsequently bring a diversity of microbes back into their nests. Pollen and bacterial species richness and community composition, however, were not correlated. Certain pollen types significantly co‐occurred with the most proportionally abundant bacteria, indicating that the plants these pollen types came from may serve as reservoirs for these bacteria. Even so, the overall diversity of these communities appears to mask these associations at a broader scale. Further study of these pollen and bacteria associations will be important for understanding the complicated relationship between bacteria and wild bees.

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Erika M. Tucker

University of New Hampshire

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Wyatt A. Shell

University of New Hampshire

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Brendan G. Hunt

Georgia Institute of Technology

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Karl M. Glastad

University of Pennsylvania

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