Sandra Rehan

York University · Department of Biology

Wild bees are vital for maintaining biodiversity and food security. However, bees are currently threatened by the conversion of their natural habitat into urban areas, among many other factors. Here, we examine how five wild bee species respond to increasing urbanization according to their functional traits across the most populous city in Canada,...

Facultatively social insects are an optimal model group for the study of the emergence of cooperation between individuals. Factors influencing the fitness benefits of social nesting are still debated. Nonreproductive subordinates can benefit from indirect fitness benefits due to increasing reproductive success of related individuals or direct fitne...

Maternal care acts as a strong environmental stimulus that can induce phenotypic plasticity in animals and may also alter their microbial communities through development. Here, we characterize the developmental metatranscriptome of the small carpenter bee, Ceratina calcarata , across developmental stages and in the presence or absence of mothers. M...

Many groups of animals have evolved social behaviours in different forms, from intimate familial associations to the complex eusocial colonies of some insects. The subfamily Xylocopinae, including carpenter bees and their relatives, is a diverse clade exhibiting a wide range of social behaviours, from solitary to obligate eusociality with distinct...

Rudimentary social systems have the potential to both advance our understanding of how complex sociality may have evolved, and our understanding of how changes in social environment may influence gene expression and cooperation. Recently studies of primitively social Hymenoptera have greatly expanded empirical evidence for the role of social enviro...

Urbanization is considered one of the major threats to biodiversity worldwide, with a special concern for native species decline, including wild bees. Through the increase of impervious surfaces, urbanization diminishes, fragments, and warms city environments, significantly reducing nesting and foraging resources for bees. Understanding the respons...

Elucidating bee response to urbanization is essential to promoting pollinator diversity in cities especially considering such landscapes are projected to expand to support future global populations. To determine how bee community composition and plant–pollinator interactions respond to urbanization, 29 sites representing three urban categories (hig...

As urbanization continues to increase, it is expected that two-thirds of the human population will reside in cities by 2050. Urbanization fragments and degrades natural landscapes, threatening wildlife including economically important species such as bees. In this study, we employ whole genome sequencing to characterize the population genetics, met...

Deciphering processes that contribute to genetic differentiation and divergent selection of natural populations is useful for evaluating the adaptive potential and resilience of organisms faced with various anthropogenic stressors. Insect pollinator species, including wild bees, provide critical ecosystem services but are highly susceptible to biod...

Anthropogenic activities and increased land use, which include industrialization, agriculture and urbanization, directly affect pollinators by changing habitats and floral availability, and indirectly by influencing their microbial composition and diversity. Bees form vital symbioses with their microbiota, relying on microorganisms to perform physi...

Anthropogenic changes highly impact the world's biodiversity. An important human‐driven change to natural environments is increasing urbanisation, which is responsible for decreasing suitable habitats for many wild species, including bees. In this study, we investigate if three levels of urbanisation (low, medium and high) affect body size, foragin...

Social insects have provided some of the clearest insights into the origins and evolution of collective behaviour. Over 20 years ago, Maynard Smith and Szathmáry defined the most complex form of insect social behaviour—superorganismality—among the eight major transitions in evolution that explain the emergence of biological complexity. However, the...

The evolution of eusociality requires that individuals forgo some or all their own reproduction to assist the reproduction of others in their group, such as a primary egg-laying queen. A major open question is how genes and genetic pathways sculpt the evolution of eusociality, especially in rudimentary forms of sociality – those with smaller cooper...

Historic and contemporary data can shed light on a species’ conservation status and work together to address two main goals in conservation biology: (1) identifying species under extinction risk and (2) the forces shaping this process. Museomics is the study of historical DNA acquired from museum specimens that allows researchers to answer myriad q...

Bees and their microbes interact in complex networks in which bees form symbiotic relationships with their bacteria and fungi. Microbial composition and abundance affect bee health through nutrition, immunity, and fitness. In ever-expanding urban landscapes, land use development changes bee habitats and floral resource availability, thus altering t...

Understanding how subordinate altruistic roles arise among genetically similar individuals is critical to understanding the evolution of animal societies. In particular, maternal manipulation of offspring resources is an understudied process by which mothers may produce cooperative phenotypes among offspring. Mothers of the small carpenter bee Cera...

Small carpenter bees (genus Ceratina) are excellent taxa for studying early stages of social evolution, as they have high within and between species variability in social and parental behavior. Most species of Ceratina studied are facultatively social, with solitary and social nests in sympatry. Here, we examined the nesting and social biology of C...

The holobiont approach proposes that species are most fully understood within the context of their associated microbiomes, and that both host and microbial community are locked in a mutual circuit of co-evolutionary selection. Bees are an ideal group for this approach, as they comprise a critical group of pollinators that contribute to both ecologi...

Despite the increasingly documented occurrence of individual specialization, the relationship between individual consumer interactions and diet-related microbial communities in wild populations is still unclear. Using data from nests of Ceratina australensis from three different wild bee populations, we combine metabarcoding and network approaches...

Many insects show plasticity in the area of the brain called the mushroom bodies (MB) with foraging and social experience. MBs are paired neuropils associated with learning and memory. MB volume is typically greater in mature foragers relative to young and/or inexperienced individuals. Long-term studies show that extended experience may further inc...

Unravelling the evolutionary origins of eusocial life is a longstanding endeavour in the field of evolutionary-developmental biology. Descended from solitary ancestors, eusocial insects such as honeybees have evolved ontogen-etic division of labour in which short-lived workers perform age-associated tasks, while a long-lived queen produces brood. I...

The importance of the holobiont has been studied across many bee species, but less is known about the changes in the microbiome throughout the course of development, particularly in subsocial bees. This study used 16S rRNA and ITS amplicon sequencing of pollen provisions and individuals of the small carpenter bee, Ceratina calcarata, across stages...

The genus Nomada Scopoli (Hymenoptera: Apidae) is the largest genus of brood parasitic bees with nearly 800 species found across the globe and in nearly all biogeographic realms except Antarctica. There is no previous molecular phylogeny focused on Nomada despite their high species abundance nor is there an existing comprehensive biogeography for t...

Agricultural intensification leads to wide ranging changes in habitats along with reduction in nesting site availability and flower resources for wild pollinators. Yet, little is known about the impact of these changes on functional traits of communal ground‐nesting bees. This study assesses the abundance and body size of a common and widespread No...

Insect pollination is among the most essential ecosystem services for humanity. Globally, bees are the most effective pollinators, and tropical bees are also important for maintaining tropical biodiversity. Despite their invaluable pollination service, basic distributional patterns of tropical bees along elevation gradients are globally scarce. Her...

Dated, geo‐referenced museum specimens are a rich data source for reconstructing species' distribution and abundance patterns. However, museum records are potentially biased towards over‐representation of rare species, and it is unclear whether museum records can be used to estimate relative abundance in the field. We assembled 17 coupled field and...

Research on cuticular hydrocarbons of solitary and eusocial bees has greatly contributed to our understanding of the evolution of eusociality. However, to understand the transition from simple to complex societies, understanding subsocial species is necessary. Subsociality, defined as prolonged parental care, is a pre-requisite for eusociality yet...

A fundamental challenge in biology is explaining the evolution of novel phenotypes such as the origins of eusocial behavior. Eusociality—defined by overlapping generations, reproductive division of labor, and cooperative brood care —has evolved at least 17 times in arthropods: widespread in the social Hymenoptera (ants, bees, and wasps) and observe...

How mutual tolerance is produced, and the role of social environment in inducing cooperation in social groups, remains unstudied in many simple societies. In particular, maternal and sibling care and conflict are challenging to manipulate experimentally for many species. Most bees are solitary, but mothers of the eastern small carpenter bee, Cerati...

Conserving bees is critical both ecologically and economically. Genetic tools are valuable for monitoring these vital pollinators since tracking these small, fast‐flying insects by traditional means is difficult. By surveying the current state of the literature, this review discusses how recent advances in landscape genetic and genomic research are...

While it is well known that the genome can affect social behavior, recent models posit that social lifestyles can, in turn, influence genome evolution. Here, we perform the most phylogenetically comprehensive comparative analysis of 16 bee genomes to date: incorporating two published and four new carpenter bee genomes (Apidae: Xylocopinae) for a fi...

How do social insects expand and adapt to new ranges and how does sociality per se contribute to their success (or failure)? These questions can become tractable with the use of population genomics. We explored the population genomics of the socially polymorphic small carpenter bee, Ceratina australensis, across its range in eastern and southern Au...

Urbanization is a major anthropogenic driver of decline for ecologically and economically important taxa including bees. Despite their generally negative impact on pollinators, cities can display a surprising degree of biodiversity compared to other landscapes. The pollinating communities found within these environments, however, tend to be filtere...

A diverse wild bee fauna can greatly enhance crop yields, but on-going declines in populations of global pollinators may jeopardize food security in the future. Diversity of wild bees in agricultural settings is shaped by a multitude of factors including farming practice, farm size and surrounding land-use type. However, these factors may vary grea...

A diverse wild bee fauna can greatly enhance crop yields, but ongoing declines in populations of global pollinators may jeopardize food security in the future. Diversity of wild bees in agricultural settings is shaped by a multitude of factors including farming practice, farm size and surrounding land-use type. However, these factors may vary great...

Background Forested landscapes are valuable sources of ecosystem services especially in areas dedicated to intense agricultural activities. Distance from forest margin is known to influence the wild bee community in the landscape surrounding forested patches. Yet little is known regarding how bee communities distribute themselves in landscapes that...

Anthropogenic activities are rapidly changing the environment, and species that do not respond face a higher risk of extinction. Species may respond to environmental changes by modifying their behaviors, shifting their distributions, or changing their morphology. Recent morphological responses are often measured by changes in body size. Changes in...

• As native bee populations decrease, there is a need to better understand their nutritional requirements to sustain healthy pollinator populations. A common native bee to eastern North America is the small carpenter bee, Ceratina calcarata. Previous studies have shown that the primary pollen sources for C. calcarata consist of clover and rose. • T...

Male hymenopterans do not typically provide help with nest construction or maintenance. This is thought to be due to the decreased relatedness of males to their siblings compared to sisters, and selection for outbreeding resulting in male dispersal from natal nesting sites. However, some instances of male 'helping' behaviors have been observed and...

Bees collect pollen from flowers for their offspring, and by doing so contribute critical pollination services for our crops and ecosystems. Unlike many managed bee species, wild bees are thought to obtain much of their microbiome from the environment. However, we know surprisingly little about what plant species bees visit and the microbes associa...

• The mutualistic interactions of plant‐pollinator networks provide myriad economic, ecological, and cultural constituents without which there would be severe environmental and societal consequences. Plant‐pollinator networks are becoming increasingly vulnerable to disturbance through intensifying anthropogenic land use and climate change. • Wild b...

1.) Wild bees provide invaluable ecosystem services in agricultural landscapes such as pollination. However, in recent decades, pollinator biodiversity, especially in wild bees, is declining on a global scale, with potentially far-reaching consequences for crop production. Thus, there is an urgent need to determine whether wild bees are present in...

Bumble bees are declining worldwide, their vital ecosystem services are diminishing and underlying mechanisms are species specific and multifaceted. This has sparked an increase in long-term assessments of historical collections that provide valuable information about population trends and shifts in distributions. However, museums specimens also co...

Changes in land use and management intensification, especially in agriculture, have led to alarming declines in bee populations and the important ecological services they provide. Little is known how wild bee communities respond to these landscape changes at the phylogenetic level. Phylogenetic diversity was found to be correlated to functional tra...

The evolutionary origins of advanced eusociality, one of the most complex forms of phenotypic plasticity in nature, have long been a focus within the field of sociobiology. Although eusocial insects are known to have evolved from solitary ancestors, sociogenomic research among incipiently social taxa has only recently provided empirical evidence su...

Agonistic interactions among individuals can result in the formation of dominance hierarches that can reinforce individual behavior and social status. Such dominance hierarches precede the establishment of reproductive dominance, division of labor, and caste formation in highly social insect taxa. As such, deciphering the molecular basis of aggress...

The small carpenter bee, Ceratina (Neoceratina) dentipes, is an invasive species throughout the South Pacific and has been identified as one of three alien Ceratina species established in Hawaii. Invasive bees are thought to be exacerbating declines of Hawaii’s native yellow-faced bees (Hylaeus) but, outside of the honey bee (Apis mellifera), relat...

Climate change is a key threat to pollination networks and has already caused shifts in the distribution and phenology of many bee species. Predictions based on species distribution models forecast that most bee species will continue to decline as climate change progresses, the few exceptions to this being common, widespread species with large disp...

Bees forage for pollen and nectar at flowers but simultaneously acquire pathogenic, commensal, and likely beneficial microbes from these same flowers. Characterizing pollen usage of wild bees is therefore crucial to their conservation yet remains a challenging task. To understand pollen usage across landscapes and how this affects microbial communi...

The shift from solitary to social living is a major evolutionary transition for social insects. In bees, this transition is marked by certain females becoming reproductive and reducing their role in nest and offspring care, duties that are assumed by other females. Biogenic amines play a significant role in regulating these behaviors in both solita...

Despite a strong history of theoretical work on the mechanisms of social evolution, relatively little is known of the molecular genetic changes that accompany transitions from solitary to eusocial forms. Here we provide the first genome of an incipiently social bee that shows both solitary and social colony organization in sympatry, the Australian...

Developmental plasticity describes the influence of environmental factors on phenotypic variation. An important mediator of developmental plasticity in many animals is parental care. Here, we examine the consequences of maternal care on offspring after the initial mass provisioning of brood in the small carpenter bee, Ceratina calcarata. Removal of...

Social organisms are some of the most pervasive on earth, with the origin of sociality considered a major evolutionary transition. Previous studies suggest a role for both genetic and environmental factors in the transition from solitary to social living, with the relative contributions of these factors varying among taxa. Eusociality has arisen up...

Social organisms are some of the most pervasive on earth, with the origin of sociality considered a major evolutionary transition. Previous studies suggest a role for both genetic and environmental factors in the transition from solitary to social living, with the relative contributions of these factors varying among taxa. Eusociality has arisen up...

Greater social complexity at lower latitudes has been observed in a variety of arthropods from termites to spiders. Social behavior in the small carpenter bees, Ceratina, has been shown to vary widely both between species and across geographic range. Our goal was to determine how social plasticity of three populations of Ceratina species, C. calcar...

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 characteriz...

Facultatively social species allow for empirical examination of the factors underlying evolutionary transitions between primitive and complex forms of sociality. Variation in climate along altitudinal and latitudinal gradients often influences social behaviour in these species. This facultative sociality has been well-documented in the ground-nesti...

Concerns about the rapid and severe declines of many bumble bee (Bombus spp.) species in Europe, and more recently North America, have spurred research into the extent and possible causes for these losses. Drawing conclusions has been difficult due to a lack of long-term data, especially for specific regions that may have different factors at play...

• Wild bees comprise a diverse group of pollinators essential to healthy ecosystems and crop pollination. Despite their importance, the way in which many driving factors affect specific bees or pollinators in specific regions remains unknown. Northern New England is one such place lacking detailed study. Accordingly, we collected bees from three di...

Kin selection theory is foundational in helping to explain the evolution of sociality; however, the degree to which indirect fitness benefits may underlie helping behavior in species of early stage sociality has received relatively little empirical attention. Facultatively social bees, which demonstrate multiple forms of social organization, provid...

By manipulating resources or dispersal opportunities, mothers can force offspring to remain at the nest to help raise siblings creating a division of labor. In the subsocial bee, Ceratina calcarata mothers manipulate the quantity and quality of pollen provided to the first female offspring producing a dwarf eldest daughter, who is physically smalle...

The above mentioned article, written by Wyatt A. Shell and Sandra M. Rehan, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 24 July 2017 without open access.With the society’s decision to grant Open Choice the copyright of the article changed to ©The Author(s) 2017 and the article is forthwith...

Provisioning for young offspring is an archetypical form of parental investment. Ceratina calcarata bees provide extended maternal care to their young and demonstrate an unusual strategy of dual-phase pollen provisioning. Most bees first gather provisions as they establish nests in spring. However, C. calcarata mothers will also feed their newly ec...

Facultatively social species exhibit behavioral plasticity in response to changes in ecological conditions and social environment, and thus provide a natural experiment to compare solitary and social behaviors in a single genome. Such species can therefore provide empirical insights into the evolution of eusociality. The small carpenter bees (genus...

Changes in gene regulation that underlie phenotypic evolution can be encoded directly in the DNA sequence or mediated by chromatin modifications such as DNA methylation. It has been hypothesized that the evolution of eusocial division of labor is associated with enhanced gene regulatory potential, which may include expansions in DNA methylation in...

The genetic mechanisms behind aggressive behaviors are important for understanding the formation of dominance hierarchies, and thus social systems in general. Studies into the effects of social experience and agonistic contest outcomes have shown significant changes in brain gene expression resulting from repeated winning and losing, as well as cha...

Social corbiculate bees such as honey bees and bumble bees maintain a specific beneficial core microbiome which is absent in wild bees. It has been suggested that maintaining this microbiome can prevent disease and keep bees healthy. The main aim of our study was to identify if there are any core bacterial groups in the non-corbiculate bees Ceratin...

Many wild bee species are in global decline, yet much is still unknown about their diversity and contemporary distributions. National parks and forests offer unique areas of refuge important for the conservation of rare and declining species populations. Here we present the results of the first biodiversity survey of the bee fauna in the White Moun...

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 mecha...