Miriam H. Richards

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

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.

It's good to be queen: classically eusocial colony structure and low worker fitness in an obligately social sweat bee

Lasioglossum malachurum, a bee species common across much of Europe, is obligately eusocial across its range but exhibits clear geographic variation in demography and social behaviour. This variation suggests that social interactions between queens and workers, opportunities for worker oviposition, and patterns of relatedness among nest mates may vary considerably, both within and among regions. In this study, we used three microsatellite loci with 12–18 alleles each to examine the sociogenetic structure of colonies from a population at Agios Nikolaos Monemvasias in southern Greece. These analyses reveal that the majority of colonies exhibit classical eusocial colony structure in which a single queen mated to a single male monopolizes oviposition. Nevertheless, we also detect low rates of multiqueen nest founding, occasional caste switching by worker‐destined females, and worker oviposition of both gyne and male‐producing eggs in the final brood. Previous evidence that the majority of workers show some ovarian development and a minority (17%) have at least one large oocyte contrasts with the observation that only 2–3% of gynes and males (the so‐called reproductive brood) are produced by workers. An evaluation of the parameters of Hamiltons Rule suggests that queens benefit greatly from the help provided by workers but that workers achieve greater fitness by provisioning and laying their own eggs rather than by tending to the queens eggs. This conflict of interest between the queen and her workers suggests that the discrepancy between potential and achieved worker oviposition is due to queen interference. Comparison of relatedness and maternity patterns in the Agios Nikolaos Monemvasias population with those from a northern population near Tübingen, Germany, points to a north–south cline of increasingly effective queen control of worker behaviour.

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

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.

Colony social organization of Lasioglossum malachurum Kirby (Hymenoptera, Halictidae) in southern Greece

SummaryWe studied the nesting and social biology of two aggregations of the obligately eusocial halictine bee Lasioglossum malachurum at Agios Nikolaos Monemvasias (ANM) in southern Greece. Observations and nest excavations carried out from May to June 2000, revealed social and demographic variation between aggregations and years at ANM, as well as notable differences between these and other European populations. In southern Greece, the colony cycle includes multiple broods: the first two broods comprise only workers, whereas the third brood comprises workers, males, and gynes. Although pleometrosis is unknown in other populations, in the ANM region, as many as 10% of nests have more than one foundress. Newly emerged workers and gynes exhibit non-overlapping size distributions, but a few queens are worker-sized, indicating that workers occasionally overwinter and become foundresses. Although the vast majority of workers are unmated and most exhibit no ovarian development, an increase in worker ovarian development at the time of male production suggests that many males may develop from worker-laid eggs. Worker reproduction seems to be inhibited by the presence of queens, and annual variation in queen mortality may underlie annual variation in worker ovarian development. Across Europe, the major demographic and social differences among L. malachurum populations are in the number of worker broods and the extent of worker ovarian development. This contrasts with the results of a principal components analysis of social traits among 15 social L. (Evylaeus) populations, which shows that interspecific social variation is defined by the proportion of males in the early brood, the proportion of workers mated, queen-worker size dimorphism, gyne overwintering locale, and the proportion of workers with developed ovaries.

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

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.

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

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.

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

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.

Microsatellite analysis of environmental and clinical isolates of the opportunist fungal pathogen Aspergillus fumigatus.

Microsatellite analysis was used to examine the genetic relatedness of 111 clinical and environmental isolates of the opportunist human pathogenic fungus Aspergillus fumigatus from Ontario, Canada. Forty-three A. fumigatus isolates were from clinical sources and 68 from environmental sources. Phylogenetic analysis of the genotypes revealed that there were no geographical or temporal associations of clinical or environmental genotypes. In fact, several of the environmental and clinical isolates showed identical (clonal) genotypes from disparate geographical areas. However, a locus by locus examination revealed that there were several significant differences in allele frequencies between clinical and environmental isolates. There may be linkage of certain microsatellite loci with genes affecting virulence in A. fumigatus. A susceptible individual may be equally predisposed to infection by any isolate of A. fumigatus. However, under transient selection as a pathogen, genes encoding alleles for enhanced virulence may not assort independently from microsatellite loci. A dynamic equilibrium may exist between random recombination of loci in the natural environment and selection for virulence factors during host infection cycles.

Demography and relatedness in multiple-foundress nests of the social sweat bee, Halictus ligatus

Summary: Female sweat bees in the species Halictus ligatus exhibit a wide range of reproductive roles, ranging from typically foundress or queen-like to typically worker-like. Nests are founded in spring and most are haplometrotic, that is, founded by a single foundress. A few (up to 12 %) are pleometrotic, founded by 2-6 foundresses. Variation in the proportion of multifoundress nests from year to year and from place to place suggests an adaptive basis for pleometrosis. We studied the demographic and social characteristics of 23 pleometrotic nests in an aggregation of 250-300 nests near Victoria, Ontario, in 1984, 1990, and 1991. In pleometrotic associations, dominant foundresses behaved in a manner typical of mid-summer, haplometrotic queens, while subordinates behaved like mid-summer workers. Dominant foundresses tended to be larger than subordinates. Pleometrotic nests were significantly more likely than haplometrotic nests to produce brood, and they also produced more workers. However, this early advantage did not result in the production of more reproductive brood per nest, nor did pleometrotic foundresses experience higher productivity per foundress than did haplometrotic foundresses. Relatively low relatedness among various categories of brood implied that subordinate foundresses were not closely related to dominants. We suggest that pleometrosis most likely results from accidental encounters between spring foundresses as they leave their hibernacula. Once formed, such associations confer a survival advantage on the nest as a whole, but do not result in greater reproductive brood productivity.

The adaptive significance of unproductive alternative splicing in primates

Alternative gene splicing is pervasive in metazoa, particularly in humans, where the majority of genes generate splice variant transcripts. Characterizing the biological significance of alternative transcripts is methodologically difficult since it is impractical to assess thousands of splice variants as to whether they actually encode proteins, whether these proteins are functional, or whether transcripts have a function independent of protein synthesis. Consequently, to elucidate the functional significance of splice variants and to investigate mechanisms underlying the fidelity of mRNA splicing, we used an indirect approach based on analyzing the evolutionary conservation of splice variants among species. Using DNA polymerase β as an indicator locus, we cloned and characterized the types and frequencies of transcripts generated in primary cell lines of five primate species. Overall, we found that in addition to the canonical DNA polymerase β transcript, there were 25 alternative transcripts generated, most containing premature terminating codons. We used a statistical method borrowed from community ecology to show that there is significant diversity and little conservation in alternative splicing patterns among species, despite high sequence similarity in the underlying genomic (exonic) sequences. However, the frequency of alternative splicing at this locus correlates well with life history parameters such as the maximal longevity of each species, indicating that the alternative splicing of unproductive splice variants may have adaptive significance, even if the specific RNA transcripts themselves have no function. These results demonstrate the validity of the phylogenetic conservation approach in elucidating the biological significance of alternative splicing.