Hot crabs with bold choices: Temperature has little impact on behavioural repeatability in Caribbean hermit crabs.

An animal's boldness is generally considered to be influenced by genetic and developmental factors. However, abiotic factors such as temperature have profound effects on the physiology of ectothermic animals, and thus can influence the expression and measurement of this behavioural trait. We examined the relationship between temperature and behaviour in the Caribbean hermit crab (Coenobita clypeatus) using field and lab experiments. Crabs captured in the sun were bolder than crabs captured in the shade, even when measured at a common temperature, which led to bold crabs experiencing higher microhabitat temperatures. In laboratory housed conditions, crabs demonstrated highly repeatable boldness behaviours at all temperatures, and as temperature increased, the mean behavioural latencies decreased across all individuals. Bolder crabs do not seem to rely on an innately higher thermal preference, since there was no association between boldness behaviours and thermal preference in the laboratory. Instead, bolder crabs seem to exploit more open, riskier habitats than shyer crabs. Our results highlight the complex interplay between physiological and ecological factors influencing the behaviour of a widespread and ecologically important ectothermic animal.

Vitellogenin expression corresponds with reproductive status and caste in a primitively eusocial bee.

Vitellogenin (vg) expression is consistently associated with variation in insect phenotypes, particularly egg-laying. Primitively eusocial species, such as eusocial sweat bees, have behaviourally totipotent castes, in which each female is capable of high levels of ovarian development. Few studies have investigated vg expression patterns in primitively eusocial insects, and only one study has focused on a primitively eusocial bee. Here we use a primitively eusocial sweat bee, Lasioglossum laevissimum, and Real Time quantitative PCR (RT-qPCR) to investigate the relationship between vg expression, castes, and variation in phenotypes associated with castes differences. These assays showed that females with high ovarian development had the highest levels of vg expression, and that vg expression levels reflected the reproductive status of females first and caste second. This is in contrast to vg expression patterns observed in advanced eusocial queens and workers, which differ in vg expression based on caste and have caste-specific vg expression patterns. Furthermore, future queens (gynes) do not have ovarian development and had similar vg expression levels to early spring foundresses, which do have ovarian development, supporting Vg's function as a transporter of lipids and amino acids before diapause.

Social trait definitions influence evolutionary inferences: a phylogenetic approach to improving social terminology for bees.

The comparative method relies not only on a good understanding of the phylogenetic relationships among taxa, but also on consistent terminology for describing phenotypes. Clear and consistent terminology allows similar phenotypes to be described and phylogenetically analyzed in different organisms, whereas inconsistent terminology is a major impediment to comparisons, even for taxonomically restricted groups such as bees. Here, I propose that the usefulness of social terminology can be judged by its value in phylogenetic trait-mapping aimed at uncovering evolutionary transitions between solitary and social behavior. I propose a four-step approach to evaluate and update social terminology, in which definitions are first updated based on recent behavioral studies (step 1), mapped onto a phylogeny (step 2), evaluated for their utility in the trait-mapping exercise (step 3), and then, if necessary, revised (step 4). To demonstrate the approach, I define four terms important for understanding social evolution in bees (solitary, social, eusocial, and hypersocial) and map them onto a very recent phylogeny of Apidae. This not only illustrates an objective method for evaluating social terminology, but also provides novel inferences about social evolution in Apidae, including support for a parasocial origin of eusociality and at least two Major Evolutionary Transitions to hypersociality.

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 ß 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 ß 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.

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.

Changing paradigms in insect social evolution: insights from halictine and allodapine bees.

Until the 1980s theories of social insect evolution drew strongly on halictine and allodapine bees. However, that early work suffered from a lack of sound phylogenetic inference and detailed information on social behavior in many critical taxa. Recent studies have changed our understanding of these bee groups in profound ways. It has become apparent that forms of social organization, caste determination, and sex allocation are more labile and complex than previously thought, although the terminologies for describing them are still inadequate. Furthermore, the unexpected complexity means that many key parameters in kin selection and reproductive skew models remain unquantified, and addressing this lack of information will be formidable. At the same time, phylogenetic questions have become more tractable, and DNA sequence-based studies have resolved questions that earlier studies could not resolve, radically changing our understanding of the number of origins and losses of sociality in these bees.

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 Hamilton's 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 queen's 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.

A novel social polymorphism in a primitively eusocial bee.

Halictine sweat bees (Hymenoptera, Halictidae) are model organisms for the evolution of altruism, reproductive castes, and eusocial colony organization. Halictine social behavior is not only extremely variable, but also ecologically and evolutionarily labile. Among social species, colony social organization ranges from communal societies of egalitarian females to eusocial and semisocial ones with reproductive queens and more or less sterile workers. A striking aspect of halictine social variation is the mutual exclusivity of communal and eusocial types of colony social organization within the same species, these two types of social behavior being characteristic of different genera and subgenera. We report a recently discovered exception to this rule in a population of Halictus sexcinctus (Fabricius) at Daimonia-Pyla in southern Greece, that contained both communal and eusocial colonies. Moreover, communal and eusocial females exhibit morphological differences that imply a preimaginal developmental switch, which could also underlie the two types of social behavior. That the communal and eusocial forms are not merely cryptic sister species with different social behavior is indicated by the comparison of mitochondrial DNA sequences of two sections of cytochrome oxidase I, which indicate that Greek specimens of both social types are more similar than they are to conspecifics from elsewhere in Europe. The phylogenetic position of Halictus sexcinctus suggests that this unusual communal/eusocial polymorphism may represent an unstable intermediate step in an evolutionary reversal from eusocial to solitary behavior.

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.