Fluid Nest Membership Drives Variable Relatedness in Groups of a Facultatively Social Bee

Kin selection theory has dominated our understanding of the evolution of group living. However, many animal groups form among non-relatives, which gain no indirect fitness benefits from cooperating with nestmates. In this study, we characterized the relatedness and inter-nest migration behavior of the facultatively social carpenter bee, Xylocopa sonorina. Nesting constraints due to costly nest construction in this species give rise to intense intraspecific competition over access to existing nests. We used mark-recapture techniques to characterize patterns of dispersal and nest relocation within a nesting aggregation of spatially clustered nests. Two-thirds of bees relocated at least once during the reproductive season, likely to seek reproductive opportunities in another nest. This fluid nest membership creates opportunities for association among non-relatives. To assess the effects of this dynamic nesting behavior on group relatedness, we used microsatellite analysis to estimate relative relatedness within and between nests in the aggregation. We found that relatedness was variable across sampling years, but that in many cases nestmates were no more related to one another than they were to non-nestmate bees in the population. Together, these results suggest that group composition in X. sonorina may result from strategies to maximize direct fitness. This study supports the hypothesis that factors beyond kinship, such as ecological constraints, are likely to drive group formation in this species.

Competition Drives Group Formation and Reduces Within Nest Relatedness in a Facultatively Social Carpenter Bee

Animals respond to competition among kin for critical breeding resources in two ways: avoidance of direct fitness costs via dispersal of siblings to breed separately, and formation of kin-based societies in which subordinates offset direct fitness costs of breeding competition via altruism and increased indirect fitness. In the facultatively social eastern carpenter bee, nests are a critical breeding resource in perpetually short supply, leading to strong competition among females. Observations of individually marked and genotyped females in conditions of high and low resource competition demonstrate that competition leads to resource sharing and group nesting. However, in contrast to almost all known animal societies, females avoid nesting with relatives, and disperse from their natal nests to join social groups of non-relatives. This is the first example of a structured insect society with cooperation nestmates, the majority of which are unrelated; thus cooperation is more likely based on selection for direct, rather than indirect fitness. By forming social groups of non-kin, females avoid the indirect fitness costs of kin competition among sisters, yet increase their chances of successful reproduction, and thus direct fitness, when forming colonies of non-relatives.

MONITORING PROPOSAL OF THE SPECIES VIOLET CARPENTER BEE XYLOCOPA VIOLACEA IN POLAND

The main purpose of this scientific publication is to present the suggested methods of monitoring the species violet carpenter bee Xylocopa violacea, which belongs to Hymenoptera of the bee family Apidae. Despite the fact that this insect is only partially protected under Polish national law, there are very few identified localities of these animals in Poland. The main problem related to the uncertainty of the number of the violet carpenter bee Xylocopa violacea is the lack of monitoring within national borders. The proposed method of population status assessment is based on the field research. These studies include the observations of many elements of the population and the environment and on predicting what are the prospects for protecting the violet carpenter bee Xylocopa violacea in Poland. The proposed method of population status assessment is based on the analysis of species presence and abundance and the proposed method of habitat status assessment is based on the analysis of area, food base, type of environment, elements of the habitat, the nature of the surroundings and habitat stability. The proposed methods can be also applied for Xylocopa valga, which can be easily confused with the violet carpenter bee Xylocopa violacea. What is the most important – regular monitoring may contribute to the recognition of other places of occurrence and will enable effective protection of the violet carpenter bee Xylocopa violacea in Poland.

Experimental Studies of Carpenter Bee (Xylocopa: Apidae) Thorax Mechanics During Defensive Buzzing

Bees and other Hymenoptera utilize thorax vibration to realize an extensive range of behaviors ranging from flight to pollination. Strong indirect flight muscles contract to deform the thoracic walls and the resulting oscillation is sustained through a mechanism called stretch activation. While the mechanics of the insect thorax and muscles have been studied extensively during flight, relatively little is known about the thorax mechanics during non-flight behaviors. In this work, we investigate the thorax mechanics of the carpenter bee Xylocopa californica during defensive buzzing. During defensive buzzing, the insect folds its wings over its abdomen and rapidly fires it flight muscles, resulting in a loud audible buzz and large forces intended to deter predators. We devised a novel experiment to measure thorax oscillation and directional force production from a defensively buzzing carpenter bee. The largest peak forces were on average 175 mN and were oriented with the insect's dorsal-ventral muscle group. Peak forces oriented with the insect's dorsal-longitudinal muscle group averaged 117 mN. Thorax velocities were about 90 mm s^-1 p-p and velocity amplitude was positively correlated to peak force. Thorax oscillation frequency averaged 132 Hz but was highly variable both within individuals and across the tested population. From our measurements, we estimated the peak mechanical power required by defensive buzzing at 8.7 mW, which we hypothesize is greater than the power required during flight. Overall, this study provides insight into the function and capabilities of the Hymenopteran indirect flight muscle during non-flight behaviors.

Social consequences of energetically costly nest construction in a facultatively social bee

Social groups form when the costs of breeding independently exceed fitness costs imposed by group living. The costs of independent breeding can often be energetic, especially for animals performing expensive behaviours, such as nest construction. To test the hypothesis that nesting costs can drive sociality by disincentivizing independent nest founding, we measured the energetics of nest construction and inheritance in a facultatively social carpenter bee ( Xylocopa sonorina Smith), which bores tunnel nests in wood. We measured metabolic rates of bees excavating wood and used computerized tomography images of nesting logs to measure excavation volumes. From these data, we demonstrate costly energetic investments in nest excavation of a minimum 4.3 kJ per offspring provisioned, an expense equivalent to nearly 7 h of flight. This high, potentially prohibitive cost of nest founding may explain why females compete for existing nests rather than constructing new ones, often leading to the formation of social groups. Further, we found that nest inheritors varied considerably in their investment in nest renovation, with costs ranging more than 12-fold (from 7.08 to 89.1 kJ energy), probably reflecting differences in inherited nest quality. On average, renovation costs were lower than estimated new nest construction costs, with some nests providing major savings. These results suggest that females may join social groups to avoid steep energetic costs, but that the benefits of this strategy are not experienced equally.

Sociality sculpts similar patterns of molecular evolution in two independently evolved lineages of eusocial bees

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 first-ever genomic comparison with a monophyletic clade containing solitary through advanced eusocial taxa. We find that eusocial lineages have undergone more gene family expansions, feature more signatures of positive selection, and have higher counts of taxonomically restricted genes than solitary and weakly social lineages. Transcriptomic data reveal that caste-affiliated genes are deeply-conserved; gene regulatory and functional elements are more closely tied to social phenotype than phylogenetic lineage; and regulatory complexity increases steadily with social complexity. Overall, our study provides robust empirical evidence that social evolution can act as a major and surprisingly consistent driver of macroevolutionary genomic change.

First record of the carpenter bee Xylocopa pubescens (Hymenoptera, Apidae) in the Canary Islands confirmed by DNA barcoding

Island ecosystems are particularly vulnerable to the introduction of exotic species that can have an impact on local fauna and flora. Here, the carpenter bee Xylocopa pubescens is reported in Gran Canaria (Canary Islands, Spain) for the first time. This species is native to North Africa and the Near East and shows a rapid dispersion across the city of Las Palmas de Gran Canaria, together with a single record in the southernmost tip of the island. Different hypotheses about its arrival to the island are discussed.

A new species of Ceratina (Ceratinula) Moure, 1941, with notes on the taxonomy and distribution of Ceratina (Ceratinula) manni Cockerell, 1912, and an identification key for species of this subgenus known from Brazil (Hymenoptera, Apidae, Ceratinini)

A new species of the small carpenter bee, genus Ceratina (Ceratinula) Moure, from the Cerrado Biome in midwestern Brazil is described and illustrated. Ceratina (Ceratinula) fioreseana Oliveira, sp. nov. is easily distinguished from its congeners by the size of the facial maculations and the honey-yellow color of the legs and antennal scape, which distinguish it especially from Ceratina (Ceratinula) manni Cockerell, 1912, the most similar species in terms of facial maculation patterns. The geographic records of C. manni, here interpreted as endemic to the semiarid Caatinga region in northeastern Brazil, are presented, with new records for the Brazilian states of Piauí, Ceará and Bahia. A morphological description of both species is provided, including a comparison with the type specimen of C. manni from the state of Paraíba (Guarabira, formerly named Independencia). An identification key is provided for the described species of Ceratina (Ceratinula) recorded for Brazil according to Moure’s Catalogue of Neotropical Bees.

Floral Visitors to Helianthus verticillatus, a Rare Sunflower Species in the Southern United States

Helianthus verticillatus Small (whorled sunflower) is a federally endangered plant species found only in the southeastern United States that has potential horticultural value. Evidence suggests that H. verticillatus is self-incompatible and reliant on insect pollination for seed production. However, the identity of probable pollinators is unknown. Floral visitors were collected and identified during Sept. 2017 and Sept. 2018. Thirty-six species of visitors, including 25 hymenopterans, 7 dipterans, 2 lepidopterans, and 2 other insect species, were captured during 7 collection days at a site in Georgia (1 day) and 2 locations in Tennessee (6 days). Within a collection day (0745–1815 hr), there were either five or six discrete half-hour collection periods when insects were captured. Insect visitor activity peaked during the 1145–1215 and 1345–1415 hr periods, and activity was least during the 0745–0845 and 0945–1015 hr periods at all three locations. Visitors were identified by genus and/or species with morphological keys and sequences of the cox-1 mitochondrial gene. The most frequent visitors at all sites were Bombus spp. (bumblebees); Ceratina calcarata (a small carpenter bee species) and members of the halictid bee tribe Augochlorini were the second and third most common visitors at the two Tennessee locations. Helianthus pollen on visitors was identified by microscopic observations and via direct polymerase chain reaction of DNA using Helianthus-specific microsatellites primers. Pollen grains were collected from the most frequent visitors and Apis mellifera (honeybee) and counted using a hemocytometer. Based on the frequency of the insects collected across the three sites and on the mean number of pollen grains carried on the body of the insects, Bombus spp., Halictus ligatus (sweat bee), Agapostemon spp., and Lasioglossum/Dialictus spp., collectively, are the most probable primary pollinators of H. verticillatus.