Wild bees respond differently to sampling traps with vanes of different colors and light reflectivity in a livestock pasture ecosystem

Microbiome and floral associations of a wild bee using biodiversity survey collections

The health of bees can be assessed through their microbiome, which serves as a biomarker indicating the presence of both beneficial and harmful microorganisms within a bee community. This study presents the characterisation of the bacterial, fungal, and plant composition on the cuticle of adult bicoloured sweat bees (Agapostemon virescens). These bees were collected using various methods such as pan traps, blue vane traps and sweep netting across the northern extent of their habitat range. Non-destructive methods were employed to extract DNA from the whole pinned specimens of these wild bees. Metabarcoding of the 16S rRNA, ITS and rbcL regions was then performed. The study found that the method of collection influenced the detection of certain microbial and plant taxa. Among the collection methods, sweep net samples showed the lowest fungal alpha diversity. However, minor differences in bacterial or fungal beta diversity suggest that no single method is significantly superior to others. Therefore, a combination of techniques can cater to a broader spectrum of microbial detection. The study also revealed regional variations in bacterial, fungal and plant diversity. The core microbiome of A. virescens comprises two bacteria, three fungi and a plant association, all of which are commonly detected in other wild bees. These core microbes remained consistent across different collection methods and locations. Further extensive studies of wild bee microbiomes across various species and landscapes will help uncover crucial relationships between pollinator health and their environment.

Influence of sexual dimorphism and dichromatism on reproductive success in a rare native cactus

Identifying plant sexual dimorphic traits is critical in advancing our knowledge on plant-pollinator interactions. For example, dimorphism in floral colors, or sexual dichromatism, is a crucial mediator of pollinator choice on foraging decisions. We studied Cylindropuntia wolfii, a model system, with diverse flower colors and a functionally dioecious sexual system. However, evidence suggests that sexual reproduction is limited in this species as it has a low seed set especially in naturally pollinated fruits. Thus, it is critical to this native species' conservation to investigate its relationship with pollinators. Our goals were to: (a) investigate the sexual dimorphism including the sexual dichromatism in the flowers of the cactus, and (b) determine whether sexually dimorphic traits affect the pollinator attraction of both the sexes. We measured several quantitative and qualitative traits and compared them between male and female flowers. Then we recorded the pollinator visitation rate in nature for both sexes and tracked pollinator color preference using fluorescent dyes as pollen analogues. Our study showed that male flowers of C. wolfii are bigger and brighter, and they attract more potential pollinators than females, supporting the hypothesis that sexual dimorphism influences pollinator visitation preference. Fluorescence dichromatism, in which female flowers' anthers fluoresce more than male flower anthers suggest this could be female flowers' strategy to compensate for their dark colors and small size. The results from this study showed that C. wolfii exhibits sexual dichromatism and fluorescence dichromatism, which is a novel finding in plant research.

Can trap color affect arthropod community attraction in agroecosystems? A test using yellow vane and colorless traps

Vane trapping is one of the most effective methods for sampling flower-visiting arthropods. Despite its importance in pollinator studies, the effects of trap color on the abundance and richness of pollinators are less understood. To test this, we conducted a 3-season field experiment over 2 years with two types of vane traps: yellow and colorless. We set up twelve traps each in three field sites within the Lower Rio Grande Valley in south Texas, planted with Vigna unguiculata, Crotalaria juncea, Raphanus raphanistrum, and Sorghum drummondii. At each site, six colorless vane and six yellow vane traps were placed equidistant from each other. The experiment was replicated three times across three seasons, first during the pre-flowering season, when the crops were in full bloom, and when there was no crop on the field. In total, we collected 1912 insects, out of which 76.7% were pollinators. Generalized Linear Regression analyses showed that yellow traps consistently attracted significantly more arthropods and pollinators, but these differences were also season dependent. Furthermore, we noticed that Hymenoptera, followed by Coleoptera, were the most prevalent orders in both the yellow vane and colorless vane traps. Interestingly, although there was no significant difference in species richness of the arthropods in the yellow and colorless vane traps, our results suggest that trap color plays a significant role in capturing pollinators, including non-target arthropods. Our data add another line of evidence suggesting that trap color should be accounted for designing experiments that estimate pollinator and arthropod community diversity.