It is quite known that bees are one of the most famous pollinators, as they are said to be one of the top pollinators. Many factors such as pesticides, introduction of pathogens, climate change and habitat fragmentation all negatively affect bees. But one factor, urbanization, seems to be still understudied. It seems that there is a mix of both negative and positive effects on bees with urbanization. Social bees seem to thrive in urban areas and have an increased survival, while bees that nest in soils seem to be negatively impact. With this study its objective was to determine how urbanization and plant availability affect the richness, species abundance, functional characteristics and composition of bee communities in medium-sized cities.

The study area were 6 cities located in Brazil (southern Minas Gerais, Brazil: Alfenas, Poços de Caldas, Pouso Alegre, Varginha, Três Corações and Lavras, figure below). The cities were primarily made up of urban ecosystems made up of x<170000 inhabitants, agricultural landscapes, and forest area. 21 locations were selected across the 6 cities selected, with each location having an increasing gradient of impervious coverage (Figure below). To evaluate bee community, an active capture method was used to sample the bees in the cities. Sampling was performed within a radius of 200m from the central point of each location. Bees were collected on each plant for an approximate of 10 minutes. If 5 minutes passed and no bee were observed then the next plant was observed. Sampling of plants was also performed during sampling of bees. Bees were characterized under 3 functional groups, these groups being social behavior, nesting habit, and trophic specialization. Social behavior had 3 subgroups highly eusocial, primitively eusocial and solitary. Nesting habit had 2 groups above ground nesting and below ground nesting. For trophic specialization 2 groups were considered, they were generalist or specialist.

From this study it found a total of 4279 bee specimens that belonged to the 5 subfamilies that occur in Brazil (Andreninae, Apinae, Colletinae, Halictinae and Megachilinae). In order the richness of the bees were Apinae, Halictinae, Megachilinae, Andreninae, Colletinae. Regarding plants a total of 858 plants of 190 species were found.

It was found that the total bee richness was mainly affected by impervious cover, grass cover, and landscape heterogeneity with a radius of 750m and 1000m. Impervious cover showed a negative effect on total richness in 1000m, while landscape heterogeneity showed a positive effect for 750m and 1000m. Grass cover was deemed important and was show in the models. (Figures below)

Richness of above ground nesting bees and generalist bees were influenced positively by the diversity of landscape radius of 750m and 1000m. The abundance and below ground nesting bees was influenced positively by an increase of grass cover in the 1000m radius.

The models that helped explain the bee community diversity to plants is added below.

Overall the study found that an increase of impervious cover led to a decrease of bee species richness, especially affecting ground nesting bees. But solitary bees abundance increase as grass cover increased. It found that greater landscape diversity in urban areas support species richness. The study helps argue for the need of habitat diversity and native plants for bees in urban environments.

I overall really enjoyed reading this study as I enjoy reading about insects and their relation to conservation, ecology, etc. Reading this study made me wonder what urban designs could help promote bee richness or promote the bee populations. I believe that if more bee friendly designs were implemented it could definitely help improve the species. Maybe a structure that could help solitary bees when an increase of impervious surfaces are abundant. I also wonder how this study would be in areas that have a higher urbanization rate. Would the results be similar or would the results be drastically different?

Tavares Brancher, K.P., Graf, L.V., Heringer, G. & Zenni, R.D. (2024) Urbanization and abundance of floral resources affect bee communities in medium-sized neotropical cities. Austral Ecology, 49, e13299. Available from: https://doi-org.prox.lib.ncsu.edu/10.1111/aec.13299