Drivers of diversity and community structure of bees in an
agroecological region of Zimbabwe.
Abstract
1. Worldwide bees provide an important ecosystem service of plant
pollination. However, environmental pressures are threatening their
survival. Information is lacking on how land-use systems and weather
patterns in developing countries influence bee populations. 2. We
investigated how environmental and land use mediated factors influence
the abundance, diversity, and distribution of bees across seasons in a
farming communal area of Zimbabwe. Bees were systematically sampled in
five land-use types (natural woodlot, pastures, homestead, field, and
garden) recording ground cover, grass height, flower abundance, and
types, tree abundance, and recorded elevation, temperature, light
intensity, wind speed, wind direction, and humidity. The hurdle model,
general linear model, and PCA were conducted to understand the influence
of explanatory variables on bee abundance and Shannon diversity. 3. We
found out that bee abundance was highly positively influenced by the
number of flower types P < 0.0001 and significantly positively
correlated to tree abundance P = 0.0475. We also highlight the high
sensitivity of bees to weather changes as wind speed increases, thus
reducing the probability of finding bees (P = 0.033). Temperatures above
28.50C significantly lowered bee abundance (P < 0.001). 4. Bee
diversity was highest in homesteads (coefficient 0.4438) and natural
woodlots (coefficient 0.4172) than gardens with fields and pastures
having a disproportionately high abundance of Apis. Bee species also
showed tolerance to different land-use types with Megachile associated
with homesteads and Nomia with grasslands. Homesteads however supported
more diverse species (P = 0.0453) highlighting the importance of some of
its components to bee conservation. 5. Synthesis and applications. Our
study showed that land-use change reduced the diversity of species and
proliferated species that could tolerate the changes. These results
highlight the importance of setting aside bee-friendly habitats that can
be refuge sites for species susceptible to land-use change.