Abstract:
The contribution of seasonality in species communities to elevational diversity
of tropical insects remains poorly understood. We here assessed seasonal patterns
and drivers of bee diversity in the Eastern Afromontane Biodiversity
Hotspot, Kenya, to understand the contribution of seasonality to elevational
biodiversity patterns. Bee species and plant species visited by bees were
recorded on 50 study plots in regrowth vegetation across four major seasons
along two elevation gradients from 525 to 2530 m above sea level. Bees were
sampled by transect walks using sweep nets and aspirators. We examined how
local species richness (α-diversity) and seasonal changes in local species communities
(β-diversity) contribute to species richness across seasons (γ-diversity)
along elevation gradients. Using a multimodel inference framework, we identified
the contribution of climate and floral seasonality to elevational patterns in
bee diversity. We found that both α- and γ-diversity decreased with elevation.
Seasonal β-diversity decreased with elevation and the high turnover of species
across seasons contributed to a considerably higher γ- than α-diversity on
study plots. A combination of seasonality in climate and the seasonal turnover of floral resources best explained the seasonality in bee species communities
(seasonal β-diversity). We, therefore, conclude that, despite the more stable,
and favorable climatic conditions in the tropics (in comparison to temperate
regions), climatic seasonality and its influence on bees’ floral resources largely
determined seasonal patterns of bee species diversity along elevation gradients
on tropical mountains.
