Temperature and Precipitation Explain Bee Diversity on Flowers Along an Elevation Gradient in the Mexican Transition Zone

Although ecologists have identified the key factors influencing species distribution along elevation gradients, each mountain’s distinct characteristics, including its geology and biotic colonization processes, are often overlooked. The uniqueness of each mountain ecosystem implies that species distribution and the factors affecting them may vary across regions and taxonomic groups. The Mexican Transition Zone (MTZ) in central Mexico is a mountainous region of significant ecological and evolutionary importance, shaped by distinct biotic colonization and distribution patterns across its elevation gradient. However, most research in this region has focused on specific taxa, neglecting the vast diversity within the MTZ. In this study, we investigated the variations in flower-visiting bee diversity along an elevation gradient within the MTZ (10 sampling sites distributed from 4 to 3425 m a.s.l..), focusing on understanding the environmental factors influencing their distribution. Our findings reveal a declining bee diversity with increasing elevation, primarily driven by decreasing temperatures. However, when considering bee abundance, we identified precipitation as the predominant factor influencing bee diversity. Therefore, water and resource availability are critical in shaping bee diversity in this region. Furthermore, as elevation increased, we observed distinct and unique bee communities, highlighting the rarity and uniqueness of highland bee species as integral components of mountain ecosystems.