Bee and Flowering Plant Communities in a Riparian Corridor of the Lower Rio Grande River (Texas, USA)

The Rio Grande in Texas serves as the geo-political boundary between the United States and Mexico. It is considered one of the world’s most at-risk rivers and has been the subject of intensified management by the inhabitants of both countries lining its banks. Additionally, invasion by non-native Arundo donax (Linnaeus) (Cyperales: Poaceae), giant reed, has been extensive in the riparian corridor, with potential impacts to native wildlife. Locally, there remains a significant lack of ecological community data of riparian and upland habitats parallel to the river. We sampled bee and flowering plant communities monthly over two years, along a 3.22 km stretch of the lower Rio Grande in Webb County, TX. Data show that bee and plant richness and abundance was highest during March-April and September among both habitat types. Analysis of bee communities showed low spatial and temporal variation at the habitat level. Although common bee taxa (Halictidae and Apidae) were numerically dominant, NMS and ISA found key bee species driving community patterns. This included higher abundances of two species in the riparian habitat Anthophora occidentalis (Cresson) (Hymenoptera: Apidae) and Lasioglossum sp.L (Curtis) (Hymenoptera: Apidae) and one showing affinity for the upland habitat Halictus ligatus (Say) (Hymenoptera: Halictidae). Additionally, ISA analysis of plant data revealed that three species were significant indicator taxa in riparian habitats. Further analysis showed a positive correlation between bee generic richness and abundance with various climate attributes. Management of the riparian corridor and associated watershed could include significant areas for ecological restoration to assist pollinators.