Limiting resources on the reproductive success of a cavity-nesting bee species in a grassland agroecosystem

Abstract

Intensive agricultural land use can impact pollinators mainly through habitat loss and/or modification. Native bees are negatively affected by agricultural intensification, isolation from natural habitats, decreases in plant diversity, and reduction in the availability of nesting sites. Despite this, in the Pampean region, there are scarce studies about the effect of agricultural activities on native bees. We studied the nesting ecology of the native leafcutter bee Megachile gomphrenoides (Megachilidae) in eight sites immersed in an agricultural matrix, where land use is a mosaic of agricultural land and some semi-natural areas. The sampling was developed using paired trap-nests in fragments without agricultural management and in soybean crops. We aimed to analyse the effects of floral and nesting resources on the abundance, the reproductive success and the parasitism rate of a population of M. gomphrenoides in a Pampean agroecosystem. Floral diversity was significantly correlated with abundance of nests and brood cells, and both parasitism rate and reproductive success of M. gomphrenoides were higher in nests built in fragments without agricultural management when compared to crop areas. Additionally, a negative correlation was found between reproductive success and flower diversity in crop areas. These results suggest that floral diversity is limiting the abundance of M. gomphrenoides nests, its reproductive success as well as its parasitism rate.

Keywords:

• Argentina
• Megachile
• trap-nest
• floral resources
• parasites

Acknowledgments

The authors thank A. Torretta and R. González-Vaquero for their help with the English revision and the Universidad de Buenos Aires for permission to conduct this study on Ea. “San Claudio.” The manuscript benefited from critical reading by three anonymous reviewers and R. González-Vaquero. This study is part of the bachelor’s degree thesis of MPR. JPT & HJM are affiliated to CONICET, Argentina.

Disclosure statement

The authors declare that they have no conflict of interest.

Supplementary material

Supplementary material is available via the ‘Supplementary’ tab on the article’s online page (http://dx.doi.org/10.1080/00218839.2020.1726034).

Additional information

Funding

The authors thank the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), the Agencia Nacional de Promoción Cientifica y Tecnológica, and the Universidad de Buenos Aires for financial support through grants UBACyT 20020130200203BA, PIP 11220110100312, and PICT 2015-2523, respectively.