Floral hosts of leaf-cutter bees (Megachilidae) in a biodiversity hotspot revealed by pollen DNA metabarcoding of historic specimens

A striking finding from the study is that most of the plant families identified were shared among bees collected from different biomes. This suggests that although bees are endemic for a particular biome they do not predominantly visit plant species specific to that biome, but prefer to visit widespread plant taxa that occur in multiple biomes. An interesting finding was the identification of high proportions of Amaranthaceae in the overall representation of both read and detection counts in all three bee groups investigated. In the arid Western region of South Africa, the three plant families most visited by the bees are Fabaceae, Asteraceae and Aizoaceae [39]. Amaranthaceae was not in the top ten most bee-visited families, or in the list of the 15 largest plant families in the area. Only seven percent of the total visits bees made in the study were to Amaranthaceae, of which the bee family with the most visits was Megachili- dae [39]. Although bees from the Megachilini tribe made no recorded visits to Amaranthaceae, it does not necessarily mean they could not be frequent visitors to this plant family. Only one of the bee species sampled for pollen in this study, M. murina, was mentioned in the compre- hensive records of Gess & Gess (2014). The presence of this family in the Succulent Karoo is Fig 5. Non-metric multidimensional scaling (NMDS) analysis using Bray-Curtis distances representing plant species OTUs detected on bees from the three

groups. Bee species from the same region are represented by the same shape, and different bee species colour-coded. Bees from the Succulent Karoo are represented by squares, circles represent bees from the Savanna, and crosses represent widespread species. https://doi.org/10.1371/journal.pone.0244973.g005 PLOS ONE Floral hosts of Megachilidae revealed by metabarcoding PLOS ONE | https://doi.org/10.1371/journal.pone.0244973 January 21, 2021 11 / 16