Abstract
South Africa is a megadiverse country with three globally recognised biodiversity hotspots within its borders. Bees in particular show high diversity and endemism in the western part of the country. Not much is currently known about the floral host preferences of indigenous bees in South Africa, with data only available from observational studies. Pollen metabarcoding provides provenance information by utilising DNA analyses instead of floral visitation and traditional microscopic identification to identify pollinator food plants, which can be time consuming and imprecise. In this study, we sampled pollen from leaf-cutter bees (Megachilidae) specimens maintained in a historic insect collection (National Collection of Insects, South Africa) that were originally collected from two florally important areas in South Africa (Succulent Karoo and Savanna) and used metabarcoding to determine pollen provenance. We also sampled pollen from leafcutter bee species with wider distributions, that extend across many different biomes, to determine if these 'generalist' species show relaxed floral host specificity in some biomes. Metabarcoding involved sequencing of the nuclear internal transcribed spacer 2 (ITS2) region. Amplicons were compared to a sequence reference database to assign taxonomic classifications to family level. Sequence reads were also clustered to OTUs based on 97% sequence similarity to estimate numbers of plant species visited. We found no significant difference in the mean number of plant taxa visited in the Succulent Karoo and Savanna regions, but the widespread group visited significantly more floral hosts. Bees from the widespread group were also characterised by a significantly different composition in pollen assemblage. The time since specimens were collected did not have an effect on the mean number of taxa visited by any of the bee species studied. This study highlights national history collections as valuable sources of temporal and spatial biodiversity data.
Highlights
The use of next-generation sequencing (NGS) technology and DNA barcoding in highthroughput identification of plant origins from pollen samples has been on the rise in recent years [1,2,3,4,5,6]
Quality and adapter trimming of samples sequenced on the HiSeq 2500 resulted in a total number of 2,947,334 high-quality, merged reads obtained across all bee species
If bees from the more plant diverse Succulent Karoo exhibited a narrower range of floral choices than bees from the Savanna, we could expect that more plant family and species operational taxonomic unit (OTU) would be identified in the pollen loads of bees from the Savanna than in those from the Succulent Karoo
Summary
The use of next-generation sequencing (NGS) technology and DNA barcoding in highthroughput identification of plant origins from pollen samples has been on the rise in recent years [1,2,3,4,5,6]. There are many advantages to this method over traditional microscopic palynology, including increased time-efficiency, multiplexing samples to reduce costs, and the relative. Floral hosts of Megachilidae revealed by metabarcoding. Data for M. venusta are available in the European Nucleotide Archive (ENA) under project accession PRJEB14178 (http://www.ebi.ac.uk/ena/data/view/PRJEB14178)
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