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Abstract An animal’s diet breadth is a central aspect of its life history, yet the factors determining why some species have narrow dietary breadths (specialists) and others have broad dietary breadths (generalists) remain poorly understood. This challenge is pronounced in herbivorous insects due to incomplete host plant data across many taxa and regions. Here, we develop and validate machine learning models to predict pollen diet breadth in bees, using a bee phylogeny and occurrence data for 682 bee species native to the United States, aiming to better understand key drivers. We found that pollen specialist bees made an average of 72.9% of their visits to host plants and could be predicted with high accuracy (mean 94%). Our models predicted generalist bee species, which made up a minority of the species in our dataset, with lower accuracy (mean 70%). The models tested on spatially and phylogenetically blocked data revealed that the most informative predictors of diet breadth are plant phylogenetic diversity, bee species’ geographic range, and regional abundance. Our findings also confirm that range size is predictive of diet breadth and that both male and female specialist bees mostly visit their host plants. Overall, our results suggest we can use visitation data to predict specialist bee species in regions and for taxonomic groups where diet breadth is unknown, though predicting generalists may be more challenging. These methods can thus enhance our understanding of plant-pollinator interactions, leading to improved conservation outcomes and a better understanding of the pollination services bees provide.
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Shifts in bee diet breadths are associated with gene gains and losses and positive selection across olfactory receptors
Abstract Bees are palynivorous insects that vary widely in the number of plant families from which they collect pollen. Their evolutionary history has been marked by multiple transitions in diet breadth between specialists that only visit specific plant genera (narrow diet breadth) and generalists that visit multiple large plant families (broad diet breadth). Understanding the evolution of sensory systems associated with changes in the detection, discrimination, and gustation of different pollen in bees can shed light on the underlying genetic mechanisms associated with transitions between narrow and broad diet breadths. We conducted a comparative study of three families of insect olfactory receptor genes (odorant receptors (ORs), gustatory receptors (GRs), and ionotropic receptors (IRs)) linked to diet breadth across 51 bee species. We calculated rates of gene gains and losses and identified genes experiencing positive selection across specialist and generalist bees. Our results show that broad generalists exhibit high rates of OR gene losses and GR gene gains. We observed accelerated rates of evolution in seven orthologous groups of genes across specialists and one group in generalists. Several orthogroups showed diversification in putative ligand-binding domains of proteins, indicating potential shifts in functional properties of the receptors. Taken together, these results indicate that dietary specialization in bees requires chemosensory system diversification of existing genes while dietary generalization is associated with the loss of ORs and gain of GRs. Our study provides important insights into the genetic architecture underlying shifts in niche occupancy across insects.
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- Award ID(s):
- 2046474
- PAR ID:
- 10680315
- Editor(s):
- Whitehead, A
- Publisher / Repository:
- Oxford
- Date Published:
- Journal Name:
- G3: Genes, Genomes, Genetics
- Volume:
- 15
- Issue:
- 8
- ISSN:
- 2160-1836
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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