XVI International Botanical Congess

Most Rosaceae agamosperms are polyploid, hybridize freely, and belong to species-rich genera. Mean species number in major Rosaceae agamospermous genera (Alchemilla, Amelanchier, Cotoneaster, Crataegus, Potentilla, Rubus, and Sorbus) is about 250, at least an order of magnitude larger than in other Rosaceae genera. Agamospermous Rosaceae genera may be species-rich simply because they are old or because agamospermy, acting in concert with hybridization and polyploidy, accelerates diversification. Numerous studies do suggest that diversification does differ between Rosacaeae agamic complexes and sexual groups. But does speciation differ? Conceptualizing agamospecies with gaps in local, morphological variation emphasizes a common process of agamospermous crystallization of hybrids. Species in agamic complexes should instead represent more significant levels of morphological, genetic, and geographic divergence.