How to classify apomictic polyploid complexes - challenges and perspectives
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Proposed Symposium Title: How to classify apomictic polyploid complexes - challenges and perspectives
Affiliations: Department of Systematics, Biodiversity and Evolution of Plants (with herbarium), University of Goettingen
Apomixis, the reproduction via asexually formed seeds, avoids cycles of meiosis and fertilization. Apomictic lineages appear scattered in the phylogenies of plants, and often comprise widespread and abundant taxa, which makes them highly relevant for biodiversity research. Apomixis poses a problem for species concepts and delimitation, because the popular biological species concept is per definition not applicable. Alternative species concepts, like the phylogenetic species concepts, cluster species concepts, evolutionary and ecological species concepts are theoretically applicable, but pose in theory and practice still many problems. A major conceptual problem is the predominant hybrid origin of many apomictic plants, which violates assumptions of tree-like diversification patterns, but also blur boundaries between clusters and lineages in the other classical concepts. Genetic clustering and vertical lineage formation remain weak without the homogenizing effects of sexuality. Pluralistic approaches for species delimitation are nowadays preferred for taxonomic decisions, ie., case-by-case applications of concepts based on combinations and multiple datasets. Apomictic lineages might be included under one species name, as it often applied to autopolyploids. In allopolyploid complexes the sexual progenitors can be normally classified on species level, but the vast majority of ill-defined asexual lineages could be lumped under a cluster concept, or named just as nothotaxa. The formal designation of hybrids is possible according to the Code if at least one parental taxon is known, which applies to most young apomictic complexes. This strategy would avoid swamping databases, floras and checklists with hundreds of species names for ill-defined taxa. Only few obligate long-term apomictic lineages exist in plants, without knowledge of progenitors. Such cases may deserve a classification as species (agamospecies). Application of genomic data and artificial intelligence tools will improve the classification process and help to delimit taxa as comparative units that can be handled in databases, floras and checklists.