Results from an online survey of family delimitation in angiosperms and ferns: recommendations to the Angiosperm Phylogeny Group for thorny problems in plant classification

The Angiosperm Phylogeny Group (APG) started with ordinal relationships for angiosperm families and later came to concentrate more on issues surrounding family delimitation, generally taking a conservative approach (favouring lumping over splitting when choices were otherwise fairly evenly balanced). The history of the APG approach to classification is elaborated here, and long-term trends in taxon size are also discussed. Twenty-three questions relating to family delimitation of angiosperms (21) and ferns (two) were identified, and an open, web-based survey was conducted to determine which solutions were preferred by the botanical community. There were a total of 441 responses from 42 countries. The full survey results are presented and discussed. In general, among respondents, there was a good balance between lumping and splitting, although a much smaller percentage self-identified as splitters. Recommendations to APG for a set of specific family delimitation issues in angiosperms and ferns are made. We followed the majority vote in all but four cases and recommended ten splitting and 13 lumping options. We found that decisions were made by respondents on a case-by-case basis. Many respondents favoured lumping as a means of gaining stability by leaving circumscription issues at the lower taxonomic levels, which are of more concern to specialists (i.e. at subfamilial and tribal levels). We estimate that APG IV will not differ substantially from APG III.(c) 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 501-528.