Species concepts and floras: what are species for?

Abstract

In 1992, in a special paper in the American Journal of Botany, Ernst Mayr attempted to 'prove' the biological species concept (BSC) worked as well in plants as it did in animals by analyzing the flora of the Concord region of northern Massachusetts. He concluded that there were minimal difficulties when applying the BSC for the plants of this particular area, and concluded that botanists were misguided in not accepting the BSC. He suggested that what he called 'typological' thinking was prevalent in the taxonomic community, and that this was a factor in botanical resistance to the BSC. Typology, as defined by Mayr in his 1992 foray into botany, is to a certain extent a straw-man and, by the late 20th Century, no longer a way of thinking in widespread use in the taxonomic community in any organismal group. Here, I examine his analysis in the light of current interest in plant diversity. Species can be characterized as hypotheses about the distribution of variation in nature, subject to test with new data of many kinds. Species concepts like the BSC, although of interest philosophically and to researchers looking at mechanisms of speciation, may actually get in the way of achieving a baseline understanding of the diversity of life on Earth.

Why was Darwin’s view of species rejected by twentieth century biologists?

“…According to Mayr, these quotations show how Darwin had changed his mind about the definition of species from an emphasis on reproductive isolation in his notebooks to a kind of nihilism in The Origin. Darwin was apparently at this time ''… increasingly influenced by the botanical literature and by correspondence with his botanical friends'' (Mayr 1982: 267;Sulloway 1979), although why Mayr felt that plant species should be any less wellformed than animal species is not clear (Knapp 2008).…”

A revision of the Old World Black Nightshades (Morelloid clade of Solanum L., Solanaceae)

“…Schilling and Heiser (1979) pointed out that the hybrids created in the greenhouse were unlikely to occur in nature and expressed views that the use of the Biological Species Concept (BSC; e.g. Mayr 1982) in this group where most species are interfertile at some level is not useful (see Knapp 2008 for a discussion of the BSC and plant species recognition).…”

“…“assemblages of individuals with morphological features in common and separate from other such assemblages by correlated morphological discontinuities in a number of features” (Davis and Heywood 1963). Biological (Mayr 1982), phylogenetic (Cracraft 1989) and the host of other finely defined species concepts (see Mallet 1995) are almost impossible to apply in practice and are therefore of little utility in a practical sense (see Knapp 2008). It is important, however, to clearly state the criteria for the delimitation of species, rather than dogmatically follow particular ideological lines (see Luckow 1995; Davis 1997).…”

Wild Relatives of the Eggplant (Solanum melongena L.: Solanaceae): New Understanding of Species Names in a Complex Group

“…For this reason, we prefer to designate cultivated plants as species distinct from their wild progenitors, as has been done for tomatoes by Peralta et al [8] rather than subsuming the cultivar as a subspecies or variety of the wild progenitor as has been done for eggplants by some authors in the past [33]. The cultivated plant is not part of the same selection regime as its relatives growing in the wild even though interfertility, sometimes considerable, might be present; see [34], [35] for discussions of species concepts.…”