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Telopea Vol. 6(4): 1996 
The composite species concept (Kornet 1993b), as its name implies, combines the 
lineage and taxon views of species. Komet first formalises the internodal species concept 
(Kornet 1993a) then reveals a significant drawback with it: every isolated population 
is a potential new lineage and it can be made permanent by extinction. Thus, internodal 
species tend to be trivial units compared with those that are generally recognised as 
species, and are more akin to populations. Moreover, the internodal species concept is 
operationally intractable, because the fate of an isolated population cannot be 
determined. Instead, Kornet defines composite species as lineages of 'internodons' 
which begin with the fixation of a novel character in an ancestral internodon and end 
with another fixation in a descendant internodon (or extinction). Composite species 
are parts of lineages because internodons have ancestor-descendant relationships and 
are mutually exclusive. Because they are diagnosed by fixed novel characters 
(autapomorpliies), they are also taxa and operationally equivalent to phylogenetic 
species. Thus the composite species concept seems to reconcile the tension between 
species-as-lineages and species-as-taxa (above). It should be noted that composite 
species are paraphyletic groups of internodons, unless they become extinct, in which 
case they become monophyletic (Komet 1993b: 69). 
Paraphyly and metaphyly 
Cladism has led to rejection of paraphyletic taxa on the grounds that they are not real 
phylogenetic units and lead to confusion about both the distribution of characters and 
the relationships of taxa (Donoghue & Cantino 1988; Humphries & Chappill 1988). 
Paraphyletic groups are considered 'artifactuaT and qualitatively different from 
monophyletic groups, which are 'real' taxa (Nelson 1989b). For every monophyletic 
taxon recognised, any of a series of paraphyletic groups may be constructed by 
excluding the monophyletic taxon from more inclusive (higher-level) monophyletic 
groups. In this way, paraphyletic groups have been treated as taxa, diagnosed by 
symplesiomorphies or the absence of the autapomorphies which circumscribe the 
excluded monophyletic groups. When taxa are discovered to be paraphyletic, 
systematists are inclined to divide them into several more narrowly circumscribed, 
monophyletic taxa (monophyly can also be achieved by amalgamation). However, 
this process of division may regress to the species level, where a problem is encountered: 
species are not divisible into monophyletic subunits. Moreover, both the phylogenetic 
species concept and the related composite species concept predict that many, if not 
most, species are not monophyletic (above). Here is a conundrum: if species are to be 
considered taxa, logically the sanction against paraphyly should apply to them (Cracraft 
1989; Nelson 1989a; Nelson 1989b). 
Empirically, it has long been recognised that many accepted species are paraphyletic 
('paraspedes': Ackery & Vane-Wright 1984). In a paraspecies, some (but not all) 
members are more closely related to members of another species than to other 
members of the paraspecies. Evidence for paraphyly would be a synapomorphy 
which some members of the paraspecies share with the other species (Fig. Ic). Some 
authors have pointed out that any species that lacks an evident autapomorphy is at 
least potentially paraphyletic; however, this is only an inference based on lack of 
evidence (it is also potentially monophyletic). The term 'metaspecies' has been coined 
(Donoghue 1985) to distinguish such species (whose phylogenetic status has not 
been resolved by cladistic analysis) from paraspecies (whose presumed monophyly 
has been tested and refuted). (Gauthier (1986) extends the metataxon concept to 
higher taxa but this is not relevant here.) Phylogenetic analysis of populations 
comprising a metaspecies may have one of three outcomes (cf. de Queiroz & 
Donoghue 1988: fig. 7): (i) a synapomorphy may be found for all populations, and 
