Crisp & Chandler, Paraphyletic species 
823 
Thiele and Ladiges made it clear that they did not wish to define species to which 
some specimens could not be reliably assigned (due to intergradation). However, 
they also rejected an alternative taxonomic solution of segregating only the distinctive 
entity aquilonia for the implicit reason that this would create a paraphyletic species: 
'However, its terminal position in the cladogram precludes separating it as a distinct 
species without also raising the other taxa to species rank' (Thiele & Ladiges 1994: 
403). They did not actually mention the term 'paraphyletic', nor discuss directly the 
problems associated with paraphyletic taxa. Nevertheless, the B. integrifolia complex 
as described by them is directly analagous to the D. iilicifolia complex, because it is 
a monophyletic group comprising a paraphyletic basal group of incompletely 
differentiated geographic forms within which is nested at least one divergent, 
autapomorphic taxon that invites treatment as a species. 
Eucalyptus caesia 
Eucalyptus caesia (Myrtaceae: Leptospermioideae) is a mallee (many stems arising 
from a woody lignotuber) confined to granite outcrops in south-west Western 
Australia. It has several evident autapomorphies including pendulous inflorescences, 
pink or red flowers, distinctive urceolate fruit shape with a descending disc, and 
ovules in 6 rows (Hopper & Burgman 1983; Brooker & Kleinig 1990). Two subspecies 
are recognised, subsp. niagtia and subsp. caesia, the latter having been segregated 
because of its red flowers, pendulous branchlets and larger leaves, buds, flowers 
and fruits (Brooker & Hopper 1982; Brooker & Kleinig 1990). The granite outcrops 
that are its exclusive habitat are naturally isolated from one another by a few to 
many kilometers, and thus the populations are well-defined and lend themselves to 
phylogenetic anaysis. 
j—- E. cruets 
-—- Boyg 
- - MtCI 
- - MtSt 
- - Waly 
- - Hump 
- - Yanm 
- - Bily 
- - Chid 
- - SCht 
- WCht 
- Coor 
Fig. 4. Phylogeny of Eucalyptus caesia populations, derived by parsimony analysis using combined 
allozyme frequency and morphometric data (Hopper & Burgman 1983: fig. 3b). The tree is rooted 
using the outgroup E. crucis subsp. lanceolata. Key to populations, all in the wheatbelt of Western 
Australia; SCht, S of Chutawalakin Hill; WCht, W of Chutawalakin Hill; Chid, Chiddarcooping 
Hill; Coor, Coorancooping Hill; Yanm, Yanneymooning Hill; Waly, Walyahmoning Rock; Bily, 
Billyacating Hill; Hump, Tlie Humps; Boyg, Boyagin Rock; MtCl, Mount Caroline; MtSt, Mount 
Stirling. Note that E. caesia subsp. magm is monophyletic and subsp. caesia is paraphyletic. 
E. caesia 
ssp. 
caesia 
E. caesia 
ssp. 
magna 
