Variation in seedling morphology in the Eucalyptus risdonii–E.tenuiramis complex

Abstract

The genetic differentiation of populations within the E. risdonii Hook.f.–E. tenuiramis Miq. complexand the affinities of isolated peppermint populations from Tasmania’s south-west World Heritage Area (WHA) wereassessed in a morphometric study of glasshouse-grown seedlings. Four well-differentiated phenetic groups withinthe E. risdonii–E. tenuiramis complex were identified : (1) E. risdonii, (2) Southern E.tenuiramis, (3) NorthernE.tenuiramis and (4) Peninsula E. tenuiramis. The differentiation between populations identified as E. risdonii andSouthern E. tenuiramis is much smaller than the separation between the extreme forms of E. tenuiramis (Northernand Peninsula E. tenuiramis). The differentiation in the E. tenuiramis complex is associated with geography andsubstrate type, with the Southern morph restricted to sedimentary substrates and the other morphs to igneoussubstrates. The WHA populations have a juvenile morphology intermediate between E.coccifera and PeninsulaE.tenuiramis, with closest affinities to E. tenuiramis and other E. coccifera–E.tenuiramis intermediates. Thecurrent taxonomic treatment of E. risdonii and E. tenuiramis as separate species is not consistent with the patternsof genetic differentiation within this complex and their presumed phylogenetic relationship. The populations fromthe WHA represent a taxonomic entity that is restricted to this area. The evolutionary processes that may haveshaped the patterns of variation within the E. risdonii–E. tenuiramis complex are discussed.