The extent of hybridisation and gene flow between the three Monocalyptus species, Eucalyptus pulchella, E. coccifera (series Piperitae) and E. delegatensis (series Obliquae) at Snug Plains (600 m) in southeastern Tasmania was examined. The flowering time of E. pulchella was two months later than usual for this normally low-altitude species. It consequently overlapped the flowering period of both sub-alpine species E. coccifera and E. delegatensis and had its peak f10wering period intermediate between the two. The movements of pollinators across the species boundaries indicated the potential for hybridisation between E. pulchella and the other two species.

Adult morphology suggested that the Snug Plains E. pulchella tended towards E. coccifera compared to typical, low-altitude E. pulchella and progeny tests reinforced this view. In addition, two out of twelve E. pulchella adults sampled appeared intermediate between this species and E. coccifera and produced progeny overlapping those from E. coccifera. These results suggest that introgression of E. coccifera genes may be occurring into E. pulchella at Snug Plains although adaptive convergence cannot be excluded. Quite a different picture is seen for the results of hybridisation between E. pulchella and E. delegatensis. Six putative F_l hybrids between E. pulchella and E. delegatensis occurred in progeny from two E. pulchella mothers. However, this appears to have had little genetic impact on the species, since no evidence of introgression or convergence was apparent in adult populations of these species.