Phenetic affinities, variability and conservation status of a rare Tasmanian endemic Eucalyptus morrisbyi J.G.Brett

Abstract

Eucalyptus morrisbyi is a rare Tasmanian endemic confined to one larger population (c. 2000 mature individuals) and two smaller populations (c. 15 and 16 mature individuals) in southeastern Tasmania. Morphological studies within the informal superspecies "Gunnii" reveal Eucalyptus morrisbyi has closest affinities to low altitude populations of E. gunnii in southeastern Tasmania and yet has distinct, phenetic differences from that species. Levels of variation in E. morrisbyi populations appear comparable to other species despite their small population size. A low frequency of hybridisation occurs with E. viminalis in natural stands but is unlikely to have affected the level of variability in the Calverts Hill and Risdon Hill natural populations. In contrast, it is shown that a high frequency of seedlings grown from a planted and a remnant stand of E. morrisbyi have affinities with E. viminalis. Several of the planted trees appeared to be hybrids and some progeny from phenotypically normal trees also appeared to be of hybrid origin. These results suggest that the genetic integrity of the species may be compromised by injudicious selection of seed for propagation from plantings and could be a major problem for the ex situ conservation of this and other rare and endangered species. Recommendations are given to enhance the conservation of this endangered Tasmanian endemic.

Mammalian herbivores reveal marked genetic divergence among populations of an endangered plant species

“…The evolutionary reasons for the clear genetically based differences in resistance of this endangered plant species are unknown, as are the reasons for differences in some of the traits that may confer this resistance. There is no evidence of seed or pollen flow between these two populations, and it is suggested that they have been genetically disjunct for thousands of years (Wiltshire et al 1991, Jones et al 2005), possibly contributing to the evolution of variation in herbivore resistance within this species. The genetic‐based resistance of the small RH population of E. morrisbyi may have evolved by chance alone through genetic drift and inbreeding causing alleles to accumulate over time (Wright 1931).…”

“…Both populations occur in coastal dry sclerophyll woodland, at similar altitudes (25–80 m above sea level), have a west–southsouthwest aspect and a low mean annual rainfall (520–620 mm). These two populations are separated by approximately 20 km and are significantly genetically differentiated based on seedling morphology (Wiltshire et al 1991) nuclear microsatellite allele frequencies and chloroplast DNA markers (Jones et al 2005).…”

“…Seed collected from one tree was considered a family and 32 families were collected across the whole native stand at CH. Seed from the CH population encompassed as much of the genetic diversity in the stand as possible and this was achieved by sampling from the most central tree in 50 × 50 m grid squares (Wiltshire et al 1991). At the RH stand, seed from 35 families was collected from the native stand on three separate occasions over a 16 year period (1983, 1989 and 1999), representing the trees that were reproductively mature.…”

“…In this paper we examine the interactions of an endangered eucalypt species, Eucalyptus morrisbyi and a high‐impact marsupial herbivore, the common brushtail possum Trichosurus vulpecula. Eucalyptus morrisbyi is one of Australia's rarest eucalypt species, confined to just three small populations in Tasmania (Wiltshire et al 1991). While there are marked molecular genetic differences between these populations (Jones et al 2005) there is little evidence that this variation translates into differences in key adaptive traits such as susceptibility to herbivory.…”

Variation in Eucalyptus barberi L. Johnson & Blaxell

“…cordata, E gunnii and possibly F. morrisbyi are the only plausible extant species. E. morrisb),i was not included in the progeny trial because of its extremely limited distribution (Wiltshire et aL 1990), and rhe fact rhat irs juveniles would be difficult to distinguish from E. gunnii in hybrid combination (e.g. Potts 1989).…”