Davidson, N. J., B. M. Potts, et al. (1987). "Gene flow between three

eucalyptus species at Snug Plains." Papers and Proceedings of the Royal

Society of Tasmania 121: 101-108.

Duncan, F. (1989). "Systematic affinities, hybridisation and clinal

variation within Tasmanian eucalypts." Tasforests 1(1): 13-25.

There are 29 species of eucalypts (Eucalyptus spp.) native to Tasmania; of

these, 17 species are considered to be endemic. Affinities of Tasmanian

species are indicated, and the factors contributing to the relatively high

levels of hybridization observed within the two Tasmanian subgenera

(Monocalyptus and Symphyomyrtus) are discussed. Clinal variation within

species, and between related species, is described and correlated with

environmental gradients. The importance of conserving genetic resources is

discussed.

Dungey, H. S., B. M. Potts, et al. (1997). "Mycosphaerella leaf disease:

Genetic variation in damage to Eucalyptus nitens, E. globulus and their F1

hybrid." Canadian Journal of Forest Research: in press.

Hardner, C. M. and B. M. Potts (1995). "Inbreeding depression and changes

in variation after selfing in Eucalyptus globulus ssp. globulus." Silvae

Genet no. 1: pp.

The effect of self pollination (selfing), open-pollination (OP) and

controlled cross pollination (outcrossing) on progeny of 11 Eucalyptus

globulus ssp. globulus seed parents was examined from seed set to 43 months

after planting. Selfing severely depressed seed set and field growth

relative to outcrossing. No effect was found on germination percent and

rate, nursery and field survival, nor the proportion of plants possessing

adult foliage or flower buds. Inbreeding depression for height first

occurred between germination and 8 months after planting but occurred later

for diameter. There was a trend for inbreeding depression to increase with

age. The performance of OP families was intermediate between self and

outcross treatments but was only significantly different from outcrossing

for volume at 43 months after planting. Selfing also appeared to increase

variation between and within families relative to outcrossing. The results

are discussed in terms of the biology and genetics of the species and the

relevance to tree improvement programs.

Jordan, G. J., N. M. G. Borralho, et al. (1994). "Identification of races

in Eucalyptus globulus ssp globulus based on growth traits in Tasmania and

geographic distribution." Silvae Genet no. 5-6: pp.

Canonical discriminant analysis of 432 open-pollinated families grouped

into 46 collection localities covering the natural geographic range of

Eucalyptus globulus ssp globulus was carried out on four year growth data

from five trial sites in Northern Tasmania. Combining results from the

analysis of growth responses with natural geographic boundaries and

reported taxonomic groupings it was possible to identify 12 geographical

races in the E. globulus ssp globulus base population. The three races from

Victoria [(1) the Otway Ranges, (2) the Strzelecki Ranges and (3) South

Gippsland], the (4) King Island, the (5) Furneaux Group, and (6) Central

Western Tasmania races, showed relatively similar growth responses. Races

from eastern Tasmania, [(7) Northeastern Tasmania, (8) Eastern Tasmania,

(9) Jericho, and (10) Southeastern Tastamania] were distinct from the

previous large group. Two small races, (11) Port Davey and (12) Lighthouse,

Wilson's Promontory had very slow growth. The trees at the Lighthouse

locality had a distinct shrub-like habit. The classification of four

localities (South West Lavers Hill, Clarke Island, Dover and Recherche Bay)

was doubtful. The variation in growth response across environments among

the different races suggest that appropriate genetic groupings (tentatively

the 12 geographic races identified here) should be made prior to further

genetic analysis of E. globulus ssp globulus breeding populations.

Li, H., J. L. Madden, et al. (1995). "Variation in volatile leaf oils of

the Tasmanian Eucalyptus species - 1. Subgenus Monocalyptus." Biochemical

Systematics and Ecology 23(3): 299-318.

Volatile oils were analysed from juvenile and adult leaves collected from

natural populations of five species from the series Obliquae (Eucalyptus

obliqua, E. delegatensis, E. regnans, E. sieberi and E. pauciflora) and

seven species from the series Piperitae (E. risdonii, E. tenuiramis, E.

pulchella, E. amygdalina, E. nitida, E. radiata and E. coccifera) of the

informal subgenus Monocalyptus (genus Eucalyptus). Oil yields (1.3-4.9% dry

weight) from adult leaves of all species were markedly higher than from

corresponding juvenile leaves (0.1-3.1% dry weight). Volatile leaf oils of

most species were rich in alpha- and beta-phellandrene, cis- and

trans-menth-2-en-1-ol, while some were rich in 1,8-cineole [eucalyptol] or

alpha, beta and gamma-eudesmol. Multivariate analyses indicated that the

Tasmanian eucalypt species from series Obliquae were well differentiated

and exhibited little intraspecific variation in percentage oil composition.

In contrast, species from the series Piperitae showed great intraspecific

variation and were poorly differentiated which is consistent with

morphological studies. The chemical composition of volatile oils of

juvenile and adult leaves were qualitatively similar but were

quantitatively different in some oil components for some species. Results

indicated that volatile leaf oils were useful for chemotaxonomic studies in

Eucalyptus.

Nesbitt, K. A., B. M. Potts, et al. (1995). "Partitioning and distribution

of RAPD variation in a forest tree species, Eucalyptus globulus

(Myrtaceae)." HEREDITY 1995 vol no. 6: pp.

Eucalyptus globulus is an important species for pulpwood production in

many countries. The pattern and partitioning of variation is important

baseline knowledge for tree breeding. Currently the species is divided into

four subspecies: globulus, bicostata, pseudoglobulus and maidenii. Random

Amplified Polymorphic DNA (RAPD) markers were used to analyse variation in

173 representatives of 37 natural populations of E. globulus: 31 localities

of ssp. globulus (148 individuals), two localities each of ssp. bicostata

(nine individuals), ssp. maidenii (ten individuals) and ssp. pseudoglobulus

(six individuals). Ten 10-mer primers amplified a total of 162 scorable

bands, of which 149 (91.9 per cent) were polymorphic. AMOVA analysis of a

Euclidean distance matrix based on presence/absence of polymorphic bands

found most variation within localities, but significant differences between

localities and regions. Principal components analysis (PCA) identified a

major latitudinal cline in RAPD phenotype that differentiated southern

Tasmanian localities from other ssp. globulus localities on mainland

Australia. Many localities previously identified as intermediate between

subspecies globulus and other subspecies in morphology were not

intermediate in RAPD phenotype. In some cases regions which showed marked

differentiation between localities in capsule and juvenile leaf morphology

showed little RAPD differentiation between localities. RAPDs also provided

new insights into the affinities of outlying localities. Although RAPD

technology has not yet been applied to many forest tree species, patterns

of variation were similar to those found in other outcrossing species

studied using both RAPDs and other molecular markers.

Potts, B. M. and L. A. Pederick (1997). Morphology, phylogeny, distribution

and genetic diversity of eucalypts. Diseases of Eucalypts and Their

Management. P. J. e. a. Keane: in press.

Potts, B. M., W. C. Potts, et al. (1987). "Inbreeding and interspecific

hybridization in Eucalyptus gunnii." Silvae Genet no. 5-6: pp.

The success and vigour of plants arising from self and close matings of

Eucalyptus gunnii are compared with wide intraspecific crosses and a range

of interspecific crosses. Strong barriers to inbreeding in Eucalyptus may

result in a disparity between pollen dispersal and gene flow in natural

stands, with more distant matings favoured.

Potts, B. M. and J. B. Reid (1983). "Hybridization between Eucalyptus

obliqua l'Herit. and E. pulchella Desf." Aust. J. Bot no. 3: pp.

The present study provides the first evidence for the occurrence of

natural hybrids between the wide-ranging species E. obliqua (series

Obliquae) and the restricted Tasmanian endemic E. pulchella (series

Piperitae). The progeny from one putative hybrid is shown to be

intermediate between the progeny from the two parental species for

virtually all characters examined. Principal component and likelihood

analyses support this intermediacy of the hybrid progeny and suggest that

no other species are involved in this hybrid system. The hybrid progeny

shows greater variability than progeny from either parental species.

Further, the hybrid tree has a lower seed output per capsule than trees of

either parental species and therefore the hybrid tree appears to be at an

evolutionary disadvantage.

Potts, B. M. and J. B. Reid (1988). "Hybridisation as a dispersal

mechanism." Evolution 42: 1245-1255.

E. risdonii can disperse much further through pollen mediated gene flow to

E. amygdalina and subsequent backcrossing or introgressio, than by seed

dispersal. Can tend back to E. risdonii type where there is selection for

them in subsequent generations. Suggest strongly against the notion of

tighty coadapted gene complexes.

Potts, B. M. and R. J. E. Wiltshire (1997). Eucalypt genetics and

genecology. Eucalypt Ecology: Individuals to Ecosystems. J. Williams and J.

Woinarski. Cambridge, Cambridge University Press: in press.

Schemske, D. W. and M. T. Morgan (1990). "The evolutionary significance of

hybridization in Eucalyptus." Evolution publ. 1991, 44(8): 2150-2151.

The recent suggestion that hybridization may be of evolutionary

significance as a means of gene dispersal in E. risdonii [Potts, B.M.;

Reid, J.B. (1988) Evolution, 42 1245-1255] is critically examined.

Conceptual problems that arise when assessing the evolutionary significance

of hybridization are discussed. It is suggested that evaluation of the

evolutionary significance of hybridization requires that full account be

taken of the selective forces that act on the production of hybrids and on

their reproduction and survival.

Smith, J. M. B. (1981). "Colonist Ability, Altitudinal Range and Origins of

the Flora of Mt. Field, Tasmania." J. Biogeogr no. 3: pp.

The seedplant flora growing above 1000 m on Mt. Field was studied. Greater

colonist ability, and larger and lower altitudinal ranges, were found to a

significant degree in alien than in the native species; in species

belonging to genera growing also in the northern hemisphere than in more

restricted genera; and in more widespread species than in Tasmanian endemic

species. These results suggest that ecological characteristics favouring

long distance migration are partly retained by younger floristic elements,

and that the derivation of Australia's alpine flora is complex and partly

only Quaternary in age.

Wiltshire, R. J. E., B. M. Potts, et al. (1992). "A paedomorphocline in

Eucalyptus . II. Variation in seedling morphology in the E. risdonii /E.

tenuiramis complex." Aust. J. Bot no. 6: pp.

Previous studies of phenotypic variation among natural populations in the

Eucalyptus risdonii /E. tenuiramis complex indicated that the two taxa are

linked by a cline in the retention of the juvenile leaf form

(paedomorphocline) and that division into the two taxa, E. risdonii and E.

tenuiramis , on the basis of these ontogenetic differences obscures the

phenetic relationships within and between the taxa. This study attempts to

remove the environmental and ontogenetic variation to reveal the

genetically based variation by examining seedling morphology. The results

suggest that genetic variation between geographically contiguous

populations of E. risdonii and E. tenuiramis is relatively small and

continuous, and classification into either taxon on the basis of seedling

phenotype is not possible for populations in this transitional area.