Isolated intermediates - products of long distance gene dispersal, phantom hybridity or convergent evolution? The case of the half-barked Eucalyptus amygdalina

Apparent intermediates between Eucalyptus amygdalina and E. pulchella occur well outside the recognized range of the latter species. Progenies of these isolated intermediates were grown in uniform conditions with progenies of trees of E. pulchella, E. amygdaline and apparent hybrids between these two species that are found where they occur parapatrically. The isolated intermediate population proved identical with E. amygdalina in seedling characteristics, while the parapatric intermediates were more variable than the other populations, this variability probably being partly the result of hybridization between E. amygdalina and either E. tenuiramis or E. risdonii. The allopatric intermediate population is more likely to have resulted from convergence of E. amygdalina in the direction of E. pulchella than from phantom hybridity or long distance gene migration

Investigating the effect of tunnelling on existing tunnels

A major research project investigating the effect of tunnelling on existing tunnels has been completed at Imperial College London. This subject is always of great concern during the planning and execution of underground tunnelling works in the urban environment. Many cities already have extensive existing tunnel networks and so it is necessary to construct new tunnels at a level beneath them. The associated deformations that take place during tunnelling have to be carefully assessed and their impact on the existing tunnels estimated. Of particular concern is the serviceability of tunnels used for underground trains where the kinematic envelope must not be impinged upon. The new Crossrail transport line under construction in London passes beneath numerous tunnels including a number of those forming part of the London Underground networ

Variation in Eucalyptus barberi L. Johnson & Blaxell

Phenetic variation within Eucalyptus barberi L. Johnson & Blaxell was examined and compared to related Tasmanian species. "Typical" northern populations were morphologically distinct from the more diverse group of populations to the south. This phenetic disjunction did not correspond to the major geographic disjunction in the range of E. barberi. Detailed study of two morphologically aberrant population indicated that they probably arose from in situ hybridisation: however, the exact identities of the progenitor species remains unclear. The type locality and several of the "southern" populations, as well as aberrant populations at Meredith Tier and Ponybottom Creek, deserve formal conservation

Tasmania's eucalypts: their place in science

While representing only 29 of the more than 700 eucalypt species, those on the island of Tasmania have a unique place in the history and scientific discovery of this iconic genus. Eucalypts entered written history when Abel Tasman discovered Tasmania in 1642 and the type specimen for the genus, Eucalyptus obliqua L’Hér., was collected from Bruny Island in 1777 during Cook’s third voyage. The discovery of some of the endemic taxa was linked with the French expedition searching for La Pérouse in 1772-3, and the return of the type specimens to France was a great triumph against adversity. Nearly half a century later British botanists contributed to the discovery of the Tasmanian eucalypts with colonial collectors sending specimens to Kew Gardens, with Australian-based botanists completing the pioneering stages of botanical discovery in the early 1900’s. Botanists in Tasmania then led experimental approaches to understanding their evolution, ensuring a place for the island’s eucalypts in 20th Century science. The first major study of eucalypt chromosomes and cell division was undertaken with the Tasmanian eucalypts in the 1930’s. The post war decade saw the establishment of many of the lines of scientific enquiry pursued today, through the research of pioneering Tasmanian scientists such as Newton H. Barber and the recently deceased Bill Jackson, both of whom served as Professor of Botany at the University of Tasmania. Their studies of the roles of natural selection and hybridization in the evolution of tree genera led to outstanding work on the nature and origins of clinal variation. Molecular techniques have now allowed many of the questions posed by the early work of Jackson and Barber to be addressed. However, just as old questions are answered, new questions arise as genomic studies on this unique Australian genus open a new era of scientific discovery

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

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, virninalis. 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

Gene flow between three eucalypt species at Snug Plains

The extent of hybridisation and gene flow between the three Monocalyptus species, Eucalyptus pulchella, E coccifera (series Piperitae) and E delegatensis (series Oh/iquae) 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 flowering 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 Fl 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