These could be new mutations that occurred during the exponential growth of the KI population. On the assumption of uninterrupted exponential growth, the population growth rate on KI can be assessed, for it is known that the population went from N 0 = 18 at the time of the founding to N t = 27 000 in 2004, 80 years later. If we assume a koala generation time of 5 years (Martin and Handasyde 1999), the number of generations is 16. Because N t = N 0 e rt , then r = [ln (N t /N 0 )]/t = 0.4570, equivalent to a per-generation rate of increase, l, of 1.5794. This value can be used to calculate the size of the population at each intervening generation, and thus the total number of individuals that have been available for mutation. This gives an estimate of 46 546 individuals in the pedigree leading to the present population. The mutation rate on KI can be derived from the following formula: mutation number divided by (microsatellite loci ¾ individuals) = 4/(15 ¾ 46 546) = 5.7 ¾ 10 -6 . This number is slightly lower than the range of the microsatellite mutation rates for eutherian mammals (between 10 -3 and 10 -5 ; Dallas 1992; Banchs et al. 1994;Ellegren 1995), possibly because of either the small number of koalas genotyped, or the assumptions inherent in the calculations.Abstract. Habitat destruction and fragmentation, interactions with introduced species or the relocation of animals to form new populations for conservation purposes may result in a multiplication of population bottlenecks. Examples are the translocations of koalas to French Island and its derivative Kangaroo Island population, with both populations established as insurance policies against koala extinction. In terms of population size, these conservation programs were success stories. However, the genetic story could be different. We conducted a genetic investigation of French and Kangaroo Island koalas by using 15 microsatellite markers, 11 of which are described here for the first time. The results confirm very low genetic diversity. French Island koalas have 3.8 alleles per locus and Kangaroo Island koalas 2.4. The present study found a 19% incidence of testicular abnormality in Kangaroo Island animals. Internal relatedness, an individual inbreeding coefficient, was not significantly different in koalas with testicular abnormalities from that in other males, suggesting the condition is not related to recent inbreeding. It could instead result from an unfortunate selection of founder individuals carrying alleles for testicular abnormalities, followed by a subsequent increase in these alleles' frequencies through genetic drift and small population-related inefficiency of selection. Given the low diversity and possible high prevalence of deleterious alleles, the genetic viability of the population remains uncertain, despite its exponential growth so far. This stands as a warning to other introductions for conservation reasons.
The cellular components of colostrum and milk of the tammar wallaby
(Macropus eugenii) have been investigated over the
period of oestrus, lactation and weaning. Macrophages, neutrophils,
lymphocytes and other vacuolated mononuclear cells were identified. The total
number and diversity of cells were higher in colostral secretions and in
secretions from post-lactational mammary glands. Neutrophils were the
predominant cell type in early secretions. Macrophages were more prevalent in
the milk of animals that no longer had young attached to the teat. These
observations are consistent with suggestions that phagocytic cells play a role
in post-lactational repair of the mammary gland but also suggest that
non-specific phagocytic protection plays a role in protection of the neonatal
marsupial.
The occurrence of self-colour pigmentation in the Australian Merino wool flock
is of considerable economic importance. The Agouti gene
is believed to be responsible for the recessive expression of pigmented
fleece. Using comparative mapping information we have investigated the
putative homologous ovine map positon of the Agouti gene
for linkage to the recessive self-colour phenotype of Australian Merino sheep.
Significant results were observed with microsatellites previously mapped to
ovine chromosome 13. Comparative data suggest that the ovine
Agouti gene would map to the same chromosome, making the
Agouti gene a positional candidate for the self-colour phenotype.
Populations of tammar wallabies (Macropus eugenii) occur in southwest Western Australia and on five Australian offshore islands, four in Western Australia and one in South Australia. The South Australia and Western Australia populations have probably been isolated from each other for 50,000-100,000 years. Studies have shown that there are morphological and genetic differences between these populations. Attempts at mating individuals from Garden Island (Western Australia) with individuals from Kangaroo Island (South Australia) indicate that while the two populations can hybridize in captivity and F1 hybrids of both sexes are fertile, a barrier to successful reproduction between these two populations is in the initial stages of development.
Echidnas and platypuses possess two haemoglobins, HbI and HbII. HbI is in the higher concentration. Genetic variation has been found in the electrophoretic mobility of both HbI and HbII in the echidna.
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