for providing expert advice during the post-workshop review stage. We thank the experts involved in the New Guinea assessment workshop, for their information on species with distributions spanning Torres

Sexual dimorphism is usually interpreted in terms of reproductive adaptations, but the degree of sex divergence also may be affected by sex‐based niche partitioning. In gape‐limited animals like snakes, the degree of sexual dimorphism in body size (SSD) or relative head size can determine the size spectrum of ingestible prey for each sex. Our studies of one mainland and four insular Western Australian populations of carpet pythons (Morelia spilota) reveal remarkable geographical variation in SSD, associated with differences in prey resources available to the snakes. In all five populations, females grew larger than males and had larger heads relative to body length. However, the populations differed in mean body sizes and relative head sizes, as well as in the degree of sexual dimorphism in these traits. Adult males and females also diverged strongly in dietary composition: males consumed small prey (lizards, mice and small birds), while females took larger mammals such as possums and wallabies. Geographic differences in the availability of large mammalian prey were linked to differences in mean adult body sizes of females (the larger sex) and thus contributed to sex‐based resource partitioning. For example, in one population adult male snakes ate mice and adult females ate wallabies; in another, birds and lizards were important prey types for both sexes. Thus, the high degree of geographical variation among python populations in sexually dimorphic aspects of body size and shape plausibly results from geographical variation in prey availability. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 77, 113–125.

This study investigated allozyme and morphometric variability within the genus Cynopterus, with particular emphasis on C. nusatenggara, which is endemic to Wallacea, the area encompassing the Oriental-Australian biogeographic interface. The genetic distances between Cynopterus species are small by mammalian standards and suggest that this genus has undergone a recent series of speciation events. The genetic distance between populations of C. nusatenggara is strongly correlated with both the contemporary sea-crossing distance between islands and the estimated sea crossing at the time of the last Pleistocene glacial maximum, 18,000 b.p. This observation, together with low levels of population substructure within islands as shown by F-statistics, indicates that the sea is a primary and formidable barrier to gene exchange. The genetic distance and the great-circle geographical distance between the populations of C. nusatenggara are not correlated, although a principal-coordinates analysis of genetic distance reveals relationships between the populations that are similar to their geographical arrangement. A strong negative correlation exists between the level of heterozygosity within island populations of C. nusatenggara and the minimum sea-crossing distance to the nearest large source population. This is interpreted as reflecting an isolation effect of the sea, leading to reduced heterozygosity in populations that have larger sea barriers between them and the large source islands. Independently of this, heterozygosity is negatively associated with longitude, which in turn is associated with systematic changes in the environment such as a gradual decline in rainfall from west to east. The association between heterozygosity and longitude is interpreted as reflecting an association between genetic and environmental variance and supports the niche-width theory of genetic variance. Morphometric variability did not show any of the main effects demonstrated in the genetic data. Furthermore, there was no evidence that, at the level of individuals, genetic and morphometric variability were associated.

With 1 plate and 4 figures in the text) Breeding, population dynamics and seasonal changes in physical and physiological parameters were examined in the northern quoll (Dasyurus hallticatus) at Mitchell Plateau, Western Australia, between September 1981 and November 1982. Females gave birth to a single litter of young in July or August. Births were earlier on near-coastal sites than on inland sites. Litter size was greater on inland sites and litter size differed between years. By September all females were either carrying pouch young or were lactating. Lactation ceased by April. Testosterone levels in males peaked in July. There were significantly more male than female pouch young. However, in only one grid was the adult sex ratio different from parity, with an excess of females in September 1981 and 1982. Embryonic mortality was > 53% but loss of pouch young was small. Although males and females moved similar distances between successive recaptures, the extent of movement varied seasonally, being greatest in September. Males were generally larger and heavier than females. Seasonal variations were recorded for most physical and physiological parameters. The most pronounced changes occurred towards the end of the dry season (July to September) for both males and females. Over this period there was a significant decline in weight (males), haematocrit (males), plasma albumin (males) and leucocytes (both males and females) and significant elevations in values of haemoglobin and both free and protein-bound cortisol in both males and females. Few males survived the post-mating period from July to September. They appeared to decline in condition over this period more markedly than females: they lost more weight, their haematocrit and plasma albumin values declined to a greater extent, and they were more heavily infected with lice (Boopia uncinata). Males with lower testosterone and higher free and protein-bound cortisol had increased prospects of surviving the breeding season, which suggests that it is the dominant males that are less likely to survive the breeding season. Individuals in the three major populations at Mitchell Plateau differed greatly in their physiological values. The high-density population in a sandstone area had intermediate levels of free cortisol and higher haematocrit values than both the other populations, and higher levels of haemogl3bin than the population on laterite substratum.

The rarity of top predators has been identified as a contributing factor in the collapse of entire ecological systems. Elucidating the ecology, evolutionary potential and population response of species before a threatening process requires a combination of measures of phenotypic variation, demography and genetic diversity using an array of markers. Here we use such information to determine the population structure and its conservation implications for a keystone marsupial carnivore in Western Australia, the northern quoll Dasyurus hallucatus, ahead of the spread of the exotic and poisonous cane toad Chaunus marinus from the east. The western populations occur in two discrete geographic regions on the mainland, the Kimberley and Pilbara, separated by the arid Great Sandy Desert, and on several continental islands. Both mitochondrial DNA sequences and 11 nuclear microsatellite loci reveal clear differentiation of the Kimberley and Pilbara regions. Offshore islands with permanent sea-channels from the mainland show reduced diversity and were genetically distinct indicating genetic isolation, whereas those separated from the mainland by very shallow channels were more similar to the adjacent mainland populations, suggesting on-going gene flow. There was little indication that any population within the distribution of the species had experienced recent declines but there was marked variation in sexual dimorphism suggesting diversity in demographic performance. These populations in Western Australia differ from those remaining to the east in Queensland and the Northern Territory, in both genetic structure and demographic parameters and represent the last intact populations in Australia that have not experienced major declines concomitant with the spread of the cane toad. Consequently, the genetic and demographic flexibility recorded by this study provides guidance for the conservation and management of a major marsupial predator before and during its potential decline associated with an invasive, threatening prey species.