Jane Prince

Metabolic ecology of cockatoos in the south-west of Western Australia

This study examined the metabolic ecology of six cockatoo taxa endemic to the south-west of Western Australia. As the availability of food is one factor that may influence the abundance and distribution of these cockatoos, we document here their baseline energy requirements and feeding patterns. Evaporative waterloss was also measured as this may correlate with the aridity of the species’ environment. Basal metabolic rate was significantly lower at 0.62 ± 0.13 mL O2 g–1 h–1 for the inland red-tailed black cockatoo than 1.11 ± 0.16 mL O2 g–1 h–1 for the forest red-tailed black cockatoo, but there was no significant difference in metabolic rate between the two white-tailed black cockatoos (0.86 ± 0.18 for Carnaby’s and 0.81 ± 0.11 mL O2 g–1 h–1 for Baudin’s) or the two corellas (0.95 ± 0.12 for Butler’s and 0.70 ± 0.04 mL O2 g–1 h–1 for Muir’s). There were no significant differences between the two white-tailed black cockatoos, and between the two corellas, with respect to evaporative water loss. The inland red-tailed black cockatoo had a significantly lower rate of evaporative water loss (0.44 ± 0.07 mg g–1 h–1) than the forest red-tailed black cockatoo (0.70 ± 0.06 mg g–1 h–1), which is presumably an adaptation to its more arid habitat. The total energy content of assorted native and introduced food items that form significant proportions of the diets for these cockatoos varied from only 0.17 kJ for a 9-mg Emex australis seed to 63.9 kJ for a 3-g Banksia attenuata nut. The energy content of each food item and the estimated daily energy requirements of the cockatoos enabled the calculation of the numbers of nuts/cones/seeds required by each species for a day, which ranged from 11 B. attenuata nuts for a Carnaby’s cockatoo to 3592 Persoonia longifolia seeds for a forest red-tailed black cockatoo.

Fish community structure in an intermittent river: the importance of environmental stability, landscape factors and within-pool habitat descriptors

In rivers worldwide, hydrological persistence and variability (i.e. environmental stability) typically parallel longitudinal changes in habitat. This interaction complicates determination of the hierarchy of mechanisms that structure fish communities along rivers. In this study, we examined fish species richness and presence–absence in pools of an intermittent river system containing underground water storages (Fortescue River, north-west Australia), a system that was predicted to uncouple this relationship. Stability, measured by pool persistence, was unrelated to a pools maximum depth or its position in the catchment, indicating partial decoupling. However, pool stability remained correlated with habitat diversity and log-transformed surface area. Model selection indicated that species richness was better described by pool stability and the landscape factor stream order than by within-pool habitat descriptors. Permanent pools low in the catchment contained more species than unstable pools in headwater streams. We conclude that the distribution of fish in the Fortescue River is shaped predominantly by processes of extirpation and re-colonisation. Management efforts in this river and similar intermittent systems should focus on the preservation of refuge pools, and limit the construction of barriers that limit dispersal.

Fauna Associated with the Coral Pocillopora damicornis at the Southern Limit of its Distribution in Western Australia

In a study of the fauna of Pocillopora damicornis from three sites at two temperate latitudes on the Western Australia coast, we collected ninetyfour species of coral symbionts, including fifty-four species of decapod crustaceans. Nine of these species are known to be obligate symbionts of living pocilloporid corals throughout the Indo-West Pacific region. At least four other species are known to be non-specifically dependent on living coral with a similarly widespread distribution. Of the remaining eighty-one species, four are known only from living and dead coral, sixty are known from a variety of reef habitats and only facultatively associated with coral, and seventeen have undescribed habits. Although regional species diversity, estimated by species richness, at these two temperate latitudes was less than that reported for some tropical sites, we could find no consistent trend of decreasing diversity with increasing latitude particularly when sample size and size of region were taken into account. More significantly, there was no consistent difference in local species diversity as measured by number of species per unit coral volume between temperate and tropical sites. We conclude that the diversity of the fauna associated with P. damicornis depends as much on the specific characteristics of the site as on latitudinal position.

Human Impacts on Cable Beach, Broome (Western Australia)

There are concerns that Cable Beach, which is of outstanding natural beauty and a major tourist attraction for Broome and the Kimberley region of northwest Australia, is suffering damage from recreational use, particularly that caused by off-road vehicles. To assess current levels of human impact on the shore and its fauna, the southern-most kilometer of the Beach, covering an area to which vehicles had access and an adjacent area closed to vehicles, was surveyed for human usage and shore crab abundance. Human usage over the recording period was high in the area with high vehicular access. The amount of litter, although considerable, was well below that recorded in some other tourist destinations elsewhere in the world. Burrows of both the ghost crabs Ocypode spp, and the sand bubbler, Scopimera inflata, were less numerous in areas of high vehicle use than those of low use. Both species may be valuable in monitoring human impacts on Cable Beach.

The fauna of thrombolitic microbialites, Lake Clifton, Western Australia

A total of 30 microbialites at two sites in Lake Clifton, Yalgorup National Park, Western Australia, were sampled by coring to quantify the associated fauna with these organo-sedimentary structures. Twenty five species of aquatic fauna were recorded from the cores, comprising 20 species of metazoan, predominantly Crustacea (including Melita kauerti (Amphipoda), Exosphaeroma cf. serventii (Isopoda); and Cyprideis australiensis(Ostracoda); Polychaeta (Capitella cf. capitata); nematodes; and five species of Foraminifera (Protista). Multivariate analysis of the five numerically most abundant taxa (amphipods, isopods, ostracods, polychaetes, nematodes) separated microbialites by season and submergence. Numbers of all taxa, particularly polychaetes and amphipods, were much higher in spring than in autumn, and in permanently-inundated than in seasonally-inundated microbialites. The exception was higher numbers of juvenile polychaetes in seasonally-inundated microbialites at the northern site in spring. This study showed that modern thrombolitic microbialites can co-exist with a diverse invertebrate fauna and serves as a baseline for future studies of interactions between microbialites and fauna.

Evidence of large, local variations in recruitment and mortality in the small giant clam, Tridacna maxima, at Ningaloo Marine Park, Western Australia

Understanding variability of recruitment and mortality is essential for attempts to conserve populations or assessing changes resulting from perceived disturbances. In the absence of long-term studies, we examined population density and size-frequency distributions of the small giant clam, Tridacna maxima, at 20 sites in Ningaloo Marine Park, Western Australia, where the clams are abundant on discontinuous, intertidal rocky platforms attached to the shoreline. Density ranged over two orders of magnitude (0.04–8.27 m–2), and size ranged from 1.5 to 31.0 cm. The shapes of the size-frequency distributions varied substantially, indicating variability in recruitment and mortality, including failures of cohorts to recruit and catastrophic events of mortality. Consistency of recruitment, as indexed by the coefficient of variation of the size-frequency distribution, was greater towards the north of the Park, on intertidal platforms with greater complexity across their widths, and with smoother surfaces in the part of the platform occupied by the clams. The average turnover time was estimated at 5.4 years, giving a median age of 13 years. However, variation among sites was large, highlighting the importance of variability of the dynamics of local populations and the need for long-term studies to understand any particular population.

MORE THAN BINDIN DIVERGENCE: REPRODUCTIVE ISOLATION BETWEEN SYMPATRIC SUBSPECIES OF A SEA URCHIN BY ASYNCHRONOUS SPAWNING

The evolution of reproductive barriers is crucial to the process of speciation. In the Echinoidea, studies have focused on divergence in the gamete recognition protein, bindin, as the primary isolating mechanism among species. As such, the capacity of alternate mechanisms to be effective reproductive barriers and the phylogenetic context in which they arise is unclear. Here, we examine the evolutionary histories and factors limiting gene exchange between two subspecies of Heliocidaris erythrogramma that occur sympatrically in Western Australia. We found low, but significant differentiation between the subspecies in two mitochondrial genes. Further, coalescent analyses suggest that they diverged in isolation on the east and west coasts of Australia, with a subsequent range expansion of H. e. erythrogramma into Western Australia. Differentiation in bindin was minimal, indicating gamete incompatibility is an unlikely reproductive barrier. We did, however, detect strong asynchrony in spawning seasons; H. e. erythrogramma spawned over summer whereas H. e. armigera spawned in autumn. Taken together, we provide compelling evidence for a recent divergence of these subspecies and their reproductive isolation without gamete incompatibility. Western Australian H. erythrogramma may therefore present an intriguing case of incipient speciation, which depends on long‐term persistence of the factors underlying this spawning asynchrony.

Aggressive interactions between freshwater turtle, Chelodina oblonga, hatchlings and freshwater crayfish, Cherax spp.: implications for the conservation of the critically endangered western swamp turtle, Pseudemydura umbrina

Interactions between turtle hatchlings of Chelodina oblonga and the marron, Cherax tenuimanus, the gilgie, C. quinquecarinatus, the koonac, C. preissii (freshwater crayfish native to Western Australia) and the introduced yabby, Cherax. sp., were observed in laboratory-based trials in uncluttered aquaria. Marron, koonacs and yabbies, but not gilgies, showed aggressive and predatory behaviour towards the hatchlings. In total, 59 attacks were observed in 26 of the 80 trials. On 12 occasions, crayfish captured hatchlings in their chelae. On two occasions, the attack of the crayfish was so quick that the hatchling was killed instantly. Compared with movement when alone, movement of hatchlings was significantly greater in the presence of koonacs and yabbies, but significantly less in the presence of marron and gilgies. The range of non-native yabbies currently is expanding into Ellen Brook Nature Reserve which harbours the last naturally persisting population of the critically endangered western swamp turtle, Pseudemydura umbrina. No native crayfish occur in the habitat of P. umbrina in this reserve. The possible invasion by the ecological generalist yabby poses a new threat to the survival of P. umbrina.

Is Tridacna maxima (Bivalvia: Tridacnidae) at Ningaloo Reef, Western Australia?

ABSTRACT Correct identification of species is fundamentally important, but field identification can be misleading in many taxa, requiring genetic comparisons to confirm identity of specimens. Recent genetic studies revealed that the giant clam Tridacna noae (Röding, 1798), previously confused morphologically with Tridacna maxima (Röding, 1798), is widespread in the Indo-West Pacific, including a subtidal site at Ningaloo Reef, Western Australia. We examined molecular and morphological variation of Tridacna from four intertidal populations at Ningaloo Reef to determine their identity and to test whether morphology is useful for distinguishing the two species in this region. DNA sequences of clams identified all individuals as T. noae, indicating that T. maxima is rare, if it occurs at all, at Ningaloo Reef. Morphological traits that distinguish the two species in the Western Pacific are highly variable at Ningaloo, indicating the need for local genetic corroboration for correct identification.

Temporal patterns in the abundance of a critically endangered marsupial relates to disturbance by roads and agriculture

The aim of this study was to investigate how landscape disturbance associated with roads, agriculture and forestry influenced temporal patterns in woylie (Bettongia penicillata) abundance before, during and after periods of rapid population change. Data were collected from an area of approximately 140,000 ha of forest within the Upper Warren region in south-western Australia. Woylie abundance was measured using cage trapping at 22 grid and five transect locations with varying degrees of landscape disturbance between 1994 and 2012. We found evidence that the distribution and abundance of woylies over time appears to be related to the degree of fragmentation by roads and proximity to agriculture. Sites furthest from agriculture supported a greater abundance of woylies and had slower rates of population decline. Sites with fewer roads had a greater abundance of woylies generally and a greater rate of increase in abundance after the implementation of invasive predator control. The results of this study suggest that landscape disturbance is less important at peak population densities, but during times of environmental and population change, sites less dissected by roads and agriculture better support woylie populations. This may be due to the role these factors play in increasing the vulnerability of woylies to introduced predators, population fragmentation, weed species invasion, mortality from road collisions or a reduction in available habitat. Strategies that reduce the impact of disturbance on woylie populations could include the rationalisation of forest tracks and consolidation of contiguous habitat through the acquisition of private property. Reducing the impact of disturbance in the Upper Warren region could improve the resilience of this critically important woylie population during future environmental change.