Striped Marsh Frog Limnodynastes Peronii Research Articles

Frog Reproduction and Community Structure in relation to Water Attributes: Setting the stage to understand effects of Climatic Variables and Climate Change

ABSTRACT As amphibians have declined more than other vertebrates and are important environmental bio-indicators for aquatic ecosystems, we must understand how attributes of such ecosystems affect individual frogs, populations, and multi-species communities. For aquatic-breeding frogs, pond physical/chemical properties influence all life-stages and therefore populations, species, and communities. However, studies have focussed on tadpoles, considered few water variables, and not considered relationships between water attributes and frog populations or communities. Inter-specific differences in how water attributes affect tadpole populations, and hence possibly adult choice of breeding site, should reflect habitats where different species occur, but has been little investigated. We studied the only frog species on Broughton Island, off the east coast of Australia: the threatened Green and Golden Bell Frog Litoria aurea (GGBF); and the widespread and abundant Striped Marsh Frog Limnodynastes peronii (SMF). Suitability of pond breeding habitat, measured by encounter rates during 57 visits over 17 years with different life stages, depended on depth, salinity, pH and temperature, with responses by the two species in essentially opposite directions. For both species, encounter rates increased with increasing depth and with decreasing salinity. Encounter rates peaked at neutral to alkaline pH for GGBF (i.e., 6.8 to 8.0 or higher) and acidic pH for SMF (i.e., 5.5 to 6.0). As water temperature increased, encounter rates increased for GGBF and decreased for SMF. Frog community structure depended on average pond temperature and how it changed over time. If recorded temperature, averaged over the year, was less than 22°C or declined to below this level, the GGBF population, as indexed by numbers of adults observed and occurrences of earlier life stages, was low or declined, while the SMF population was high or increased. This threshold yearly average temperature translates into a required temperature at onset of spring breeding for the GGBF of about 20°C. The GGBF population on the island has declined since 1998, when our study began, due to increased aquatic vegetation and consequent decline in water temperature in major breeding ponds. As ponds are small, manual vegetation removal should reverse the trend. A comprehensive understanding of the biological effects of climate change, past and future, can now be pursued.

Host species determines whether infection load increases beyond disease‐causing thresholds following exposure to the amphibian chytrid fungus

AbstractIntroduced pathogens are increasingly being implicated in population declines and their effects are difficult to manage. In the absence of methods to eradicate pathogens acting as threatening processes, intervention before population decline is necessary. Such an intervention requires an ability to predict when population declines will occur, and therefore, an understanding of when exposure will lead to infection, disease, death and population decline. This study investigates when pathogen exposure leads to disease for the amphibian chytrid fungus Batrachochytrium dendrobatidis, which has been implicated as a causal agent in the global amphibian decline. Susceptibility studies were conducted on two anuran species, the green and golden bell frog Litoria aurea and the striped marsh frog Limnodynastes peronii, when exposed to the fungus as either tadpoles or juveniles. Host species was found to significantly affect the outcome of exposure, with infection loads in L. aurea increasing over time and resulting in significantly lower survival rates than unexposed. By comparison, infection loads in L. peronii remained the same or decreased over time following the initial infection, and survival rates were no different whether exposed to B. dendrobatidis or not. These outcomes were independent of the life stage at exposure. Individuals with higher infection loads were not found to have lower survival rates; rather, an infection load threshold was identified where individuals with infection loads that crossed this threshold had high likelihoods of showing terminal signs of chytridiomycosis. Therefore, host species determined whether infection load crossed this threshold and the crossing of the threshold determined the incidence of disease and survival. The quantification of infection load thresholds for survival, along with the time it takes to reach them, will enable infection loads in wild populations to be related to the likelihood of disease and is the first step in the understanding and prediction of when exposure will result in population decline.

Interactions between tadpoles of Green and Golden Bell FrogLitoria aureaand Striped Marsh FrogLimnodynastes peronii

Abstract: Experiments with tadpoles have been used to distinguish between intra- and inter-specific interactions and between interactions that arise through direct physical contact or indirectly through water-born movement of chemicals or micro-organisms. In the case of two Australian frog species, the Green and Golden Bell Frog Litoria aurea and the Striped Marsh Frog Limnodynastes peronii, it has been suspected that there are negative chemical interactions between the tadpoles of these two species, and that management of the former species, which is considered ‘threatened’ with extinction, may have to consider such interactions. We therefore sought to evaluate the nature of any interactions between tadpoles of these two species using three experimental treatments in which each tadpole species occurred on its own (i.e., “separate”), in the same water as the other species but separated by a mesh partition (i.e., “adjacent”), and intermingling together in the same water (i.e., “mixed”). We minimized any ef...

Mining a museum frog collection for environmental bio-indicators using specimens of the Striped Marsh Frog Limnodynastes peronii

Museum specimens of the Striped Marsh Frog, (Limnodynastes peronii; Myobatrachidae), were examined to evaluateits potential role in providing bio-indicators of environmental quality and change. I hypothesized that chemical pollutionof their breeding habitat would have peaked during the 1960s or 1970s, and that the levels of physical abnormality and morphological asymmetry for this frog species would tend to increase with increasing pollution. Consistent with this, I found that both the proportion of frogs with physical abnormalities and the average difference in length between the left and right lower legs peaked for specimens collected during the 1960s or 1970s and were lower for specimens collected during earlier and later decades. I also found that the overall proportion of specimens of this species with physical abnormalities was high relative to presumed background levels, which is consistent with relatively elevated levels of pollution in the degraded habitats where this species generally occurs. In this and similar ways, biological collections may be mined to provide environmental bio-indicators.