Potential for water-resource infrastructure to act as refuge habitat

Permanent sources of natural water are expected to decline in Mediterranean-climate regions under future climate change. Therefore, stable water bodies that act as refuge habitats will become increasingly important to the maintenance of freshwater biodiversity. Man-made water bodies such as those associated with water-resource infrastructure could contribute to the available refuge habitat but little is known about fish, zooplankton and frog assemblages in such water bodies. We quantified the diversity and abundance of fish, zooplankton and frogs that reside within raw water storages and water reclamation plants and compared them to assemblages from nearby natural water bodies over a total of 19 water bodies.Overall, the faunal assemblages within the man-made water bodies showed similarities to the nearby natural water bodies with very few differences found among the three water body types. Diversity of available substrates and of submerged and emergent macrophytes were the habitat variables best correlated with diverse faunal assemblages. This study suggests that the faunal assemblages within raw water storages and water reclamation plants resemble those found within nearby natural water bodies and that there is therefore potential for water-resource infrastructure to act as an important refuge habitat during drought. Furthermore, small changes in the management of these storages to maximise habitat diversity could increase the value of the refuge, complementing their role in water-resource delivery.

Decline and re-expansion of an amphibian with high prevalence of chytrid fungus

The disease chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is a key driver of global amphibian declines. While chytridiomycosis can cause extinction, many susceptible species persist after an initial period of decline, albeit with reduced abundance and distribution. Emerging evidence indicates that amphibian abundance can recover within remnant populations, but to date, the capacity of amphibian populations to re-expand into historically occupied habitat has received limited research attention. We surveyed 145 sites in 2011 and 2012 to determine if populations of the whistling tree frog (Litoria verreauxii verreauxii) have re-expanded compared with historical data from 1975-1976, 1990 and 1996. L. v. verreauxii underwent a major range contraction likely caused by chytridiomycosis between the first two time periods. Populations have recently re-expanded, with 39 new sites colonised despite high prevalence of Bd. We suspect that changes in disease dynamics have resulted in the increased coexistence of L. v. verreauxii and Bd. Habitat attributes at sites that retained frogs for the duration of the study indicate that high quality habitat may contribute to buffering against population level effects of Bd. Colonised sites had more coarse woody debris, suggesting a possible habitat management strategy to encourage range expansion for this species. Given sufficient time and adequate source populations in high quality habitat, it is possible that other amphibian species may re-expand from chytridiomycosis-induced declines. This provides an impetus for the protection of historical, but currently unoccupied amphibian habitats and highlights the importance of maintaining high quality habitat to help species survive novel shocks such as pandemic diseases.

The taxonomy, zoogeography and ecology of amphibians and reptiles of Hin Nam No National Protected Area (Laos) in comparison with data from Phong Nha – Ke Bang National Park (Vietnam).

In this thesis the mostly unknown herpetofauna in Hin Nam No National Protected Area Laos in the northern Truong Son Range was for the first time intensively investigated, and its diversity was compared to the bordering, and well-investigated Phong Nha - Ke Bang National Park in Vietnam. Twelve new vertebrate species were described comprising 11 geckonids (Cyrtodactylus bansocensis, C. calamei, C. hinnamnoensis, C. jaegeri, C. rufford, C. sommerladi, C. soudthichaki, Gekko boehmei, G. bonkowskii, G. sengchanthavongi, G. thakhekensis, Lycodon banksi and one colubrid snake (Lycodon banksi). Seven species were discovered for the first time in Laos including three frogs (Gracixalus quyeti, G. supercornutus, Rhacophorus maximus), two geckos (Cyrtodactylus cryptus, C. pseudoquadrivirgatus) and two snakes (Lycodon futsingensis, L. ruhstrati abditus). The main hypothesis that the Truong Son Range acted as a biogeographic barrier for the distribution of amphibians and reptiles could be confirmed at least for karst adapted gekkonids. Compared to other herpetofaunal groups the number of gekkonids in karst formations was particularly high (seven bent-toed geckos, four true geckos). By comparing the relative amounts of shared species in Hin Nam No and Phong Nha - Ke Bang, it is interesting to note that fewer reptile species (38%) than amphibian species (66%) were shared between both regions. This might indicate that the Truong Son Range acts as a stronger biogeographical barrier for reptiles than for amphibians. Two pairs of karst-adapted cryptic gecko species (i.e. species with distinct genetic differences, but a similar phenotype) occurred on both sides of the Truong Son Range. Only in one case these were sibling species (Crytodactylus sommerladi in Laos versus C. roesleri in Vietnam), but not in the other (C. hinnamnoensis in Laos versus C. phongnhakebangensis in Vietnam). On the Laotian side, nine gecko species (Cyrtodactylus bansocensis, C. calamei, C. darevskii, C. hinnamnoensis, C. khammouanensis, C. multiporus, C. sommerladi, G. boehmei, G. sengchanthavongi) currently have to be regarded as endemic to the Hin Nam No region. On the Vietnamese side, seven species including two bent-toed geckos (Cyrtodactylus phongnhakebangensis and C. roesleri), three skinks (Lygosoma boehmei, Sphenomorphus tetradactylus and Tropidophorus noggei), and two snakes (Hebius andreae and Boiga bourreti) are currently only known from Phong Nha - Ke Bang and adjacent regions. These high numbers of potential endemic species together with the cryptic species complex in Cyrtodactylus provide strong evidence that the karst formations in the northern Truong Son Range represent a hot spot of reptile diversity and of speciation in Crytodactylus in particular. Correct species identification is a fundamental requirement for conservation measures. The discovery of cryptic species complexes poses a challenge for alpha taxonomy and species conservation, because the true distribution ranges of the species are in fact much smaller than previously assumed. Species conservation in this area of Laos is facing a number of further problems. New and potentially endemic species were discovered in highly populated and disturbed areas. Conversion of the Ho Chi Minh Trail into a highway provided easy access for farmers and still continues to accelerate the destruction of remote forest areas. Southern Hin Nam No with its high diversity of endemic species was identified as the first priority area for conservation. Also Ban Soc, an area isolated from Hin Nam No, should be among the conservation priorities because this region houses a so far overlooked population of the critically endangered Siamese crocodile. Efforts to establish a legal conservation status for this habitat are in progress.

Can the intermediate disturbance hypothesis and information on species traits predict anuran responses to fire?

Fire is a common form of recurrent disturbance in many ecosystems, but ecological theory has a poor record of predicting animal responses to fire, at both species and assemblage levels. As a consequence, there is limited information to guide fire regime management for biodiversity conservation. We investigated a key research gap in the fire ecology literature; that is, the response of an anuran assemblage to variation in the fire return interval. We tested two hypotheses using a spatially-explicit fire database collected over a 40 year period: 1) species richness would peak at intermediate levels of disturbance. 2) Species with traits which enabled them to escape fire - burrowing or canopy dwelling - would be better able to survive fires, resulting in higher levels of occurrence in frequently burned sites. We found no evidence for either a reduction in species richness at locations with short fire return intervals, or a peak in species richness at intermediate levels of disturbance. Although we found some support for individual species responses to fire return intervals, these were inconsistent with the interpretation of burrowing or climbing being functional traits for fire-avoidance. Instead burrowing and climbing species may be more likely to be disadvantaged by frequent fire than surface dwelling frogs. More generally, our results show that many species in our study system have persisted despite a range of fire frequencies, and therefore that active management of fire regimes for anuran persistence may be unnecessary. The responses of anurans to fire in this location are unlikely to be predictable using simple life-history traits. Future work should focus on understanding the mechanistic underpinnings of fire responses, by integrating information on animal behavior and species' ecological requirements.

Limited influence of stream networks on the terrestrial movements of three wetland-dependent frog species

Quantifying functional connectivity is essential for understanding factors that limit or promote animal dispersal in fragmented landscapes. Topography is a major factor influencing the movement behavior of many animal species, and therefore the extent of functional connectivity between habitat patches. For pond-breeding frogs, areas of low topographic relief (such as streams or drainage lines) offer damp microhabitats that can facilitate movement through otherwise dry landscapes. However, the extent of topographic bias of frog movements has rarely been quantified. We used a replicated study to compare captures in high- and low-relief transects, for three species from a pond-breeding frog community in southeastern Australia. We captured frogs significantly more often on low-relief transects. However, capture rates decreased with increasing distance from water at similar rates on both high-relief and low-relief transects, and we observed few differences between adult and juvenile movements. Our results suggest that although low-relief drainage lines are important for the pond-breeding frogs in question, ecologists and landscape managers should not discount the role of high-relief locations. Because low-relief drainage lines represent a low proportion of the pond margin, >90% of movements are likely to occur across high-relief locations. Therefore, for the species that we studied, buffer zones designed to conserve only hydrological networks would provide insufficient protection of frequently used pond margins, while drainage lines are unlikely to act as vital networks facilitating connectivity between breeding ponds. Our study suggests that movement across slopes may be most important for facilitating functional connectivity.