Review of the Amphibian Immune Response to Chytridiomycosis, and Future Directions

The fungal skin disease, chytridiomycosis (caused by Batrachochytrium dendrobatidis and B. salamandrivorans), has caused amphibian declines and extinctions globally since its emergence. Characterizing the host immune response to chytridiomycosis has been a focus of study with the aim of disease mitigation. However, many aspects of the innate and adaptive arms of this response are still poorly understood, likely due to the wide range of species' responses to infection. In this paper we provide an overview of expected immunological responses (with inference based on amphibian and mammalian immunology), together with a synthesis of current knowledge about these responses for the amphibian-chytridiomycosis system. We structure our review around four key immune stages: (1) the naïve immunocompetent state, (2) immune defenses that are always present (constitutive defenses), (3) mechanisms for recognition of a pathogen threat and innate immune defenses, and (4) adaptive immune responses. We also evaluate the current hot topics of immunosuppression and immunopathology in chytridiomycosis, and discuss their respective roles in pathogenesis. Our synthesis reveals that susceptibility to chytridiomycosis is likely to be multifactorial. Susceptible amphibians appear to have ineffective constitutive and innate defenses, and a late-stage response characterized by immunopathology and Bd-induced suppression of lymphocyte responses. Overall, we identify substantial gaps in current knowledge, particularly concerning the entire innate immune response (mechanisms of initial pathogen detection and possible immunoevasion by Bd, degree of activation and efficacy of the innate immune response, the unexpected absence of innate leukocyte infiltration, and the cause and role of late-stage immunopathology in pathogenesis). There are also gaps concerning most of the adaptive immune system (the relative importance of B and T cell responses for pathogen clearance, the capacity and extent of immunological memory, and specific mechanisms of pathogen-induced immunosuppression). Improving our capacity for amphibian immunological research will require selection of an appropriate Bd-susceptible model species, the development of taxon-specific affinity reagents and cell lines for functional assays, and the application of a suite of conventional and emerging immunological methods. Despite current knowledge gaps, immunological research remains a promising avenue for amphibian conservation management

Repeatability and reproducibility of Population Viability Analysis (PVA) and the implications for threatened species management

Conservation triage focuses on prioritizing species, populations or habitats based on urgency, biodiversity benefits, recovery potential as well as cost. Population Viability Analysis (PVA) is frequently used in population focused conservation prioritizations. The critical nature of many of these management decisions requires that PVA models are repeatable and reproducible to reliably rank species and/or populations quantitatively. This paper assessed the repeatability and reproducibility of a subset of previously published PVA models. We attempted to rerun baseline models from 90 publicly available PVA studies published between 2000-2012 using the two most common PVA modelling software programs, VORTEX and RAMAS-GIS. Forty percent (n = 36) failed, 50% (45) were both repeatable and reproducible, and 10% (9) had missing baseline models. Repeatability was not linked to taxa, IUCN category, PVA program version used, year published or the quality of publication outlet, suggesting that the problem is systemic within the discipline. Complete and systematic presentation of PVA parameters and results are needed to ensure that the scientific input into conservation planning is both robust and reliable, thereby increasing the chances of making decisions that are both beneficial and defensible. The implications for conservation triage may be far reaching if population viability models cannot be reproduced with confidence, thus undermining their intended value

Net Effects of Ecotourism on Threatened Species Survival.

Many threatened species rely on ecotourism for conservation funding, but simultaneously suffer direct ecological impacts from ecotourism. For a range of IUCN-Redlisted terrestrial and marine bird and mammal species worldwide, we use population viability analyses to calculate the net effects of ecotourism on expected time to extinction, in the presence of other anthropogenic threats such as poaching, primary industries and habitat loss. Species for which these calculations are currently possible, for one or more subpopulations, include: orangutan, hoolock gibbon, golden lion tamarin, cheetah, African wild dog, New Zealand sealion, great green macaw, Egyptian vulture, and African penguin. For some but not all of these species, tourism can extend expected survival time, i.e., benefits outweigh impacts. Precise outcomes depend strongly on population parameters and starting sizes, predation, and ecotourism scale and mechanisms. Tourism does not currently overcome other major conservation threats associated with natural resource extractive industries. Similar calculations for other threatened species are currently limited by lack of basic population data

Triage in Conservation

Ecosystems and their constituent species the world over face a barrage of ongoing, and often escalating, threats. Conservation efforts aim to reduce the impact of these threats to ensure that global biodiversity continues to provide essential ecosystem services. As is most often the case, these efforts to protect threatened species and their environments are constrained by limited resources. Conservation biologists have therefore had to increase the efficiency of their conservation practices to deliver the greatest benefit at the lowest cost. This requires decision making using the best available knowledge to prioritise actions. A concept that has received considerable attention in this area is that of conservation triage. This eBook brings together perspectives from researchers and conservation practitioners who share their views and results in an effort to extend the discussion on this topic. A number of the papers in this eBook tackle the philosophical elements of conservation triage, while others take a more directed practical approach providing examples from conservation practice globally

Connecting tiger (Panthera tigris) populations in Nepal: Identification of corridors among tiger‐bearing protected areas

Abstract Habitat fragmentation and isolation threaten the survival of several wide‐ranging species, such as tigers, through increased risk from diseases, disasters, climate change, and genetic depression. Identification of the habitat most likely to achieve connectivity among protected areas is vital for the long‐term persistence of tigers. We aimed to improve the mapping of potential transfrontier protected area corridors for tigers by connecting sites within the Terai Arc Landscape in Nepal and to those in India, highlighting targeted conservation actions needed along these corridors to maintain long‐term connectivity. We used least‐cost corridor modeling and circuit theory to identify potential corridors and bottlenecks in the study area. The landscape's resistance to tigers' movement was gathered from expert opinions to inform corridor modeling. We identified nine potential tiger corridors in the Terai Arc Landscape—Nepal that aligned strongly with the remaining intact habitats of the Siwalik landscape, which could facilitate tiger movement. Banke‐Bardia and Chitwan‐Parsa‐Valimiki complexes and Lagga‐Bhagga and Khata corridors were identified as high‐priority conservation cores and corridors. While our model exhibited congruence with most established corridors in the landscape, it has identified the need to enhance existing corridors to improve landscape connectivity. Several pinch points posing an increased risk to connectivity were identified. Most of these were located near the protected area boundaries and along the Nepal–India border. The Siwalik landscape holds the key to long‐term connectivity in the study area; however, immediate conservation attention is needed, particularly at pinch points, to secure this connectivity for tigers. Validation of identified corridors through empirical research and their conservation is a priority

Forest Conservation Policy Implementation Gaps: Consequences for the Management of Hollow-bearing Trees in Australia

Hollow-bearing trees in native forests and woodlands are significant habitat resources for many Australian fauna but habitat removal, commercial timber harvesting and urban development continue to threaten these ecosystems. Protection for these habitats and their species is purportedly provided for in legislation, policy, and strategic management plans. However, public debate and disagreement surrounding forest management has resulted in the disintegration of national plans as interpreted by states and territories as well as individual stakeholders, resulting in gaps in policy implementation. This paper presents a hierarchical review of the current legislation and policy mechanisms underpinning forest conservation in Australia, with specific attention paid to important habitat features such as hollow-bearing trees. Apart from federal and state legislation acknowledging the importance of hollow-bearing trees to biodiversity, sufficient mechanisms to halt the ongoing loss of this resource from Australian landscapes at the local level appear to be lacking. Hollow-bearing tree conservation strategies from 46 local councils in Victoria, New South Wales, Tasmania, and Queensland were reviewed. Very few (<5%) respondents from local councils across all states indicated that they have specific plans for the conservation and management of hollow-bearing trees, highlighting policy implementation gaps at the local level. Furthermore, apparent environmental management strategies and actions rank relatively low on local council priorities. Therefore, a stronger focus on conservation actions towards management of critical habitat features across the landscape supported by robust local, national, and international policy is needed

Big changes in backyard birds: An analysis of long-term changes in bird communities in Australia's most populous urban regions

Urban environments are increasingly acknowledged as a priority for biodiversity conservation. Birds in particular are capable of persisting, and sometimes thriving, in cities and towns globally. However, the process of urbanization results in the loss of many bird species due to the resulting changes in habitat conditions. Urban expansion and densification present a threat to both urban bird biodiversity and bird conservation more broadly. Australian urban areas, including suburban and peri-urban areas, currently support moderate bird species richness, but the rapidly changing urban landscape threatens these communities. Unfortunately, many bird species' population trends are not actively studied, resulting in a poor understanding of species persistence in urban environments. Here, we used bird survey data from long-running citizen science databases in a Bayesian List Length Analysis to determine changes in bird species prevalence (the probability of observing a species in a given survey event) over time in Australia's four most populous urban regions. We found that introduced species, historically prominent in Australian urban bird communities, are decreasing in prevalence in all four regions, while a small group of native urban exploiters are becoming more prevalent. Our results also show that many species perceived to be “iconic” or “common” are experiencing declines in prevalence in urban areas, highlighting the importance of monitoring and conservation action in urban areas