Biodiversity conservation is a worldwide concern and proper management of threatened species or communities depends on reliable and accurate data collection. Despite the broad utility of environmental DNA (eDNA) for conservation management and the necessity for appropriate biodiversity management in the tropics, eDNA-based research conducted in tropical regions so far comprises only a small proportion of the cumulative eDNA literature. To address the growing demand for rapid and reliable species and community level ecological data in tropical regions, we provide an aquatic eDNA-focused review of (1) challenges and considerations for sampling design and inference of eDNA data in the tropics, and (2) eDNA applications relevant to ecological research and biodiversity management in the tropics. We propose that the collaborative incorporation of eDNA sampling with conventional field surveys harbours the potential to revolutionize the effectiveness of biodiversity conservation management in tropical regions.

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1. Pressures on coastal ecosystems are increasing and aquatic species that are restricted to these habitats are facing the threat of extinction. However, the true extent of many threatened and rare aquatic species, especially elasmobranchs, remains unclear due to high levels of data deficiency and poor efficacy of traditional survey methods. Sawfishes (Pristidae), a family of shark-like rays, are among

Environmental DNA (eDNA) methods are increasingly applied in the marine environment to identify species and community structure. To establish widely applicable eDNA techniques for elasmobranchs, we used the Critically Endangered largetooth sawfish (Pristis pristis Linnaeus, 1758) as a model species for: (1) assessing eDNA particle size distribution; (2) assessing the efficiency of long-term preservation of water samples; and (3) comparing the efficiency and detection sensitivity of filtration and precipitation methods. Water samples (1 L) collected from a tank containing one largetooth sawfish specimen were sequentially filtered through five filter membranes of decreasing pore size (20, 10, 5, 1.2, and 0.45 μm). The proportion of sawfish eDNA retained within each size class was determined through quantitative real-time PCR (qPCR) using a species-specific TaqMan probe assay. A linear mixed-effects model (lme) showed that the 1.2 and 20 µm filters captured most of the eDNA particles present in the sampled water. Additionally, whole water samples (0.375 L) were preserved in Longmire's buffer, stored at tropical ambient temperatures (26.3°C ± 3.0 SD) and extracted at five time points: immediately, one, two, and three months after collection, as well as frozen and extracted three months later, to assess the preservation efficiency of Longmire's buffer via qPCR analysis. A linear mixed-effects model showed that samples maintained maximal eDNA yield for at least three months after collection at ambient storage. Lastly, when comparing the filtration and precipitation methods, filtration using 0.45 µm pore size was more sensitive to capture of largetooth sawfish eDNA than filtration with 20 µm filter or water precipitation. However, water precipitation was more efficient when accounting for volume of water processed. These results provide options for best capture and preservation of elasmobranch eDNA.

Environmental DNA (eDNA)‐based methods are increasingly used by government agencies to detect pests and threatened species, and for broader biodiversity monitoring. Given rapid technological advances and a growing number of commercial service providers, there is a need to standardize methods for quality assurance and to maintain confidence in eDNA‐based results. Here, we introduce two documents to provide best‐practice guidelines for Australian and New Zealand eDNA researchers and end‐users (available from https://sednasociety.com/publications): the Environmental DNA protocol development guide for biomonitoring provides minimum standard considerations for eDNA and environmental RNA projects across the complete workflow, from ethical considerations and experimental design to interpreting and communicating results. The Environmental DNA test validation guidelines outline key steps to be used in assay development and validation for species‐specific testing and metabarcoding. Both guidelines were developed as an initiative of the Australian Government Department of Agriculture, Fisheries and Forestry and led by the Southern eDNA Society in a collaborative process including multiple consultation rounds with eDNA experts, end‐users, and stakeholders to adapt the guidelines to Australian and New Zealand needs. The aim of these guidelines is not to be prescriptive, but to set minimum standards to support a consistent and best‐practice approach to eDNA testing. We anticipate that the guidelines will be reviewed and regularly updated as required. Our aspiration is that these best‐practice guidelines will ensure environmental managers are provided with robust scientific evidence to support decision‐making.

Toxoplasma gondii atypical type II genotype was diagnosed in a pet peach-faced lovebird (Agapornis roseicollis) based on histopathology, immunohistochemistry, and multilocus DNA typing. The bird presented with severe neurological signs, and hematology was suggestive of chronic granulomatous disease. Gross post-mortem examination revealed cerebral hemorrhage, splenomegaly, hepatitis, and thickening of the right ventricular free wall. Histologic sections of the most significant lesions in the brain revealed intralesional protozoan organisms associated with malacia, spongiform changes, and a mild histiocytic response, indicative of diffuse, non-suppurative encephalitis. Immunohistochemistry confirmed the causative organisms to be T. gondii. DNA isolated from the brain was used to confirm the presence of T. gondii DNA. Multilocus genotyping based on SAG1, altSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico markers demonstrated the presence of ToxoDB PCR-RFLP genotype #3 and B1 gene as atypical T. gondii type II. The atypical type II strain has been previously documented in Australian wildlife, indicating an environmental transmission route.

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