Scope for genetic rescue of an endangered subspecies though re-establishing natural gene flow with another subspecies.

Genetic diversity is positively linked to the viability and evolutionary potential of species but is often compromised in threatened taxa. Genetic rescue by gene flow from a more diverse or differentiated source population of the same species can be an effective strategy for alleviating inbreeding depression and boosting evolutionary potential. The helmeted honeyeater Lichenostomus melanops cassidix is a critically endangered subspecies of the common yellow-tufted honeyeater. Cassidix has declined to a single wild population of ~130 birds, despite being subject to intensive population management over recent decades. We assessed changes in microsatellite diversity in cassidix over the last four decades and used population viability analysis to explore whether genetic rescue through hybridization with the neighbouring Lichenostomus melanops gippslandicus subspecies constitutes a viable conservation strategy. The contemporary cassidix population is characterized by low genetic diversity and effective population size (N(e) < 50), suggesting it is vulnerable to inbreeding depression and will have limited capacity to evolve to changing environments. We find that gene flow from gippslandicus to cassidix has declined substantially relative to pre-1990 levels and argue that natural levels of gene flow between the two subspecies should be restored. Allowing gene flow (~4 migrants per generation) from gippslandicus into cassidix (i.e. genetic rescue), in combination with continued annual release of captive-bred cassidix (i.e. demographic rescue), should lead to positive demographic and genetic outcomes. Although we consider the risk of outbreeding depression to be low, we recommend that genetic rescue be managed within the context of the captive breeding programme, with monitoring of outcomes.

Per- and Polyfluoroalkyl Substances in Ducks and the Relationship with Concentrations in Water, Sediment, and Soil.

The present study examined the occurrence and concentration of per- and polyfluoroalkyl substances (PFAS) measured in game ducks (13 compounds), water, sediment, and soils (33 compounds) in waterways in Victoria, Australia. The study aimed to identify potential ecological and human health risks from measured PFAS concentrations. Four species of duck and samples of water, sediment, and soil were collected from 19 wetlands, which were chosen based on their popularity as hunting locations. The risks posed by 3 PFAS (perfluorooctanoic acid, perfluorohexane sulfonic acid [PFHxS], and perfluorooctane sulfonic acid [PFOS]) to the environment and human health were assessed using available national ecological and human health guidelines. A diverse range of short- and long-chain carboxylic and sulfonic acids were found in the environment and in ducks. Concentrations were generally low and varied between wetlands, duck species, tissue analyzed (breast or liver), and environmental compartment (water, sediment, soil). Higher PFOS concentrations in water and sediments were observed at wetlands near sources of contamination (i.e., a defense base or urban environment). Elevated PFOS and PFOS + PFHxS concentrations in ducks were observed near local point sources but also at wetlands with no known point sources of contamination. There were clear differences in PFAS concentrations detected in duck tissues versus the environment, highlighting complexities of bioaccumulation, movement of animals, and spatiotemporal variation and raising questions about the relevance of using abiotic criteria to assess risk to biota. Human health risk assessment showed that only ducks inhabiting wetlands near local sources of PFAS were likely to pose a risk to consumers. Further studies are required to improve our knowledge of PFAS toxicokinetics and chronic impacts in biota to guide management decisions. Environ Toxicol Chem 2021;40:846-858. © 2020 SETAC.

Lifetime Fitness Costs of Inbreeding and Being Inbred in a Critically Endangered Bird.

Reduced fitness as a result of inbreeding is a major threat facing many species of conservation concern [1-4]. However, few case studies for assessing the magnitude of inbreeding depression in the wild means that its relative importance as a risk factor for population persistence remains under-appreciated [5]. The increasing availability and affordability of genomic technologies provide new opportunities to address knowledge gaps around the magnitude and manifestation of inbreeding depression in wild populations [6-12]. Here, we combine over three decades of individual lifetime reproductive data and genomic data to estimate the relative lifetime and short-term fitness costs of both being inbred and engaging in inbreeding in the last wild population (<250 individuals remaining) of an iconic and critically endangered bird: the helmeted honeyeater Lichenostomus melanops cassidix. The magnitude of inbreeding depression was substantial: the mean predicted lifetime reproductive success of the most inbred (homozygosity = 0.82) individuals was on average 87%-90% lower than that of the least inbred (homozygosity = 0.75). For individual reproductive events and lifetime measures, we provide rare empirical evidence that pairing with a genetically dissimilar individual can reduce fitness costs associated with being an inbred individual. By comparing lifetime and short-term fitness measures, we demonstrate how short-term measures of reproductive success that are associated with only weak signatures of inbreeding depression can still underlie stronger lifetime effects. Our study represents a valuable case study, highlighting the critical importance of inbreeding depression as a factor influencing the immediate viability of populations in threatened species management.

The immune response and fertility of koalas (Phascolarctos cinereus) immunised with porcine zonae pellucidae or recombinant brushtail possum ZP3 protein.

To evaluate the potential contraceptive effect of immunisation with zona pellucida antigens, 50 free-ranging koalas were immunised with either porcine zonae pellucidae (PZP), recombinant brushtail possum ZP3 (recBP-ZP3) or buffer, in complete Freund's adjuvant. A single booster immunisation in incomplete Freund's adjuvant was administered 3-5 months later. Where possible animals were recaptured, reproductive status was assessed and blood was collected at 1-3-month intervals for the next 33 months. Forty-three koalas were recaptured at least three times allowing reliable assessments of their fertility. Fourteen animals were observed never to have a pouch young. Of the remaining 29 animals the reproductive productivity of PZP treated females was reduced compared with control and recBP-ZP3 treated females, in terms of both total number of young produced, and failure to produce further young in females of proven fertility. One month after the initial immunisation, serum antigen-specific antibody titres were higher in animals immunised with PZP or recBP-ZP3 compared to controls, and reached a plateau by 4 months. Antibody against the relevant immunising antigen was also detected in ovarian follicular fluid, uterine fluid and vaginal secretions. Epitope analysis suggested that immune responses other than antibodies directed against the ZP3 amino acid sequence were responsible for mediating infertility. The results demonstrate that the fertility of female koalas can be compromised by immunisation against zona pellucida antigens. However, unlike in the eastern grey kangaroo and the brushtail possum, immunisation with bacterial recombinant brushtail possum ZP3 did not compromise fertility in the koala.

Accounting for management costs in sensitivity analyses of matrix population models.

Traditional sensitivity and elasticity analyses of matrix population models have been used to inform management decisions, but they ignore the economic costs of manipulating vital rates. For example, the growth rate of a population is often most sensitive to changes in adult survival rate, but this does not mean that increasing that rate is the best option for managing the population because it may be much more expensive than other options. To explore how managers should optimize their manipulation of vital rates, we incorporated the cost of changing those rates into matrix population models. We derived analytic expressions for locations in parameter space where managers should shift between management of fecundity and survival, for the balance between fecundity and survival management at those boundaries, and for the allocation of management resources to sustain that optimal balance. For simple matrices, the optimal budget allocation can often be expressed as simple functions of vital rates and the relative costs of changing them. We applied our method to management of the Helmeted Honeyeater (Lichenostomus melanops cassidix; an endangered Australian bird) and the koala (Phascolarctos cinereus) as examples. Our method showed that cost-efficient management of the Helmeted Honeyeater should focus on increasing fecundity via nest protection, whereas optimal koala management should focus on manipulating both fecundity and survival simultaneously. These findings are contrary to the cost-negligent recommendations of elasticity analysis, which would suggest focusing on managing survival in both cases. A further investigation of Helmeted Honeyeater management options, based on an individual-based model incorporating density dependence, spatial structure, and environmental stochasticity, confirmed that fecundity management was the most cost-effective strategy. Our results demonstrate that decisions that ignore economic factors will reduce management efficiency.