Helmeted Honeyeater Lichenostomus Melanops Cassidix Research Articles

Benefits of genetic rescue of a critically endangered subspecies from another subspecies outweigh risks: Results of captive breeding trials

Small, isolated populations risk extinction through inbreeding depression, chance loss of beneficial variation, and reduced adaptability to changing environments. Genetic rescue via gene flow from genetically diverse sources is the most effective way to improve fitness of such populations. However, when the only potential source of immigrants is a different subspecies that diverged long ago and occupies a different environment, genetic rescue may lead to reduced fitness of admixed offspring through outbreeding depression or maladaptation. Test cases are needed to evaluate how to manage such potentially risky rescues to deliver enhanced population fitness. The helmeted honeyeater Lichenostomus melanops cassidix is a critically endangered subspecies of the yellow-tufted honeyeater. The sole remaining natural wild population experiences strong inbreeding depression for lifetime reproductive fitness. Captive genetic rescue trials are underway using a neighbouring subspecies, gippslandicus, which diverged from cassidix thousands of years ago and differs in morphology, mobility and preferred habitat. We evaluated short-term reproductive fitness for captive cassidix-cassidix pairs, first- and second-generation intersubspecific crosses and backcrosses to cassidix, while accounting for breeding season, sex, age at breeding, and wild/captive origin of each bird. Most admixed pair-types more readily engaged in breeding, raised more nestlings per nest, and had less male-biased chick sex-ratios than did cassidix-cassidix pairs, with negligible evidence of outbreeding depression. Continuing monitoring of fitness after releases into the wild is recommended, to ensure local adaptation is retained. With potentially riskier rescue increasingly becoming the only option for many populations, our study provides an encouraging test case.

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 ofthe 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 ofinbreeding depression as a factor influencing the immediate viability of populations in threatened species management.

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.

Use of spider silk for nest building by the Regent HoneyeaterAnthochaera phrygiaand the Helmeted HoneyeaterLichenostomus melanops cassidix

The Regent Honeyeater Anthochaera phrygia and Helmeted Honeyeater Lichenostomus melanops cassidix have both suffered a dramatic decline in number and reduction in range as a result of extensive habitat clearance. As part of recovery plans aimed toward reintroduction to the wild, both species are part of an intensive captive breeding program being conducted at a number of institutions, including Taronga Zoo, Sydney. These honeyeaters incorporate arthropod silk into their nests, as has been reported for other small passerines. However, little is known about how birds choose and use the silk that they collect during nest building. We presented breeding pairs with cribellate silk from the Black House Spider Badumna sp. and ecribellate silk from the Golden Orb-weaver Nephila plumipes or ‘clean/fresh’ and ‘dirty/old’ Badumna sp. silk and observed which were taken by the birds. Lichenostomus melanops cassidix showed a preference for the cribellate silk of Badumna sp., always selecting this silk type first. Never...

Annual cycle of the Helmeted Honeyeater Lichenostomus melanops cassidix, a sedentary inhabitant of a predictable environment

The annual cycle of breeding, moult and weight variation in the Helmeted HoneyeaterLichenostomus melanops cassidix, a sedentary bird of temperate southeast Australia, is documented. Breeding and moult were sequential unimodal annual events, whose timing was highly consistent between years. However, overlap of breeding and moult was frequent, and some individuals even commenced primary moult before laying their final clutch. The timing of the post‐juvenile moult was coincident with that of adults. Early‐hatched young moulted within a few months of hatching, but late‐hatched young deferred moult for a year. Helmeted Honeyeaters were heaviest in autumn and early winter, and lightest in spring and early summer, a cycle most consistent with the redirection of all available resources to reproduction. The long breeding season (seven‐and‐a‐half months) of the Helmeted Honeyeater, extensive overlap of breeding and moult, and other life‐history attributes including small clutch size, are more consistent with the described bio‐rhythmic patterns for birds in the humid tropics than the temperate zone. However, the Helmeted Honeyeater has a fairly rapid primary moult rate, unusual amongst species that overlap moult and breeding. This combination of attributes reflects the stable, somewhat seasonal environment occupied and the resource monopoly established by this tightly territorial subspecies. We speculate that extension of the breeding season, by overlapping breeding and moult, is one of the few options available to vary life‐history strategies amongst ‘old‐endemic’ Australian birds of the temperate zone.

A study of Resource Partitioning Within the Helmeted Honeyeater Lichenostomus melanops cassidix During the Non-breeding Season

SummaryIntraspecific variation in resource partitioning was evaluated in the Helmeted Honeyeater Lichenostomus melanops cassidix according to age, sex and breeding status during the 1994 non-breeding season. The home ranges of males and females within a breeding pair were highly overlapping, of similar size (males: X = 0.32 ± 0.07 ha; females: X = 0.26 ± 0.04 ha) and did not differ significantly in vegetational composition. Breeding adults and their juvenile off-spring also had similar-sized, highly overlapping home ranges. For one juvenile the degree of overlap decreased markedly as the bird matured. Non-breeding adults tended to occupy different vegetation communities to those inhabited by breeding adults. Male breeding adults spent significantly more time in the canopy stratum than females, who were observed more frequently in the lower strata. Both juveniles and non-breeding adults spent less time in the canopy than breeding adults. Analysis of activity budgets did not reveal specialised foraging behaviour according to height in the vegetation, or seasonal change from autumn to winter. Male and female Helmeted Honeyeaters showed similar levels of aggression when present in the canopy region. The distribution of manna points was random at Green site, but occurred in areas with little tea-tree understorey at Mauve site.

Linking landscape data with population viability analysis: management options for the helmeted honeyeater Lichenostomus melanops cassidix: H. R. Akcakaya, M. A. McCarthy & J. L. Pearce, Biological Conservation, 73(2), 1995, pp 169–176

Linking landscape data with population viability analysis: management options for the helmeted honeyeater Lichenostomus melanops cassidix: H. R. Akcakaya, M. A. McCarthy & J. L. Pearce, Biological Conservation, 73(2), 1995, pp 169–176

Linking landscape data with population viability analysis: Management options for the helmeted honeyeater Lichenostomus melanops cassidix

Habitats used by most species are becoming increasingly fragmented, requiring a metapopulation modelling approach to population viability analysis (PVA). Recognising habitat patchiness from an endangered species' point of view requires utilisation of spatial information on habitat suitability. Both of these requirements may be met by linking metapopulation modelling with landscape data using GIS technology. We present a PVA model that links spatial data directly to a metapopulation model for extinction risk assessment, viability analysis, reserve design and wildlife management. The use of the model is demonstrated by an application to the spatial dynamics of the helmeted honeyeater Lichenostomus melanops cassidix, an endangered bird species endemic to Victoria, Australia. We use spatial data, organised by a GIS, on the habitat requirements of the helmeted honeyeater to define the patch structure. We then combine this patch structure with demographic data to build a metapopulation model, and use the model to analyse the effectiveness of translocations as a conservation strategy for the helmeted honeyeater.

Linking landscape data with population viability analysis: management options for the helmeted honeyeater Lichenostomus melanops cassidix

Linking landscape data with population viability analysis: management options for the helmeted honeyeater Lichenostomus melanops cassidix

The importance of demographic uncertainty: An example from the helmeted honeyeater Lichenostomus melanops cassidix

Models that account for aspects of the behaviour and ecology of helmeted honeyeaters Lichenostomus melanops cassidix are developed. These highlight the importance of demographic uncertainty in population viability analysis. Differences between and relationships among individuals are important components of population dynamics. Adding individual detail to demographic models can change estimates of extinction risk. Demographic uncertainty can cause greater variation in population size than indicated by standard modelling procedures. Accurate prediction of this level of variation is limited by ignorance of population dynamics. Implications for metapopulation dynamics and reserve design are discussed. The helmeted honeyeater population faces an appreciable risk of decline from demographic uncertainty alone.

Decline and extinction of the helmeted honeyeater at Cardinia Creek

Until recently the helmeted honeyeater Lichenostomus melanops cassidix was known from only two areas near the Dandenongs in Victoria. This paper records the probable extinction of populations in one of those areas, the Cardinia Creek system, and chronicles the gradual decline of the taxon in that area during this century. Some information on the ecology of birds in the colony is presented. It is suggested that the decline and extinction has resulted from changes in the drainage pattern of the creek which have affected susceptibility of Eucalyptus trees to attacks by psyllids. This has led in turn to expansion of range in another aggressive colonial species, the bell miner Manorina melanophrys, at the expense of the helmeted honeyeater.