Document ID: chunk:federal_register_of_legislation:F2024L00006:reg:3:p27
Version: federal_register_of_legislation:F2024L00006
Segment Type: reg
Provision Reference: reg 3 (pt 27/58)
Character Range: 77294–80507

to support classification of the northern population as a subspecies. Both the northern and southern populations were less genetically diverse then the central population, consistent
 with their smaller population sizes (Weeks et al. 2016). Using a limited dataset of six microsatellites, Roberts et al. (2011) found broad-scale genetic subdivision by region. They cautioned against mixing genetics across regions to preserve genetic
 integrity of the local populations. However, it has been suggested that this study was underpowered and management recommendations were not based on gene flow between units and time of divergence (P. Sunnucks pers. comm. cited in NESP 2018). Both these factors highly affect the likely response of a population to genetic rescue. The genetic distinctiveness of the northern population is likely due to random genetic drift following historically recent fragmentation and small population size, rather than a reflection of longer-term evolutionary adaptation (Sunnucks 2013). Because of this, it is unlikely that cross-breeding between the phylogenetically similar southern and northern populations would cause outbreeding depression.

 More recently, a genetic assessment of Eastern Bristlebirds from Howe Flat, Victoria (southern population, 15 samples), compared with samples from the northern captive population (15 samples), Budderoo National Park (central population, 24 samples),

           and Nadgee NR (southern population, five samples) revealed lower allelic richness and heterozygosity in the Howe Flat birds than those from the northern captive population and central population (Cesar 2020). Cesar (2020) concluded that the distinct northern and southern populations have low genetic diversity, most likely as a result of contemporary and/or past small population sizes.

           Genetic rescue is the term given to conservation efforts that aim to restore adaptive potential of small, isolated, genetically depauperate populations that are showing signs of inbreeding depression through the introduction of novel genetic material (Weeks et al. 2011). Due to concerns regarding accumulating inbreeding and infertility, genetic rescue has been recommended for the northern population of the eastern bristlebird (NESP 2018). This population is likely to become extinct unless serious consideration is given to its genetic management (Stone 2018b) as there is evidence of inbreeding depression in both the wild and captive birds (D Charley & A Beutel pers. comms. cited in NESP 2018).

           The potential benefits of assisted gene flow for northern bristlebirds may be high, particularly if undertaken at low levels to minimise any concerns over loss of local adaptations (NESP 2018). These actions must co-occur with on-ground habitat management actions (intensive fire management, extensive weed and feral animal control, sustainable stock grazing and habitat protection) to be effective. Genetic samples of wild Eastern Bristlebirds across their entire range have been collected to inform selective breeding.

           Additional genetic sampling and analysis will help inform future recovery management actions. Genetic methods using higher resolution