Data from: 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 (Ne < 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.

遗传多样性（genetic diversity）与物种的生存力及进化潜力呈正相关，但受胁类群（threatened taxa）的遗传多样性往往会受损。通过同一物种内更多样化或分化程度更高的源种群间的基因流（gene flow）开展遗传拯救（genetic rescue），可有效缓解近交衰退（inbreeding depression）并提升进化潜力。盔吸蜜鸟（helmeted honeyeater, Lichenostomus melanops cassidix）是普通黄簇吸蜜鸟（common yellow-tufted honeyeater, Lichenostomus melanops）的极危亚种。尽管近数十年来已实施高强度种群管理，但该亚种目前仅存一个野生种群，个体数量约130只。本研究评估了近四十年来该亚种的微卫星多样性（microsatellite diversity）变化，并通过种群生存力分析（population viability analysis），探讨了通过与邻近亚种吉普斯兰黄簇吸蜜鸟（Lichenostomus melanops gippslandicus）杂交开展遗传拯救是否为可行的保护策略。当前的该亚种种群遗传多样性较低，有效种群大小（effective population size, Ne < 50），表明其易受近交衰退影响，且应对环境变化的进化能力有限。研究发现，相较于1990年前的水平，吉普斯兰黄簇吸蜜鸟向盔吸蜜鸟的基因流已大幅下降，因此我们认为应恢复两个亚种间的自然基因流水平。允许吉普斯兰黄簇吸蜜鸟向盔吸蜜鸟的基因流（约每代4个迁移个体）——即遗传拯救——结合持续每年放归人工繁育的盔吸蜜鸟——即种群拯救（demographic rescue）——应能带来积极的种群及遗传效应。尽管我们认为远交衰退（outbreeding depression）的风险较低，但仍建议在人工繁育计划框架内开展遗传拯救，并对拯救结果进行监测。