Optimising conservation translocations of threatened Caladenia (Orchidaceae) by identifying adult microsite and germination niche.

Context. Conservation translocations are increasingly being used in the management of rare plants, yet have low success in maintaining populations through recruitment. Aims. We investigated whether the survival of translocated plants, recruitment and, therefore, cost effectiveness, can be improved by selecting optimal microsites for both adults and seedlings. Methods. Caladenia colorata plants propagated symbiotically with Serendipita australiana (n = 735) were introduced to four sites where the pollinator was present and vegetation matched wild populations. Plant demography was monitored over 6 years. The relationship between microsite variables and measures of orchid survival, re-emergence, flowering and recruitment were analysed with generalised linear mixed-effects models. We then estimated potential improvement in emergence and recruitment, if microsite selection was optimised. Key results. A total of 77% of plants survived translocation, and populations grew by 84% through recruitment (n = 615). Survival was positively associated with cover of leaf litter, graminoids and cryptogams. Recruitment was positively correlated with soil moisture. The majority of recruitment was within 5 cm of adult C. colorata plants. The potential improvement by selecting favourable microsites increased adult survival by up to 8% and recruitment by 10-40%. Conclusions. Incorporating both the germination niche and adult plant niche within plant translocations more broadly could significantly improve long-term population persistence and the utilisation of conservation funding. Implications. Our results are directly applicable to 58 endangered Caladenia species in the subgenus Calonema, owing to their shared mycorrhizal association with S. australiana. Furthermore, our results are applicable to all plant translocations as understanding germination niche and microhabitat requirements is likely to improve success overall. [ABSTRACT FROM AUTHOR]