Differences in emergence and flowering in wild, re-introduced and translocated populations of an endangered terrestrial orchid and the influences of climate and orchid mycorrhizal abundance

Abstract

Re-introduction and translocation are conservation strategies often employed to circumvent declining wild orchid populations but their efficacy as conservation strategies is widely debated. The aim of this study was to investigate the long-term efficacy of re-introduction and translocation strategies for an endangered orchid as its climate changed. Vital rates of the wild, re-introduced and translocated populations of an endangered terrestrial orchid Caladenia amoena were compared from 2008 to 2019. Emergence and flowering declined at significantly faster rates in the translocated and re-introduced populations than in the wild population. Emergence and flowering declined as mean maximum temperatures rose, whereas flowering increased with rainfall. Both emergence and flowering were positively correlated with the length of the growing period, which decreased by >33% during the study. The relevant orchid mycorrhizal fungi (OMF) (Serendipita sp.) were more abundant in soil at the wild population than at the translocated or re-introduced populations. However, the limited soil sampling used to minimise disturbance may not have detected true fungal heterogeneity. This study suggests that translocation and re-introduction may not be effective long-term solutions for C. amoena. Reduction in above-ground growing period length was probably the over-riding influence in the decline of all populations. Greater OMF abundance in the soil may be the critical factor that renders the wild population more able to withstand the influences of climate change. Future research should consider methods to reduce the impacts of increased temperature and reduced rainfall on threatened orchid taxa.