Specific niche requirements drive long-term survival and growth of translocated epiphytic orchids in an urbanised tropical landscape

Abstract

Urbanisation is expanding at an unprecedented rate, affecting multiple taxa the world over. Ex situ conservation practices in urban areas (e.g. managed relocation) can help mitigate species extinction. However, systematic evaluations of ex situ practices and quantification of niche spaces, especially in urban areas, are largely lacking. Using epiphytic orchids as a study system, we translocated 13 propagated native species (2251 individuals) on 99 host trees across six urban sites. After 5 years, 12 of 13 species showed survival rates above 50% and 9 of 11 species exhibited positive growth. Generalised linear mixed models revealed that species and presence of humus corresponded to orchid survival, whereas the fork microsite and height from ground corresponded to orchid growth. Species-wise, the biophysical factors that were associated with survival and growth varied widely, with 7 of 11 species showing distinct interactions with more than one factor. Notably, the presence of humus and relative humidity influenced the survival of 4 of 11 species. This study suggests that managed relocation can serve as a viable conservation strategy for native orchids and possibly other epiphytes as well. We propose that species-specific niche requirements are identified and integrated into intervention actions.