Overcoming extreme weather challenges: Successful but variable assisted colonization of wild orchids in southwestern China

Abstract

Assisted colonization of endangered species to locations outside their native ranges in response to projected climate change has emerged as a potential, but highly controversial conservation tool. The debate has been largely philosophical and hypothetical as little biological data exist in the literature. In 2006, nearly 1000 endangered wild orchid plants belonging to 29 species were translocated to higher elevations in subtropical southwestern China in response to inundation threats from a hydropower project. We took advantage of this upward translocation to address one of the main biological concerns associated with assisted colonization, i.e. whether the target endangered species can survive in the novel environment that is projected to be suitable for them, sometime in the future. We assessed the impacts of two extreme weather events, translocation shock and herbivory, on survival of 20 of these species and 462 individuals that were translocated beyond their current range vs. within that range. A cold spell in 2008 on average caused 10% mortality, less than the mortality rate from herbivores. However, the cold spell was the only force that extirpated an out-of-range population. No mortality resulted from a drought event in 2010. The 5-year survival percentages were not different between low and wide elevation species (69.3% mean±36.3% standard deviation vs. 67.3%±30.9%). Orchids represent 10% of flowering plant diversity and are among the most endangered group of organisms due to a combination of their often specialized ecological requirements, habitat destruction, and overexploitation. The demonstrated ability to survive extreme environmental challenges indicates that assisted colonization may be a viable conservation tool for the many endangered orchids worldwide due to climate change and/or other reasons.