Active Management of Exceptional Species is Needed to Maintain Robust Ex situ Collections

Zoe Diaz-Martin, Chicago Botanic Garden

Are botanic gardens effectively managing populations of exceptional plant species held across collections? Do garden collections represent the amount of genetic diversity that characterizes the in situ population? We explore these questions in the rare palm Attalea crassispatha, an exceptional species endemic to Haiti with fewer than 50 individuals found in the wild. We used next-generation sequencing data to genotype all known living individuals and compared levels of genetic diversity and inbreeding between ex situ and in situ populations. In addition, we assigned parents to wild born, ex situ founders as well as captive born ex situ individuals. We found that genetic diversity is lowest in captive born individuals, intermediate in wild born ex situ founders, and highest in the in situ individuals. Similarly, inbreeding is highest in captive born individuals, intermediate in wild born ex situ founders, and lowest in the in situ individuals. Furthermore, we assigned four of the fourteen in situ individuals as parents to the wild born ex situ and found that many founders are the result of inbreeding in the wild. Finally, we identified eight of the fifteen captive born individuals as potential hybrids that are genetically distinct. These results demonstrate that passive management of exceptional species does not ensure that ex situ populations remain genetically robust. We suggest that additional collections of in situ individuals are needed to ensure that the diversity found in the in situ population is represented in garden collections. It is also likely that hand pollination of in situ individuals is required to ensure outcrossing. We also encourage the development of pollen storage and hand pollination of inflorescences across gardens. These results show important steps for improving the management of exceptional species found across garden collections.