Rapid Genetic Decline in a Translocated Population of the Endangered Plant Grevillea scapigera

:Grevillea scapigera is one of the world's rarest plant species, currently known from only five plants in the wild. In 1995, 10 plants were selected from the 47 plants known at the time to act as genetically representative founders for translocation into secure sites. Ramets were micropropagated and introduced into one of these secure sites (Corrigin) in 1996, 1997, and 1998. By late 1998, 266 plants had been successfully translocated and were producing large numbers of seeds. With the development of an artificial seed-germination technique and because of an absence of seed germination in situ, seed was collected from these plants and germinated ex situ, and 161 seedlings were returned to the field site in winter 1999. We used the DNA fingerprinting technique of amplified fragment-length polymorphism (AFLP) to (1) assess the genetic fidelity of the clones through the propagation process, (2) contrast genetic variation and average genetic similarities of the F1s to their parents to assess genetic decline, and (3) assign paternity to the reintroduced seeds to assess the reproductive success of each clone. We found that 8 clones, not 10, were present in the translocated population, 54% of all plants were a single clone, and the F1s were on average 22% more inbred and 20% less heterozygous than their parents, largely because 85% of all seeds were the product of only 4 clones. Ultimately, effective population size (  Ne ) of the founding population was approximately two. Our results highlight the difficulty of maintaining genetic fidelity through a large translocation program. More generally, rapid genetic decline may be a feature of many translocated populations when Ne is small, which may ultimately threaten their long-term survival. Strategies to reverse this genetic decline include equalizing founder numbers, adding new genotypes when discovered, optimizing genetic structure and plant density to promote multiple siring and reduce kinship, promoting natural seed germination in situ rather than artificially germinating seeds ex situ, and creating a metapopulation of numerous translocated populations to restore historical distribution patterns and processes. Resumen:Grevillea scapigera es una de las especies de plantas mas raras del mundo, conocida solo por cinco plantas silvestres. En 1995, 10 plantas fueron seleccionadas de las 47 que se sabia entonces eran fundadores geneticamente representativas para translocacion a sitios seguros. Se micropropagaron ramulas y fueron introducidas en uno de esos sitios seguros (Corrigin) en 1996, 1997 y 1998. A fines de 1998, se habian translocado con exito 266 plantas y estaban produciendo abundantes semillas. Con el desarrollo de una tecnica de germinacion artificial de semillas debido a la ausencia de germinacion in situ, se recolectaron semillas de estas plantas y semillas germinadas ex situ, y 116 plantulas fueron reintroducidas al sitio en el invierno de 1999. Utilizamos una tecnica de marcaje de ADN de longitud del fragmento polimorfismo amplificado (LFPA) para (1) evaluar la fidelidad genetica de los clones durante el proceso de propagacion, (2) contrastar la variacion genetica y las similitudes geneticas promedio de las F1 con sus progenitores para evaluar la declinacion genetica y (3) asignar paternidad a las semillas reintroducidas para evaluar el exito reproductivo de cada clon. Encontramos que 8 clones, no 10, estaban presentes en la poblacion translocada, 54% de todas las plantas eran de un solo clon, y las F1 tenian en promedio 22% mas de consaguinidad y 20% menos de heterocigosidad que sus progenitores, principalmente debido a que el 85% de las semillas eran producto de tan solo 4 clones. Finalmente, el tamano efectivo de la poblacion (  Ne ) fundadora era de aproximadamente dos. Nuestros resultados resaltan la dificultad de mantener fidelidad genetica por medio de un programa de translocacion. En general, la rapida declinacion genetica puede ser una caracteristica de muchas poblaciones translocadas cuando Ne es pequeno, lo que al final puede amenazar su supervivencia a largo plazo. Las estrategias para revertir esta declinacion genetica incluyen igualar el numero de fundadores, agregar nuevos genotipos cuando sean descubiertos, optimizar la estructura genetica y la densidad de plantas para promover reproduccion multiple y reducir la consaguinidad, promover la germinacion natural in situ en lugar de germinar semillas artificialmente ex situ y crear una metapoblacion de numerosas poblaciones translocadas para restaurar los procesos y patrones historicos de distribucion.