Jabis, Meredith, D , Ayers, Tina , Allan, Gery .
Pollinator-mediated gene flow fosters genetic variability in a narrow alpine endemic, Abronia alpina (Nyctaginaceae).
For rare endemic plants which exist in small isolated habitat fragments, natural selection is expected to favor self-compatibility, or at a minimum, a mixed breeding system due to potential pollinator limitation. In this paper we present the results of both a pollination experiment and a molecular genetic study to relate the reproductive system of Abronia alpina to its genetic variability and population structure using AFLP (Amplified Fragment Length Polymorphism). Using controlled hand-pollination and observation, we examined the breeding system, pollination ecology, and mechanism for self-incompatibility in Abronia alpina. This rare plant exhibits an allogamous mating system with probable self-incompatibility in the pollen tube. Only xenogamous crosses and open-pollinated controls produced fruit or seed, and only xenogamous crosses produced pollen tubes that reached the ovary. Seven primary insect pollinators in the Sphingidae, Hesperiidae, Papilionidae, and Bomyliidae were observed visiting the flowers during the morning and afternoon. To determine whether Abronia alpina has a limited gene pool, leaf samples were collected from 30 individuals from 10 sub-populations. Several patters emerge: first, A. alpina has substantial genetic diversity for a rare, endemic species. This is evidenced by high percentage of polymorphic loci, expected average heterozygosity, and gene diversity. Second, there is substantial gene flow between sub-populations documented using four separate analyses. Third, the Kern River is the most important physical barrier to gene flow, which is indicated by non-significant geographic by genetic distance and a significant regional AMOVA. Finally, no correlation was found between sub-population size and genetic diversity. High genetic diversity and low sub-population differentiation concur with an outcrossing mating system documented for this species. This study suggests that pollinators are crucial to the long-term adaptive potential of rare, endemic plants, and for true conservation of rare endemics these community-level interactions such as plant-pollinator mutualisms must be identified and protected.
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1 - Northern Arizona University , Department of Biological Sciences, PO Box 5640, Flagstaff, AZ , 86011, USA
2 - Northern Arizona University, Department of Biological Sciences, P.O. Box 5640, Flagstaff, Arizona, 86011-5640, USA
3 - Northern Arizona University, Biological Sciences Department and Environmental Genetics and Genomics Laboratory, PO Box 5640, Flagstaff, AZ, 86011, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood D/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 9:15 AM