Advisors: Dr. Jenny Xiang, Dr. Jon Stucky

Species delimitation is an important issue in systematics and evolution, and is vital to conservation of biodiversity. Gonolobus suberosus (Apocynaceae - Asclepiadoideae), a climbing milkweed endemic to the southeastern US, is a state listed threatened species in Florida. Delimitation of the species has long confronted taxonomists and has been additionally complicated by nomenclatural confusion (see Small 1933; Perry 1938; Fernald 1950; Gleason 1952; Radford et al. 1968; Drapalik 1969; Rosatti 1989; Reveal & Barrie 1992). Prior to 1969, two species were recognized in the genus Gonolobus (see Small 1933). Since 1969 (Drapalik 1969), only a single species, G. suberosus, has been recognized. However, our recent, detailed morphological examination provided evidence of two distinct groups corresponding to geographic subdivisions within the complex (Krings & Xiang, in prep.). In the present study, we conduct phylogeographic analysis using the highly variable AFLP genetic markers to test the morphology based hypothesis. Specific questions to be addressed in the study include: (1) How is the genetic variation distributed geographically? (2) Is the pattern of genetic variation correlated with the pattern of morphological variation? (3) How many distinct evolutionary lineages within the complex merit conservation? 4) Are there additional evolutionary entities that are not recognizable based on morphology alone and would thus be missed in a conservation plan designed solely on morphological considerations?

Analysis of AFLPs (Amplified Fragment Length Polymorphisms) allows the generation of a large number of DNA markers. The analysis involves first the digestion of DNA using two different restriction enzymes. Specific oligonucleotide adapters, complementary to the restriction sites, are subsequently ligated to the resulting DNA fragments. The fragments are then used as the templates for PCR using primers specific to the adapters. The PCR-amplified DNA fragments are separated on a denaturing polyacrylamide gel on a LI-COR automated sequencer and are scored using the AFLP Quantar software. The analysis generates multi-locus genotypic data for comparison across samples and permits the survey of numerous DNA loci across the entire nuclear genome by using multiple PCR primers to allow the detections of genetic variation between closely related individuals.

References

Drapalik, D.J. 1969. A biosystematic study of the genus Matelea in the southeastern United States. Ph.D. Dissertation, University of North Carolina, Chapel Hill.

Fernald, M.L. 1950. Gray's Manual of Botany. American Book Company, Boston.

Gleason, H.A. 1952. The new Britton and Brown illustrated flora of the northeastern United States and adjacent Canada. New York Botanical Garden, New York.

Krings, A. and Q.-Y. Xiang. In prep. The Gonolobus complex (Apocynaceae: Asclepiadoideae) in the southeastern United States.

Perry, M.L. 1938. Gonolobus within the Gray's Manual range. Rhodora 40:281-287.

Radford, A.E., H.E. Ahles, and C.R. Bell. 1968. Manual of the vascular flora of the Carolinas. University of North Carolina Press, Chapel Hill.

Reveal, J.L. and F.R. Barrie. 1992. Matelea suberosa (L.) Shinners (Asclepiadaceae) – once again. Bartonia 57:36-38.

Rosatti, T.J. 1989. The genera of suborder Apocynineae (Apocynaceae and Asclepiadaceae) in the southeastern United States. J. Arnold Arbor.70:443-514.

Small, J.K. 1933. Manual of the southeastern flora. University of North Carolina Press, Chapel Hill.