12835 – Hybridization in an isolated population: an example from Penstemon (Scrophulariaceae)

Investigator’s Annual Reports (IAR’s) for Crater Lake National Park

Hybridization in an isolated population: an example from Penstemon (Scrophulariaceae)


Report Number: 12835

Reporting Year: 1998

Permit Number: CRLA199802-002

Date Received: Jan 01, 1999

Principal Investigator: Shannon Datwyler, Department of Evolution, Ecology and Organismic Biology, Ohio State University, Columbus, OH

Park-assigned Study Id. #: CRLA199802-002

Permit Expiration Date: Jan 01, 2000

Permit Start Date: Jan 01, 1998

Study Starting Date: Jan 01, 1997

Study Ending Date: Jan 01, 1999

Study Status: Completed

Activity Type: Research

Subject/Discipline: Plant Communities (Vegetation)

Objectives: To investigate the patterns and frequency of natural hybridization between Penstemon rupicola and Penstemon davidsonii var. davidsonii on Wizard Island, Crater Lake National Park, with special focus on the potential for hybrid speciation in an isolated habitat.

Findings and Status: Currently, I am investigating the gene flow patterns observed in three different hybrid swarms on Wizard Island based on both morphological and molecular data. Preliminary results indicate a unidirectional pattern of gene flow from P. rupicola into P. davidsonii based on sampling from the 1997 field collections. In the 1998 field season I increased sampling of hybrid swarms to add two new populations (total of three populations for both 1997 and 1998 field seasons).

Leaf tissue was collected from a total of 68 hybrid plants representing two hybrid swarms on the island in addition to 12 individuals of P. rupicola and 24 individuals of P. davidsonii. In addition to sampling on the island, five populations (12 individuals per population, 60 total individuals) were sampled at various points around the western portion of the rim of the lake in order to examine population structure of these populations and to subsample the genetic variation existing around the rim. For each population sampled, voucher specimens were collected that will be deposited at Ohio State University. ;Pollinator observations were also made and several insect pollinators were collected for identification.

Two Bombus species were collected after being observed visiting Penstemon flowers and three leafcutter bees (Megachilidae) were also collected. In addition to these pollinators, hummingbirds and syrphid flies were observed to visit Penstemon flowers but were not collected. ;In addition to investigations of gene flow patterns in hybrid swarms, I have initiated a study to develop molecular markers that can be used to study gene flow distances within populations using microsatellite markers in paternity analysis of seeds. Seed capsules were collected from 60 individual plants representing two hybrid swarms (20 capsules from one population, 40 from the other). Currently, these seeds are being germinated and will be used for DNA extractions following germination. The pollen donor for each seed will then be determined by paternity analysis to calculate gene flow distances within and between populations. Preliminary pollinator observations suggest that bumblebees may facilitate pollen flow over long distances because of long flights between flower visits, whereas hummingbirds were observed to travel very short distances between floral visits, such as visiting the nearest neighbor plant.

These observations suggest that pollen flow would be limited in populations that are visited largely by hummingbirds and may be greater in populations visited largely by bumblebees. These predictions can be tested with the paternity study. ;The final year of investigation (1999) will be focused on augmenting the pollinator observations collected in 1998 as well as elucidating the underlying factors related to the pattern of unidirectional gene flow that I have observed, including experiments testing pollen tube growth rates in interspecific crosses.

For this study, were one or more specimens collected and removed from the park but not destroyed during analyses? Yes

Funding provided this reporting year by NPS: 0

Funding provided this reporting year by other sources: 1500

Full name of college or university: n/a

Annual funding provided by NPS to university or college this reporting year: 0


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