Kenneth S. Norris Rancho Marino Reserve

16 Mar, 06 AM - 16 Mar, 10 AM

Geographic variation in the life histories of plant and animal taxa is widespread. Often, parthenogenetic forms are more common as one moves towards the poles, in environments that are characterized as being more extreme. The explanations are usually based on correlative evidence because the species studied cannot easily manipulated in experiments. The rhodophyte seaweed, Mastocarpus papillatus, occurs in the marine rocky intertidal zone from Baja, California to Alaska. It exhibits geographic parthenogenesis in which asexual individuals predominate in the northern part of its range (north of San Francisco) and sexual individuals predominate in the southern part of its range (south of San Francisco). Mastocarpus papillatus provides a model organism for experimentally testing alternative hypotheses that explain geographic parthenogenetic patterns. There are several alternative hypotheses for the trend of decreasing sexuality with increasing latitude, including historic accidents associated with geologic changes like glaciation and post-glacial sealevel changes, differences in dispersal or migration of organisms which require mates and those which don?t and differential selection on nonreproductive characteristics. This research program has two main objectives. The first addresses potential biological limitations to the maintenance of sexual populations at northerly latitudes. We will establish the pattern of reproductive effort and its undelying causes in sexual and asexual life cycle variants with respect to latitude. To carry out this objective, we will test whether or not sporulation, productivity, growth and survivorship of adults of sexual M. papillatus is less successful in the north. We will sample individuals along the California coast and at different tidal heights. The second objective uses molecular methods to examine biogeographic history of sexual and asexual variants of M. papillatus. We seek to identify genetic markers to distinguish life cycle variants and establish whether asexuality appeared several times, dispersal barriers in recent geological history affected migration, and if local populations are indeed genetically divergent. Overall, this research will determine what factors cause geographic variation in the life history traits of one common intertidal organism on Pacific seashores and will test evolutionary theories about the role of biogeographic history and environmental interactions in maintaining both asexual and sexual patterns of reproduction in a single species. Our research program is aimed at studying latitudinal variation in the life history of this red seaweed. We plan on working at several sites in central and northern California. Our need to work at the Rancho Marino Reserve is driven by the critical geographic location of the Reserve in the range of M. papillatus along the California coast and the need to have experimental field sites in the central coast region to which the public does not have access and cannot impact our experiments. There are very few places along the coast south of San Francisco that provide suitable places for marine ecologists to conduct field experiments that cannot be impacted by the general public. The Norris Reserve is one such location. Moreover, this region of the coast south of San Francisco appears critical in the pattern of life history variation of the species. South of San Francisco females of M. papillatus exhibit a mix of mostly sexual, bu some asexual, life histories whereas north of it females exhibit asexual life histories. The Norris reserve appears to have a very abundant Mastocarpus population, especially the crustose sporophyte phase and may be a source of sexual life history variants in the region. Moreover, despite being on the central coast, it is among the more southerly abundant populations of Mastocarpus, which is virtually non-existant between Pt. Conception and Baja, Mexico. Mastocarpus was very common in the mid-intertidal zone where I initiated a transect line on the 3rd point down from the N end of the reserve. The mid to mid-high rocky intertidal zone at these Reserve sites is where we anticipate working. The Mastocarpus papillatus population will be the only taxon affected directly. There may be minor indirect effects on the other flora and invertebrates of the mid intertidal zone inhabited by Mastocarpus. Our impact is expected to be minimal as we will only collect 30 in situ cross sections of the crustose tetrasporophyte and 9 encrusted rocks. We will also collect a small to moderate number of individuals per visit for laboratory and culture and genetic analyses. We expect to sample less than 50 fronds of the species per visit. As for resources that we would need during a visit, we will likely require housing.

Visit #12261 @Kenneth S. Norris Rancho Marino Reserve

Approved

Under Project # 1301 | Research

Geographic Parthenogenesis in the genus Mastocarpus

faculty - California State University (CSU), Northridge

Reservation Members(s)

Steve Dudgeon Mar 16, 2007 (1 days)
Group of 2 Volunteer Mar 16, 2007 (1 days)

Reserve Resources(s) | Create Invoice

Day Use Only 3 Mar 16 (4 hours)