Hastings Natural History Reservation

17 Feb, 02 AM - 17 Feb, 09 AM

Introduction: We have learned in recent years that coevolution between plants and animals is a complex process with an important geographic element. This geographic complexity is likely to be particularly pronounced within the California Floristic Province. The steep environmental gradients and high levels of species richness within genera create tremendous geographic complexity in how species interact with each other. Although we know much about the process of coevolution at the local level (1-3), we know little about how coevolution progress as plants and animals diversify in species across complex landscapes. As we continue to fragment the landscapes of California, it is becoming increasingly important for us to understand how human activity affects this ongoing process of coevolution. We need to know how these networks of closely related plants and insects are shaped ? and are now being reshaped ? across landscapes. Interactions between species could differ across landscapes due to differences in network structure, and human disturbance could alter interaction networks by breaking important links between species in certain habitats. The proposed work will use a common herbaceous genus in California, Lithophragma (Saxifragaceae), and pollinating seed parasite moth genus, Greya (Prodoxidae), to evaluate how coevolving networks are organized at multiple geographical scales along the Coast Ranges. The pollination biology of a Lithophragma species has already been studied in detail in populations in Idaho, Washington, and Oregon (4, 5). These studies have revealed that Greya politella, a pollinating seed parasite, shows complex geographic patterns of interaction with Lithophragma parviflorum, varying from a mutualist to antagonist at different sites depending on the abundance or efficiencies of other pollinators present (3). This interaction with Greya becomes even more complex as additional Lithophragma species and Greya species are added, forming a complex network, and provides a unique opportunity to examine how these interaction networks are structured within habitats and across landscapes. I will focus on how interactions between the plants and moths differ among populations, how these differences have influenced floral trait evolution, and how populations are differentiated at the molecular level. My work will concentrate on two Lithophragma species that commonly occur together in California, but have very different floral shapes. Study System: I will use the network involving two Lithophragma species (L. heterophyllum and L. affine) and two Greya species (G. obscura and G. politella) occurring together in some regions and apart in others across the coastal ranges of CA. L. affine has an inferior, narrow ovary and franciscan stigma. In contrast, L. heterophyllum is phylogenetically distinct withing the context of the genus from L. affine and has a superior, wide ovary, and zambesi stigma (6). Greya politella is a pollinating seed parasite with a life cycle that is intimately timed with the phenology and development of Lithophragma. Developing larvae consume a fraction of the seeds in the maturing fruit. G. obscura may be a cheater by ovipositing into the side of the ovary of Lithophragma without pollinating (7). Study Objectives: With the network of interactions between Lithophragma and Greya along the California Coast Ranges, I will address the following objectives: 1. How do the interactions between Lithophragma spp. and Greya spp. differ among populations within the Coast Ranges of California? How do these interactions differ when two rather than one species of Lithophragma are present? 2. How have these differences shaped the evolution of floral traits within Lithophragma? Are floral traits of one Lithophragma altered by the presence of another Lithophragma? 3. How do these differences correspond to patterns of molecular divergence among these plant populations, and how can we use the combined ecological and molecular data to inform decisions about conservation of California oak woodlands? Methods: I compiled field collections of Lithophragma leaves, seeds, underground or aerial bulbils, and flowers in Spring 2002 from the Coast Ranges of California. Sites were selected that had either L. heterophyllum, L. affine, or both and include populations spanning from Mendocino National Forest in Mendocino county to Hastings Natural History Reserve in Monterey county. Additional sites will be located and collected from in Spring 2003. Objective #1: How do interactions between Lithophragma and Greya differ within and among populations? How are these interactions different in areas where the two species of Lithophragma occur together vs. separately? Detailed pollination studies will determine the selection pressures imposed by the two Greya on the two Lithophragma while they occur together and separately. In Spring 2003 I will conduct floral visitor observations in seven populations across central California to examine how pollinator suites differ among sites and between Lithophragma species. In Spring 2004 I will determine pollination efficiencies of G. politella and G. obscura in populations with one or two Lithophragma species in comparison to other pollinators at each site. I will then compare these measurements across sites and between the two Lithophragma species. Objective #2: How do interactions with Greya influence floral trait evolution? How do floral traits differ in areas where the Lithophragma species occur together vs. separated in space? I will collect additional flowers from field sites in Spring 2003. These collections will be combined with the Spring 2002 collections and morphological measurements will be made of traits that are likely to be affected by pollinator selection pressures. I will examine how floral traits are associated with interactions with Greya and how they differ in areas where one vs. two Lithophragma species occur. Greenhouse oviposition preference trials will examine the effects of floral traits on Greya behavior and how these behaviors contribute to selection pressures by Greya on Lithophragma. Objective #3: What is the correspondence of interaction structure to molecular divergence across landscapes? I will determine the fine scale genetic differentiation of Lithophragma across the California Coast Ranges using Amplified Fragment Length Polymorphisms (AFLPs). This molecular tool gives hundreds of informative markers to evaluate fine scale gene flow and population differentiation and has already been used successfully with Lithophragma populations from the Northwest U.S. Comparisons of genetic divergence among populations with respect to interactions with Greya would form a hypothesis as to how the interactions between Lithophragma and Greya have diversified across complex geographic landscapes and lineages. Significance: Studying how multispecific networks of interactions are structured across space and lineages will increase our understanding of the structure of coevolution and the organization of biodiverse landscapes. The California Floristic Province contains a high percentage of California?s endemics and California itself is a geologically complex area with demonstrated fine scale genetic differences among populations of plants and animals. Therefore, this area offers an unique opportunity to study the geographic and genetic structure of a network of interactions. If networks, not pairs of interactions influence evolutionary trajectories or the genetic structure of populations, then these must be our units of conservation, not individuals, groups, or genera. Works Cited: 1. J. N. Thompson, The coevolutionary process (University of Chicago Press, Chicago, Illinois, USA, 1994). 2. C. W. Benkman, American Naturalist 153, S75-S91 (1999). 3. J. N. Thompson, B. M. Cunningham, Nature 417, 735-738 (2002). 4. O. Pellmyr, J. N. Thompson, Oecologia 107, 595-604 (1996). 5. J. N. Thompson, O. Pellmyr, Ecology 73, 1780-1791 (1992). 6. R. L. Taylor, The Genus Lithophragma (Saxifragaceae), University of California Publications in Botany (University of California Press, Berkeley, 1965), vol. 37. 7. D. R. Davis, O. Pellmyr, J. N. Thompson, Biology and Systematics of Greya Busk and Tetragama, new genus (Lepidoptera: Prodoxidae), Smithsonian Contribution to Zoology (Smithsonian Institution Press, Washington, D.C., 1992), vol. 524.

Visit #1013 @Hastings Natural History Reservation

Approved

Under Project # 868 | Research

University of California Santa Cruz - Ecology and Evolutionary Biology

graduate_student - University of California, Santa Cruz

Reservation Members(s)

Katherine Horjus Feb 17, 2003 (1 days)

Reserve Resources(s) | Create Invoice

Day Use Only 1 Feb 17 (7 hours)