Santa Cruz Island Reserve

13 Apr, 05 AM - 16 Apr, 05 AM

STATEMENT OF PROPOSED PURPOSE OF RESEARCH PROJECT Prepared: 28 March 2007 Purpose: as described in the complete research prospectus, the purpose of my visit to Santa Cruz Island this spring season (April 16-19, 2007) is to obtain herbarium sheets, tissue samples, and stem segments of Ceanothus megacarpus var. insularis and Ceanothus arboreus. In addition, I would like to set seed traps to capture seeds of Ceanothus megacarpus var. insularis. These materials will be used in my Ph.D. research on the diversification of the Cerastes group of Ceanothus, of which Ceanothus megacarpus var. insularis is a member. See the complete research description for more on the overall project. Field work ? Field work for the entire Ceanothus project will take place in California, Arizona, and Northern Mexico. At each field site I will prepare herbarium sheets for up to 10 individuals of each species encountered. These herbarium sheets will consist of small branch segments of each plant, in addition to a sample of branch wood obtained from dead branches, when available. On Santa Cruz Island I plant to collect within three populations of Ceanothus megacarpus var. insularis and one population of Ceanothus arboreus. These collections will consist of branch segments. Tissue samples for DNA extraction will be taken from these samples and stored on ice. I will also collect soil samples from each site (one pint volume) for nutrient analysis. I also plan to place cloth capture devices on fruiting branches of one or two plants of Ceanothus megacarpus var. insularis at two localities to trap seeds. The seed traps consist of brown nylon mesh bags that will be attached to fruiting branches using plastic zip-ties. This method allows capture of seeds from the explosively dehiscent capsules of Ceanothus. I plan to geo-reference each plant locality and would also like to mark the location of each trap using flags. I would like return at the end of the summer to collect seeds that have ripened. These seeds will be used for germination and greenhouse experiments that will be conducted for most species of Ceanothus, subgenus Cerastes as part of the overall project. Unused seeds can be returned for restoration work on Santa Cruz Island. Duplicates of herbarium sheets will be distributed to various herbaria, including Santa Cruz Island, at the end of my research project. Collections of root nodules, as described in the complete research prospectus (see below) will not be conducted during the Santa Cruz Island project. Locations of work? I would like to work in chaparral or forest habitats on Santa Cruz Island where Ceanothus occurs, at a maximum of four sites (three for Ceanothus megacarpus var. insularis and one for Ceanothus arboreus). I would like to collect at the following sites: a) Canada del Puerto, 1.5 km SW of Prisoners' Harbor. b) Christi Ranch, on south side of canyon immediately south of bunkhouse. c) Near the UC research station. d) Christie Pass Ridge (Ceanothus arboreus) These localities were obtained from the literature and have been confirmed based on visual inspection of herbarium sheets hosed at the California Academy of Sciences. Significance to conservation?The taxa that I would like to study (Ceanothus megacarpus var. insularis and Ceanothus arboreus) are virtually limited to the Channel Islands. This study will provide information on the origin and diversity of these narrowly endemic plants, and thus could prove useful in planning for habitat conservation, management of genetic diversity, and restoration. Schedule of work: Field work on Santa Cruz Island will take place between April 16 and 19, 2007. If seed traps are installed, I will return in early fall 2007 to retrieve the traps and collect seeds. Potential impacts: This field work is unlikely to impact the populations of plants, or their habitats, to a large degree. Branch and tissue samples are small, and are taken using clippers that are sanitized between populations using bleach. Soil samples are taken using a small trowel that is also sanitized between sites, thus minimizing transfer of soil-born pathogens. Seed traps are intended to capture around 100 seeds from each plant, which usually represents just a small fraction of the total reproductive output of the plants. The traps themselves are fairly benign and do not appear to adversely affect the plants based on limited field trials in Northern California. COMPLETE PROJECT PROSPECTUS: Origin and diversification of the genus Ceanothus (Rhamnaceae) Introduction ? Rapid bursts of speciation and adaptive evolution have played an important role in the diversification of flowering plants (Doyle & Donoghue 1993). Our understanding of both large and small scale angiosperm evolution depends critically on our ability to determine the mechanisms at work in such diversifications. I am specifically interested in understanding the phenomenon of adaptive radiation within plant lineages under mediterranean-climate regimes. Mediterranean-climate regions, defined by the alternation of hot, dry summers and cold, wet winters, occur in five widely separated locations outside the Mediterranean basin itself, including California, Southwestern Australia, central Chile, and the South African Cape. All mediterranean-climate regions are recognized as global hotspots of biological diversity (Meyers 2002). In each of these areas, a large proportion of botanic diversity originates from a small number of speciose lineages (Cowling 1996). In a few cases it has been possible to use calibrated molecular phylogenies to show that the age of onset for diversification of a given taxon roughly coincides with the hypothesized date for the advent of a mediterranean-climate regime (e.g., Richardson et al. 2001). However, the adaptive underpinnings of these radiations have not attracted as much attention. For my thesis research, I plan to use the woody plant genus Ceanothus (Rhamnaceae) which has a center of diversity in the mediterranean-climate region of California, to test hypotheses on the adaptive shifts and environmental influences at work during such a diversification. Research components ? My research plan for Ceanothus consists of three interrelated components. The first deals with the origin of the genus from within the family Rhamnaceae, the second with the evolution of symbiotic nitrogen fixation within the family, and the third with the dynamics of adaptive radiation within a single subgenus of Ceanothus. The first and second components are intended to provide context for the understanding of the third component, which is the focus of my research. 1) Origin of the genus Ceanothus and a phylogeny of the ziziphoids Rhamnaceae is a cosmopolitan family consisting of approximately 50 genera and around 900 species. The fossil record for the group may go back as far as 93 million years (Richardson et al. 2000a), which means that the broad distribution of the family may have been attained before the breakup of Gondwana (Richardson et al. 2000a, b). Within the Rhamnaceae, molecular phylogenetic results indicate a major split into several major lineages, the largest of which has been called the ?ziziphoid group,? a predominantly southern-hemisphere clade of plants that could be of Gondwanan origin. Within this clade, however, molecular phylogenetic results are ambiguous with respect to relationships among the major groups, including Ceanothus. The goal of this section of my research is to clarify relationships within the Ziziphoid clade of Rhamnaceae, including the placement of Ceanothus. This information may clarify the geographic origin of Ceanothus and the history of symbiotic nitrogen fixation within the family(see below), which will provide context for studies on the diversification of Ceanothus itself. 2) Co-evolution of Ceanothus with bacteria of the genus Frankia Most species of Ceanothus are symbiotic with nodulating, nitrogen-fixing bacteria of the genus Frankia (Jeong & Myrold 1999). Ten relatively closely related families of flowering plants (part of the ?core rosids?) have members that are symbiotic with nitrogen fixing bacteria, two with Rhizobium and eight with Frankia, which has led to the idea that a propensity for such symbiosis evolved only once near the base of this group of plants, with a subsequent history of diffuse co-evolution in which many lineages lost and sometimes re-gained the relationship (Clawson et al. 2004). Ceanothus-infective Frankia, none of which have been isolated in axenic culture, form a single clade in most molecular phylogenetic analyses (Swensen 1996). However, evidence for a co-evolutionary relationship between Frankia and Ceanothus is limited to the finding by Oakley et al. (2004) that on a large geographic scale, host plant species is the best although not the exclusive predictor of Frankia strain. Nevertheless, I think that the microbe-centric perspective of these studies (no more than eight species of Ceanothus were included in any study) has hindered their ability to discover patterns in the Frankia-Ceanothus relationship. The high rate of Frankia infection in Ceanothus, combined with the apparently obligate symbiotic lifestyle of the bacteria, indicates that there is some degree of dependence in the relationship, and thus the possibility for co-evolution. This idea is especially interesting in light of the poor, azonal substrates on which many species of Ceanothus grow (McMinn 1942), conditions which could be ameliorated by association with nitrogen-fixing bacteria. During the course of my field work, I plan to obtain root nodules from as many species of Ceanothus as possible, over a large portion of the range of this genus, with an emphasis on sites of co-occurrence. If time constraints allow me to pursue this avenue of research, perhaps with the help of undergraduate researchers, I would like to test the hypotheses that (1) species of Ceanothus specialized on nutrient-poor azonal substrates have a greater dependence on Frankia as indicated by nitrogen-isotope ratios in plant tissues (Amarger et al. 1979), and that (2) in cases of sympatry, Ceanothus host species is the best predictor of Frankia strain, which might indicate that a form of local, fine-scale specialization is occurring, akin to co-evolution. These two hypotheses bear directly on the overall focus of my thesis research, the dynamics of environmental influences and adaptive shifts during an adaptive radiation. It is possible that increasing dependence on nitrogen-fixing bacteria, as indicated by nitrogen-isotope ratios, has promoted adaptive shifts along edaphic gradients within multiple lineages of Ceanothus, and that local-scale specialization on Frankia strains helps multiple species of Ceanothus persist at a community scale, thus promoting the accumulation of ecologically similar taxa. 3) Diversification of Ceanothus, subgenus Cerastes, under a mediterranean-climate. The Genus Ceanothus contains 51 species of trees and shrubs distributed almost exclusively in western North America, with a center of diversity in California (Mason 1942). Morphological and bio-systematic studies have split Ceanothus into a pair of distinct subgenera, Cerastes and Euceanothus (McMinn 1942, Nobs 1963). Independent and simultaneous diversification within each of these deeply divergent lineages has been attributed to the recently derived (~5 mya) mediterranean-climate regime of California (Mason 1942), an idea that is supported by recent molecular phylogenetic studies (Jeong et al. 1997, Hardig et al. 2000). For my studies on the diversification of Ceanothus, I plan to concentrate on the subgenus Cerastes (22 species). This group is geographically localized in comparison to Euceanothus, with a center of diversity in the Coast Ranges of California, where the mediterranean-climate regime is most pronounced. In addition, species from subgenus Cerastes display a suite of morphological features that have been interpreted either as pre-adaptations for the mediterranean-climate, or novelties that arose in response to this climate (Ackerly 2004, Ackerly et al. 2006). In order to study adaptive trends and test hypotheses on diversification within Cerastes, I will probably need to obtain a better-resolved phylogenetic tree for the subgenus. As mentioned above, current gene-trees (nrDNA and matK) of Ceanothus contain broad species sampling, but are poorly resolved, containing few well-supported ancestor-descendant relationships, even near the tips of the tree (Hardig et al. 2000). In order to obtain more data on genetic relationships, I plan to sequence several single copy nuclear genes (e.g., NIA, LEAFY, WAXY, INO), one nuclear ribosomal gene (ETS), and at least two chloroplast genes (e.g., trnL-F) from multiple samples of each Cerastes OTU. The study by Hardig et al. (2000) also uncovered conflicting phylogenetic signals from nuclear and chloroplast genes, which could indicate either lineage sorting or introgression. By sequencing multiple genes from the chloroplast and nuclear genomes, I hope to overcome this potential difficulty, or learn more about the processes that have resulted in the incongruence. Recent studies on the evolutionary ecology of Ceanothus (Ackerly et al. 2006) using the data sets of Hardig et al. (2000) have suffered from an inability to determine the directionality of adaptive change in poorly resolved lineages. If I am able to better resolve genetic relationships within Cerastes, I will be able to make more sophisticated tests of hypotheses on adaptive trends and modes of diversification (see ?potential problems? for more discussion). In their studies on the evolutionary ecology of Ceanothus and other mediterranean-climate shrubs, David Ackerly and his colleagues (Ackerly 2004, Ackerly et al. 2006) have relied on a single variable, specific leaf area (SLA) as a proxy for water use efficiency and drought tolerance, traits that are probably under selection in plants living in arid environments. I intend to refine the adaptive perspective within Cerastes by collecting data on anatomical and physiological traits that are directly linked to water use efficiency and drought tolerance, including photosynthetic rate, xylem resistance to embolism, and wood density (reviewed in Ackerly et al. 2006). Analysis of nitrogen isotope ratios for different tissue types in addition to those obtained for the Frankia research may reveal contrasting strategies of nutrient use and storage. I also intend to survey the perennial plant community at each field site References Cited Ackerly, D.D. 2004. Adaptation, niche conservatism, and convergence: comparative studies of leaf evolution in the California chaparral. The American Naturalist 163: 654-671. Ackerly, D.D., Schwilk, D.W., & Webb, C.O. 2006. Niche evolution and adaptive radiation: testing the order of trait divergence. Ecology 87: S50-61. Amarger, N., Mariotti, A., Mariotti, F., Durr, J.C., Bourguignon, C., & Lagacherie, B. 1979. Estimate of symbiotic fixed nitrogen in field grown soybean using variations in 15N natural abundance. Plant and Soil 52: 269?280. Anderson, E. 1948. Hybridization of the habitat. Evolution 2: 1-9. Anderson, E. & Stebbins, G.L. 1954. Hybridization as an evolutionary stimulus. Evolution 8: 378-388. Axelrod, D.I. 1956. Mio-Pliocene floras from west-central Nevada. University of California Publications in Geological Sciences 33: 1-316. Cavender-Bares, J., Ackerly, D.D., Baum, D.A., & Bazzaz, F.A. 2004. Phylogenetic overdispersion in Floridian oak communities. The American Naturalist 163: 823-843. Cowling, R.M., Rundel, P.W., Lamont, B.B., Arroyo, M.K., & Arianoutsou, M. 1996. Plant diversity in mediterranean-climate regions. Trends in Evolution and Ecology 11: 362-366. Doyle, J.A., & Donoghue, M.J. 1993. Phylogenies and Angiosperm diversification. Paleobiology 19: 141-167 Ellstrand, N.H., & Schierenbeck, K.A. 2000. Hybridization as a stimulus for the evolution of invasiveness in plants? Proceedings of the National Academy of Sciences USA 97: 7043-7050. Hardig, T.M., Soltis, P.S., & Soltis, D.E. 2000. Diversification of the North American shrub genus Ceanothus (Rhamnaceae): conflicting phylogenies from nuclear ribosomal DNA and chloroplast DNA. American Journal of Botany 87: 108-123. Hardig, T.M., Soltis, P.S., Soltis, D.E., & Hudson, R.B. 2002. Morphological and molecular analysis of putative hybrid speciation in Ceanothus (Rhamnaceae). Systematic Botany 27: 734-746. Jeong, S.-C., Liston, A., & Myrold, D.D. 1997. Molecular phylogeny of the genus Ceanothus (Rhamnaceae) using rbcL and ndhF sequences. Theoretical and Applied Genetics 94: 852-857. Jeong, S-C., & Myrold, D.D. 1999. Genomic fingerprinting of Frankia microsymbionts from Ceanothus co-populations using repetitive sequences and polymerase chain reactions. Canadian Journal of Botany 77: 1220-1230. Mason, H.L. 1942. Distributional history and fossil record of Ceanothus. In Ceanothus Part III. Santa Barbara Botanic Garden, Santa Barbara, California. McMinn, H.E. 1942. A systematic study of the genus Ceanothus. In Ceanothus Part II. Santa Barbara Botanical Gardens, Santa Barbara, California, USA. Myers, N., Mittermeier, R.A., Mittermeier, C.G., da Fonseca, G.A.B, & Kent, J . 2000. Biodiversity hotspots for conservation priorities. Nature 403:853-858. Nobs, M.A. 1963. Experimental studies on species relationships in Ceanothus. Carnegie Institute of Washington. Washington, DC. Oakley, B., North, M., Franklin, J.F., Hedlund, B.P., & Staley, J.T. 2004. Diversity and distribution of Frankia strains symbiotic with Ceanothus in California. Applied and Environmental Microbiology 70: 6444-6452. Raven, P.H. & Axelrod, D.I. 1978. Origin and Relationships of the California Flora. University of California Press, Berkeley, CA. Ree, R.H., Moore, B.R., Webb, C.O., & Donoghue, M.J. 2005. A likelihood framework for inferring the evolution of geographic range on phylogenetic trees. Evolution 59: 2299-2311. Richardson, J,E., Weitz, F.M., Fay, M.F., Cronk, Q.C.B., Linder, H.P., Reeves, G., & Chase, M.W. 2001. Phylogenetic analysis of Phylica L. (Rhamnaceae) with an emphasis on island species: evidence from plastid trnL-F and nuclear internal transcribed spacer (ribosomal) DNA sequences. Taxon 50: 405-427. Richardson, J.E., Fay, M.F., Cronk, Q.B.C, Bowman, D., & Chase, M.W. 2000a. A phylogenetic analysis of Rhamnaceae using RBCL and trnL-F plastid DNA sequences. American Journal of Botany 87: 1309-1324. Richardson, J.E., Fay, M.F., Cronk, Q.C.B., & Chase, M.W. 2000b. A revision of the tribal classification of Rhamnaceae. Kew Bulletin 55: 311-340. Swensen, S.M. 1996. The evolution of actinorhizal symbioses: evidence for multiple origins of the symbiotic association. America Journal of Botany 83: 1503-1512. Sanderson, M.J., & Donoghue, M. 1994. Shifts in diversification rate with the origin of angiosperms. Science 264: 1590-1593.

Visit #12375 @Santa Cruz Island Reserve

Approved

Under Project # 7893 | Research

Diversification of Ceanothus

graduate_student - Duke University

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Dylan Burge Apr 13 - 16, 2007 (4 days)

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Dorm 1 Apr 13 - 16, 2007
Jeep 1 Apr 13 - 16, 2007