Bodega Marine Laboratory/Reserve February 26-28, 2010

Participant Abstracts

The intra- and interspecific impact of evolutionary-feedback in the wild: An experimental assessment
Martin M. Turcotte
Department of Evolution, Ecology, and Organismal Biology
University of California, Riverside

Rapid evolution, occurring within a dozen generations or less, is now commonly observed in nature. Yet, most ecological studies assume that evolution is too slow to impact short-term ecological dynamics. Recent theoretical models and a few laboratory studies, however, have shown that rapid evolution can feedback to impact concurrent population dynamics (Ecological-Evolutionary Feedback). This remains to be experimentally tested in the wild. Using a natural aphid (Myzus persicae) and mustard (Hirschfeldia incana) system, I tested the following hypotheses/predictions: (1) if evolution can influence ecological dynamics, then evolving populations will increase in population size at a faster rate than non-evolving controls, (2) if aphid evolution has interspecific feedback, then plants harboring evolving aphids will suffer greater damage, and (3) if Ecological-Evolutionary Feedback depends on the rate of evolution, then populations with more genetic variation will differ from their controls to a greater extent. These hypotheses were tested by manipulating the amount of genetic variation in intrinsic growth rate within replicated populations at the Motte Rimrock reserve. This created treatments that differ in the occurrence and rate of evolution (changes in clonal frequencies). As expected, populations with more genetic variation evolved faster. Aphids were counted twice a week, and evolving populations grew at a faster rate than appropriate non-evolving control populations. Moreover, I observed that the rate of rapid evolution was positively correlated with its impact on population dynamics. These results have important implications for applied studies of population dynamics, such as pest management.

Examination of a highly variable plumage trait in the sexually dichromatic American kestrel (Falco sparverius)
Elizabeth A. Wommack
Department of Integrative Biology and the Museum of Vertebrate Zoology
University of California, Berkeley

The American Kestrel (Falco sparverius) is the only kestrel within the New World and is arguably the most sexually dichromatic falcon in coloration. Male kestrels display distinct plumage coloration from females starting in their first year and will continue to do so throughout their lives. In addition to these dichromatic plumage traits, male American Kestrels also show a high degree of variability in individual coloration for certain color patterns, particularly in the patterning on their tail. The high degree of variability found in the plumage traits of male kestrels has often been considered a detriment in attempts to understand the mechanisms generating these dichromatic colors. Previous work has focused on traits that are found to be consistent in color and have ignored variable plumage colorations. However, this approach has led to little understanding on why certain traits are maintained or allowed to vary within the species. This study aims to examine the presence of variation in these unique plumage characteristics at an individual level, by testing the use of highly variable patterns in the tail of male American Kestrels during the breeding season. Three basic behavioral hypotheses will be tested at nest box sites in Northern California. The hypotheses to be examined are: (i) intersexual selection, where females show preference for one tail pattern over another; (ii) status signaling, in which the trait is used as a signal in competition between individuals; and (iii) individual recognition, where the pattern aids in the correct identification of specific individuals.

Effects of nitrogen enrichment on the functioning of microbial communities in California
Irina C. Irvine
Department of Ecology and Evolutionary Biology
University of California, Irvine

Salt marsh ecosystems are sensitive to the effects of eutrophication. To examine the relationship between nitrogen (N) enrichment, microbial composition, and ecosystem functioning, I established a gradient of N addition treatments in three southern California salt marshes that differ in their sedimentary N levels [Carpenteria Salt Marsh Reserve (CSM), Morro Bay Estuary (MBE) and Tijuana River Estuary (TRE)]. In July 2008, I began adding slow-release urea to 35 plots (seven levels with five replicates) in each of the three marshes. In February 2009, I measured a variety of plant, microbial, and nutrient variables. I assayed changes in ecosystem functioning in terms of gas fluxes and carbon mineralization. At 7 months, the methane and carbon dioxide emissions, carbon mineralization (CO2), sedimentary ammonium and C:N, plant biomass and C:N, methanotroph abundance, ammonification and nitrification rates exhibit linear responses to N-addition. Importantly, I found striking differences in the responses to N addition between marshes. In CSM, NH4 appears to be accumulating. CSM has slower N process rates, suggesting that CSM is not cycling N as quickly as either TRE or MBE, which appears to cycle the fastest. The salt marsh ecosystem service of taking up nitrogen (minus N leaching) may be diminished at CSM. I also observed significant differences in carbon mineralization among plots, suggesting that plot-scale differences in substrates and/or microbial composition affect this process rate. In the future, this experimental gradient will assist in making quantitative predictions of how salt marshes will respond under future nutrient scenarios.

Investigating tree mortality at multiple spatial and temporal scales in the Bishop pine forest on Santa Cruz Island, California
Sara Baguskas
Department of Geography
University of California, Santa Barbara

The rate of tree mortality has increased across the western United States in recent decades, and many studies attribute the cause to water-stress induced by regional warming. To date, the geographical scope of study regions affected by widespread tree mortality in the American West has largely been limited to continental, montane climates. Much less is known about mortality events in other climatic regions, such as coastal forests. The relatively unvarying nature of the coastal, maritime climate has traditionally been assumed to buffer these forests from large climate variations; however, we have observed rapid tree mortality in this region, which suggests coastal forests may be as susceptible to drought-induced mortality as inland forest locations. Santa Cruz Island (SCI), one of the California Channel Islands, harbors numerous relict and endemic plant species, including Bishop pine (Pinus muricata). Following extreme drought in southern California in two of the last three years, widespread mortality of Bishop pines on Santa Cruz Island (SCI) has become evident. Bishop pine populations are restricted to the fog-belt of coastal California and northern Baja California; therefore, a major reduction of existing populations on SCI would greatly reduce the distribution of the species as a whole. Because this population is at a range boundary, determining controls mortality and range dynamics for this species should be more easily elucidated. The focus of my research is to investigate the spatial and temporal patterns of Bishop pine mortality on SCI and to identify the key biotic and abiotic factors that best explain the mortality event.

Non-chemical restoration techniques in California sage scrub: Testing variations of agricultural solarization adapted for use in wildlands
Kristin A. Weathers
Department of Botany and Plant Sciences
University of California, Riverside

Exotic propagules often greatly outnumber native seeds in the soil seed bank of invaded plant communities. This makes restoration very difficult, often requiring multiple years of invasive species management to establish native species. Solarization, a technique used in agriculture, places clear plastic over moist soil during the summer. This heats the soil as high as 55o C, killing weed seed. Two studies used variations of the method successfully in a wildland setting. One study used irrigation and clear plastic during the summer, while another applied black plastic during the winter with no irrigation. Our goal was to compare the success of plastic color (black, clear, and no plastic), season of application (winter and summer) and level of soil disturbance (tilling, scraping, and no disturbance) in reducing exotic weed seeds in the seed bank. Plots were not irrigated. Preliminary results show that clear plastic placed in the summer controlled the most species. Black plastic winter treatment did not control exotic broadleaf species as well as clear plastic. The study shows that combinations of winter and summer solarization with black and/or clear plastic provide a range of techniques for managers who need an alternative non-chemical invasive control method in invaded plant communities.

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