Landels-Hill Big Creek Reserve

13 Apr, 07 AM - 13 Apr, 11 AM

I will be looking for Lupinus bicolor sites on this trip. Here is my full research project description: With less than 25% of the original California Floristic Provence (CAFP) vegetative habitat left intact, restoration is a necessary supplement to conservation (website). The remnant areas of undisturbed habitat are shrinking quickly, and with this habitat loss comes reduced population numbers, and, in many cases, extinction (Fahrig 1997, Rannap et al. 2007). The most effective way to counteract the effects habitat reductions have wrought on our ecosystems is to restore previously altered habitats, thus reestablishing a healthy ecosystem large enough to stabilize itself and buffer the effects of disturbance and invasion (Bakker 2004, Blomqvist et al. 2003, Fahrig 1997). The overall goal of this study is to better understand how to successfully restore a degraded site with a population that has the best chance at long-term survival. Specifically, I will compare the genetic variance and fitness of seed collected from a local population with that of seed collected regionally, to determine whether it is more effective to restore habitats with local seed or regional seed. The overall goal of this study will be met by achieving the following objectives: Objective 1: To determine whether there is an increase of variation due to the breakdown of canalization or gene by environment interactions in a new restoration population. Objective 2: To examine fitness differences between locally collected and regionally collected seed populations. Objective 3: To determine whether there is a greater increase in variation for a population when moved to a foreign restoration site than for one planted in a neighboring restoration site. B. Study System I will use Lupinus bicolor as my study organism. Nitrogen fixing plants are commonly used in habitat restoration. Not only do these plants stabilize the soil and provide shelter for other establishing seedlings, they also facilitate the growth of other natives by increasing the availability of nitrogen in the soil (Huss-Danell and Lundmark 1988). In California, L. bicolor is a popular addition to restoration seed mixes, as it is widespread throughout the CAFP and easy to collect (Boyer 2005, Schultz 2001, Ward 2007). L. bicolor is also ideal for this study because, since it is a selfing plant, there is less chance for genetic contamination from nearby populations (Karloy, 1994). In transplant studies, there is a chance for foreign pollen to fertilize individuals from a thriving native population, thus resulting in maladaptation or outbreeding depression (Barbour et al. 2006, Roberts et al. 2007), but with a primarily selfing species this risk is negligible, as pollen transfer does not often occur between plants. C. Rationale I will focus on the genetic diversity of L. bicolor, as high genetic diversity prevents bottlenecking, and allows the new population to adapt quickly to its environment (Davis and Shaw 2001, Fischer et al. 2003, Storfer, 1999). The rate of adaptation is especially important in restoration attempts, because disturbed habitats are inherently different from even the closest pristine site. Even if the abiotic environment of the source seed resembles, on a large scale, the environment of the restoration site, the disturbance itself could alter the environment enough that establishment of a population will require rapid adaptation. For example, a site that has been bulldozed may have the same rainfall, air temperature, and soil composition as a nearby source seed area, but the disturbed location will have less water availability due to increased runoff, greater soil temperature variation due to lack of overstory buffering, and increased soil compaction. The restoration population will need sufficient genetic diversity to adapt quickly to these environmental differences. The source of this genetic variation has generally been sought in the seeds used for restoration (Ramp et al. 2006). Studies have been conducted detailing the deleterious effects of collecting from populations with limited genetic variation, or from a small population (Broadhurst and Young 2006, Tomimatsu and Ohara 2003). Now ecologists go to great lengths to ensure the seeds they collect cover a large range of genotypes, so that when this seed is sewn in the restoration site, the new population will not suffer the consequences of low genetic diversity. There is, however, another way to achieve a large amount of variation in a population. If individuals are introduced to a new environment that is quite different from the environment in which they evolved, the total phenotypic variation of that population will increase (Eshel and Matessi 1998, Hermission and Wagner 2004, Waddington 1959). Phenotypic variation is comprised of both a genetic and an environmental component. When a population is introduced into an extremely different environment, the total phenotypic variation increases, but the environmental component of this variation remains relatively constant. The increase in phenotypic variation is largely due to an increase in the genetic component of variation, which remained hidden until a large enough change (either a large mutation or change in environment) causes the concealed genetic variation to be expressed. An increase in expressed genotypic variation means a larger amount of phenotypic variation for selection to work on, resulting in a higher rate of adaptation (Fischer et al. 2003). There are two mechanisms by which genetic variation can be concealed: canalization and gene by environment interactions. Canalization is a buffering mechanism that keeps phenotypes within narrow boundaries, even in the presence of high genetic diversity. Organisms, in general, are capable of much more phenotypic variation than that which is actually exhibited. Canalization reduces this potential variability into the more or less uniform phenotypes we see in the natural environment. This mechanism inhibits or constrains the potential trait expression so that individuals are kept similar enough (anatomically, behaviorally, and physiologically) to have viable offspring (Waddington 1942). Canalization breaks down, however, in novel environments, allowing the population to express more genotypic variation, and thus fueling adaptation (Eshel and Matessi 1998, Kimbrell and Holt 2007, Waddington 1959). Recently, Hermission and Wagner (2004) pointed out a second mechanism by which genetic variation might increase in expression in a novel environment. If there is epistasis or a gene by environment interaction, then, when placed in a new location, mutations that had been neutral will come to light. New environmental pressures will reorder the importance of the loci contributing to a trait, so loci that had been neutral might become visible to selection. Hypothesis 1: Moving L. bicolor to a restoration site removes the environmental stimuli that upheld canalization and kept certain alleles neutral. The increase of expressed genetic diversity that results from the disruption of these mechanisms has been documented over a wide range of species, including both plants and animals (Eshel and Matessi 1998, Hastle et al. 2003, Hermission and Wagner 2004, Kimbrell and Holt 2007, Okamuro et al. 1993, Rathcke and Lacey 1985, Waddington 1942, Waddington 1959). Because this phenomenon is so widespread, I hypothesize that I will see an increase in phenotypic variance, caused primarily by and increase in the genetic component of variance, when I move a population of L. bicolor from the pristine site of the parental generation to a restoration area. The results of investigating this hypothesis will prove interesting whether it is supported or not. If it is supported, I will look for patterns of the breakdown of canalization based on home and away populations, but, if it is not supported, I will use polymorphic microsatelites to look at the genetic variation of the populations. If there is no visible breakdown of canalization, it might be indicative of very little genetic variation in the population. This could be due to the selfing nature of these plants, as plants with low outcrossing rates tend to have lower genetic variation than plants with a high rate of outcrossing (Schoen 1982). This would be an important finding, because a species with low genetic diversity would be slow to adapt to a new environment, such as a restoration site, making L. bicolor a less than ideal candidate for a common restoration species. In this case, I would compare fitness between sites, because a population with low genetic diversity and low fitness would not be able to increase its fitness through quick adaptation to the restoration site. In addition to the importance of genetic diversity, the location of the source seed has also been explored by restorationists. Some large scale projects need large quantities of seeds, and use commercially distributed seed, arguing that the source seed location is less important than the quantity of seed distributed. Most operations, however, contend that source seed location is exceedingly important. Plant species adapt to their native microclimates (McKay et al. 2001), and this adaptation can lead to a reduction in fitness if these species are planted in foreign habitats. Lower germination rates, lower establishment rates, and the breakdown of beneficial plant animal or plant microbial interaction are all possible consequences of reintroducing individuals in foreign locations (Keller and Kollman 1999, Keller et al. 1999, Thrall 2005). Initially research was conducted looking at the distance between the source seed and the transplant sites, but, more recently, habitat matching has been discussed as an important component of source seed collection. The basic concept looking only at spatial components predicts that the greater the geographic distance between the source seed habitat and the restoration habitat, the less well adapted those seeds will be to the restoration habitat (Keller et al. 2000, Waser and Price 1985, Waser and Price 1989). The habitat matching model adds to this, stating that the distance from the source seed population is less important, while the environmental components of the source seed habitat are paramount. Plants located far away from the transplant site that have adapted to a similar set of microclimatic conditions will be able to thrive more easily than plants in nearby populations experiencing disparate environmental conditions. O?Brien et al. (2007), for instance, found that it was most important to restore areas with Eucalyptus marginata source seed from populations of a similar rainfall zone. Hypothesis 2: I hypothesize that there will not be a significant decrease in fitness between locally collected populations and regionally collected populations, because I will conform to the habitat matching model. To be consistent with the theory of habitat matching, I will use three coastal sites for this project: Bodega Marine Reserve, A?o Nuevo State Reserve, and Big Creek Reserve. L. bicolor grows throughout California, but to try and reduce the decrease in fitness due to different habitat types, this research will include only coastal populations. While the need for genetic variation and habitat matching in source seed have been studied extensively, these two concepts have not been synthesized. In this study I will merge these two concepts to better evaluate where source seed should be collected. I will compare populations from different areas planted in a single restoration site to see how the genetic variation of the populations changes based on the distance of the source seed populations to the restoration site. Hypothesis 3: While I expect that the similarity in these habitats will keep fitness from decreasing significantly, this overall habitat matching may not prevent canalization breakdown, because the cues for development are very specific (Steingraeber et al. 2007). I predict that seed samples from distant source sites will exhibit a greater breakdown in canalization and a greater shift in the gene by environmental interaction than seed samples from local source sites. This will lead to an increased genetic variation, and thus, an advantage in adaptation rate. Although it is generally assumed that collecting source seed from an adjacent area with a similar environment is advantageous, because the population is preadapted to that area, this study may provide a case for the distribution of regional seed mixes, as they might provide a faster rate of adaptation to the degraded habitat. If hypothesis 2 is not supported, however, and there is a significant decrease in fitness, then seeds for restoration should be collected from a nearby site regardless of the increase of variation that may ensue, because low fitness will slow down the colonization of the population. A large decrease in fitness would override the importance of an increase in genetic diversity, because even if the population had the ability to adapt quickly, if the fitness of that population is below a critical level it might not be able to establish, and will be more susceptible to factors such as invasion by exotics (Bakker and Wilson 2004). Approach Based on Principal Component Analyses I conducted on preliminary data, I determined that flower length, banner height, and leaflet length before and after flowering would be important traits for measuring genetic variation. After measuring these traits in the parental generation, growing in the pristine home environments, I will collect seed from 20 maternal families. I will plant 10 seeds from each maternal family in the homesite (the pristine environment in which the parents are growing), and each of the three restoration sites (fig 1). To calculate the genetic variation of the offspring generation I will use both a parent-offspring regression and a full-sib family analysis. The parent-offspring regression is a relatively simple analysis that separates the phenotypic variation (Vp) from the gentic variation (Vg), using the equation h2=Vg/Vp. The heritability (h2) is estimated by the slope of the regression line when the mean trait values of the parents are graphed against the mean trait values of the offspring (Falconer and Mackay 1996). In the full-sib analysis, the phenotypic variance is split into the within family component (Vw) and the among family component (Va). The genetic variance is calculated as Va /2. These two analyses will be used jointly, because, while significance is easily detected in full-sib analyses, they are often artificially high, because common environment and maternal effects cannot be teased out of the measurements (Meril? and Sheldon 2001). These estimates of genetic variance will be used in the following comparisons: Methods 1: To test Hypothesis 1 I will compare the genetic variance component of bo with that of b1, b2, and b3. If bo has a smaller genetic component to phenotypic variance than b1, b2, or b3 , my hypothesis that there is a breakdown of canalization or a gene by environment interaction will be supported for Bodega Marine Reserve. I will repeat this procedure with A?o Nuevo State Reserve and Big Creek Reserve. If this hypothesis is not supported I will continue to test hypothesis 2, and also look at the genetic variation of each homesite using microsatelites (fig 1). Methods 2: To test Hypothesis 2 I will compare the fitnesses of b1 with that of b1, c1, and a1 (regional mix). If there is no significant decrease in fitness between b1 and the regional mix, my hypothesis will be supported for Bodega Marine Reserve. I will repeat this procedure with A?o Nuevo State Reserve and Big Creek Reserve (fig 1). Methods 3: To test Hypothesis 3 I will compare the difference in expressed genetic variation of bo with that of b1, b2, and b3. If there is a greater increase in genetic diversity between bo and b2 or b3 than between bo and b1, my hypothesis that there is a greater breakdown of canalization or a greater shift in gene by environment interaction in populations moved to foreign restoration sites in comparison with populations move to local restoration sites will be supported for Bodega Marine Reserve. I will repeat this procedure with A?o Nuevo State Reserve and Big Creek Reserve (fig 1). Environmental Applications Degraded habitat not only threatens biodiversity, it is a source of pollution, as it increases sediment runoff, reduces topsoil through erosion, and decreases water quality (Casatti and Ferreira 2006, Hickley et al. 2004, Lenihan et al. 2001). This study will address how to restore a habitat most successfully and most cost effectively. If foreign seed, or regional mixes, can be used as or more effectively than native seed, then restoration can be done more affordably and on larger scales. This study may also have applications for the problem of climate change. Climate change will soon be a significant driver of species extinction (Root et al. 2003, Thomas et al. 2004). It may not be enough to simply restore degraded habitat with species that were native to that location previous to disturbance. Some scientists are now advocating the need for assisted migration, where species that are threatened with extinction due to climate change are introduced into new areas that are climactically and ecologically compatible (McLachlan et al. 2007). This method is still under debate, but if it is adopted, this study will provide a framework for deciding where to collect seed for these assisted migrations. 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Visit #15008 @Landels-Hill Big Creek Reserve

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Under Project # 9382 | Research

Seed source location: regional collection versus local collection

graduate_student - University of California, Berkeley

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Jessica Shade Apr 13, 2008 (1 days)

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