Research Projects

Restoration genomics of endangered vernal pool annuals: sourcing seeds through space and time to maximize adaptive variation

The future of restoration depends on the development of methods that are adaptive to a changing climate. For plants, best practices recognize that the choice of source populations for restoration can greatly affect restoration success. However, restoration practice suffers from a lack of evidence-based methods for sourcing seeds with the genetic resources to adapt to rapid environmental change.

LACO_NOON_POOL 3_tag 3283_20190513_1.JPG

Seeds sourced from the same site over multiple years may provide genetic variation and population buffering akin to that of soil seed banks, which are critical to the resilience of annual plant communities. Using seed collections made over 17 sites and 4 years, I will test the efficacy of sourcing methods through time and across space to introduce climate-resilient genomic diversity into restoration populations.

This investigation will be conducted with Lasthenia conjugens and L. burkei, two endangered asters that are endemic to California vernal pool wetlands, a highly threatened habitat that was once widespread throughout western North America. Vernal pools exhibit high, and increasing, year-to-year variation due to fluctuating precipitation patterns and represent a habitat in which seed banks may be particularly critical to the evolutionary potential and long-term success of restored populations. I will combine transplant experiments under different hydrologic conditions in the field and greenhouse with next generation sequencing to characterize the distribution of both neutral and adaptive genomic variation among populations and across generations. This project will provide concrete recommendations for conserving rare and specialized plant taxa while serving as a case study for restoration sourcing methodologies.

Regional Seed Sourcing Practices: What factors limit restoration practitioners' ability to source "the right seed in the right place at the right time"?

Expert panel on regional seed sourcing facilitated by Dr. Kottler at the California Native Plant Society Meeting 2023.

Seeding is one of the most complex and variable aspects of ecological restoration. Land managers make decisions about what species they will plant in a restoration, and where they will obtain the seed they plant. Similarly, seed suppliers, including native plant nurseries, make choices regarding where they will obtain the seeds they collect, grow, and sell for restoration use.

Conventional wisdom once stated that “local seed is best”, i.e., that seeds planted in a restoration should be from as close to the site to be restored as possible. Many conservation and land management organizations have strict seed sourcing policies that specify maximum distances for seed collection or purchase. However, given uncertainties in future climate, among other issues, local seed sourcing may not be the best option for restoration. Researchers have suggested other sourcing strategies for promoting resilience to future climate. These strategies include mixing seeds from multiple source populations, as well as strategically sourcing seeds from areas that resemble the restoration site’s future climate conditions. While these discussions have been taking place in the scientific literature for more than a decade, little is known about actual, on the ground seed sourcing, and the decisions land managers are making around where to obtain their seeds for restoration. We propose collecting information through a survey to better understand the following:

1. What methods are currently used to source native plant materials for restoration projects in the California Floristic Region?

2. What factors limit practitioners’ abilities to adopt their ideal practices?

Supply-side: seed availability, price
Funding: funder-imposed constraints on what materials are used, timeline too short to source ideal plant materials
Accessibility of research: journal access, perceived applicability of research to practice, Standards/certifications

Institutional and affinity group supports for nonbinary scientists

Nonbinary people belong to a gender minority that is just beginning to gain larger societal recognition in the United States and elsewhere. As a result, more nonbinary individuals are coming out in the workplace and navigating social networks and institutional systems which may or may not be supportive and/or inclusive of their identity. This project serves to fill an identified gap in the Educational research literature, looking at the experiences of nonbinary students and working professionals in various workplace contexts and investigating the role that institutional and affinity group supports play in their wellbeing and persistence in their careers.

Phenotypic plasticity and fitness of a migrating marsh grass

One of the most rapid and visible impacts of climate change in the US is sea level rise, a global phenomenon with a local hotspot along the Mid-Atlantic coast, where oceanographic and geologic factors lead to rates that are ~3-4 times the global average [1]. As sea levels rise, flooding threatens coastal marshes that provide crucial ecosystem services: they store 40 times more carbon than terrestrial forests [2]; are nursery grounds for commercially fished species [3] and reduce storm surge impacts on coastal communities including major population centers.

Where the vertical slope and permeability of upland habitats allow, marsh migration may prove a critical process for the successful conservation of coastal marshes under threat from sea level rise. But to do this, native marsh grasses must successfully colonize adjacent upland habitats such as coastal loblolly pine forest that provide novel biotic and abiotic challenges.

I am investigating the role of clonal identity vs. phenotypic plasticity in the plant physiological traits and fitness of salt marsh hay, Spartina patens, as it migrates across a coastal ecotone from high marsh to coastal forest understory and experiences novel abiotic stressors. In the past three years I have conducted a series of manipulative field-based experiments investigating the separate and cumulative impacts of light availability & salinity on plant phenotype, survival and reproductive fitness and documented the remarkable plasticity of salt marsh hay in response to these abiotic factors.

Plant phenotype in marsh (left) vs. forest

understory (right)

Unearthing S. patens genetic diversity and resilience to climate change

In order to conserve marsh habitat effectively, we need to better understand how much genetic diversity is present in marsh meadows, as well as how this diversity is shaped by geography, history, and environmental conditions.

I am conducting a landscape genetics study of Spartina patens in order to evaluate the relationship between genetic diversity at both the patch and site scale with ecological and landscape variables.

In 2018-2019 I sampled 10 sites across NY state. Using microsatellite data from these samples, along with DEC spatial data from 1974 & 2005/2008 which were used in the Tidal Wetlands Trend Analysis [4], I will test the following hypotheses:

Hypothesis 1 Habitat Loss: Genetic diversity of salt marsh hay will be correlated with current habitat area.

Hypothesis 2 Legacy effect of marshes past: Genetic diversity of salt marsh hay will be correlated with historic habitat area; formerly expansive marshes will exhibit higher levels of genetic variation.

Hypothesis 3 Disturbance erodes diversity: Genetic diversity will be lower in areas affected by various forms of ecological and anthropogenic disturbance – flooding, eutrophication, and non-native plant invasion.

Re-evaluating the Genetic Swamping Hypothesis with modern empirical data

A central question in ecology is what determines range limits. One of the most popular ideas is the genetic swamping hypothesis, which proposes that gene flow limits range expansion by introducing maladaptive alleles to the range margin. I have been reviewing the empirical work that tests assumptions of the swamping hypothesis, using the following criteria to evaluate the role of gene flow in setting range limits: 1) molecular evidence for asymmetrical gene flow from central to peripheral areas of species’ ranges 2) evidence that the fitness of range edge populations is negatively affected by gene flow from central populations.

Despite a number of studies which explicitly test for it, we find a lack of empirical evidence in support of the genetic swamping hypothesis (i.e. center-to-edge gene flow decreasing fitness in range edge populations). We advocate for more studies going forward to integrate methods that quantify gene flow occurring along a species range with methods such as reciprocal transplant studies that quantify the fitness of range edge populations. It is critical to understand the evolutionary dynamics occurring at species range edges in order to accurately predict how they may shift in response to climate change.

Expected population dynamics across a species' range under the Genetic Swamping Hypothesis

Works Cited: [1] Sallenger et al. Nature Climate Change 2 (2018). [2] Chmura et al. Global Biogeochemical Cycles 17 (2003). [3] Barbier et al. Ecological Monographs 81 (2011). [4] Long Island Tidal Wetland Trends Analysis, DEC, 2015. https://www.dec.ny.gov/docs/fish_marine_pdf/bmrwetlandstrends1.pdf