Research themesEcology was once described to me by a mentor as “the most challenging of the sciences”, being the highest-order manifestation of scientific phenomena at all other levels of study – that how species interact with each other and their environment is the outcome of organismal differences, of physical, biochemical, and energetic constraints, of processes that unfold over space and time. Though this complexity offers endless opportunities for discovery at many intersections of science, it also poses a great challenge towards finding simple general rules that explain the distribution of biodiversity on Earth.
Research in my lab is motivated by deconstructing the complexity of our natural world, pairing experiments with ecological models, to weigh multiple drivers of ecological patterns against each other. Specific themes include: Coexistence mechanisms across space and time Competition and persistence in variable environments What processes determine how many species co-occur on local scales at any given point in time? What proportion of co-occurring species coexist stably due to niche partitioning vs. transient persistence due to other mechanisms, and to what degree are niches partitioned within environments vs. between environments? It is these types of mechanisms that our lab seeks to disentangle using experiments designed to quantify the intensity of competitive interactions among species in different environments. We can then link competitive interactions to species’ functional traits and life history strategies (e.g., plasticity, maternal environmental effects, dormant seed banks) that confer persistence in temporally varying environments. The spatial scale and distribution of ecological processes That ecological processes transition in importance with spatial scale is implicit in the design of all ecological research, and is fundamental to the concept of “local” and “regional” communities. Unlike local processes, however, regional processes are trickier to quantify. Our lab takes two approaches to doing so: First, we apply principles from island biogeography to test how species distributions are constrained by landscape features, and the scales at which those constraints manifest. For example, our current work shows that plant species distributions do not reflect dispersal limitation from far-away habitat patches, but rather, dispersal limitation from habitat patches that are not intersected by their dispersal vectors (e.g., deer). Second, we use manipulative experiments in the lab and field (e.g., seed additions) to test hypotheses that emerge from our observational work. Evolution in ecological communities Ecological communities are complex, yet tests of selection, local adaptation, and character displacement are generally performed in simplistic ecological contexts, such as in the absence competitors or in homogenous environments. Although parsing out and comparing sources of ecological complexity important for evolution is a big task, recent theoretical and empirical developments in ecology provide the quantitative tools to do so. Our goal is to apply theory and empirical methods from community ecology to answer unresolved questions in evolutionary ecology, towards a general understanding of the mechanisms which generate (evolutionary) and maintain (ecological) biological diversity. Specific questions include: How do competitive differences evolve on microevolutionary timescales, and to what degree is their evolution driven by interactions with other species, divergent abiotic environments, or genetic drift? How does evolution unfold in diverse communities, and which competitors exert the strongest selection on focal species - the most common ones in the community, or the most related (ecologically similar) ones, or the community as a whole? What role does dispersal among localities play in determining which populations succeed or fail to establish and evolve in new sites? Species invasions and biodiversity change In California grasslands and many ecosystems across the world, habitat patches are fragmented not by road building or agriculture, but by the widespread invasion of annual grasses that form a dense impermeable matrix between habitat patches. As a consequence, the diversity and spatial distribution of native plant diversity we see today may be quite different from pre-invasion communities. Although species invasions have been studied for decades, many pressing questions remain unanswered, specifically about their spatial and temporal impacts. Our lab is interested in: (1) understanding how invasive species impact the dynamics of native plant communities even if they are not directly interacting, by limiting dispersal among habitat patches, changing the size and shape of habitat patches, and concentrating herbivore pressure; (2) reconstructing diversity of plant communities pre-invasion, when and how invasions spread, and the spatial distribution of post-invasion species losses through time; (3) quantifying adaptation of invaders to refuge habitat conditions, which threaten to shrink remaining habitat patches. |
Testing the functional trait
underpinnings of coexistence
Seed bank (temporal coexistence mechanism) assay across species and environments
Plant composition surveys on serpentine "islands"
Lasthenia californica, an abundant early-flowering annual
Manipulating the spatial scale of dispersal using a seed vacuum
Field estimates of intensity of seed predation
Testing character displacement of root traits via clear pots
|
Note: I am completely redoing this page. Content below is a work in progress - as of Feb. 2026
Add a little preamble unifying research subthemes. In each sub theme, describe goal / impacts in terms of heart of why the topic is interesting, then describe a few key findings and also show any perspective articles, maybe a schematic. Describe the ecology & evolution of ecology & evolution thing. Mention coexistence theory for certain goals/apporach but for others clever methods. Also mention lab study systems maybe at the end. Curiosity driven
Research Themes
interactions among processes across scales. field vs greenhouse and hybrid (mensurative approach)
add life history/uncertainty stuff here?
food webs metacommunity stuff, behavior, meta-ecosystems
Study Systems
Choose a system to match the question, but also benefits from deep systems knowledge. Cool things we can do with each. Replicated microcosms
|
This is the lab's main study system, which Rachel has been using since undergrad. Experiments can be done in the lab, growth chamber, greenhouse, and field (McLaughlin Natural Reserve).
A huge benefit of annual plants is that they stay where you put them, meaning you can:
1. manipulate entire communities in the field by moving whole seedbanks (e.g., with a vacuum)
2. track focal individuals to quantify all fitness components in a single year
3. grow species at specific densities/combinations, in order to parameterize ecological models.
In the field, we primarily work with annual plants that are associated with serpentine soils. These plant communities have been heavily impacted by invasion (European grasses), fragmentation (due to invaders), and climate change (extreme drought to extreme deluge), despite remaining a natural biodiversity hotspot of conservation concern; most of the endemic species now reside on the harsh serpentine soils (up to 25 species in a 1 sq. m plot) in refuge from invaders. We often like to do what I call "set it and forget it" field experiments, where we set something up in the field in the fall, leave, and then come back in the spring to collect data.
Cons of annual plants: observing population dynamics through time either takes years to observe (e.g., Kowalski et al. PNAS) or need to be estimated using space for time substitutions (i.e., Blackford et al. AmNat). This is where Tribolium or duckweed can have an advantage.
We maintain seed stocks of certain species/populations in the lab and others can be collected in the field. In addition, depending on a project's goals, we can order specific species online, for example, from S&S Seed.
A huge benefit of annual plants is that they stay where you put them, meaning you can:
1. manipulate entire communities in the field by moving whole seedbanks (e.g., with a vacuum)
2. track focal individuals to quantify all fitness components in a single year
3. grow species at specific densities/combinations, in order to parameterize ecological models.
In the field, we primarily work with annual plants that are associated with serpentine soils. These plant communities have been heavily impacted by invasion (European grasses), fragmentation (due to invaders), and climate change (extreme drought to extreme deluge), despite remaining a natural biodiversity hotspot of conservation concern; most of the endemic species now reside on the harsh serpentine soils (up to 25 species in a 1 sq. m plot) in refuge from invaders. We often like to do what I call "set it and forget it" field experiments, where we set something up in the field in the fall, leave, and then come back in the spring to collect data.
Cons of annual plants: observing population dynamics through time either takes years to observe (e.g., Kowalski et al. PNAS) or need to be estimated using space for time substitutions (i.e., Blackford et al. AmNat). This is where Tribolium or duckweed can have an advantage.
We maintain seed stocks of certain species/populations in the lab and others can be collected in the field. In addition, depending on a project's goals, we can order specific species online, for example, from S&S Seed.
Tribolium is a classic model system and has been studied for hundreds of years. It has been of interest both because it is an agricultural pest, causing billions of dollars of damage per year, but also because many replicate populations can be reared with very little space and has population dynamics that can be characterized by relatively simple models (yielding some of the best tests we have of chaos, priority effects, etc.). Tribolium are extremely easy to keep alive - all they need is flour!
For some research questions, Tribolium have several perks. Namely, they have a generation time of ~1 month, have complex behaviors, and reproduce sexually. For these reasons, they are well suited for eco-evo experiments, as population dynamics (and underlying evolution) can be tracked in real time, as well as studies exploring feedbacks between population dynamics and behavior.
Specific stocks can be ordered from the USDA or collaborators, including multiple species of Tribolium, which is great for multi-species competition experiments.
For some research questions, Tribolium have several perks. Namely, they have a generation time of ~1 month, have complex behaviors, and reproduce sexually. For these reasons, they are well suited for eco-evo experiments, as population dynamics (and underlying evolution) can be tracked in real time, as well as studies exploring feedbacks between population dynamics and behavior.
Specific stocks can be ordered from the USDA or collaborators, including multiple species of Tribolium, which is great for multi-species competition experiments.
|
Annual plants
This is the lab's main study system, which Rachel has been using since 2009. Experiments can be done in the lab, growth chamber, greenhouse, and field (McLaughlin Natural Reserve). Benefits of annual plants: They stay where you put them, meaning you can 1. manipulate entire communities through seedbanks in the field (e.g., with a vacuum), 2. track focal individuals to quantify all fitness components in a single year, and 3. grow plants at specific densities of different species, in order to parameterize ecological models. Cons of annual plants: dynamics through time either take many years to observe (e.g., Kowalski et al.) or need to be estimated using space for time substitutions (i.e., Blackford et al.). |
Tribolium flour beetles
|
Duckweed
|
in silico
|
Other
|