The California Poppy Project

California poppy (Eschscholzia californica) is the state flower, and an iconic species known for its superblooms. In 2017, Liz Ryan collected seeds from California poppy across its range (see photos of the plants across these sites to the right), and we have been growing these populations under experimental common garden conditions at UCSD. The range of this species spans wide climatic gradients, and variations among the populations likely reflect a history of past selection in response to the environment. Our work has found that populations from southern, more arid sites are more likely to be annual, flower faster and are more drought tolerant, compared with the northern populations. We are currently performing experimental crosses to evaluate whether assisted gene flow would help northern populations adapt to long-term drought. Liz is also working to parameterize a species distribution model incorporating the clinal variation we observed across the species range. This work is funded by a Gordan H. Sato Endowed Faculty Fellowship, and the California Conservation Genomics Project.

How does invasion influence ecosystem responses to global change?

Annual exotic species are invading many regions with a Mediterranean type climate, including Southern California. These fast- growing, short-lived species have functional traits that differ from the native woody shrubs that have traditionally dominated these landscapes. Increasingly frequent and intense drought events are predicted for our region with climate change; how will shifting species composition alter ecosystem-level responses to regional global change? Results from a large rainfall manipulation experiment showed that drought reduced the abundance of invasive species more than native species, but the invaders rebounded faster than native species in the first high-rainfall year following the cessation of drought treatments. We also found that drought reduced the productivity of invaded areas more than areas dominated by native shrubs; this was in part due to the shorter growing season of the dominant invaders in this system, which was also shortened more by drought than for the dominant native species. This work was funded by NSF DEB-1154082.

Esch, EH, D. Lipson & E. E. Cleland (2019) Invasion alters ecosystem response to drought via increased phenological sensitivity. Ecology 100: e02802

Puritty, C.E., E.H. Esch, S. Pérez Castro, E.M. Ryan, D.A. Lipson & E.E. Cleland (2019). Drought in Southern California coastal sage scrub reduces biomass of exotic species more than native species, but exotic growth recovers quickly when drought ends. Plant Ecology 220:151–169. doi:10.1007/s11258-019-00912-5

Phenology and global change

Shifts in timing, or phenology, observed worldwide provide some of the most compelling evidence that species and ecosystems are already responding to global environmental changes. Observational evidence suggests that as global temperatures have risen, both plants and animals have accelerated the timing of their springtime activities. Many projects in the lab have focused on this key functional trait, documenting how shifting plant phenology has consequences for plant performance, community assembly and ecosystem functioning. Our lab has become increasingly interested in the potential for plant species to adapt their phenology to shifting abiotic (i.e. climate change) and biotic (i.e. invasion by exotic species) factors. For instance, work conducted by PhD student José Waterton focused on germination timing in two abundant grasses in California (Stipa pulchra and Bromus diandrus). Clinal variation in germination timing, and the correlated trait of seed dormancy, suggests a history of past selection on these traits in relation to site aridity. He also found that biotic interactions, including competition and herbivory, influence the strength of phenotypic selection on in response to the environment.

Waterton, J. and E.E. Cleland. (2021) Mammalian herbivores weaken selection for early emergence in competition. Evolution Letters doi:10.1002/evl3.222 

Waterton, J., Mazer, S.J., Meyer, J.R. and E.E. Cleland. (2020) Trade‐off drives Pareto optimality of within‐ and among‐year emergence timing in response to increasing aridity. Evolutionary Applications,