Invasion Biology

Introduced species can sometimes have major impacts on ecosystems and human societies; however, they can also be a rich subject for studying ecological and evolutionary processes. My research program uses this dichotomy to do innovative ecological research while contributing to restoration goals. For the past 5 years, I have been studying Dittrichia graveolens (stinkwort), a recent invader to California, with an interdisciplinary research team. Together, we investigate D. graveolens across replicate invasion fronts and multiple stages of invasion in California and compare it to its range expansion in Europe, where it is native. We are addressing questions about the role of evolution during spread, the interplay of life history, competition, and disturbance in plant distributions, and how soil microbiomes may facilitate or limit plant invasion.

Invasive plants can significantly threaten wild ecosystems and native biodiversity, but they often establish their first foothold along transportation corridors. Dittrichia graveolens, still a recent invader, primarily inhabits roadsides in California but is increasingly spreading into adjacent plant communities. In my dissertation, I investigated whether the evolution of stronger competitive ability has exacerbated D. graveolens invasion into plant communities in the County of Santa Clara (Melen et al. 2024). My finding that adaptation has not contributed to invasiveness provides new insight into risk assessment in the face of evolution. In my other work, I have identified soil disturbance as a driver of invasion, pointing to a critical role for maintaining a robust community of resident species as a management technique to reduce invasion in grasslands.

Our bigger research team also studies how evolution occurs across the genome during invasion along replicated invasion fronts in response to a range of biotic and abiotic factors. We published the reference genome for D. graveolens (McEvoy et al. 2023), which is the foundation for several ongoing genetics projects. In addition, using parallel experiments in California and the Netherlands, we identified that plant-soil interactions are highly idiosyncratic across both the native and invaded ranges, suggesting that these interactions may be more strongly driven by local ecological and coevolutionary dynamics than by large-scale biogeographic shifts (Lustenhouwer et al. 2024). Finally, I am studying how seed dormancy evolves during invasion, and the implications of seed dormancy for management, with ongoing experiments at Blue Oak Ranch Reserve in San José. 

Collaborators: Dr. Ingrid Parker and Dr. Nicky Lustenhouwer.
For more information about our Dittrichia Collaboration, please go to our Stinkwort Information for Practitioners webpage.

Publications

Melen MK, Snyder ED, Fernandez M, Lopez A, Lustenhouwer N, Parker IM. 2024. Invasion away from roadsides was not driven by adaptation to grassland habitats in Dittrichia graveolens (stinkwort). Biological Invasions. https://doi.org/10.1007/s10530-024-03359-6

Melen M. 2024. Stinkwort workshop: Biology, control, and management. California Invasive Plant Council Dispatch Newsletter, Spring Issue. https://www.cal-ipc.org/wp-content/uploads/2024/06/Cal-IPC_Dispatch_News_Spring-2024_FINAL.pdf

Lustenhouwer N, Chaubet TMR, Melen MK, van der Putten WH, Parker IM. 2024. Plant-soil interactions during the native and exotic range expansion of an annual plant. Journal of Evolutionary Biology, voae040. https://doi.org/10.1093/jeb/voae040

McEvoy SL, Lustenhouwer N, Melen MK, Nguyen O, Marimuthu MPA, Chumchim N, Beraut E, Parker IM, Meyer RS. 2023. Chromosome-level reference genome of stinkwort, Dittrichia graveolens (L.) Greuter: A resource for studies on invasion, range expansion, and evolutionary adaptation under global change. Journal of Heredity 114(5): 561-569. https://doi.org/10.1093/jhered/esad033

Lustenhouwer N, Parker IM. 2022. Beyond tracking climate: Niche shifts during native range expansion and their implications for novel invasions. Journal of Biogeography 49:1481–1493. https://doi.org/10.1111/jbi.14395

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We gratefully acknowledge support from the United States Department of Agriculture, National Institute of Food and Agriculture (USDA-NIFA) grant # 2020-67013-31856.