About

Ingrid M. Parker is a plant evolutionary ecologist whose research encompasses a broad range of topics including plant disease ecology, the invasion of non-native species, the evolution of domestication, ecological restoration, and plant conservation. She serves as the Faculty Director of UCSC's Norris Center for Natural History, where she supports natural history field courses, student internships, Art+Science initiatives, and the campus museum collections. At the Norris Center, she fosters a community of individuals passionate about the natural world, integrating this enthusiasm into various aspects of their lives. Her work reflects a commitment to understanding and preserving plant ecosystems through both research and education.

Research topics

• Sociology
• Ecology
• Biology
• Political Science
• Gender studies
• Psychology
• Geography
• Law
• Environmental ethics
• Environmental science
• Environmental planning
• Environmental resource management
• Medicine

Selected publications

• Carpobrotus taxa benefit more from clonal integration in their non-native than native ranges

  Biological Invasions · 2026-04-17

  articleOpen access

  Abstract Understanding physiological integration in invasive clonal plants is relevant to invasion biology because resource transfer across ramets may allow alien plants to buffer spatial heterogeneity in their introduced areas. However, experimental evidence across native and non-native ranges is limited. Here, we tested whether physiological integration provides greater performance benefits to Carpobrotus taxa in non-native than native ranges. We grew clonal fragments under controlled conditions from eleven populations representing different genetic clusters across their native and non-native ranges. Connected recipient ramets showed higher growth than severed ones, with increased ramet length, node number, Branching and Vigor Indices, while connected donor ramets showed reduced growth, indicating resource redistribution within the clone. Plants from non-native ranges exhibited overall higher growth-related traits and chlorophyll content, suggesting enhanced growth and stress tolerance across genetic backgrounds. These results indicate that physiological integration allows Carpobrotus taxa to overcome environmental heterogeneity by reallocating resources among ramets, promoting clonal growth and expansion, and potentially increasing competitive ability in non-native ranges. Our findings provide experimental evidence across multiple populations that physiological integration can promote the ecological success of clonal invaders.

  PublisherOA PDFDOI

• Overcoming barriers to build partnerships for managing plant invasions under global change

  Conservation Biology · 2025-11-29

  articleOpen access

  Non-native plant invasions are a cross-boundary conservation challenge, requiring coordinated management and policy responses underpinned by science. Global change is expected to exacerbate this challenge by changing abiotic and biotic drivers of invasive plant distribution, abundance, and impact. Current approaches may no longer be effective, and management must adapt to new threats and conditions. Collaborative personal and institutional partnerships are crucial to link research to practice and policy in order to better manage the complex drivers of invasions and mitigate their impacts under ongoing global change. We used examples from local to global scales to demonstrate how reciprocal knowledge exchange and project codesign among researchers, practitioners, and policy makers can improve conservation outcomes and benefits from invasive species management. Researchers provide expertise needed to apply concepts to new contexts, practitioners hold essential local knowledge, and policy makers balance competing priorities. Combining these strengths leads to more effective and resilient management of plant invasions. This highlights the central importance of collaboration among people, including Indigenous peoples and other local communities, in decision-making and management. Best practices for developing partnerships between individual researchers and local and Indigenous communities, practitioners, and policy makers include engaging respectfully across knowledge and value systems, testing assumptions with data, considering ecological significance, and connecting across spatial scales. Structural solutions to overcome institutional and implementation barriers and develop effective partnerships include funding knowledge brokers and liaisons, collaboratively reviewing policies and practices, incentivizing long-term relationships and goals, and codeveloping data collection and storage. The resulting intentional, long-term partnerships will enable direct application of ecological knowledge to plant invasions and their management, support sustainable and locally backed solutions, and overcome lags in applying science to practice.

  PublisherOA PDFDOI

• Jack of all trades and master of most: <i>Carpobrotus</i> taxa show no trade-off in reproductive strategies

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-01-23 · 1 citations

  preprintOpen access

  Abstract The ability to reproduce via multiple strategies is crucial for the invasion success of alien plant species. Here, we use Carpobrotus taxa (species and hybrids) to explore how trade-offs between and within these strategies may influence plant invasion dynamics. Native to South Africa, Carpobrotus plants are globally prominent in coastal ecosystems, reproducing by seed and clonally, and frequently hybridizing in both native and introduced regions. Three genetically distinct clusters were previously identified, with evidence of hybridization within and between these clusters in native and non-native ranges. We collected fruit samples from populations representing the genetic clusters and their hybrids across native and non-native ranges (i.e., Europe, California, and New Zealand). These genetic clusters reflect the complex taxonomy of Carpobrotus , where species boundaries are unclear due to hybridization and morphological similarity. We then assessed seed set, seed mass, germination rates, and early growth under varying abiotic conditions alongside genetic estimates of clonality. Germination rates were influenced by temperature, moisture, and nutrient levels. Non-native populations demonstrated higher seed set, seed mass, and germination success compared to native populations, indicating a stronger investment in sexual reproduction. These populations also showed higher levels of clonality, shown by lower genotypic richness, suggesting that both reproductive strategies enhance invasive potential. High-clonality populations produced more seeds, demonstrating that the two reproductive strategies are not mutually exclusive. These results highlight the importance of multiple reproductive strategies for the establishment and spread of Carpobrotus taxa and provide insights into the mechanisms driving their global success.

  PublisherOA PDFDOI

• Interacting effects of invasion and soil microbes on Douglas‐fir seedling response to drought

  Ecosphere · 2025-10-01

  articleOpen accessSenior author

  Abstract Global change is affecting native species and communities through multiple anthropogenic drivers which likely interact, complicating our ability to predict the net effects of global change. In the Pacific Northwest region (USA), Cytisus scoparius (L.) Link (Scotch broom) invasion has dramatically altered many ecosystems, including postharvest timber lands. Simultaneously, the intensity of summer drought conditions associated with climate change is making successful reforestation increasingly difficult. We investigated how Douglas‐fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ) responds to the multiple stressors of drought and Cytisus invasion. We further evaluated whether the soil microbial community, including mycorrhizal fungi, ameliorates or exacerbates Douglas‐fir's response to drought and Cytisus competition. Drought and the presence of the invader both increased stress (measured by chlorophyll fluorescence) and decreased survival of Douglas‐fir seedlings, and their combined effects on stress were more than additive. Douglas‐fir grew bigger in live than in sterile soil, but this effect was strongly reduced in the presence of Cytisus ; we also found that mycorrhizal colonization was reduced in the presence of the invader. Surprisingly, however, Douglas‐fir survival in live soil was lower than in sterile soil, especially in the presence of Cytisus . Our results suggest that the impact of drought on Douglas‐fir seedlings is likely to be exacerbated by the invasion of Cytisus . Our results further suggest that in a warming climate, the presence of impactful invasive species can affect whether soil microbes have a net positive or negative effect on native plant performance. Our results illustrate the value of studying multiple stressors simultaneously to understand their interactions and combined impacts on native species.

  PublisherOA PDFDOI

• Invasive grasses do not always exhibit superior and faster plant life-history traits in the introduced range than in the native range

  NeoBiota · 2025-11-27

  articleOpen access

  Many invasive plants are larger, and produce more seeds in populations from the introduced range compared to those from their native range. Annual invasive plants might also benefit in their introduced range from fast germination, early seed production and shorter life cycles. Using three species of annual grass native to Spain and invasive in California ( Avena barbata , Bromus hordeaceus and Brachypodium distachyon spp. complex), we tested the hypothesis that plants from the introduced range are not only larger and more fecund, but they also have faster life cycles than plants from the native range. Additionally, these plant traits are expected to vary along climate gradients, both in the introduced and in the native populations. Hence, we collected seeds from introduced and native populations across different climate conditions and then grew them all under a common outdoor condition. In support of our hypothesis, we found that Avena plants from the introduced range were larger, more fecund and had a shorter lifespan than from the native range. By contrast, Bromus plants invested less biomass in reproduction in the introduced range. In Brachypodium , seeds from the introduced range germinated later and flowering was delayed compared to the native range. These plants also produced fewer seeds and had a shorter lifespan in the introduced range. Genome size analysis indicated that Brachypodium plants from the introduced range are tetraploid while, in the native range, diploid and tetraploid individuals co-occur. We found some trait variation could be explained by climate differences amongst populations, but this was mostly within the native range, suggesting that our study taxa are not yet locally adapted to climatic conditions of their introduced range. Overall, our common garden experiment indicated that the invasion success of these annual grasses is not clearly associated with superior biomass, reproduction or fast plant life-history traits. For Brachypodium , polyploidy may play a role in its invasion success.

  PublisherOA PDFDOI

• Association with roadsides reflects escape from competition in stinkwort ( <i>Dittrichia graveolens</i> )

  Invasive Plant Science and Management · 2025-01-01

  articleOpen accessSenior author

  Abstract Invasive plants commonly establish and spread along roadsides, and understanding the mechanisms underlying this pattern is essential for risk assessment and effective management. Stinkwort [ Dittrichia graveolens (L.) Greuter], a recent California invader, primarily inhabits roadsides but is beginning to spread into nearby plant communities. We tested whether D. graveolens grows best along roadsides due to a preference for soil conditions or is limited to these disturbed environments by plant competition. Lab and greenhouse experiments showed no germination advantage in engineered fill (simulating roadside soils), and D. graveolens grew slightly better in field topsoil. Competition trials with two annual grasses [soft brome ( Bromus hordeaceus L.) and Italian ryegrass ( Lolium perenne L.)] showed strong growth suppression of D. graveolens by both grasses, but competition was stronger in field topsoil than engineered fill. Engineered fill limited growth for all species, suggesting that roadside soils may provide a refuge from competition. In 2 yr of field experiments, we examined mechanisms of competition by comparing responses to (1) removal of thatch, aboveground biomass, and above- and belowground biomass; (2) shading; and (3) water and nutrient addition and protection from belowground competition via trenching. Belowground competition in particular strongly affected D. graveolens ’ performance. Our findings suggest that competition confines D. graveolens to disturbed roadsides; management should prioritize reducing bare, disturbed areas, and enhancing plant competition in areas vulnerable to invasion.

  PublisherOA PDFDOI

• Unfriendly neighbors: When facilitation does not contribute to restoration success in tidal marsh

  Ecological Applications · 2025-01-01 · 3 citations

  articleOpen access

  Large-scale restoration projects are an exciting and often untapped opportunity to use an experimental approach to inform ecosystem management and test ecological theory. In our $10M tidal marsh restoration project, we installed over 17,000 high marsh plants to increase cover and diversity, using these plantings in a large-scale experiment to test the benefits of clustering and soil amendments across a stress gradient. Clustered plantings have the potential to outperform widely spaced ones if plants alter conditions in ways that decrease stress for close neighbors. Here, we test whether intraspecific facilitation improves restoration outcomes using a suite of seven high marsh species native to central California salt marshes. We also applied a biochar treatment to test whether soil amendment boosts restoration success. We compared the performance of clustered and uniform plantings across the high marsh elevation gradient for 3 years. There was a strong effect of elevation on plant performance and clear signs of plant stress related to soil conditions. Clustering slightly improved the survival of one species out of seven, although clustering did not benefit that species in a follow-up experiment under more stressful conditions. By contrast, clustering had strong negative effects on the growth and/or cover of all species tested. The stressors in this system-likely related to compaction and soil salinity-were not mitigated by neighbors or biochar. The prevailing negative effect on seven species from distinct evolutionary lineages lends strong generality to our findings. We therefore conclude that for this and similar high marsh systems, intraspecific facilitation confers no benefits and practitioners should space plants widely to minimize competition. To take full advantage of the learning opportunities provided by large-scale restoration projects, we recommend including experimental treatments and monitoring the response of multiple species across years to refine best practices and inform adaptive management.

  PublisherDOI

• Invasion away from roadsides was not driven by adaptation to grassland habitats in Dittrichia graveolens (stinkwort)

  Biological Invasions · 2024-06-05 · 1 citations

  articleOpen accessSenior author

  Abstract Invasive plants along transportation corridors can significantly threaten ecosystems and biodiversity if they spread beyond anthropogenic environments. Rapid evolution may increase the ability of invading plant populations to establish in resident plant communities over time, posing a challenge to invasion risk assessment. We tested for adaptive differentiation in Dittrichia graveolens (stinkwort), an invasive species of ruderal habitat in California that is increasingly spreading away from roadsides into more established vegetation. We collected seeds from eight pairs of vegetated sites and their nearest (presumed progenitor) roadside population. We assessed differentiation between populations in roadside and vegetated habitat for germination behavior and for response to competition in a greenhouse experiment. We also tested for increased performance in vegetated habitat with a grassland field experiment including a neighbor removal treatment. Germination rates were slightly reduced in seeds from vegetated sites, which may indicate lower seed viability. Otherwise, plants did not show consistent differences between the two habitat types. Competition strongly reduced performance of D. graveolens in both the greenhouse and in the field, but plants originating from vegetated sites did not show enhanced competitive ability. Our findings show no evidence of adaptive differentiation between D. graveolens populations from roadside and vegetated habitats to date, suggesting that invasiveness in grasslands has not been enhanced by rapid evolution in the 40 + years since this species was introduced to California. Evolutionary constraints or potentially high levels of gene flow at this small scale may limit adaptation to novel habitats along roadsides.

  PublisherOA PDFDOI

• Plant–soil interactions during the native and exotic range expansion of an annual plant

  Journal of Evolutionary Biology · 2024-03-27 · 8 citations

  articleOpen accessSenior author

  Range expansions, whether they are biological invasions or climate change-mediated range shifts, may have profound ecological and evolutionary consequences for plant-soil interactions. Range-expanding plants encounter soil biota with which they have a limited coevolutionary history, especially when introduced to a new continent. Past studies have found mixed results on whether plants experience positive or negative soil feedback interactions in their novel range, and these effects often change over time. One important theoretical explanation is that plants locally adapt to the soil pathogens and mutualists in their novel range. We tested this hypothesis in Dittrichia graveolens, an annual plant that is both expanding its European native range, initially coinciding with climate warming, and rapidly invading California after human introduction. In parallel greenhouse experiments on both continents, we used plant genotypes and soils from 5 locations at the core and edge of each range to compare plant growth in soil inhabited by D. graveolens and nearby control microsites as a measure of plant-soil feedback. Plant-soil interactions were highly idiosyncratic across each range. On average, plant-soil feedbacks were more positive in the native range than in the exotic range. In line with the strongly heterogeneous pattern of soil responses along our biogeographic gradients, we found no evidence for evolutionary differentiation between plant genotypes from the core to the edge of either range. Our results suggest that the evolution of plant-soil interactions during range expansion may be more strongly driven by local evolutionary dynamics varying across the range than by large-scale biogeographic shifts.

  PublisherOA PDFDOI

• Chromosome-level reference genome of stinkwort, <i>Dittrichia graveolens</i> (L.) Greuter: A resource for studies on invasion, range expansion, and evolutionary adaptation under global change

  Journal of Heredity · 2023-06-01 · 4 citations

  articleOpen accessCorresponding

  Dittrichia graveolens (L.) Greuter, or stinkwort, is a weedy annual plant within the family Asteraceae. The species is recognized for the rapid expansion of both its native and introduced ranges: in Europe, it has expanded its native distribution northward from the Mediterranean basin by nearly 7 °C latitude since the mid-20th century, while in California and Australia the plant is an invasive weed of concern. Here, we present the first de novo D. graveolens genome assembly (1N = 9 chromosomes), including complete chloroplast (151,013 bp) and partial mitochondrial genomes (22,084 bp), created using Pacific Biosciences HiFi reads and Dovetail Omni-C data. The final primary assembly is 835 Mbp in length, of which 98.1% are represented by 9 scaffolds ranging from 66 to 119 Mbp. The contig N50 is 74.9 Mbp and the scaffold N50 is 96.9 Mbp, which, together with a 98.8% completeness based on the BUSCO embryophyta10 database containing 1,614 orthologs, underscores the high quality of this assembly. This pseudo-molecule-scale genome assembly is a valuable resource for our fundamental understanding of the genomic consequences of range expansion under global change, as well as comparative genomic studies in the Asteraceae.

  PublisherOA PDFDOI

Recent grants

• Phylogenetic Disease Ecology of Plants

  NSF · $800k · 2017–2023

• Collaboration: The Role of Plant-Pathogen Interactions in Explaining and Constraining Weed Invasions: Testing Theories of Biotic Resistance and the Natural Enemies Hypothesis

  NSF · $188k · 1998–2002

• Doctoral Dissertation Improvement: Mycorrhizal legacy effects of a plant invasion may limit forest restoration

  NSF · $15k · 2012–2013

Frequent coauthors

• Gregory S. Gilbert

  University of California, Santa Cruz

  67 shared

• Joel E. Cohen

  36 shared

• Norman C. Ellstrand

  University of California, Riverside

  30 shared

• John N. Thompson

  University of California, Santa Cruz

  30 shared

• Kimberly A. With

  Kansas State University

  30 shared

• David E. McCauley

  30 shared

• David M. Lodge

  Atkins (United States)

  30 shared

• Jodie S. Holt

  University of Kentucky

  30 shared

Labs

• Parker LabPI

Awards & honors

• Fellow, Ecological Society of America
• Fellow, California Academy of Sciences
• UCSC Committee on Teaching, Excellence in Teaching Award
• Chancellor’s Achievement Award for Diversity
• Fulbright Fellow