Collecting alpine plants in the Sawtooth Mts., Idaho
Community phylogeography of alpine “sky islands”
Mountains inspired Humboldt to synthesize his thoughts about how species diversity changes across space, yet we know relatively little about the diversity of multi-species assemblages within and among alpine regions. In these remote and understudied areas, evolutionary history can be particularly useful for providing insights into macro-ecological and evolutionary processes driving diversity in the absence of detailed information on functional traits.
To understand what drives diversity at the limits of plant life, we explore floristic patterns across alpine summits. We combine field-based floristic plant collections, publicly available data repositories, and advances in sequencing technologies to describe diversity and unravel processes that shape alpine plant communities from regional to global scales.
Key Publications:
Figueroa H, Marx HE, Beatriz de Souza Cortez M, Grady C, Engle-Wrye NJ, Beach J, Stewart A, Folk R, Soltis D, Soltis P & Smith S. 2022. Contrasting patterns of phylogenetic diversity and alpine specialization across the alpine flora of the American mountain range system. Alpine Botany 132: 107–122. https://doi.org/10.1007/s00035-021-00261-y
Marx HE, Richards M, Johnson GM, Tank DC. 2019. Increasing phylogenetic stochasticity at high elevations on summits across a remote North American wilderness. American Journal of Botany.106(7): 958-970. DOI: 10.1002/ajb2.1328 GitHub Dryad Data
Marx HE, Dentant C, Renaud J, Delunel R, Tank DC, Lavergne S. 2017. Riders in the sky (islands): using a mega-phylogenetic approach to understand plant species distribution and coexistence at the altitudinal limits of angiosperm plant life. Journal of Biogeography. DOI: 10.1111/jbi.13073 GitHub Dryad Data
Field kit for RNA sampling
Metatranscriptomics and community plasticity
Predicting how species respond to environmental change is of critical importance, but quantifying ecological responses over biogeographic scales remains challenging. The ability to produce different phenotypes in heterogeneous environments—phenotypic plasticity—can be essential for responding successfully to change. Short-term (seasonal) plasticity might reflect a broad physiological niche that is adaptive in the long-term. There is recent evidence from experimental studies that plasticity at the level of gene expression can be adaptive under changing environments, but genomic plasticity has not been connected with ecological success in nature.
I’ve been working with colleagues to develop an approach to use genomic plasticity to track community-wide responses to environmental change. Follow the progress of our community plasticity research at the Harvard Forest NEON site here!
Key Publications:
Marx HE, Carboni M, Douzet R, Perrier C, Delbart F, Thuiller W, Lavergne S, Tank D. 2021. Can functional genomic diversity provide novel insights into mechanisms of community assembly? A pilot-study from an invaded alpine streambed. Ecology and Evolution 11: 12075– 12091. https://doi.org/10.1002/ece3.7973
Marx HE, Jorgensen SA*, Wisely E*, Li Z*, Dlugosch KM & Barker MS. 2021. Pilot RNA-seq data from 24 species of vascular plants at Harvard Forest. Applications in Plant Sciences 9(2): e11409. https://doi.org/10.1002/aps3.11409
Yang Y, Moore MJ, Brockington SF, Timoneda-Monfort A, Feng T, Marx HE, Walker JF, Smith SA. 2017. An efficient field and laboratory workflow for plant phylotranscriptomic projects. Applications in Plant Sciences . DOI: 10.3732/apps.1600128
San Juan Islands, Washington
Invasion dynamics on oceanic islands
Species introductions provide a unique opportunity to address diversity dynamics in nature, particularly within insular island systems. As alien species continue to accumulate across the globe, it is increasingly important to predict their future spread and impact. Darwin was one of the first to note the potential for species introductions for understanding the distributions we observe, predicting the success of alien species would depend on their similarity to the native community they invade. Since then, invaded communities have become an important study system for understanding community assembly and eco-evolutionary feedbacks in natural systems due to the replication of invasions at different scales.
My work has illuminated biogeographic and functional trends in island invasions. I am interested in continuing to incorporate anthropogenic, biogeographic, and climatic parameters to predict the spread of alien species given phylogenetic structure.
Key Publications:
Bach W, Kreft H, Craven D, König C, Schrader J, Taylor A, Dawson W, Essl F, Lenzner B, Marx HE, Meyer C, Pergl J, Pysek P, van Kleunen M, Winter M, Weigelt P. Phylogenetic composition of native island floras influences naturalized alien species richness. 2022. Ecography e06227 https://doi.org/10.1111/ecog.06227
Lu-Irving P, Marx HE, Dlugosch K. 2018. Leveraging contemporary species invasions to test phylogenetic hypotheses of trait evolution. Current Opinion in Plant Biology. 42: 95–102. DOI: 10.1016/j.pbi.2018.04.011
Marx HE., Giblin DE, Dunwiddie PW, Tank DC. 2016. Deconstructing Darwin’s Naturalization Hypothesis in the San Juan Islands using community phylogenetics and functional traits. Diversity and Distributions. 22: 318–331. DOI: 10.1111/ddi.12401. GitHub Dryad Data
Lantana growing in Tucson, AZ
Plant phylogenetics & systematics
The tree-of-life (TOL) provides a context to relate species across the planet and a foundation for testing ecological and evolutionary hypotheses about processes generating the great biodiversity we observe. Building and understanding the TOL has always been an important part of my research program. In particular, I view transcriptomics as a powerful tool for resolving species relationships (phylotranscriptomics) and for understanding the processes of diversification through patterns of gene expression and organization.
Key Publications:
One Thousand Plant Transcriptomes Initiative. 2019. One thousand plant transcriptomes and the phylogenomics of green plants. Nature. DOI: 10.1038/s41586-019-1693-2
Baniaga AE, Marx HE, Arrigo N, Barker MS. 2019. Polyploid plants have faster rates of multivariate climatic niche evolution than their diploid relatives. Ecology Letters. DOI: 10.1111/ele.13402
Landis JB, Soltis DE, Li Z, Marx HE, Barker MS, Tank DC, Soltis PS. 2018. Impact of wholegenome duplication events on diversification rates in angiosperms. American Journal of Botany–Special Issue: Using and Navigating the Plant Tree of Life. 105(3): 348–363. DOI: 10.1002/ajb2.1060
Marx HE, O'Leary N, Yuan YW, Lu-Irving P, Tank DC, Múlgura ME, Olmstead RG. 2010. A molecular phylogeny and classification of Verbenaceae. American Journal of Botany. 97(10): 1647-1663. DOI: 10.3732/ajb.1000144
Yuan YW, Liu C, Marx HE, Olmstead RG. 2009. The PPR (pentatricopeptide repeat) gene family, a tremendous resource for plant phylogenetic studies. New Phytologist. 182: 272-283. DOI: 10.1111/j.1469-8137.2008.02739.
15 million-year-old leaf, lifted from fossil beds in Clarkia, Idaho
Paleo-community diversity
Few localities can claim to be a Lagerstätte—a fossil site with exceptional preservation. The Miocene fossil beds in Clarkia, Idaho are one of them. In this ancient lake sediment, anoxic preservation compressed leaf tissues before they were able to decompose. Today, you can open blocks of this lakebed and watch leaves change from green to black before your eyes. While extracting ancient DNA remains challenging, I am intrigued by the idea of comparing genetic variation of 15 million year old sub-tropical plant communities with the coniferous forest that has since replaced it. Watch a video of us lifting leaves that fell from tress during the Miocene below!