Finding “hidden” effects of nonnative plant invasion

In my post-doc work on how colonisation and diversification of plant lineages can have a legacy effect on extant plant communities, we previously showed that understanding evolutionary priority effects is necessary to predict the structure and function of pristine ecological communities. In a paper just published in New Phytologist, we tested whether anthropogenically-driven changes in available habitat and mass immigration (i.e. non-native invasion) eliminate the role of evolutionary priority effects in community assembly. We advanced the theory that radiating lineages can monopolize niche space by showing that evolutionary drivers of community assembly also operate in new habitat created by anthropogenic disturbance. However, we also demonstrated that non-native invasion can erase the otherwise strong role of evolutionary priority effects in shaping native community composition. This work is important and timely because it indicates that effects of human-induced global change on community assembly extend beyond purely ecological dynamics to the ecological consequences of plant radiations.

Burns lab paper out in Oecologia

Our newest paper from our common garden experiment testing whether plant-induced soil heterogeneity promotes plant species coexistence is out in the April issue of Oecologia. In this paper we show that soil heterogeneity increases per capita biomass of invaders  (i.e. the disadvantaged species in a competing pair). By using a reciprocal invasion among species pairs in our experimental design, this indicates mutual invasibility by this species pair, which is a criterion for stable coexistence. Moreover, we unlock the “black box” of mechanistic drivers of plant-soil feedbacks by measuring the spatial arrangement in both biotic and abiotic soil properties within our experimentally-created soil treatments. We show that soil biota (bacteria and fungi) and phosphorous may be important drivers of the reproductive biomass response to the spatial arrangement of plant-soil feedbacks.

This paper wouldn’t have been possible without the outstanding work of Ph.D. student, Jennifer Murphy, and undergraduate student, Angela Kaczowka, along with many other students of the Burns lab who assisted with experimental set-up and data collection over the 4 years of the experiment.

Our paper is Editor’s Choice in Journal of Ecology

Our paper on evolutionary priority effects in New Zealand forests has been selected as the Editor’s Choice article in the upcoming issue of Journal of Ecology — the editors wrote this great blog post summarising our findings and the implications for our understanding of ecological communities. And one of my co-authors and one of our lab’s PhD students kindly supplied me with useful (and attractive!) photos to include in the blog post.

Evolutionary drivers of assembly in NZ forests

Our paper showing an evolutionary legacy of community assembly in New Zealand forests, an evolutionarily older and more structurally complex ecosystem than investigated to date, is now in early view online at the Journal of Ecology. We have shown that evolutionary priority effects — where early-arriving ancestral taxa diversify and preempt niche space, precluding later arrivals from dominating new habitats — shape extant communities of both pteridophytes and angiosperms. These physiologically-contrasting taxonomic groups exhibit different responses to precipitation gradients, however. Evolutionary priority effects in pteridophyte communities become stronger with increasing precipitation, as predicted by the hypothesis that competition has a greater role in structuring communities in benign or resource-rich environments (i.e. the Stress Gradient Hypothesis). Angiosperms show a different pattern, with stronger priority effects in the drier eastern portion of the mountain range we sampled, suggesting that environmental drivers other than precipitation may be more important in structuring angiosperm communities. Our work thus advances current understanding by showing a remarkable consistency of clade age effects on community dominance across different ecological conditions — more structurally complex ecosystems and longer evolutionary timescales, as well as across physiologically-contrasting taxonomic groups.

Delving into taxonomy – in the marine realm

I’ve recently had the opportunity to expand my academic horizons by assisting a Ph.D. student (who has now completed his degree!) with statistical analysis of morphological data from two purported species of New Zealand brachiopods, which are shelled marine animals in their own phylum that is closely related to the molluscs. Though we were unable to statistically distinguish the species based on morphometrics, enzyme analysis indicated that they should remain separated. Moreover, we confirmed that morphological differences between brachiopod species in other genera range from very small to quite large. It’s been quite a novel experience for this plant community ecologist to have a hand in taxonomic research, and on marine animals at that!

Paper out in New Phytologist

My first publication from our Marsden-funded project on evolutionary priority effects in the New Zealand flora is now available for early view in New Phytologist. Led by Dr. Andrew Tanentzap at the University of Cambridge, this paper tests the hypothesis that early-arriving plant lineages had greater access to niche space in the alpine zone and were thus able to diversify within that space, preventing later arrivals from dominating the community. We find evidence to support all of our predictions. This paper was first inspired by a Radiations Symposium in Switzerland last June, attended by Dr. Tanentzap and my supervisor, Dr. Bill Lee. I also spoke about this work at the New Zealand Ecological Society’s annual meeting last November.

Two new papers out – co-authored with undergraduates from CWRU

After a busy couple of months doing final revisions and checking proofs for two manuscripts co-authored with stellar undergraduates from the Burns Lab at CWRU, I was happy to find that both manuscripts went online yesterday!

First, in an experiment that manipulated the timing of plant establishment in competition between congeners, we found evidence for plasticity in two functional traits that is consistent with predictions for adaptive trait plasticity in some species, where the later-establishing plant’s trait values would maximize resource capture. The type of plastic response — either a difference between late- vs. early-establishing plants of the same species or divergence in trait values between potmates — differed by genus. Moreover, divergence in specific leaf area between potmates positively correlated with combined biomass of those potmates, consistent with putatively adaptive trait plasticity. This work, co-authored with Conor Leahy and Nicole Zimmerman as well as Dr. Jean Burns, is now published in Oecologia. Nicole has now completed a Master’s degree in biostatistics from the University of Michigan and I especially appreciated her help with the statistical analysis in this paper.

Second, in a paper led by Gaston del Pino and now published in Plant Ecology, we show evidence for functional trait plasticity in response to experimentally-manipulated heterogeneity in both the above- and belowground environment (light and soil heterogeneity, respectively). We found that above- and belowground heterogeneity can interact to affect trait expression. We also found non-additive effects of mixing soils of two origins (i.e. collected from the zone of root influence of different plant species in the field), which is consistent with findings in my previous work with Dr. Burns (here and here).