Contaminants from human activities are ecological stressors

Global change goes beyond temperature as synthetic contaminants increasingly permeate our world, yet ecology and evolution research tends to focus on changing climate alone. An alarming amount of plastic enters the environment as trash, where it fragments into smaller and smaller particles. These particles persist, and have under-explored effects on organisms and their interactions, such as plants and their associated microbes. Some of my recent work seeks to understand effects of plastic.

Tire tread wear is a common microplastic, accumulates near roads, and leaches contaminants toxic to some animals into water. Dosing duckweed with his leachate increased growth but caused normally beneficial interactions with the microbiome to become costly, and induced plant-microbe fitness conflicts. Of course, the effects of tire wear particle leachate also depended on other manipulated aspects of global change: temperature and carbon dioxide. Check it out at Environmental Research, or the associated preprint to learn more.

Relatedly, work lead by Leah Chibwe identified that leachate from tire wear particles is more toxic to fathead minnows when particles leach for longer, or when fish are simultaneously exposed to the particles themselves. While leachate from tire wear particles is a highly complex mixture with many unknown compounds, the paper newly out at Environmental Toxicology and Chemistry, also identifies known chemical components of the leachate that are more correlated with toxic effects.

In work led by recent Master’s graduate Yawen Guo, we explored how background pollution with nanoscale plastic fragments may alter the effectiveness of hydrogen peroxide as a control measure for harmful algal blooms. Nanoplastics interfered with some of the toxic effects of hydrogen peroxide, but also had a toxic effect on algae themselves. We therefore expect that hydrogen peroxide will remain an effective control measure, though, as with duckweed, ecological context (light, temperature) matters. Out recently at ES & T Water.

Whose trait is it anyways?

We keep finding ways beneficial microbes affect traits of the organisms on which they live. I, @ChandraJack1, @symbiomics & @ME_Frederickson ask the obvious follow-up: how do traits evolve when selection acts on variation in both host and microbe genomes? Our manuscript is out now at ProcB: https://doi.org/10.1098/rspb.2020.2483

One key insight is that counter-intuitiively, conflict can increase mutualism. When hosts and microbes have fitness peaks at different trait values, this evolutionary conflict can actually cause hosts to depend MORE on microbes for optimal trait expression, thereby enhancing the degree of mutualism we would obsesrve.

Another key insight is that the evolution of traits in multiple genomes may favor local adaptation. If hosts are paired with microbes with which they did not share an evolutionary history, this would likely lead to trait mis-expression and appear as a signal of increased fitness with local microbes.

Quoted in the Christian Science Monitor

Tire wear particles are abundant and ubiquitous, but what are the consequences? and what can we do about it? I am happy to have been a part of this insightful piece in @csmonitor by Lindsey McGinnis @BylineLindsey featuring some truly innovative work by @Tyre_Collective, in addition to a small bit on my favorite tiny plant (duckweed, obviously) https://www.csmonitor.com/Environment/2020/1109/A-pollution-solution-where-the-rubber-meets-the-road?src=shared 

Paper in science!

Work led by Rebecca T Batstone shows that microbes evolve to benefit local hosts. One neat aspect of our work is that benefits occurred because loci increasing microbe fitness on local hosts also increased the fitness of local hosts — e.g. microbes were neither “altruistic” nor “cheaters.” Indeed alleles underlying mutual benefits more commonly contributed to evolved microbial differences for host and microbe growth than expected by chance.

See article: Experimental evolution makes microbes more cooperative with their local host genotype

Hear Rebecca discuss our results

Two duckweed papers recently out!

Co-occurring winter stressors reduce duckweed survival and growth, as well as benefits from microbiomes, at AJB:
Resilience to multiple stressors in an aquatic plant and its microbiome

Duckweed host a much simpler microbiome, yet different microbiomes still shift host growth & traits, as in terrestrial plants, at Microbial Ecology:
Mutualistic Outcomes Across Plant Populations, Microbes, and Environments in the Duckweed Lemna minor

Teosinte phenotypes that differ from low elevation, warm sites (later flowering, larger root mass) to high elevation, cold sites (early flowering, small roots) are shifted by root microbes. More interesting yet, microbes shift the genetic variation and covariation between traits, potentially altering plant responses to selection pressures, e.g. climate change.