I am an evolutionary ecologist broadly interested in understanding the causes and consequences of biodiversity under the evolutionary timescale. My current research is mainly based on laboratory experiments with plankton and microorganisms from freshwater and soil ecosystems. I aim to work at the interface of ecology and evolution, with two primary interests—community phylogenetics and eco-evolutionary dynamics.
I recently started as a postdoc with Mart Turcotte at the University of Pittsburgh to study the eco-evolutionary dynamics in duckweed communities.
Species phylogenetic relationships and community processes
Phylogeny describes the evolutionary relationships between species. As suggested by Charles Darwin, closely related species may be more similar in traits. These species may require more similar resources and compete more strongly with each other (i.e., Darwin’s relatedness-competition hypothesis). Phylogenetic distance between competing species, therefore, can be used as a predictor for the trait similarity and competitive strength between related species. Based on this idea, I have been testing the explanatory power of phylogenetic distance for community assembly, invasibility, and ecosystem functioning.
Ecological regulations of adaptive radiation
Adaptive radiation is an important evolutionary process, through which a single species lineage diversifies rapidly to utilize various niches within a habitat. I am interested in exploring those mechanisms that drive biodiversity during adaptive radiation.
I use the bacterium Pseudomonas fluorescens SBW25 as the laboratory model of adaptive radiation. The ancestral phenotypes of SBW25, smooth morph, rapidly evolves biofilm forming phenotypes, including wrinkly and fuzzy spreaders in static microcosms.
Adaptive radiation of Pseudomonas fluorescens SBW25
From an ecologist's perspective, ecological factors influence adaptive radiation, either through affecting the population size of diversifying lineages or through modifying niche availability for the establishment of newly emerged mutants. My research has shown that temporal and spatial fluctuations in environmental conditions, which constitute temporal and spatial niches, promote biodiversity during adaptive radiation. Meanwhile, the presence of competitors reduces the population size of diversifying species, and thus, suppresses their adaptive radiation. The negative impact of competition on adaptive radiation, however, decreases as if the diversifying lineages arrive in the habitat earlier.
Smooth morph and wrinkly spreader phenotypes colonizing an agar plate
Exploring the impact of artificially engineered nanoparticles on evolution
I recently started a new project, testing the long-term impacts of copper oxide nanoparticles (CuO NPs) on the multicellularity evolution in yeast. Artificially engineered nanomaterials have become an indispensable component of modern life, and CuO NPs are the materials that have been applied in almost every piece of electronic device and eventually released in the environment.
Microorganisms may develop unique, heritable traits in response to such novel environmental stressor. One possible trait is multicellularity, which reduces the surface-to-volume ratio of individuals and minimizes the impacts of the adverse environment.
In the interdisciplinary project, we show that copper oxide nanoparticles promote the evolution of multicellularity in Baker’s yeast in 280 generations. The multicellularity yeast, most of which carry mutations in the transcription factor ACE2, maintain the copper homeostasis in their cells and yield higher ATP production through increasing aerobic respiration. Therefore, yeast evolutionary adapt to the nano stress through developing multicellularity.
Top left: Copper oxide nanoparticles under a transmission electron microscope.
Top right: A multicellularity yeast cluster under an optical microscope.
Bottom: The dynamics of average cluster size of yeast indicate that larger multicellular yeast evolves in the presence of copper oxide nanoparticles.
Tan, J. *, Q. He*, J. P. Pentz, C. Peng, X. Yang, M.-H. Tsai, Y. Chen, W. C. Ratcliff, and L. Jiang. Nanoparticles promote the evolution of multicellularity in yeast. Nanotoxicology, accepted. DOI:10.1080/17435390.2018.1553253. (*Authors contributed equally)
Li, S.-P.*, J. Tan*, X. Yang, C. Ma, and L. Jiang. Species niche and fitness differences predict invasion success and impact in experimental microbial communities. ISME Journal, in press. (*Authors contributed equally)
Yang, X., Z. Yang, J. Tan, G. Li, S. Wan, and L. Jiang. 2018. Nitrogen fertilization, not water addition, alters plant phylogenetic community structure in a semi-arid steppe. Journal of Ecology, 106:991-1000.
Tan, J., J. B. Rattray, X. Yang, and L. Jiang. 2017. Spatial storage effect promotes biodiversity during adaptive radiation. Proceedings of the Royal Society of London B, 284:20170841.
Tan, J., X. Yang, and L. Jiang. 2017. Species ecological similarities modulate the impact of species colonization history on adaptive radiation. Evolution, 71:1719-1727.
Ma, C., S. Li, Z. Pu, J. Tan, M. Liu, J. Zhou, H. Li, and L. Jiang. 2016. Contrasting effects of invader-native phylogenetic relatedness on invader success and impact: A meta-analysis of Darwin’s naturalization hypothesis. Proceedings of the Royal Society of London B, 283:20160663.
Tan, J., M. R. Slattery, X. Yang, and L. Jiang. 2016. Phylogenetic context determines the role of competition in adaptive radiation. Proceedings of the Royal Society of London B, 283:20160241.
Tan, J., Z. Pu., W. A. Ryberg, and L. Jiang. 2015. Phylogenetic relatedness between resident and invading species, not phylogenetic diversity of resident communities, determines invasibility. American Naturalist, 186:59-71.
Pu, Z., P. Daya, J. Tan, and L. Jiang. 2014. Phylogenetic diversity stabilizes community biomass. Journal of Plant Ecology, 7:176-187.
Tan, J., C. K. Kelly, and L. Jiang. 2013. Temporal niche promotes biodiversity during adaptive radiation. Nature Communications 4, doi:10.1038/ncomms3102.
(Featured by the Georgia Tech Research Horizon)
Tan, J., Z. Pu, W. A. Ryberg, and L. Jiang. 2012. Species phylogenetic relatedness, priority effects, and ecosystem functioning. Ecology, 93:1164-1172.
(Recommended by the Faculty of 1000)
Jiang, L., L. Brady, and J. Tan. 2011. Species diversity, invasion, and alternative community states in sequentially assembled communities. American Naturalist, 178:411-418.
Jiang, L., J. Tan, and Z. Pu. 2010. An experimental test of Darwin's naturalization hypothesis. American Naturalist, 175:415-423.
(Recommended by the Faculty of 1000)