I am extremely excited to announce that I will be joining Earlham College, as an Assistant Professor of Biology, in July 2018. I admire the strength of the Biology Program at Earlham College and its dedication to the education of the next generation of global thinkers, leaders, and citizens, and I am honored to have the opportunity to join the Faculty.
Climatic niche shifts are common in introduced plants.
I am very excited to announce that our paper has just been accepted for publication by Nature: Ecology & Evolution. In it, we show that almost 1000 invasvie plant species occupy much different climates in their introduced range than in their native range.
This finding is significant for several reasons. First, it means that species do not necessarily occupy the same environments everywhere they are found on Earth. Second, it casts doubt on the viability of using information about species’ native-range habitat preferences to predict where they will invade.
However, we found that niche shifts depended upon species growth form, life expectancy, and degree of cultivation, suggesting that ‘niche shifts’ might be predictable.
Particular congratulations go to Carissa Ervine, who contributed to this manuscript as an undergraduate student. She was responsible for assembling the first version of our database of 13 million occurrence records for 1135 species–a major undertaking!
Competition and propagule density affect sexual and clonal propagation of a weed.
Atwater, Kim, Tekiela, Barney
This study was pioneered by Wonjae Kim, an undergraduate student at Virginia Tech who designed and executed it on a grant from the Fralin Life Sciences Institute.
Wonjae confirmed that Johnsongrass establishes readily both from seed and from buried rhizome fragments, although these two modes of reproduction differed in their sensitivity to competition and soil quality. In fact, a single plant produces enough seeds and rhizomes to establish over more than a hectare (if spread out evenly)!
Wonjae’s results show that effective management of Johnsongrass must limit spread from both seeds and underground rhizomes.
A great way to ring in the new year!
Ecotypic diversity of a dominant grassland species resists exotic invasion
Yang, Callaway, Atwater
In this study, Lixue Yang showed that bluebunch wheatgrass (Pseudorogneria spicata) populations with greater within species diversity were pound-for-pound more resistant to invasion by spotted knapweed (Centaurea stoebe) than populations with less species diversity, by an order of magnitude.
Dr. Yang attributed this to two processes: 1) as seen in our previous study, more diverse bluebunch populations had greater yield, and 2) even accounting for their increased yield, diverse populations were more resistant to invasion than suspected.
This paper takes an important step towards demonstrating the extreme–yet cryptic–effects that within-species diversity has on plant communities.
Evidence for fine-scale habitat specialization in an invasive weed
Atwater, Fletcher, Dickinson, Paterson, Barney (pdf)
In previous studies, we found evidence for striking genetic and phenotypic differentiation in Johnsongrass (Sorghum halepense) populations collected throughout the United States. Here, we report that Johnsongrass may be adapting to local habitat variation.
Johnsongrass from non-agricultural populations competed better in a field community than Johnsongrass from agricultural populations. Agricultural and non-agricultural populations were separated by less than a kilometer, suggesting that this species may be adapting to habitat variation at extremely fine spatial scales.
These results contribute to a growing list of studies revealing the importance of fine-scale habitat specialization in invasive species, with possible ecological and management implications.
Multi-phase US spread and habitat switching of a post-Columbian invasive, Sorghum halepense
Sezen, Barney, Atwater, Pederson, Pederson, Chandler, Cox, Cox, Dotray, Kopec, Smith, Schroeder, Wright, Jiao, Kong, Goff, Auckland, Rainville, Pierce, Compton, Lemke, Philips, Kerr, Mettler, Paterson (pdf)
I’m happy to announce that PLoS One has accepted Uzay Sezen’s paper documenting the population genetics of colonizing Johnsongrass (Sorghum halepense).
Using a panel of almost 500 Johnsongrass accessions from 70 sites throughout the US, Dr. Sezen showed that Johnsongrass was introduced to the US at two locations. It has subsequently colonized much of North America, demonstrating surprising genetic variation even at range margins.
Johnsongrass populations have also differentiated strikingly along habitat boundaries, with genetic clusters segregating strongly between crop populations and those found in roadsides and other disturbed environments.
The mechanisms and consequences of interspecific interactions among plants
Aschehoug, Brooker, Atwater, Maron & Callaway (pdf)
I’m very pleased to announce that Annual Reviews of Ecology, Evolution and Systematics has accepted our review article documenting recent advances in our understanding of interspecific plant interactions.
I am proud to have been a part of this group. Erik spearheaded this effort and has worked very hard to bring the finished product together. I look forward to the publication of our review in November!
Intraspecific diversity buffers the inhibitory effects of soil biota
Congratulations to Wenbo Luo for recently having a paper accepted to Ecology! In this paper, Wenbo shows that soil microbes inhibit the growth of related bluebunch wheatgrass plants (Pseudoroegneria spicata).
To do this, he collected soil from bluebunch populations varying in their genetic diversity. He then grew bluebunch seedlings in that soil and compared their growth.
Seedlings did not grow well in soil from populations with low genetic diversity. This effect went away when the soil was sterilized, suggesting that soil microorganisms were responsible.
Soil feedbacks such as these are thought to result from adaptation by soil pathogens. Wenbo’s results suggest that soil pathogens specialize not only on species but on related individuals. This also provides a mechanism affecting the high productivity we see in genetically diverse bluebunch wheatgrass populations.