Every year the McLachlan, Medvigy, and Rocha labs take on the Archie lab (+ friends) in bowling. For the 6th straight year in a row, we are the 2nd best bowlers around!
We once again will display the DNA helix with pride until next year’s battle!
2018 2nd Best Bowling Champs
New paper co-authored by Megan Vahsen from her master’s work has just come out in PNAS!
Abstract
Colonization and expansion into novel landscapes determine the distribution and abundance of species in our rapidly changing ecosystems worldwide. Colonization events are crucibles for rapid evolution, but it is not known whether evolutionary changes arise
mainly after successful colonization has occurred, or if evolution plays an immediate role, governing the growth and expansion speed of colonizing populations. There is evidence that spatial evolutionary processes can speed range expansion within a few generations because dispersal tendencies may evolve upwards at range edges. Additionally, rapid adaptation to a novel environment can increase population growth rates, which also promotes spread. However, the role of adaptive evolution and the relative contributions of spatial evolution and adaptation to expansion are unclear. Using a model system, red flour beetles (Tribolium castaneum), we either allowed or constrained evolution of populations colonizing a novel environment and measured population growth and spread. At the end of the experiment we assessed the fitness and dispersal tendency of individuals originating either from the core or edge of evolving populations or from nonevolving populations in a common garden. Within six generations, evolving populations grew three times larger and spread 46% faster than populations in which evolution was constrained. Increased size and expansion speed were strongly driven by adaptation, whereas spatial evolutionary processes acting on edge subpopulations contributed less. This experimental evidence demonstrates that rapid evolution drives both population growth and expansion speed and is thus crucial to consider for managing biological invasions and successfully introducing or reintroducing species for management and conservation.
Post by Erin Nguyen
The McLachlan team recently headed out into the field for some late season sampling. Jason, Megan, and two undergrads, Aleah and Erin, went to the Smithsonian Environmental Research Center (SERC) in Maryland to work with Pat Megonigal, Matt Kirwin and Nikki Brazzola. The group’s goal was to obtain live samples of Schoenoplectus americanus as well as sediment cores. These efforts were the latest chapter of the lab’s ongoing project to study S. americanus’s changing genetic landscape in the Chesapeake Bay through space and time.
On the team’s first day out in the marshes, Jason and company took a boat to reach a number of promising sites. With an expanse of blue sky above and golden grasses and sedges below, it was a stunning morning for sampling.
Under the heat of a blazing sun, the team collected a staggering 12 sediment cores to be later sieved through in hopes of obtaining ancient scirpus seeds that can be germinated and compared to their modern descendants.
The day was long and the work was hard but the journey and people were fantastic! To top off a productive and exciting field trip, the team caught one last stunning sight before heading home to ND.
The McLachlan lab is happy to be back in the Bend, and working on exciting, new developments with the marsh project!
Lumibao, C.Y., S.M. Hoban and J.S. McLachlan. 2017 Ice ages leave genetic diversity ‘hotspots’ in Europe but not in Eastern North America. Ecology Letters. doi:10.1111/ele.12853
In this paper the McLachlan lab studied the spatial pattern of genetic diversity of trees following glaciation in Eastern North America compared to that of Europe. While in Europe southern populations are more genetically diverse compared to northern populations, this is not the case in Eastern North America.
As noted in the paper: A common expectation in phylogeographic studies is that low latitude populations are reservoirs of genetic endemism due to long-term population isolation, and high latitude populations are genetically reduced due to post-glacial species migration (Taberlet et al. 1998). This expectation is largely based on European data, but has been assumed to be generally true across temperate forests (e.g. Roberts & Hamann 2015; Zinck & Rajora 2016). However, we did not find evidence that endemism across taxa was concentrated in southern latitudes in Eastern North America and we did not find reduced genetic diversity in northern latitudes in Eastern North America. (See figure 2 for example).
These findings have implications for genetic diversity in forests as they respond to future climate change. Based on previous work conducted in Europe, there was concern that in Eastern North America the southern reservoirs of genetic diversity were at risk and that northern populations may lack the genetic diversity needed to withstand new environmental challenges. However, our results indicate that temperate trees in Eastern North America may not be as vulnerable to the genetic impacts of climate change as European taxa.
The undergrads who work in our lab are awesome! Currently we have 10 students working on a diverse range of projects this semester. There are students sieving and germinating seeds from cores taken from a marsh in Maryland. These seeds will help us assess how the sedge Schoenoplectus americanus, has evolved over the past 100 years in response to changes in CO2, temperature, salinity and flooding regimes. We have students entering Public Land Survey data from the 1800s to help us recreate the composition, density, and biomass of historical forests of Indiana and Illinois. Other students are working on a different tree project that involves counting tree rings from 100-200 year old trees in oak savannas compared to those in woodlands to examine the trees’ response to climate change through time. This project also involves cutting up the tree rings to run isotope analyses to asses the water use efficiency of the trees throughout the trees’ lives and in the different conditions. Finally, we have a student working on a project that will use the ecosystem model Linkages within the PEcAn tool to improve predictions of tree growth.
Our undergrads work hard, but they also have lots of fun and they make the lab fun!
Look at this huge old tree undergrads Emily Miller, Alec Helmke and Erin Nguyen found while taking the summer course at Notre Dame’s field station, UNDERC!
All 3 students have entered an extensive amount of historical Public Land Survey tree data for the lab. Even when students aren’t in the lab, they can’t get away from thinking about old trees.
The McLachlan lab welcomes new graduate student Megan Vahsen!
Megan is joining us to work on the marsh evolution and ecology project. See this page to learn more about Megan and the project.
Jason coordinated Quant Camp, an optional full emersion short course on quantitative skills for early career BIOS grad students from all disciplines.
The goals of the course were to provide hands on practical experience in problem solving, to introduce best practices in scientific computing, overview of scientific workflows and project management, integrating models, theory, & data and basic concepts in statistics and probability.
Students learned about random variable, data distributions & disease on Day 1, state space models and ecosystem measurements on Day 2, and uncertainty and cancer on Day 3. They also worked in groups to develop their own independent projects where they applied the quantitative skills they learned.
Other course instructors were Beth Archie, Alex Perkins, Stuart Jones and a call-in by Zach Schafer. Incoming McLachlan graduate student Megan Vahsen was the TA for the course.
Here are some pictures from the course.
We’ve been awarded a new grant from NSF (DEB- Ecosystem Studies) for our project on Eco-evolutionary dynamics of coastal marsh responses to rishing CO2!
Here’s the overview of our proposed work:
Current projections of coastal marsh ecosystem responses to global environmental change (i.e., rising atmospheric carbon dioxide, sea level rise) assume static relationships between climate-related stressors and plant performance. However, the performance of ecologically dominant plants can rapidly evolve in response to climate-related stressors, which suggests that evolution could be driving ecological change in coastal marshes. Utilizing a 100+ year seed bank of the foundational sedge Schoenoplectus americanus (formerly Scirpus olneyi), we aim to examine the evolutionary dimensions of coastal marsh responses to environmental change. Building on preliminary findings, our goal is to determine whether ecosystem processes that regulate surface elevation are shaped by heritable responses of S. americanus to salinity, inundation, and carbon availability. To do so, we will first propagate and genotype modern and “ancestral” cohorts of plants from seeds retrieved from Chesapeake Bay marsh sediment cores. Taking ecological interactions into consideration, we will then conduct fully crossed exposure experiments with contemporary and ancestral cohorts to measure heritable, non-heritable and environmental contributions to plant traits, growth, and surface elevation. We will assess the aggregate importance of evolution to carbon and sediment accumulation (and allied processes) through a mechanistic model that accounts for data and model uncertainty. We will validate model predictions against independent estimates from sediment core profiles, and we will use a Bayesian assimilation framework to integrate all data streams (i.e., experiments, paleo observations, model predictions, prior studies) to determine the extent to which a century of evolution has affected Chesapeake Bay marshes, and how further data collection and model improvements might strengthen predictive forecasting.
It’s time for a change! The McLachlan lab has transferred to this new website. We are currently in the process of updating our website content, so please excuse our dust for a little bit.
