Rudgers & Whitney Labs

For links to lab members’ individual research projects, see the ‘Lab Personnel’ page. Below are the major funded projects currently active in the lab:

Species fundamentally vary in their abundance, spanning a range from federally endangered species to severely weedy invaders. Several hypotheses have been proposed to explain this pattern, but none sufficiently account for observed variation. In part, this failure might reflect the fact that microbial symbioses (widespread, mutually beneficial associations between microbes and plants) have been largely ignored. This proposal forges a new direction by evaluating the role of microbial symbioses in governing rarity and invasiveness. Taking advantage of the experimentally tractable symbioses between grasses and microbial endophytes (fungi that live within plant leaves), proposed experiments and demographic models test whether and how symbionts increase host abundance. In grasses, endophytes may improve host resistance to herbivory through the production of alkaloids toxic to insects and mammals and also may enhance host drought tolerance. Comparative experiments on paired rare and common grass species will test predictions that symbionts’ benefits are greater for common than rare host species and differ between native and non-native hosts, providing the most comprehensive study to date on the ecology of grass-endophyte symbioses. A clearer understanding of endophyte ecology can offer novel strategies for rare plant conservation and invasive plant control (e.g., via endophyte additions or eliminations). Through networks established in both Indiana and Texas, information will be broadly communicated to state agencies, preserve managers, seed companies, and conservation organizations. The work will additionally integrate teaching and research, by training graduate and undergraduate students as well as bringing contemporary research into the classroom.

Hybridization is a widespread phenomenon, yet its role in evolution is still under debate. Is it a maladaptive, homogenizing force (think mules) or can it contribute to adaptation and evolutionary diversification? We are currently implementing a novel approach that compares long-term evolutionary change in experimental hybrid and control (non-hybrid) lines in the field. These lines are modeled on (i.e. derived by crossing the parents of) a well-studied hybrid sunflower lineage, thus providing a rich context for interpretation. The proposed project asks: (1) Can introgression increase rates of adaptation?, (2) Can introgression increase rates of phenotypic evolution?, and (3) Are evolutionary trajectories in hybrid populations predictable? These questions will be addressed by tracking fitness, 20 traits, and 20 molecular markers (linked to quantitative trait loci, QTL) in the experimental hybrid and control populations over 5-10 generations. Evolutionary change will be distinguished from phenotypic plasticity by comparing the lines in replicated common gardens. The long-term predictability of change in hybrid systems will be examined by assessing whether the experimental hybrids converge phenotypically and genotypically on the natural hybrid upon which they are modeled. The proposed research is first experimental field study to examine the impact of hybridization on adaptive evolution over multiple generations in a wild (non-crop) system.

Invasive species pose one of the greatest threats to global biodiversity, and tropical oceanic islands are particularly vulnerable to their negative impacts. For these systems, invasion by the yellow crazy ant (Anoplolepis gracilipes) is a major threat. Identified by the International Conservation Union as one of the world’s 100 worst invaders, this species has already decimated some tropical island ecosystems. In Samoa, an island group integral to the Polynesia/Micronesia biodiversity hotspot, presence of the yellow crazy ant is of acute concern. Our data suggest that yellow crazy ants are at a critical stage in their invasion, possibly transitioning from low-level persistence into a phase of rapid population growth with potentially severe ecological consequences. We will investigate the ecological mechanisms that underlie yellow crazy ant success, examine early impacts of the invasion on native communities, and test how community dynamics, specifically novel beneficial relationships with native species, may feed back to influence the invasion. This work will both advance ecological theory and provide critical information needed for conservation planning.