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KEN WHITNEY |
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| Dr. Kenneth Whitney |
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Research interests |
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My interests are in the interplay between ecology and genetics in plant-animal interactions. These interactions range from mutualistic (seed dispersal, protection) to negative (seed predation, herbivory). Major questions include how genetic diversity is maintained in nature, how invasive plant species acquire their invasive traits, and how genome size might affect plant ecology and evolution. To examine these interactions I use a variety of techniques, including experimental field and greenhouse studies, molecular genetic techniques, stable isotope analyses, and (with collaborators) chemical analyses of plant secondary compounds. I work in systems ranging from Texas oak woodlands to central African forests and Australian deserts.
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| Funded Research | |
| Long-term natural selection and adaptive introgression in weedy sunflowers NSF DEB-0716868; co-PI L. Rieseberg; 9/2007 - 8/2012; $577,527 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. Yellow Crazy Ant invasion of the Samoan Archipelago: Do novel mutualisms amplify the ecological impacts? National Geographic Society 8237-07; co-PIs Amy Savage, Jennifer Rudgers; 5/2007-9/2008; $20,000 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.
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Joining the lab |
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Postdocs, graduate students, and undergraduates interested in joining the lab are encouraged to contact me by email. See the Lab Webpage for more information on the lab itself. |
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| Current Projects | |
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Ecology and evolution of fruit color polymorphism in Acacia ligulata Color polymorphisms (genetically-based differences in color among individuals in a population) are powerful tools for examining links between population genetics and ecology. One can identify different genotypes simply by looking. A major question is how multiple genotypes are maintained in populations – the genetic equivalent of asking how multiple species are maintained in ecological communities. The Australian desert shrub Acacia ligulata has a carotenoid-based polymorphism in which an individual produces either red, orange, or yellow arillate seeds. Both avian seed dispersers and (unexpectedly) insect seed predators mediate selection on fruit color, such that the identity of the most fit morph varies among populations. This suggests that fluctuating selection acts to maintain genetic diversity in this system. Future work will involve more ecological fieldwork (how and why do insect seed predators discriminate among the morphs?) and development of microsatellite markers to examine genetic structure and gene flow among populations.
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| Arillate seeds of the three Acacia ligulata color morphs | |
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Hybridization and invasion: is there a causal link? Many invasive plant species are known to have a history of hybridization, but it is not known whether hybridization is actually causal. What traits are changed by hybridization, and do these altered traits affect the invasive potential of plants? In collaboration with Rebecca Randell, Loren Rieseberg, and others, I am investigating the role of hybridization in the invasive success of Helianthus annuus ssp. texanus, a sunflower that has colonized central and southern Texas in recent historical times. This subspecies is both morphologically similar to, and contains genetic material from, the Texas endemic H. debilis ssp. cucumerifolius. However, the adaptive value, if any, of the introgressed genes is unknown. I am examining the hypothesis that herbivore resistance traits have introgressed from H. debilis to H. annuus and that they contribute to invasiveness in the latter. Significantly, I have shown that H. debilis is more resistant to both leaf herbivores and seed predators than H. annuus. In artificial hybrid populations, herbivore resistance is under positive selection, indicating that debilis-derived alleles may have increased adaptation in H. annuus. I am currently using QTL mapping to ask whether increased resistance is the result of H. debilis alleles, as predicted. Ongoing, long-term field experiments are tracking allele frequency changes in hybrid populations to test the long-term adaptive value of the introgressed alleles.
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| Hybrid sunflower in central Texas | |
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Ecology and evolution of genome size in plants Plant species differ tremendously in the amount of DNA comprising their genomes. Most of this variation can be accounted for by two sources: differences in the amount of noncoding (so-called ‘parasitic') DNA, and polyploidy (genome duplication). How genome size differences arise, and whether they have fitness consequences for plants, are currently areas of great interest. In collaboration with Eric Baack, I am investigating several questions in this area, including whether plant breeding system (inbreeding vs. outcrossing) is related to genome size, whether hybridization can trigger changes in genome size, whether reported instances of intrapopulation variation in genome size actually exist, and how genome size differences affect plant ecology. |
| Parasitoid wasp emerging from a sunflower achene | |
updated Sep 2007 |