Anna K. Greenwood, Ph.D.
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Research Interests
What are the genetic and developmental changes that underlie phenotypic evolution? Anti-predator adaptations are particularly well-suited phenotypes for addressing this question due to the obviously strong selective pressure for successfully avoiding predation. Using a variety of approaches, my postdoctoral work has examined the anatomical, developmental, and genetic basis for evolution of anti-predator morphology and behavior in two different fish lineages.
Developmental and Genetic Basis for Divergence in Cryptic Pigmentation Patterns
In the Peichel Lab, we exploit the natural diversity among recently formed threespine stickleback populations and the expanding array of genetic tools that have been developed for sticklebacks to explore the genetic changes underlying adaptive evolution. One of my projects examines the genetic and developmental basis for variation in cryptic pigmentation in juvenile sticklebacks from different environments. Lake sticklebacks exhibit dramatic vertical barring whereas several populations of marine sticklebacks do not. These pigment pattern differences emerge quite early in development. Pigment cells can be easily visualized, enabling a detailed comparison of pigment cell behavior during pattern formation in lake and marine fish. In addition, I have performed quantitative trait locus (QTL) analysis in order to identify the genetic changes that account for these differences in pigment pattern development (Greenwood et al, in press).
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Pigment patterns of juvenile sticklebacks from different habitats. |
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Neural and Genetic Basis for Schooling Behavior Divergence
In a second project, I am examining divergence in schooling behavior among stickleback populations from different habitats. Marine sticklebacks exhibit robust schooling behavior, but benthic lake sticklebacks show a reduced tendency to school. Abby Wark and I developed an assay that uses a school of model sticklebacks to elicit schooling behavior in the lab. We used this assay to phenotype marine-benthic F2 hybrids and have identified two QTL that are associated with divergence in schooling behavior. We are currently in pursuit of the genetic and neural correlates of differences in schooling behavior.
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| Video frames of a marine and benthic stickleback interacting with the model school, as viewed from above. The heads of the live fish are indicated with an asterisk. |
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Neural Basis for Evolution of Startle Responses in Pufferfish
I spent the summer of 2007 as a Grass Fellow at the Marine Biological Laboratory in Woods Hole, MA studying a completely different type of anti-predator adaptation in pufferfish. I identified variation in startle responses among species of pufferfish, and connected these behavioral differences to changes in neural circuitry (Greenwood et al, 2010). In particular, I found that the green spotted puffer (Tetraodon nigroviridis) has robust fast-starts and has the key neurons (Mauthner cells) that regulate this response in most fish. In contrast, spiny puffers (Diodon holocanthus) do not exhibit true fast-starts and they do not have Mauthner cells. I also discovered that puffers exhibit a novel startle response that implies a link between puffer-specific inflation behavior and the ancestral fast-start escape.
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| Silhouettes of pufferfish at 2 ms intervals during a startle response. | |
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Publications
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Wark AR*, Greenwood AK*, Taylor EM, Yoshida K and Peichel CL (2011). Heritable differences in schooling behavior between marine and freshwater sticklebacks revealed by a novel assay. PLoS ONE, 6: e18316. |
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Greenwood AK, Jones FC, Chan YF, Brady SD, Absher DM, Grimwood J, Schmutz J, Myers RM, Kingsley DK and Peichel CL (2011). The genetic basis of divergent pigment patterns in juvenile threespine sticklebacks. Heredity. doi:10.1038/hdy.2011.1. |
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Greenwood AK (2010). Sensory evolution: Picking up good vibrations. Current Biology 20: R801-802. |
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Greenwood AK, Peichel CL and Zottoli SJ (2010). Distinct startle responses are associated with neuroanatomical differences in pufferfishes. Journal of Experimental Biology 213: 613-620. |
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Greenwood AK, Wark AR, Fernald RD and Hoffmann HA (2008). Expresion of arginine vasotocin in distinct preoptic regions is associated with dominant and subordinate behavior in a cichlid fish. Proceedings of the Royal Society B doi:10.1098/rspb.2008.0622. |
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Au TM, Greenwood AK and Fernald RD (2006). Differential social regulation of two pituitary gonadotropin-releasing hormone receptors. Behavioural Brain Research 170: 342-346. |
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Grens KE, Greenwood AK and Fernald RD (2005). Two visual processing pathways are targeted by gonadotropin-releasing hormone in the retina. Brain, Behavior and Evolution 66: 1-9. |
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Greenwood AK and Fernald RD (2004). Social regulation of the electrical properties of gonadotropin-releasing hormone neurons in a cichlid fish (Astatotilapia burtoni). Biology of Reproduction 71: 909-918. |
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Greenwood AK, Butler PC, White RB, DeMarco U, Pearce D and Fernald RD (2003). Multiple corticosteroid receptors in a teleost fish: distinct sequences, expression patterns, and transcriptional activities. Endocrinology 144: 4226-4236. |
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Flaherty CF, Greenwood A, Martin J and Leszczuk M (1998). Relationship of negative contrast to animal models of fear and anxiety. Animal Learning & Behavior, 26: 397-407. |
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| *co-first authors |
Page Last Updated: 19 April 2011
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