Dr. James Gallagher
Postdoctoral Research Scholar, University of California, Davis
Date: August 28th
Time: 12:00pm – 1:00pm
Location: Science Building 1111
The Emergence of Phenotypic Variation: From Individual Development to Evolutionary Change
Across taxa, populations with greater phenotypic variation are generally better able to adapt to changing environments and are more likely to produce new species. Therefore, understanding how that variation is generated, from individual development to evolutionary change across populatios, is essential to explaining biodiversity. I begin at the individual level, disentangling the developmental drivers of behavioral variation. Differences in behavior among individuals (“behavioral individuality”) have long been assumed to stem from among-individual genetic or environmental variation. Using a naturally clonal fish species, I tested the contributions of early-life environment and among-individual genetic variation in a pair of studies, continuously tracking individuals from birth through development with machine learning. Surprisingly, behavioral individuality arose at comparable magnitudes across contexts. Other influences, such as the identity of an individual’s mother, explained substantial behavioral variation, pointing to developmental influences established before birth, and challenging our long-standing assumptions about the mechanisms that generate behavioral variation. Next, I shift to the origins of variation at the population level, examining a living case study of evolution in action. In Hawaii, male cricket song attracts both mates and a deadly parasitoid fly. Over the past two decades, this interaction led to an increase in morphological and associated song variation. I capitalized on this rare case of observable evolution to better understand how new variation arises in populations by 1) characterizing these new sexual signals, 2) revealing the physical mechanisms underlying their production, and 3) following the resulting evolutionary dynamics in populations over time. I show that there has been a recent explosion of novel phenotypes with unique wing-song relationships that each serve as different evolutionary solutions to the challenge of attracting mates while evading parasitism. These dynamics have resulted in the continued emergence and maintenance of new song variation across Hawaii. My work shows that phenotypic variation can emerge in surprising ways and on more rapid timescales than expected.