| Description |
To understand the process of speciation, evolutionary biologists have traditionally researched extant groups of organisms that have undergone adaptive radiation. Studying speciation in this way relies on inferences about past selective events that have shaped contemporary patterns of diversification. A complimentary approach to studying speciation is to experimentally evolve an adaptive radiation from a single population to examine the initial processes driving adaptive divergence. In my dissertation, I used feather lice ( Columbicola columbae) and their avian hosts (Columba livia ) to examine the earliest stages of adaptive radiation. I used domesticated pigeon breeds that vary in size and color as divergent habitats in which to experimentally evolve a single species of feather louse. The first part of my dissertation explored two aspects of host behavior that may be important defenses against lice. First, I tested if the effectiveness of preening improves with experience. I found that pigeons removed about the same number of lice regardless of prior experience. I then tested for an ectoparasite control function of allopreening. My data suggest that allopreening is, indeed, important for ectoparasite control. The remainder of my dissertation focuses on adaptation by lice to new hosts. Specifically, I examined changes in three phenotypic traits of feather lice: louse color, louse size, and louse behavior. First, I explored the evolution of cryptic coloration in lice. I showed that lice transferred to white pigeons evolved significantly lighter coloration than those on darker pigeons. Second, I tested whether louse size is also an adaptation for avoiding host defense. I found that when lice were transferred to larger pigeons they evolved larger size. However, lice transferred to smaller pigeons did not get smaller; instead, these lice altered their behavior to escape preening. I then further explored these changes in louse behavior and found that lice shifted microhabitat when transferred to smaller hosts. However, the direction and magnitude of this shift depended on the preening ecology of their host. Finally, I showed that increases in louse body size on larger hosts directly affects louse mating success. My work demonstrates how local adaptation can drive diversification among host-specific parasites. |
