Thesis (Ph. D.)--University of Chicago, Committee on Evolutionary Biology, August 2000. / Includes bibliographical references. Also available on the Internet.

Thesis (M.Sc.)--York University, 2004. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 56-82). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ99333

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My dissertation focuses on the evolutionary forces that have shaped the chemical signaling system of plethodontid salamanders. Pheromones mediate two phases of plethodontid reproduction: mate attraction prior to courtship and female persuasion during courtship. Substrate-borne chemical signals are believed to play an important role in mate attraction for these animals. A behavioral assay of sex- and species-specific odor preferences in closely related species of Plethodon indicates that: (1) there is asymmetry on the receiver side of the system, wherein male salamanders invest more energy searching for mating partners than do females; (2) substrate-borne chemical signals are sexually dimorphic and male preference strongly favors the female odor versus the male odor; (3) females of allopatric salamander species have evolved distinctive chemical cues; and (4) female chemical signals of sympatric species are divergent and may play a role in sexual isolation. Sexual persuasion is another phase of plethodontid reproduction that is mediated by chemical signals. Plethodontid Receptivity Factor (PRF) is a proteinaceous pheromone that is produced by the male and delivered to the female during courtship. Female receptivity increases following application of this pheromone. PRF is a recent innovation of the male courtship signal, originating in eastern Plethodon (~27 MYA). Codon-substitution models indicate that several amino acid sites along the PRF protein have experienced positive selection. Structural modeling suggests that many of these selected residues are important for receptor binding. Adaptive change in this pheromone is likely driven via a coevolutionary association with female receptors. The male plethodontid courtship signal, however, is comprised of multiple chemical components. I investigate micro- and macro-evolutionary divergence in plethodontid chemical communication by surveying two additional pheromone component genes, PMF and SPL. Like PRF, regions of the PMF and SPL genes have experienced adaptive change. At least one of these components (SPL) has been retained in the signaling system for ~100 MY. However, significant differences in the composition of the courtship pheromone are evident in some plethodontid lineages. It appears as if at least two lineages (Desmognathus and eastern Plethodon) use different major pheromone components and yet achieve the same behavioral response in the female (increased receptivity). / Graduation date: 2005

Early theoretical models for the evolution of male-female pairing were based largely on studies of birds. These models assumed that biparental care of eggs and young was an essential component of pairing. However, male-female pairing is also a relatively common social system in coral-reef fishes, and biparental care of young is extremely rare in this group. Although pairing has been documented in at least 13 families of reef fish, surprisingly little is known about the environmental and social factors that may maintain heterosexual pairs as the basic social units. I tested two hypotheses for pairing in a common Caribbean fish, the cleaning goby Gobiosoma evelynae, a territorial species which inhabits living coral heads. According to the Environmental Constraints Hypothesis, pairing in G. evelynae is simply a consequence of three related environmental parameters--low male mobility, low female density, and a uniform distribution of resources required by females. On reefs off St. Thomas, U.S. Virgin Islands, I found positive size-assortative pairing, frequent male movement between territories, rapid re-pairing by both males and females after experimental removal of a partner, and random distributions of apparently suitable coral heads required by females for territory space. These patterns are inconsistent with the Environmental Constraints Hypothesis for pairing. Mate Guarding is an alternative hypothesis for pairing and is based on social interactions. This hypothesis, which states that paired gobies maintain exclusive access to their partners by expelling all potential sexual rivals, predicts sex- and size-specific aggression toward conspecifics. released large and small male and female gobies directly onto the territories of pairs, and recorded the behavioral responses of the resident fish. As predicted, residents exhibited the greatest aggression toward large intruders of the same sex, and the least aggression toward large intruders of the opposite sex. Unpaired territorial females also responded aggressively to experimentally added females, and ignored added males. These results indicate that male-female pairs are maintained by mutual intrasexual aggression in this species, and that females (and possibly males) defend both partners and other resources associated with their territories. / Graduation date: 1994

Signal detection theory predicts that costs associated with recognition errors, specifically failing to respond to relevant stimuli (missed detection) and responding to erroneous ones (false alarms), shape receiver permissiveness in animal communication systems. Fitness costs of missed detection and false alarms in response to sexual signals differ between the sexes, and are usually higher for females than males. This asymmetry in costs predicts that males should be more permissive than females in their responses to signals. In my dissertation I investigate the behavioral responses of male and female túngara frogs, Physalaemus pustulosus, to mating signals and sounds associated with such calls. Specifically I explore the following topics: i) responses of the sexes to call complexity, ii) perception of congeneric mating calls by males and females, iii) responses of males to the conspecific call compared to those of extant heterospecifics, iv) effect of sounds associated with increased predation risk in reproductive decisions, and v) effect of the task performed by each sex on signal permissiveness. My findings indicate that recognition errors are higher for males than females as predicted by the different costs associated with recognition errors for each sex. Males respond to a broader range of calls than females. Despite the differences, evolutionary history has left a footprint on the brain of both sexes. In addition, I found that females behaved more cautiously than males suggesting that the sexes balance the risk of predation and the cost of cautious mating strategies differently. In the mating system of túngara frog, as in many others, sexual signals elicit different tasks in the different sexes, female phonotaxis and male calling. Therefore, the sexual differences in decision making I found could be either sex-specific independent of task, or task-specific independent of sex. Here I show that sexual differences in receiver permissiveness are motivated by differences due to the typical reproductive tasks displayed by the sexes. / text

Thesis (M.S.)--Ohio University, August, 2007. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph.D.) -- McMaster University, 2000. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph.D.) -- McMaster University, 2000. / Includes bibliographical references. Also available via World Wide Web.