UMD Theses and Dissertations
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Item CONSERVATION GENETICS OF THE ENDANGERED HAWAIIAN PETREL (PTERODROMA SANDWICHENSIS) ACROSS SPACE AND TIME(2011) Welch, Andreanna J.; Hawthorne, David J; Fleischer, Robert C; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The endemic Hawaiian Petrel (Pterodroma sandwichensis) is a long-lived pelagic seabird. Although endangered, subfossil evidence indicates that it was formerly more abundant in the past. In addition to a wider distribution on islands where the petrel currently breeds, two colonies, one on Oahu and one on Molokai, have been extirpated since humans colonized the Islands. Despite this, little is known about this species. Here I use conservation genetic and ancient DNA techniques to investigate the taxonomic status and population dynamics of the Hawaiian petrel. Investigation of the timing and magnitude of divergence between the Hawaiian petrel and its sister species, the Galapagos petrel (P. phaeopygia), revealed that these taxa diverged approximately 550,000 years ago. In a phylogenetic tree constructed from mitochondrial data Galapagos and Hawaiian petrels were reciprocally monophyletic, however, trees from the nuclear data set were unresolved. Low estimates of gene flow between taxa indicate that incomplete lineage sorting is causing the difference in resolution between data sets and that Galapagos and Hawaiian petrels are likely separate species. In addition to the mitochondrial and nuclear intron data sets, I developed a suite of 20 polymorphic microsatellite loci: I developed 10 specifically for the Hawaiian petrel, and characterized an 10 additional previously reported loci in this species. Using these three data sets I investigated the pattern of gene flow and divergence between modern, historical, and ancient populations of the Hawaiian petrel. The mitochondrial data set showed strong levels of differentiation between modern populations. The two nuclear data sets also revealed significant population structure, although it was weaker. Mitochondrial DNA sequences obtained from subfossil bones indicate that populations were significantly differentiated in the past, although there was low divergence between the extirpated Oahu and Molokai populations and modern birds from Lanai, suggesting that perhaps as colonies dwindled individuals dispersed to that island. Investigation of the effective population size indicates that no significant change has occurred on Hawaii or Maui. It appears that the long generation time of this species may have allowed it to escape a genetic bottleneck after the arrival of humans in the Hawaiian Islands.Item EVOLUTION, DEVELOPMENT, AND GENETICS OF OPSIN GENE EXPRESSION IN AFRICAN CICHLID FISHES(2011) O'Quin, Kelly E; Carleton, Karen L; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The molecular genetic mechanisms that underlie phenotypic evolution include mutations within protein-coding, cis-regulatory, and trans-regulatory factors. Although many studies have examined how these mutations individually contribute to phenotypic divergence and the formation of new species, none have examined how they may do so collectively. In this study, I examine how these molecular genetic mutations collectively contribute to the evolution of color vision among African cichlid fishes. I show that phenotypic divergence in cichlid color vision is achieved by mutations affecting the coding sequence and expression of seven opsin genes. After contrasting the roles of these two mechanisms, I use bioinformatic-, association-, and experimental genetic analyses to determine what role mutations in cis- and trans-regulatory DNA play in the evolution of cichlid opsin expression. Specifically, I demonstrate that: (1) Protein-coding mutations primarily affect cichlid opsins sensitive to the ends of the visible light spectrum (SWS1 [ultraviolet-sensitive] and LWS [red-sensitive]). (2) Changes in opsin gene expression contribute to large differences in color vision among closely related species. These analyses also reveal that the expression of the SWS1 and SWS2B opsins have diverged among closely related cichlids in association with foraging preferences and ambient light intensity, suggesting that their expression has evolved due to natural selection. Ancestral state reconstructions reveal that changes in opsin expression have evolved repeatedly among cichlids in Lakes Tanganyika and Malawi; further, I find that this repeated evolution has likely been achieved by repeated changes to cichlid development. (3) Bioinformatic analyses suggest that cichlids have diverged in multiple cis-regulatory sequences surrounding the opsin genes, and association mapping identified three putative single nucleotide polymorphisms upstream of the SWS2A (blue), RH2B (blue-green), and LWS (red) opsins that may contribute to cichlid opsin expression differences in cis. (4) Genetic mapping in experimental crosses suggests that divergence in multiple trans-regulatory factors also contribute to the evolution of SWS2B (violet), RH2A (green), and LWS (red) opsin expression. The contribution of these trans-regulatory factors to the evolution of cichlid opsin expression may outweigh those in cis. These results reveal that multiple molecular genetic mechanisms can contribute to phenotypic evolution among closely related species.Item The effect of relatedness on mating behavior in the satin bowerbird (Ptilonorhynchus violaceus)(2010) Reynolds, Sheila Mayo; Borgia, Gerald; Braun, Michael J.; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Behavior is a main component of sexual selection theory in which male competition and female mate choice influence the evolution of a species. Relatedness commonly affects behavioral interactions, but the potential for relatedness to influence sexual selection is often overlooked. Here I show that relatedness affects mating behaviors in satin bowerbirds. Bowerbirds are a model species for non-resource based mating systems in which males provide only sperm to females, and females are free to mate with their preferred males, typically resulting in high skews in male mating success. Males build stick structures (bowers) on the ground to attract, and copulate with, females. Males compete, in part, by destroying neighboring males' bowers. Females search among multiple adjacent bowers and then select subsets of these males for courtship and then copulation. Automated video monitoring of bowers allows identification of males that destroy bowers and females that visit bowers for courtship or copulation. Using microsatellite genetic markers to estimate relatedness, I show that paternity assignments based on observed copulations match the genetic sires of offspring, supporting the hypotheses that copulations occur only at bowers and that male reproductive success can be reliably estimated from observed copulations. Next, I report that competing males are less aggressive, in the form of bower destructions, towards relatives than non-relatives and that this restraining effect of relatedness on aggression favors the close spatial association of relatives' bowers. These results support the hypothesis that relatedness affects male competition and ability to maintain attractive displays for females. Lastly, I investigate the influence of relatedness on female mate choice. I show that females do not actively prefer or avoid relatives in mate choice. However, females bias the areas in which they search for mates to be inclusive of relatives and then mate randomly with respect to relatedness within their search areas, resulting in tendencies to mate with relatives in some years. This effect of relatedness on female mate searching may be due in part to the spatial association of related males, and highlights the influence of mate searching rather than active mate preferences on overall mate choice patterns.