Levels of Selection in a Polymorphic Species

Phenotype is affected by many factors, including but not limited to environment, conspecifics, and genetics. Evidence of phenotypic variation is everywhere, some of which is controlled solely by environment, and others that are fixed by genetics. Genetic polymorphisms are rare, but very useful for the study of selection and genetics. These genetic polymorphisms provide a phenotypic link to the underlying genetics and are even more useful when there are associated behavioral differences. I examine multiple levels of selection that are acting upon a polymorphic passerine, the white-throated sparrow (Zonotrichia albicollis). Males and females of this species occur in two morphs, white or tan, based upon the color of their crown strips. This plumage polymorphism is absolutely correlated with a complex chromosomal rearrangement on the second largest autosome. Within this dissertation I explore how climate needs to be addressed in ecological studies to fully understand the mechanisms behind variation. I explore whether sexual selection is acting within this species and the differences between the morphs through the use of Bateman Gradients. Darwin suggested that sex ratios influence sexual selection, but what about morph ratios? I examine the frequency variation of morphs within this species. Variation in morph production may be favored by a potential tradeoff between the number of males and the number of white offspring produced in a clutch that suggests greater costs associated with producing white morph individuals. Mendelian segregation is inconsistent in this species, and transmission distortion may contribute to morph ratio variation. I show that white male sperm varies in production from 0% - 100% white sperm/individual consistent with transmission distortion. Finally, candidate gene mapping was used to identify the genes sequestered in this rearrangement that may be responsible for the polymorphism and the evolution behind the rearrangement.Marisa L. KorodyTuttle, Elaina M.Bierly, GregGonser, RustyLear, TeriStuart, GaryDoctor of PhilosophyDepartment of BiologyCunningham Memorial Library, Terre Haute, Indianan State University.ISU-Dissertation-May-2013DoctoralTitle from document title page. Document formatted into pages: contains 173p.:Includes appendix and bibliography

Data from: Extrapair mating and the strength of sexual selection: insights from a polymorphic species

Extra-pair mating could drive sexual selection in socially monogamous species, but support for this hypothesis remains equivocal. We used lifetime fitness data and a unique model species, the dimorphic white-throated sparrow (Zonotrichia albicollis), to examine how extra-pair mating affects the potential for sexual selection. The morphs of this species employ distinct reproductive strategies, with white males pursuing extra-pair mating at higher rates than tan counterparts. Social and extra-pair mating is disassortative by morph, with paternity exchange occurring primarily between pairs composed of white males and tan females. We predicted stronger sexual selection as quantified by Bateman gradients and standardized variance in reproductive success in white compared to tan males. Furthermore, because males drive extra-pair mating, we predicted costs of multiple mating and a negative Bateman gradient in tan females. The Bateman gradient for lifetime reproductive success was larger in white than tan males, and extra-pair mating contributed more to the Bateman gradient for white males. However, the Bateman gradient was positive in tan females. White males had higher variance in annual reproductive success than tan males or females, but variance in lifetime reproductive success did not differ between the morphs or sexes. Moreover, extra-pair mating did not increase variance in male reproductive success relative to apparent patterns, and within-pair success accounted for much more variance than extra-pair success. Although extra-pair mating in white males increases Bateman gradients, and potential for sexual selection via mate numbers, these latter results call the overall importance of extra-pair mating in driving selection into question

Behavioral genomics in the white-throated sparrow

Most behavioral traits are complex and are the product of interactions between multiple genes and/or environments. Therefore, ideal models in which to examine the relative roles of genetic effects should have, 1) variation in behavioral phenotypes, 2) the potential to identify the genetic bases of these behavioral traits, 3) an obvious association between phenotype and genotype, 4) the potential to identify relevant environmental conditions contributing to the establishment of behavioral phenotypes so that partitioning of gene-by-environment effects is possible, and 5) a strong understanding of the evolutionary forces influencing the system. Given these desires, an unexpected new animal model emerges for the study of behavioral genomics – morphs of the white-throated sparrow (Zonotrichia albicollis) exhibit alternative strategies of monogamy/high parental effort vs. promiscuity/low parental effort. These behaviors are absolutely correlated with the presence or absence of a large chromosomal rearrangement. We have amassed 22+ years of detailed behavioral, physiological, ecological, and evolutionary data on this species making it possible to identify the genetic, epigenetic, and environmental bases of behavior. Here we further outline the utility of the species, as well as present current cytogenetic and molecular data showing that rearrangements and linkage in multiple chromosomes are key to the evolution of alternative phenotypes. In addition, comparative analyses among the Zonotrichia suggest an interesting and slightly counterintuitive evolutionary pathway in this group. Genomic studies in the white-throated sparrow will identify the gene(s) associated with complex behaviors, as well as provide us with information on how environment interacts with genetic architecture to affect aggressive, social, sexual, and parental phenotypes. Morphs of the sparrow provide us with a unique opportunity to study intraspecific genomic differences, which have resulted from two separate, yet linked evolutionary trajectories. Such results can transform our understanding of the evolution of genomes

The value of avian genomics to the conservation of wildlife

Background: Genomic studies in non-domestic avian models, such as the California condor and white-throated sparrow, can lead to more comprehensive conservation plans and provide clues for understanding mechanisms affecting genetic variation, adaptation and evolution. Developing genomic tools and resources including genomic libraries and a genetic map of the California condor is a prerequisite for identification of candidate loci for a heritable embryonic lethal condition. The white-throated sparrow exhibits a stable genetic polymorphism (i.e. chromosomal rearrangements) associated with variation in morphology, physiology, and behavior (e.g., aggression, social behavior, sexual behavior, parental care). In this paper we outline the utility of these species as well as report on recent advances in the study of their genomes. Results: Genotyping of the condor resource population at 17 microsatellite loci provided a better assessment of the current population's genetic variation. Specific New World vulture repeats were found in the condor genome. Using condor BAC library and clones, chicken-condor comparative maps were generated. A condor fibroblast cell line transcriptome was characterized using the 454 sequencing technology. Our karyotypic analyses of the sparrow in combination with other studies indicate that the rearrangements in both chromosomes 2(m) and 3(a) are complex and likely involve multiple inversions, interchromosomal linkage, and pleiotropy. At least a portion of the rearrangement in chromosome 2(m) existed in the common ancestor of the four North American species of Zonotrichia, but not in the one South American species, and that the 2(m) form, originally thought to be the derived condition, might actually be the ancestral one. Conclusion: Mining and characterization of candidate loci in the California condor using molecular genetic and genomic techniques as well as linkage and comparative genomic mapping will eventually enable the identification of carriers of the chondrodystrophy allele, resulting in improved genetic management of this disease. In the white-throated sparrow, genomic studies, combined with ecological data, will help elucidate the basis of genic selection in a natural population. Morphs of the sparrow provide us with a unique opportunity to study intraspecific genomic differences, which have resulted from two separate yet linked evolutionary trajectories. Such results can transform our understanding of evolutionary and conservation biology

WTSP Covariates

This file contains the datasets used to examine rates of actuarial senescence in the four morph-sex classes of the white-throated sparrow (Zonotrichia albicollis) in R package BaSTA. Three files total are required: (1) A birth-death year file, containing the birth and death years (unknown entered as 0) for all individuals included in the data set, (2) A survival matrix, with a line entered for each time an individual was re-sighted, (3) A covariate matrix, listing the sex and morph of each individual. This is the covariate file

White-throated sparrow survivorship data

This file contains the datasets used to examine rates of actuarial senescence in the four morph-sex classes of the white-throated sparrow (Zonotrichia albicollis) in R package BaSTA. Three files total are required: (1) A birth-death year file, containing the birth and death years (unknown entered as 0) for all individuals included in the data set, (2) A survival file, with a line entered for each year in which an individual was re-sighted, (3) A covariate matrix, listing the sex and morph of each individual. This is the survivorship data