Thesis (M.S.)--Humboldt State University, 2008. / Includes bibliographical references (leaves 63-68). Also available via Humboldt Digital Scholar.

Morphological, biochemical, and trophic evidence from other studies indicate that two populations of stickleback (Gasterosteus) co-exist in Enos Lake, Vancouver Island. One population is limnetic and the other is benthic (the names allude to their foraging behaviour and use of space). In this study, field observations, mate selection experiments, and courtship behaviour experiments were conducted to determine if the two stickleback populations are reproductively isolated. When breeding, limnetic males develop red throats whereas benthic males become uniformly black. In the field limnetic and benthic males nest in different habitats. Despite this difference, reproductive males and females of each population encountered each other, but in the few cases where courtship occurred, it never went beyond the initial stages of the lead-follow sequence. Apparently behavioural differences in courtship contributed to the break off of these natural courtships. In mate selection experiments, males and females of each population preferred mates from their own population. In the courtship experiments, behavioural differences between limnetics and benthics were found to be greatest in the early stages of courtship. With females from their own population, benthic males were more aggressive in their approach and leading sequences than limnetic males. In the beginning of the lead-follow phase, benthic females tend to position themselves above benthic males whereas limnetic females tend to position themselves alongside limnetic males. Male courtship behaviour was sometimes dependent on the phenotype of the female courted; benthic males bit and chased limnetic females whereas, limnetic males bit and led benthic females in a meandering path to the nest. Since the mate choice experiments indicated total positive assortative mating between limnetics and benthics, it is likely that the behavioural differences found in courtship behaviour contribute to reproductive isolation between the limnetic and benthic sticklebacks in Enos Lake. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

I here explore the dual roles of gene flow in determining evolutionary and demographic processes in the Misty Lake threespine stickleback (Gasterosteus aculeatus L.). In the Misty watershed, the lake fish have streamlined bodies and numerous gill rakers whereas the inlet stream fish have deeper bodies and reduced number of gill rakers, differences that are adaptive for lake and stream environments respectively. The outlet stream population, however, is morphologically intermediate between the lake and inlet populations as a result of high gene flow from the lake preventing adaptation to the stream environment. First, I quantify the constraining effect of gene flow on adaptive divergence in the Misty outlet using two complementary approaches. By comparing phenotypic values and environmental differences between the three habitats (i.e. lake, inlet and outlet), I estimate that the constraint imposed by gene flow on phenotypic divergence is in the order of 80%, i.e. the outlet population only achieves 20% of the phenotypic divergence expected in the absence of gene flow. Parameterization of a quantitative genetic model confirms this value is possible given a biologically realistic range of parameter values. Second, I demonstrate that this constraint imposed by gene flow on adaptation likely contributes to an observed reduction in abundances along the outlet stream. I do so using a transplant experiment and a three-year selection experiment. Quantification of the amount of dispersal suggests that the negative influence of gene flow offsets the positive demographic influence of the immigration of individuals. In summary, gene flow has profound consequences for both evolutionary and demographic processes taking place in the Misty system.

Descent with modification (Darwin, 1859) overwhelmingly occurs through the process of natural selection on genetically variable traits. Following deglaciation in the Pleistocene, morphologically conservative marine stickleback (Gasterosteus aculeatus) from two distinct mitochondrial DNA lineages colonized freshwater habitats on the Haida Gwaii archipelago. These freshwater populations have radiated in response to a diverse selective landscape on the archipelago and exhibit morphological diversity that equals or exceeds the known range for the species in the circumboreal distribution. I investigated the body shape of 3808 stickleback from 125 isolated populations from Haida Gwaii using geometric morphometrics. Relative warp and discriminant function analysis were used to quantify lateral shape differences based on partial warp scores. which were generated from twelve homologous landmarks digitally placed on each specimen's image. The possibility of ontogenetic shifts and sexual dimorphism of body shape were examined for each population on the archipelago. Stickleback body-shape changes during ontogeny were highly variable, and cannot be predicted by the volume and water clarity of the habitat. I found a slight sexual dimorphism in adult body shape, the magnitude of which could not be predicted by habitat volume and clarity. A number of comparisons were made to elucidate the possible causes for selection for divergence of adult body shape among Haida Gwaii populations. Body shape of parapatric lake-river stickleback populations differed significantly in concordance with hydrodynamic principles. Comparing the body shape of Haida Gwaii populations to the shape of sympatric benthic-limnetic species pairs from southwestern British Columbia. I found that benthic and limnetic body-shape ecotypes differ by up to 56% of the total variation among Haida Gwaii populations. Tests for phenotypic plasticity of body shape were conducted with two morphologically distinct stickleback populations that had been transplanted into two separate experimental ponds that were the ecological opposites of the respective source lakes. I found evidence for some phenotypic plasticity in body shape; the difference between each source and experimental population was approximately 11% of the total variation in body shape among populations throughout the archipelago. Throughout the islands adult body shape and size can be predicted by both abiotic and biotic factors of the habitat. Populations with derived shape (CV1+), including thicker peduncles, posteriad and closely spaced dorsal spines, anteriad pelvis, short dorsal and anal fins, and smaller body size occur in small, shallow, stained ponds, and populations with less derived shape (CVI-). with smaller narrow peduncles. anteriad and widely spaced dorsal spines. posteriad pelvis. longer dorsal and anal fins, and larger size occur in large, deep. clear lakes. There were large-bodied populations with derived shape (CV2-). including smaller heads and shallower elongate bodies in open water habitats of low productivity, and populations with smaller size and less derived shape (CV2±), with larger heads and deeper bodies, in higher productivity, structurally complex habitats. Populations with robust defensive adaptations have less derived shape (CV1-) and larger size, in response to salmonid predation, while populations with weak defences had derived shape (CV 1+), in response to bird/invertebrate predators. The ecomorphological relationships were consistent between mitochondrial lineages and replicated in each geographical region on the archipelago among geographically distant populations, suggesting the parallel evolution of body shape governed by the hydrodynamic constraints of each habitat. Although initially colonized by ancestors with conserved morphology, the stickleback populations on Haida Gwaii exhibit body shapes suited to the hydrodynamic landscape of the habitat, demonstrating the predictability of natural selection in adaptive radiations.

Issued also as Thesis--Leyden. / Bibliography: p. [158]-159.

xvi, 112 p. : ill. (some col.) / In seasonal environments, the ability to take advantage of the favorable seasons and avoid or mitigate the effects of the unfavorable ones is essential for organismal fitness. Many polar and temperate organisms use photoperiod (length of day) to time seasonal life history events because photoperiod's regular annual cycle makes it a very reliable indicator of seasonality. This reliability allows organisms to anticipate and properly prepare for seasonal change. Although photoperiodism is widespread in polar and temperate vertebrates, little is known relative to invertebrates regarding how its use varies with environment and this method's underlying genetic and physiological basis. This dissertation is focused on demonstrating the proper methodology for the study of photoperiodism and establishing the threespine stickleback as a model of vertebrate photoperiodism. Chapter I is an introduction to photoperiodism, how it is influenced by environment, the physiological basis of its output, and a summary of the chapters that follow. Chapter II explains an analytical method to test for causality and applies this method to data that have been interpreted as evidence that the circadian clock is causally involved in photoperiodism. Chapter III describes the photoperiodic response of threespine stickleback Gasterosteus aculeatus populations from two latitudes. These results are used to inform an empirical examination of the previously described assertion that the circadian clock is causally involved in photoperiodism. Chapter IV examines the physiological basis of early photoperiodic response using the threespine stickleback as a model teleost fish. Chapter V summarizes the previous chapters, describes their significance, and suggests future research directions. This dissertation includes both previously published and co-authored material. Supplementary Excel files demonstrating the analyses used in Chapter III are also included in this dissertation. / Committee in charge: Eric Johnson, Chairperson; William Cresko, Advisor; William Bradshaw, Member; Judith Eisen, Member; Patricia McDowell, Outside Member

Across vertebrates, skeletal shapes are diverse, and much of this variation appears to be adaptive. In contrast, the early developmental programs of these structures are highly conserved across vertebrates. The question then becomes where in the conserved genetic programs of skeletal development does variation lie to direct diversity? In threespine stickleback, rapid changes in head and body shape have been documented during repeated and independent invasions of oceanic fish into freshwater habitats in regions deglaciated approximately 13,000 years ago. However, recent research indicates that similar phenotypic and genetic divergence can occur in decades. A remaining challenge is to link stickleback population genomic variation to causal genes that underlie such rapid phenotypic evolution. Here I use genome wide association studies (GWAS) in natural populations of stickleback to uncover genomic regions that contribute to variation of two dermal bone derived traits, lateral plate number and opercle shape. The decrease of lateral plate body armor and change in opercle bone shape, important for feeding mechanics, are classically associated with freshwater divergence. GWAS has recently begun to be used in natural populations but is still under scrutiny for performance among different populations. Using a population of phenotypically variable stickleback in Oregon, GWAS proved an effective method to uncover genomic regions and genetic variants known to contribute to lateral plate number and opercle shape, as well as new genomic regions and candidate genes not previously implicated in phenotypic variation. Although successful, using similar methods on decades old stickleback populations in Alaska revealed the challenges that accompany controlling population structure created by strong natural selection. Together, I found that although lateral plate number and opercle shape rapidly evolve in a coordinated fashion during adaptation from marine to freshwater environments, phenotypic variation is largely driven by independent genetic architectures. However, in very rapidly evolving populations, despite this independence of genetic architecture, the genetic variants contributing to the traits co-localize to similar genomic regions. This finding could be either biological or methodological which highlights the promise and limitations of using GWAS to identify genetic variation that gives rise to phenotypic diversity. This dissertation includes unpublished co-authored material.

Evolution shapes ecosystems but the processes by which this occurs are not well understood. Adaptive change in resource expensive traits may underlie one such process, as evolution altering a species’ resource needs may effect how that species interacts with ecosystem resources. For this, Ecological Stoichiometry (ES) may be a tractable framework, as it simplifies organisms into elemental ratios and then applies mass-balance to predict changes in diet and waste interactions. ES detects variation in resource expensive traits as variation in elemental ratios, and predicts compensation via parallel changes in diet (e.g. high phosphorous individuals consume high phosphorus diets) and/or offsetting changes in waste (e.g. high phosphorous individuals release low phosphorus waste). To test the utility of this framework and improve our understanding of eco-evolutionary dynamics, I studied variation in phenotypic traits, genetics, elemental content and resource interactions within and across natural populations of highly regarded eco-evolutionary model species threespine stickleback (Gasterosteus aculeatus). First, I related heritable variation in phosphorus rich bony traits and genetics commonly under natural selection with variation in elemental content (N:P) to determine the magnitude and basis of intraspecific variation in N:P. Second, I investigated the ecosystem consequences of variation in elemental content by determining whether stickleback compensate through changes in diet choice and excretion rates. I found stickleback vary widely in elemental composition (3.0 – 9.4:1 N:P) which models explained well with four bone related traits: bone mineralization, body size, lateral plating and pelvis size (R2 > 0.52). Additional genetic models linked variation in Eda alleles (which underlie lateral plating) with a 12% shift in stickleback N:P. Stickleback compensated for this variation in N:P demand by altering diet choice rather than excretion rates, and by maximizing dietary inputs through changes in gut morphology. Within and across populations, high phosphorus stickleback consumed a larger proportion of high phosphorus prey and contained longer gastrointestinal tracts that more efficiency process diet resources. These results demonstrate that heritable variation in elemental composition is ecologically relevant with individual traits and genetics having large effects. As individuals compensated by altering resource acquisition rather than release, the direct ecological consequences of evolutionary change in these resource expensive traits is likely larger for food web structure and abundance than nutrient dynamics. / Graduate / 2018-12-19

The threespine stickleback (Gasterosteus aculeatus) is an important model for studying evolution. Sticklebacks are widely distributed in the northern hemisphere and inhabit freshwater, brackish, and marine waters. Anadromous and marine populations (hereafter marine) are assumed to be homogenous in space and invariant in time in their phenotypic characteristics, despite marine environments varying on regional and local scales. Recent studies suggest there is in fact genetic and phenotypic structure in marine sticklebacks, yet the ecological causes remain unclear. My goal was to assess trait variation in marine stickleback populations around Southern coastal British Columbia (BC), and to determine whether or not oceanographic and habitat characteristics explained this variation. The area around Vancouver Island was ideal because four distinct oceanographic regions surround the island with varying coastal habitat types. Between May-July 2019, I sampled ~600 sticklebacks from 15 sites. I then characterized trait variation using two-dimensional (2D) geometric morphometric analysis to compare individuals between oceanographic regions and coastal habitats. I focused on five traits: armour phenotype, head size, body size, head shape, and body shape. I chose these traits because they are ecologically important and well-studied in freshwater populations, where their ecological drivers are known. I found that marine sticklebacks did vary morphologically among and between regions and habitats, but the variation was not immediately related to environmental variation, nor obviously comparable to variation in freshwater populations. Sexual dimorphism was the largest source of variation in the data, a well-established finding. But oceanographic and habitat variables influenced differences between males and females. I concluded that marine sticklebacks offer abundant opportunities for expanding our knowledge of drivers of morphology in nature. / Graduate / 2022-04-11