Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The prickly sculpin, Cottus asper, is a polytypic species characteristically represented by very prickly, fresh-water spawning "inland" forms, and less prickly, brackish-water spawning "coastal" forms. Its widespread geographic distribution, pronounced phenotypic variability, and the effects of the contrasting environments in which it occurs are the subject of this investigation. A complete nomenclatural history and synonymy of the species for the period 1836-1936 is presented. Morphological evidence is interpreted in the light of field and laboratory studies of the migration and reproductive behavior. Differences found in distribution and intensity of body prickles (modified scales), geographical distribution, and migratory behavior, support the contention that the polytypy of "coastal" and "inland" forms of Cottus asper has a genetic basis. Other morphological evidence is equivocal in support of this interpretation. Differences in fin ray counts, e.g., pectoral rays, between "coastal" and "inland" forms are correlated positively with the presence or absence of salinity in the environment. However, it is not known whether such differences are the result of individual modifications induced by the local environment, or due to long term genetic fixation. Evidence from studies of closely-related species supports the interpretation that Cottus asper is a polytypic species which has become, and is in the process of becoming, modified into several characteristic genotypes. Evolution within this “asper species group" probably occurred in three stages, each correlated with past geologic history. During the first stage, perhaps in the Pliocene or Late Miocene, "coastal" and "inland" forms were derived from an ancestral marine cottid. The second stage, during the Pleistocene, was characterized by fragmentation of the gene pool of the "inland" form into a series of geographically isolated populations which have since evolved into valid species. The third stage, in Recent Time since the retreat of the Cordilleran glaciers, has occurred primarily within the northern representatives of the "coastal" form. At least two derivatives can now be distinguished within the "coastal" form. / Science, Faculty of / Zoology, Department of / Graduate

The new mutation, synpalpi, which was found in the Xple Stock obtained from the Biological Supply House, Chicago, is so named because of the fusion of the antennae along the midline, all other Xple characteristics being normal except for a slight protrusion of the forehead. In stock cultures the mutant appears in greater numbers from normal Xple crosses than from synpalpi Xple crosses - with a predominance of female synpalpi. Experiments were carried out in order to determine the nature of the mutation, the type of inheritance involved, and the linkage group with which the mutation is associated. The mutant is not a gene mutation but a chromosomal aberration since Mendelian ratios were not observed to occur and since the mutation appeared irregularly but persistantly. A lethal factor is suggested by the small number of flies resulting from synpalpi crosses; the absence or small number of synpalpi in the F¹ of synpalpi crosses but its reappearance in 2-8% of the F² progeny; and by the death of flies in two different stages of development - early and late pupal stages. The association of the lethal factor with the "X" chromosome is assumed because few male synpalpi emerge. A deficiency of a part of the "X" chromosome would explain the death of the males and homozygous females. The possibility of a deficiency of a few bands at the tip of the “X” chromosome was substantiated by a review of the literature on deficient "X" chromosomes. It is believed that synpalpi flies are those deficient flies which do manage to survive and that the fused antennae are caused by the movements of the fly and forcing of fluid to the head in its efforts to extricate itself from the pupa case (its tracheae being attached posteriorly to the case). The Xple stock is very sensitive to variations from the optimum temperature of 25°C. Temperatures of 35°C., 29°C, and 15°C. increased the lethal effect of the deficiency - no synpalpi appearing in the F¹ or F² of temperature-treated cultures. In the test for linkage, the mutant appears to be associated with chromosomes I and III - therefore the mutant is not a simple deficiency of the "X" chromosome alone but appears to involve the third chromosome as well. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

Differences in progeny characteristics arising from differences in maternal age at time of birth are discussed as a possible source of ecologically important variation. The literature on effects of maternal age on progeny guality is reviewed. Experiments designed to document any effects of maternal age on two biological processes are described. The processes selected were production of alatae by an aphid, ASiSiioSiEiiOS. £isum , and incidence of diapause in a sawfly, Eriocamoa ovata . Maternal-age effects influenced the production of alatae by the aphid. Early-born progeny of wingless aphids were more likely to respond to a standard crowding stimulus by producing alatae than were late-born progeny. Early-born alata-producers also produced higher numbers of alatae than late-born ones. Maternal age affected the progeny of winged aphids, but in the opposite manner. Early-born progeny of this morph usually did not produce alatae at all, whereas late-born progeny did. The inhibition of alata-prcduction in the lineage of an alate aphid was satisfactorily explained by maternal age effects alone. A timing mechanism such as the "interval timer" proposed by Lees (1966) did not apply. Ho significant effects of maternal age on the incidence of diapause in the sawfly could be found. However, diapause was shown to be influenced by at least two factors. More animals diapaused at low humidities. Seven-instar larvae diapaused more frequently than did six-instar larvae. Larval developmental times varied with the number of instars, the occurrence of diapause, and the date of egg-laying. Length of the cccocn stage of ncn-diapausing individuals varied with the date of egg-laying. It is concluded that maternal age effects, although not universal, are a common biological phenomenon, and probably of ecological significance as a source of variation. / Land and Food Systems, Faculty of / Graduate

Plectritis congesta and P. brachystemon are two very closely related species which grow sympatrlcally, and differ in their: breeding system, some associated morphological (floral) characters, and isozyme phenotypes. Plectritis congesta is approximately 70% outcrossed in nature, while P. brachystemon is less than 3% outcrossed in natural populations. Theory would predict that, all other things being equal, the outcrossed species would be more variable genetically than the selfed species. Since selection acts on genetic variability, the two species could be expected to respond differently to it. Six generations of plants of both species were grown under controlled conditions, and measured for a number of characters. Control and treatment (selection for tall and short height, and for early and late anthesis) populations were maintained. Two sets of P. congesta populations were maintained, one outcrossed (approximately 65%) and one selfed (outcrossed approximately 15%); the P. brachystemon populations were naturally self-pollinating. Selection pressure in the experiment was approximately 90%; 20 of the 200 plants in any population were selected to form the next -generation, on the basis of height or flowering time in the treatment populations, and at random in the control populations. The P. congesta populations responded to divergent selection for height at anthesis, indicating that genetic variability for this character was present in the populations. The outcrossed lines, PCO, diverged 66% or 148 mm from the control line; the selfed lines, PCS, diverged 78% or 175 mm. There were no significant differences between the outcrossed and selfed P. congesta lines over the course of the experiment. Two estimates of narrow sense heritability - realised heritability (b[sub=c]) and parent-offspring: regression (h²) - quantified this genetic variability: in PCO b[sub=c] = 0.53, h² = 0.45: in PCS b[sub=c] = 0.58, h² = 0.44. There was a decline in the phenotypic variance for height at anthesis in the P. corigesta lines selected for this character. In contrast, the P. brachystemon populations did not respond to selection for height at anthesis, and appear to have no detectable genetic variability for this character. Both species appear to have significant genetic variability for flowering time, as both responded to divergent selection for this character. The PCO lines diverged 33.5% or 31.8 days from the control line, the PCS lines diverged 28.7% or 27.3 days, and the P. brachystemon lines, PBS,-diverged 18.5% or 21.5 days. According to the heritability estimates, P. congesta is more variable genetically: in the PCO lines b[sub=c]=0.77, h² = 0.60; in PCS b[sub=c]= 0.75, h² = 0.72; while in PBS b[sub=c]= 0.49, and h²= 0.42. There was a decline in the phenotypic variance for flowering time in all three species groups. Of the other measured but unselected characters - number of days to emergence, number of nodes at anthesis, number of primary branches at anthesis, and fruit production - some responded to the selection pressure with divergence, notably those characters which were correlated with the selected characters (for example, number of nodes at anthesis, correlated with flowering time). With others there was no change which could be attributed to the selection procedure. There was no evidence from two qualitative characters - fruit wing phenotype and fruit pubescence pattern phenotype - for any response to selection; dispersion in both characters was not significantly different from that expected to result from random drift. The relatively high increase in aberrant characters in the P. congesta lines compared to the P. brachystemon lines is probably indicative of inbreeding depression in the normally outcrossed P. congesta. It appears that despite the difference in breeding system, the two Plectritis species are able to maintain variability by similar processes (genetic) in some characters, as in flowering time, and by different processes (genetic in P. congesta, phenotypic in P. brachystemon) in other characters, as in height at anthesis. Thus one quantitative character, height at anthesis, follows the pattern predicted by the breeding system difference, with the outcrossed P. congesta being much more variable genetically than the selfed P. brachystemon. This agrees with the levels of variability observed by Layton (1980) in electrophoretically detectable isozymes, and observed by Ganders and Maze (unpublished) in metrical fruit characters. The other quantitative character, flowering time, shows considerable genetic variance in the populations of the selfed P. brachystemon, though less than in the populations of P. congesta. The maintenance of such relatively high levels of genetic variability in the face of the strong inbreeding pressures which must be present in P. brachystemon populations is certainly adaptive, and probably comes about through occasional outcrossing and multiniche selection for variability among the segregating lines. / Science, Faculty of / Botany, Department of / Graduate

A dynamic model in which multiple consumers of a single nutrient may coexist in a fluctuating environment is given. Only one consumer can persist in a fixed environment, but coexistence may be produced by effects of a fluctuating environmental variable on nutrient utilization differing between consumers. An approximate solution is given for the non-autonomous Lotka-Volterra-Verhulst ordinary differential equations of the model together with heuristic sufficient conditions for construction of a persistent multispecies consumer community. Computational examples demonstrate persistence of an idealized example community for periodic and random environmental fluctuation. Two further examples demonstrate that environmental fluctuation can produce coexistence when environmental variables, standing crops, assimilation efficiencies, primary productivity, utilization rates, and respiration rates are comparable to a tropical grassland, and an oligotrophic temperate lake. The sensitivity of model solutions to functional variations of the component species may be rapidly and accurately calculated. This allows the identification and estimation of unknown species functional responses from time series data of biomasses and a measured environmental variable. Unknown functions of an environmental variable are approximated by a Tchebycheff polynomial expansion in that variable. Unknown coefficients of these expansions are the parameters of the model. These parameters are determined by the unconstrained minimization of the squared deviations of the logarithm of biomass observations and model differential equation solution using a Quasi-Newton algorithm. This least squares estimator was applied to a one year biomass time series of four zooplankton grazers, phytoplankton, and average lake temperature of a small oligotrophic lake. Application of the model to this grazer zooplankton community gives evidence of partial stabilization due to environmental fluctuation in a natural community. It is concluded that environmental variation, which is often assumed on theoretical grounds to be destabilizing, should rather be considered as one of the bases of community persistence. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

No description available.

No description available.

No description available.