The cornerstone of life-history theory is the expectation that current reproduction will have a detrimental effect on survival and (or) future reproduction. When fecundity increases with body size, the cost to future reproduction arises through decreased growth of reproductive individuals...
Hypotheses about the role of selection on body-shape evolution assume a heritable component to this phenotypic character. To examine the influence of environmental induction on body shape, offspring form two morphologically differentiated populations of northern redbelly dace (Phoxinus eos...
Extra–pair mating has been proposed as a source of sexual selection responsible for secondary sexual traits that are common among socially monogamous birds, although supporting evidence is scant. In the socially monogamous yellow warbler, males are larger than females, and...
Much recent attention has been given to patterns of asymmetry in animals with bilaterally paired characters, and the extent to which such asymmetry might reflect individual quality. Central to much of this research is the assumption that there exists a...
The evolution of distyly from tristyly has occurred repeatedly, especially in the Lythraceae. However, the evolutionary forces involved remain unclear since species exhibiting transitional stages between tristyly and distyly have rarely been studied. The self‐compatible, wetland perennial Decodon verticillatus (Lythraceae)...
In this study we tested the hypothesis that ENS occupancy by Tree Swallows results from avoidance by floaters of nest sites near settled pairs. To date, most explanations of this behavior have assumed that a differential cost to defending the...
Evidence from a long-term study of red-winged blackbirds, Agelaius phoenicus, in Washington has indicated that females preferentially nest in territories of males that are familiar with their neighbours, perhaps because familiar males cooperate in nest defence. Data presented here from...
Breeding density, synchrony, and experience are expected to influence the frequency of extrapair paternity in birds. Female tree swallows can influence the fertilization success of extrapair males by active selection and rejection of copulation partners. We suggest that this ability...
Removed male Eastern Bluebirs to examine the importance of male parental care and the behavioural responses of unaided females to loss of male assistance
Parental male burying beetles, Nicrophorus spp. (Coleoptera: Silphidae), are presented with a dilemma when conspecific females intrude on their nests. Although these females provide males with additional mating opportunities, they also pose a threat to the survival of the male's...
Studies of the mating strategies of birds are increasingly shifting their focus to the role that females take in controlling copulation (Hunter et al. 1993, Petrie 1992, Birkhead and Moller 1993). In some avian species, females appear able to control...
Therefore, we suggest that most extra-pair copulations occur at some unknown location, possibly at a feeding or roosting area where females may be able to choose from many more potential extra-pair fathers than at their nest-site.
We assessed the level of extrapair paternity in an Ontario population of Eastern Bluebirds. We examined the relationship between mate guarding and paternity by looking at the correlation between mate guarding and paternity for individual males, and by comparing paternity...
Here we ask whether the population structure, reproductive systems, gene flow and patterns of genetic differentiation in aquatic plant populations is best attempted using demographic and genetic techniques for estimating effective population size.
Multilocus DNA fingerprinting of offspring of monogamous pairs of tree swallows revealed that 50% of broods contained young seed by extra-pair males, totalling 38% of all offspring analysed.
We sampled haematozoa in Red-winged Blackbirds (Agelaius phoeniceus) over three consecutive breeding seasons in eastern Ontario to identify factors that affect the reliability of quantifying parasites as this pertains to testing Hamilton and Zuk's hypothesis of sexual selection...
I found that single male damselflies, Enallagma ebrium, were significantly and consistently parasitized by more larval water mites than were males caught either in tandem or copula with females.
Pumpkinseed (Lepomis gibbosus) inhabiting two shallow ponds that experienced major winterkills matured 1-2 yr earlier and at a smaller size (difference >20 mrn in length) than conspecifics living in an adjacent, nonwinterkill lake.
This article presents the observations of egg laying times of American Robins and test the hypothesis that birds lay their eggs at times when they are normally inactive, because carrying a developing egg constrains female activity.
Field experiments were conducted over the summer of 1983 to determine food-evacuation rate and measure stomach fullness of bluegill sunfish (Lepomis macrochirus). A combination of these data gave estimates of daily food intake of fish. Fish were captured...
The population dynamics and feeding ecology of pumpkinseeds (Lepomis gibbosus) were examined inhabiting two isolated Ontario beaver ponds and adjacent Lake Opinicon to determine the persistence of and reasons for small body size in pond populations.
Reverse-phase thin layer chromatography was used to quantify algal carotenoid degradation resulting from grazing by Daphnia magna in suspensions of lyophilized Oscillatoria utermöhlii, O. limnetica, Anabaena flos-aquae and Synechococcus sp. Three samples were removed every 24 h...
Testing predictions of mate-choice models often requires knowing the time a female settles in a particular territory. Because the effort necessary to observe settlement usually precludes direct observation of a large sample of females, researchers often rely on indices of...
Sexually selected infanticide, the killing of young to secure a mating opportunity, appears to be rare in birds, although it is relatively common in mammals. To examine the frequency of occurrence and the conditions under which male tree swallows, Tachycineta...
Young-of-the-year largemouth bass, Micropterus salmoides, were exposed to four concentrations of sulphuric acid (pH levels 7.2, 6.1, 4.8, and 3.7) for 30 days, and the frequencies of feeding acts and activity bouts, and time budgets were recorded. Juveniles at...
Energy content and fruiting patterns were examined for eight species in the genus Vaccinium Section Cyanococcus, the blueberries. Blueberries varied in both seed and berry production. Fresh fruit contained approximately 85 % moisture. A mg of dried pulp yielded...
We investigated the division of labor in male and female tree swallows by measuring the rate of food delivery to nestlings at 36 nests. By observing natural nests and performing brood manipulations we found that males and females divided the...
We examined the continuous variation in the breeding plumage of male yellow warblers (Dendroica petechia) to determine if the amount of brown streaking on the breast functions as a badge of relative status in territorial males. Conspecific mounts...
Using plausible assumptions, we propose "transitive odds" and "intrinsic preferences" models of food preference transitivity to account for observed behaviour when animals are feeding on items of pairs of food types from a set of such types for which preferences...
Phosphate uptake by the blue-green alga Oscillatoria limnetica Lemmerman is stimulated by micromolar concentrations of Ca2". The calmodulin antagonists 4-(3-(2(trifluoromethyl) phenylthiazin-1O-yljpropyl)- I-piperazine ethanol-Ha and its monofluoro-analog inhibit orthophosphate uptake of Oscillatoria limnetica by over 97% implying involvement of calmodulin in...
I analyzed the auditory characteristics of a variety of tympanate moths from areas representing low and high levels of bat (= echolocation signal) diversity. Moths sampled in two African (high diversity) sites reveal significantly higher sensitivities than those analyzed at...
Heat penetration and thermal lag in the submersed soil surrounding the roots of aquatic plants depends on two fundamental thermal properties of the substrate, volumetric heat capacity (CV) and thermal conductivity (k). The relationship of these parameters to the fractions...
We have compared the echolocation and feeding behaviours of Myotis lucifugus, M. californicus, M. volans, and M. auriculus based on observations and recordings of bats in the field. Myotis lucifugus and M. californicus...
The exploration of new objects and new environments by Peromyscus leucopus was observed in laboratory pens and inferred from the number of smoked paper track records obtained from track shelters (milk cartons or tin cans) in the field. The exploration...
