Dichogamy is very common in flowering plants and is widely thought to reduce pollen‐pistil interference, especially self‐pollination. Yet, the functional significance of dichogamy has rarely been studied. We investigated the nature and functioning of dichogamy in eastern Ontario populations of ...
In many avian species, a part of the population is present at the breeding grounds but does not breed. Current theories generally assume that floaters are younger or lower-quality individuals, and empirical data confirm this. However, floating could also arise...
T.--We used data from an 11-year study of Red-winged Blackbirds (Agelaius phoeniceus) totest the hypothesis that fledging success is a reliable index of recruitment at the population and the individual level. Natal philopatry was only 2.37% overall (3.51% for males...
It has been suggested that fluctuating asymmetry (FA) is an indicator of perturbed development. Our study tests the validity of a fundamental assumption of asymmetry theory: that environmental stress imposed during development increases FA. We deprived tree swallow (Tachycineta...
Traditional population genetics theory assumed that at some level in the hierarchy of genetic diversity there existed 'demes' in which males and females mate at random. Polygynous mating systems or individual variance in reproductive success were considered complications which altered...
Catch‐and‐release angling of black bass Micropterus spp. during the parental care period may lead to brood predation and premature nest abandonment. Furthermore, physiological disturbance incurred while landing angled males may impair their ability to provide parental care long after release...
Least Flycatcher Empidonax minimus pairs form dense clusters of territories on the breeding grounds. We describe pair formation and copulation behavior (both within- and extra-pair) in Least Flycatcher clusters. Pair formation involved a complex behavioral sequence of trill vocalizations and...
Paleolimnological techniques were used to infer long-term changes in trophic status of Lake Opinicon (Ontario), a mesotrophic, shallow, macrophyte-dominated lake, and to assess whether these patterns support the hypothesis of 'alternative equilibria' proposed for shallow lake systems. Analysis of the...
Many breeding systems include ‘multiple mating’ in which males or females mate with multiple partners. We identify two forms of multiple mating: ‘single‐sex’, where the next‐generation individuals (NGIs) are the product of multiple mating by one sex; and ‘two‐sex’, where...
Substantial individual variation in timing of emergence from hibernation has been reported among reptiles. Here we report patterns of spring emergence by black snake rat (Elaphe obsoleta obsoleta) observed at 13 communal hibernacula in eastern Ontario from 1992-1997. Because our study is...
We investigated whether the thermal history of Black Rat Snakes (Elaphe obsoleta) and Northern Water Snakes (Nerodia sipedon) during development affected their preferred body temperatures (PBT) after hatching or birth. Eggs of black rat snakes were...
Interspecific comparisons suggest that a trade-off exists between development and somatic growth rate. We provide evidence for a trade-off between cranial ossification and growth rate within a single species, the pumpkinseed sunfish (Lepomis gibbosus). We compare fish derived...
Avian populations often consist of breeding residents and nonbreeding floaters. It is usually assumed that floaters are lower-quality individuals that do not reproduce, but floater tactics and potential reproductive success have rarely been examined carefully. To assess the potential reproductive...
We tested the responses of two bird species which nest on unmovable substrates (e.g., cavities and walls) to simulated and actual egg damage in their nest. Tree Swallows (Tachycineta bicolor) and Barn Swallows (Hirundo rustica) removed...
Sexual dimorphism is a widespread phenomenon among animals (Darwin, 1871; Andersson, 1994). Differences between the sexes come in many forms, in- cluding both morphology (e.g., size, shape, coloration) and behavior (e.g., risk-taking or defensive behavior). Sexual differences in physiology also...
Genomic introgression among divergent taxa following human-mediated secondary contact is a growing concern for the management and conservation of aquatic biodiversity. We simulated the composition of taxa following admixture and hybridization by independently altering three variables: (1) initial proportion of...
We examined the availability and motility of sperm from parental and sneaker male bluegills (Lepomis macrochirus), a colonially nesting sunfish (Family Centrarchidae) with male parental care and a high incidence of cuckoldry by both sneaker and satellite males...
We used more than 326 000 observations of temperature collected by radio telemetry from 38 individuals over three years to investigate thermoregulation and thermal relations of northern water snakes (Nerodia sipedon) near the northern limit of their distribution in...
Different snake species respond differently to various anesthetic agents. Hence, an anesthetic procedure developed for one species cannot necessarily be safely transferred to another species. The goal of this paper is to summarize our experience using inhalant anesthetics on three...
Butomus umbellatus L. is an invasive emergent aquatic plant that exhibits wide variation in seed production. Native European populations are fertile and diploid or sterile and triploid. However, adventive North American populations are widely reported to be sexually sterile. We...
Brown recently proposed that the “good genes” that females pursue when choosing mates may be individual heterozygosity because more heterozygous mates sire offspring with higher fitness. Further, because heterozygosity might enhance developmental stability, males with more heterozygosity are recognized by...
We used data from a 9-year mark–recapture study to determine whether demographic factors could explain female-biased sexual size dimorphism in northern water snakes (Nerodia sipedon). Most males reached sexual maturity at 3 years of age, while most females delayed maturity...
It is widely thought that many apomictic angiosperms exhibit variation in sexual versus apomictic seed production, yet there has been little investigation of the extent to which apomixis varies among or within natural populations. In dioecious Antennaria parlinii, previous...
We examined whether experimental parasitism by a mite Limnochares americana (Lundblad) affected survivorship and maturation of adult damselflies Enallagma ebrium (Hagen). We then tested whether differences in grooming activity between control and exposed individuals (within different age or sex categories...
In self-compatible plants, small populations may experience reduced outcrossing owing to decreased pollinator visitation and mate availability. We examined the relation between outcrossing and population size in eastern Ontario populations of Aquilegiacanadensis. Experimental pollinations showed that the...
Tree swallows (Tachycineta bicolor) show one of the highest levels of extrapair paternity in birds, and there is evidence that females have control over who fathers their offspring. However, it is unclear which benefits female tree swallows obtain...
The proportion of extrapair paternity is known to vary greatly among species, but differences between populations of the same species have rarely been considered. We used microsatellite DNA markers to assess parentage of offspring in a subarctic population of the...
The theoretical construct of an optimal offspring size remains widely cited in life history literature, despite the regular failure of the central prediction of that theory, that offspring size should not vary within populations. Here we used data from 77...
Mating systems and sexual selection are assumed to be affected by the distribution of critical resources. We use observations of 312 mating aggregations to compare mate-searching success of male northern water snakes (Nerodia sipedon) in two marshes in...
Floaters are sexually mature yet nonbreeding, nonterritorial individuals (Smith 1978). They are common in many passerine species and avian social systems (see Zack and Stutchbury 1992) but relatively little is known about them. Floating behavior ultimately arises through an excess...
We used data from a nine-year study to assess how these factors contribute to female-biased sexual size dimorphism in males, although both sexes approached their asymptotic size at the same rate.
We investigated the distribution of variation at six microsatellite loci in the black rat snake (Elaphe obsoleta obsoleta). Sampling occurred at three hierarchical scales ranging from communal hibernacula to regional populations, with most locales situated within the Frontenac...
The loss of traits that no longer increase fitness is a pervasive feature of evolution, although detailed studies of the genetic, developmental, and evolutionary factors involved are few. Most perennial plants practice both sexual and clonal reproduction, and it has...
We describe the isolation and genetic characterization of eight microsatellite DNA loci from the northern water snake, Nerodia sipedon sipedon and use these loci to analyse levels of genetic differentiation between local (<2km apart) populations of these snakes in Ontario...
We describe 10 microsatellite loci from bluegill (Lepomis macrochirus) and discuss their evolution within the Centrarchidae. All of the loci exhibit Mendelian inheritance and are unlinked. While six loci are conserved within the Centrarchidae (found also in pumpkinseed...
Female Black-capped Chickadees (Poecile atricapillus) solicit extrapair copulations (EPCs) from neighboring high-ranked males, and these EPCs result in extrapair young. Females might choose to locate their nests near the territory boundaries of attractive males to facilitate access to...
Using field surveys and histological methods, we show that a dragonfly species (Sympetrum internum) has an effective resistance, not seen previously in other odonates, to a mite parasite (Arrenurus planus). This mite is a generalist parasite...
The size and shape of the black bib in Black-capped Chickadees varies among individuals and may signal information about age and sex, as found in other species with similar plumage badges. By photographing and measuring bibs of wintering adults in...
Studies aimed at determining why female birds often produce offspring sired by males other than their social mates generally compare traits of social and genetic mates. Here I examine paternity patterns in nests of the same female red–winged blackbirds (...
Data from five pumpkinseed sunfish (Lepomis gibbosus) populations were used to generate age‐specific survival rates and to test the prediction of life history theory that early maturity and high annual reproductive effort are favored by low adult survival...
In this study, we examined the constraints of nestbox size on nestling growth and survival while controlling for variation in clutch size and parental quality.
Ears exist in moths primarily for the purpose of detecting hunting bats at night to avoid predation. The ears of four species of day-flying Nearctic moths are as sensitive as those of a common, night-flying genus to the frequencies emitted...
here has been much recent interest in subtle departures from perfect symmetry in bilaterally paired morphological characters, and the extent to which such departures reflect aspects of individual quality. We used data from aviary contests involving pairs of wild-caught male...
Recent evidence suggests that in many animal taxa, males characterized by low levels of bilateral asymmetry realize a mating advantage. The mechanisms responsible are poorly understood, but there is much interest in the possibility that symmetry reflect, aspects of underlying...
Extra-pair paternity is common in many socially monogamous passerine birds with biparental care. Thus, males often invest in offspring to which they are not related. Models of optimal parental investment predict that, under certain assumptions, males should lower their investment...
Male birds are often faced with low confidence of paternity in their mates' offspring, raising the question of how paternal care covaries with confidence of paternity. We tested the hypothesis that male eastern bluebirds (Sialia sialis) reduce care...
Previous studies have shown that some female black-capped chickadees (Poecile atricapillus) solicit copulations from males that rank higher in winter flocks than their social mates, and extra-pair paternity in nests occurs commonly enough to be considered a potential...
The ability to produce seeds when pollinators or potential mates are scarce is thought to be one of the main advantages of self-fertilization in flowering plants. However, whether autonomous selfing increases seed set in natural populations has seldom been tested...
The effects of shoot apex removal may be used to evaluate the cost of apical dominance and the cost of reproduction in plants. Plants that have shoot apices removed may have lateral meristems released from apical dominance and thus, may...
Before the onset of female fertility, we removed 12 early–settling male tree swallows (Tachycineta bicolor) from their nest–boxes and mates, and allowed replacement males which had been floaters to settle with the original female residents. We predicted that...
Our aim was to determine the rate of extrapair paternity in Eastern Phoebes using DNA fingerprinting. We also wanted to see if the frequency of EPY changed between the first and second broods of the season.
We inadvertently examined homing ability in Tree Swallows when we removed twelve males from their nestboxes in 1993 as part of another study. These males were removed just prior to their mate's fertile period and released either 125 or 250...
It has been proposed that the most sensitive auditory receptor cell (A1) in the two-celled ears of certain noctuoid moths is inhibited by its partner, the A2 cell, at high stimulus intensities. We used the single-celled ears of notodontid moths...
We used morphological and breeding data from a 2-year field study of red-winged blackbirds (Agelaius phoeniceus) to test the hypothesis that males characterized by low levels of bilateral asymmetry (i.e., high developmental competence) realize a reproductive advantage. Specifically...
We used data from 88 litters of northern water snakes (Nerodia sipedon) to test predictions about how mothers would adaptively vary the sex ratios of their offspring. Larger mothers produced significantly more daughters (r2 = 0.04, P = 0.05), and...
In an experimental study in Denmark, it was previously found that male barn swallows (Hirundo rustica) with elongated tail streamers obtained an apparent fitness advantage through earlier pairing, an increased frequency of second clutches, and higher total reproductive...
Using data from a 6-year paternity study of red-winged blackbirds, I tested the hypotheses that increased nesting synchrony should either promote extra-pair mating by increasing the advantage of extra-pair mating to females, or decrease extra-pair mating by constraining males from...
The influence of frequent water-column mixing on phytoplankton succession and species composition was studied by comparing plankton dynamics in two lakes (Lake Opinicon and Upper Rock Lake) which have similar water chemistry, but differ widely in their basin morphometries: Opinicon...
Larval damselflies resist infestation by parasitic larval mites by exhibiting behaviours such as grooming, crawling, swimming, and striking at host-seeking mites. Larval damselflies are known to increase time spent in these behaviours in the presence of mites but reduce time...
