Non-verbal behavior as courtship signals: the role of control and choice in selecting partners

In this work, we provide evidence based on direct observation of behavior in encounters of opposite-sexed strangers, that women initiate and “control” the outcome. In the first minute of these videotaped 10-min interactions, neither female “solicitation” behavior nor “negative” behavior is strongly related to professed interest in the man, while female “affirmative” behavior at this stage modulates male verbal output in later stages (4–10 min). Although the rate of female courtship-like behavior is significantly higher in the first minute, it is only in the fourth to tenth minute that the rate of female courtship-like behavior is correlated with professed female interest. We hypothesize that this serves as a strategic dynamic reflecting sexual asymmetry in parental investment and the potential cost of male deception to women. Ambiguous protean behavioral strategies veil individuals' intentions and make their future actions unpredictable. These behavioral strategies may result in men's overestimation of female sexual interest.     

Chelicerae as male grasping organs in scorpions: sexual dimorphism and associated behaviour

Specialised structures that enable males to grasp females during sexual interactions are highly susceptible to selection and thus diverge relatively rapidly over evolutionary time. These structures are often used to test hypotheses regarding sexual selection such as sexually antagonistic co-evolution and sexual selection by female choice. In the present study, we determine whether there is a relationship between a novel record of scorpion sexual dimorphism, the sexual dimorphism of chelicerae (CSD), and the presence of the mating behaviour termed “cheliceral grip” (CG). The presence of both traits in the order Scorpiones is also reviewed from a phylogenetic perspective. The results confirm a strong relationship between CSD and the presence of CG. The morphological and behavioural patterns associated with “CSD–CG” are opposed to the predictions postulated by the hypothesis of sexually antagonistic co-evolution. However, if the female shows resistance after the deposition of the spermatophore, the possibility that the male exerts pressure as a “cryptic form” of coercion to prevent the interruption of mating cannot be ruled out completely. Female choice by “mechanical fit” could be another explanation for some aspects of the CG's contact zone. The possibility that the “CG–CSD” complex has evolved under natural selection in order to ensure sperm transfer is also considered.     

A high standard metabolic rate constrains juvenile growth

The allocation of energy to various components of an individual's energy budget is often viewed as a competitive process. As such, a tradeoff may exist between production (growth) and maintenance metabolism. One view of a potential tradeoff, termed “the principle of allocation”, suggests that individuals with lower maintenance metabolic expenditures may have higher growth rates. To determine whether such a tradeoff exists, I analyzed the relationship between growth rate and maintenance metabolism of 225 juvenile snapping turtles housed in the laboratory. I measured growth from hatching to 6 months of age, and then measured oxygen consumption and calculated standard metabolic rate. Mean growth rate was 0.19 g d⁻ and mean standard metabolic rate (SMR) was 1.41 kJ d⁻. Maintenance metabolism and growth were negatively correlated after both were adjusted for body mass. The results support the “principle of allocation” theory: individuals with higher standard metabolic rates tended to have low growth rates.     

Comparison of linear and nonlinear models for human population dynamics

In standard demographic practice, population projections are commonly based on one-sex linear models of the Lotka-Leslie type. We demonstrate here that such projections based solely on time-invariant, age-specific male fertilities and mortalities are incompatible with those based solely on female fertilities and mortalities. This incompatibility obtains even in the singular case where effective male and female fertility functions are equal, and generate equal ultimate rates of growth. In standard demographic practice, the incompatibility is initially masked, since one-sex fertility functions are generally calculated from the same initial-time data and thereby tautologically forced to initially concur; however, with the passage of any finite time, the incompatibility reasserts itself—the only exception being the uninteresting case where the system is already in the stationary age and sex distribution of balanced exponential growth.An example is adduced of a nonlinear (age-free) system whose true rate of ultimate growth is correctly bracketed by the male and female one-sex rates of ultimate growth. Analysis of more general two-sex models shows that the two one-sex growth rates, calculated for arbitrary male and female initial age distributions, need not bracket the true rate. We show, however, that models exist such that with appropriate choices of initial conditions, this bracketing will occur.     

The two-sex problem with persistent unions: a generalization of the birth matrix-mating rule model

The birth matrix-mating rule (BMMR) model solves the two-sex problem of classical stable population theory by allowing births to adjust to changes in a population's age-sex composition. To avoid complications the BMMR model assumes that unions last for only a single period. This paper drops that assumption and presents the BMMRPU (BMMR persistent unions) model. To establish the existence of equilibrium in the BMMRPU model, the existence proof used in the BMMR model is supplemented by a fixed-point argument.     

Adaptive Host Preference and the Dynamics of Host–Parasitoid Interactions

Models of two independent host populations and a common parasitoid are investigated. The hosts have density-dependent population growth and only interact indirectly by their effects on parasitoid behavior and population dynamics. The parasitoid is assumed to experience a trade-off in its ability to exploit the two hosts. Three alternative types of parasitoid are investigated: (i) fixed generalists whose consumption rates are those that maximize fitness; (ii) “ideal free” parasitoids, which modify their behavior to maximize their rate of finding unparasitized hosts within a generation; and (iii) “evolving” parasitoids, whose capture rates change between generations based on quantitative genetic determination of the relative attack rates on the two hosts. The primary questions addressed are: (1) Do the different types of adaptive processes stabilize or destabilize the population dynamics? (2) Do the adaptive processes tend to equalize or to magnify differences in host densities? The models show that adaptive behavior and evolution frequently destabilize population dynamics and frequently increase the average difference between host densities.     

On the interaction between stabilizing social factors and destabilizing trophic factors in small rodent populations

Mathematical models are developed in order to analyze whether or not social factors, such as, for example, the “social fence” (J. B. Hestbeck, 1982, Oikos 39, 157–163) will stabilize population density: the dynamic interaction between social factors and (dynamic) trophic factors is analyzed. It is concluded that social factors such as the “social fence” tend to stabilize population density; hence, if density cycles (as, e.g., seen in many microtine rodents) are observed in nature, it seems reasonable to conclude that density cycles are driven by, for example, trophic interactions and not by social factors. It is suggested that the “social fence” may explain why so many populations including several microtine populations have fairly stable densities despite the ever-existing destabilizing trophic interactions. Contrary to what is implied by J. B. Hestbeck (1983, “A Mathematical Model of Population Regulation in Cyclic Mammals,” Lecture notes in biomathematics, Vol. 52, Springer-Verlag, Berlin/New York), the analysis presented in this paper demonstrates that seasonal environmental changes are not essential for the generation of regular density cycles. Seasonal changes may, however, be necessary for generating a microtine-like density cycle. Empirical information on microtine rodents relating to the “social fence hypothesis” is discussed.     

An interactive nonrandom-mating two-sex model whose intrinsic growth rate lies between one-sex rates.

In a recent paper, the author has presented an interactive two-sex model and applied it to the U.S. population, 1940–1971. While the model has removed many inconsistencies in the one-sex models for males and females, it has two major limitations. First, the model assumes random mating of men and women within their reproductive ages. Second, it gives an intrinsic growth rate that is not necessarily intermediate between the male and the female intrinsic growth rates, as obtained from the one-sex models. A new two-sex model is provided in this paper that removes both these limitations. The new model is applied to the U.S. population for the years 1940–1974.     

Limiting genotype frequencies of Y-linked genes through bisexual branching processes with blind choice

The limiting genotype growth rates and the limiting genotype frequencies of Y-linked genes are studied in a two-sex monogamous population. To this end, the evolution of the numbers of females, males, and mating units of each genotype is modelled by a multitype bisexual branching process in which it assumed that the gene has no influence on the mating process. It is deduced from this model that the average numbers of female and male descendants per mating unit of a genotype determine its growth rate, which does not depend on the behaviour of the other genotypes. Hence, the dominant genotype is found. Conditions for the simultaneous survival of genotypes to have positive probability are also investigated. Finally, the main results are illustrated by means of examples.     

Emergence patterns in male butterflies: A hypothesis and a test

A game theoretical model is advanced to explain the emergence time schedule of male butterflies under temporal “apostatic” selection, so that males emerging on different days enjoy equal fitness in evolutionary equilibrium. The model predicts not only the position of the peak date but also the shape of the male emergence curve for any given female emergence schedule. Where the female emergence curve is smooth with one peak, a flight season can be divided into an earlier phase, when some males emerge every day, and a later phase in which no male emerges. The male emergence curve is truncated at the boundary of the phases. The position of the truncation point is determined by the difference between pre- and postemergence mortality. Preemergence mortality also determines the rate coefficient of the decrease in sex ratio through the season. The model is applied to a well-studied population of the butterfly Euphydryas editha. The male presence curve fits well, but no clear truncation exists in male emergence, and some males emerge earlier than predicted. Reasons for deviations are discussed.     

On the concept of the effective population size

The concept of the effective population size is discussed. It is shown that the “eigenvalue” and the “inbreeding” effective population sizes are in principle different, even though they have been sometimes identified in the literature. On the other hand the “eigenvalue” and “variance” effective sizes are usually both close when the latter exists. Since, however, there are many models for which a variance effective size cannot in principle exist, it seems useful to introduce the eigenvalue effective size and to examine some of its properties.     

Use of genital inspection and female urine tests to detect oestrus in captive Asian elephants

Captive Asian elephant (Elephas maximus) populations are decreasing due to low birth rates compared to wild elephants. Improving oestrous detection in female elephants is required to ensure successful mating in captive and semi-captive herds. Responsive behaviours of eight semi-captive bull elephants to the uro-genital area (genital inspection test) or urinary pheromones (urine test) of 14 female elephants throughout the oestrous cycle were evaluated. Weekly blood samples were collected for 27 consecutive months (14 months for the genital inspection test and 13 months for the urine test) from female elephants to characterize the patterns of circulating progestagen. Responsive behaviours of bulls were compared between females in the follicular versus the luteal phase of the cycle. The sensitivity and specificity of the genital inspection test were 65% and 68%, while those of the urine test were 52% and 61%, respectively. The bulls showed significantly higher “genital inspection”, “flehmen from genital area” and “trunk on back” behaviours during the genital inspection test, and “flehmen” behaviours during the urine test in oestrous than in non-oestrous females. In sum, this study showed that monitoring sexual behaviours of Asian elephant bulls towards females or their urine can be used to detect the oestrous period. Although the sensitivity and specificity of both tests were not as high as expected, still, these methods appear to be more efficient at detecting oestrous than traditional methods based on mahout estimations of female receptivity. The use of genital inspection and urine tests may lead to more successful matings and thus to creating self-sustaining populations of captive elephants in range countries.     

Preference for an estrous female over a non-estrous female evinced by female rats requires dihydrotestosterone plus estradiol

The effects were studied of long-term treatment with testosterone metabolites (dihydrotestosterone, DHT, and estradiol, E2, in sc Silastic implants) on preference behavior of ovariectomized female rats for an estrous female over a non-estrous female. For measuring this behavior a residential plus-maze was used which harbored two ovariectomized “stimulus” females on the top of peripheral boxes, one of which was made estrus by injection of estradiol benzoate and progesterone. When both steroids (DHT plus E2) were circulating simultaneously they evoked preference for an estrous female, while neither steroid by itself sufficed. In earlier work with adult male rats castrated on the day of birth, E2 was effective in the absence of DHT. This sex difference, therefore, seems to have arisen before birth. Further, administration of DHT alone caused a profound lack of interest in both “stimulus” females, which cannot be fully explained by the reduced locomotor activity which has been found to be induced by DHT in earlier Studies.     

The fast–slow continuum and mammalian life-history patterns: an empirical evaluation

The fast–slow continuum hypothesis has been proposed to explain the diversity of life-history patterns exhibited by biological populations, but the quantification and population-dynamic consequences of the continuum has remained unclear. I used the ratio of fertility rate to age at first reproduction (F/α ratio) to quantify the tempo of life-history of 138 populations of mammals, and investigated the life-history and population-dynamic consequences of being “fast” or “slow”. “Fast” mammals (F/α>0.60) were characterized by early maturity, short lifespans, low survival rates, and high fertility and projected population growth rate (λ) compared to “slow” (F/α<0.15) mammals. In “fast” populations, λ was overwhelmingly most sensitive to changes in reproductive parameters (age at first reproduction and fertility rates) and relatively insensitive to changes in survival rates. In “slow” populations, λ was very sensitive to changes in juvenile or adult survival rates, and relatively insensitive to changes in reproductive parameters. The pattern of relationships between the F/α ratio and life-history variables, λ, and elasticity of λ to changes in life-history variables persisted even after the effects of body size and phylogeny were statistically removed. These results suggest that fast–slow continuum in mammalian life-history is independent of body size or phylogeny, that the F/α ratio adequately quantifies the position of a population along a fast–slow continuum, and that the tempo of life- histories has substantial population-dynamic consequences.

Zusammenfassung

Die r-K-Kontinuum-Hypothese wurde aufgestellt, um die Diversität von ,,life-history“-Mustern biologischer Populationen zu erklären, aber die Quantifizierung und die Kosnsequenzen für die Populationsdynamik des Kontinuums blieben unklar. Ich benutze das verhältnis der Fortpflanzungsrate zum Fortpflanzungsalter (F/α-Verhältnis) um die Geschwindigkeit der ,,life-history“ von 138 Populationen von Säugetieren zu quantifizieren und untersuchte die Konsequenzen fur die Lebensweise sowie die Populationsdynamik des,,schnell“oder,,langsam “-Seins. ,,Schnelle“Säugetiere (F/α>0.60) waren durch eine frühe Reife, kurze Lebenszeiten, geringe Überlebensraten sowie durch eine große Fertilität und hochgerechnete Populationswachstumsrate (λ) im Vergleich zu ,,langsamen“(F/α<0.15) Säugetieren charakterisiert. In ,,schnellen“ Population reagierte (λ) überwältigend sensibel auf Änderungen in den Fortpflanzungsparametern (Fortpflanzunsalter und Fertilitätsrate) und relativ gering auf Veräanderungen in der Überlebensrate. In ,,langsamen“ Populationen reagierte (λ) sehr sensibel auf Veräanderungen in den reproduktiven Parametern. Das Muster der Beziehung zwischen dem (F/α-Verhältnis) und den Variablen der ,,life-history“,λ, und die Elastizität von λ gegenüber Veränderungen in den variablen der Lebensweise bliev sogar bestehen, nachdem die Effekte von Körpergröße und Phylogenese statistisch eliminiert wurden. Diese Ergebnisse lassen vermuten, dass das r-K-Kontinuum in der ,,life-history“der Säugetiere unabhängig von der Körpergröße und Phylogenie ist, dass das F/α-Verhältnis die Position einer Population im r-K-Kontinuum quantifiziert und dass die Geschwindigkeit der,,life-history“beachtliche konsequenzen fur die Populationsdynamik hat.     

Invasion Waves in Populations with Excitable Dynamics

Whilst the most obvious mechanism for a biological invasion is the occupation of a new territory as a result of direct ingress by individuals of the invading population, a more subtle “invasion” may occur without significant motion of invading individuals if the population dynamics in a predator prey scenario has an “excitable” character. Here, “excitable” means that a local equilibrium state, either of coexistence of predator and prey, or of prey only, may, when disturbed by a small perturbation, switch to a new, essentially invaded state. In an invasion of this type little spatial movement of individuals occurs, but a wave of rapid change of population level nevertheless travels through the invaded territory. In this article we summarise and review recent modelling research which shows that the macroscopic features of these invasion waves depend strongly on the detailed spatial dynamics of the predator–prey relationship; the models assume simple (linear) diffusion and pursuit-evasion, represented by (non-linear) cross-diffusion, as examples. In the context of plankton population dynamics, such waves may be produced by sudden injections of nutrient and consequent rapid increase in plankton populations, brought about, for example, by the upwelling caused by a passing atmospheric low pressure system.     

Biology, life table and predation of Feltiella acarisuga (Diptera: Cecidomyiidae) feeding on Tetranychus cinnabarinus eggs (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common predatory gall midge, which feeds on many species of spider mites. All major life history and life table parameters of F. acarisuga were determined using the carmine spider mite, Tetranychus cinnabarinus (Boisduval) eggs as prey under laboratory conditions [26.7 ± 2 °C, 75 ± 5% RH, and a photoperiod of l4:10 (L:D) h]. Developmental times of F. acarisuga were 2.6, 7.1, and 6.7 d for eggs, larvae, and pupae, respectively, with an average of 16.4 d from egg to adult emergence. Female immatures development took ≈1 d longer than male immatures did. Adult F. acarisuga lived an average of 12.8 d, and the female adults (13.3 d) lived significantly longer than male adults did (11.9 d). After an average of 1.5 d preoviposition period, each female laid an average of 27.3 eggs in its life span with an average of 2.1 eggs per day and an average of 2.8 eggs on each of its oviposition day. The raw data were analyzed using an age-stage, two-sex life table method that takes into consideration of the variable developmental rates among individuals and between sexes. The intrinsic rate of natural population increase (r), net reproductive rates (R_o), gross reproductive rate (∑m_x), generation time (T), and doubling time (DT), and the finite rate of increase (λ) of F. acarisuga were estimated using the age-stage, two-sex (male and female) life table analysis as 0.122 d⁻¹, 16.19 eggs per female, 20.81 eggs per female, 22.81 d, 1.1298 d, and 5.7 d⁻¹, respectively. Each of the first, second, and third instar larvae of F. acarisuga consumed an average of 35.5, 54.0 and 86.9 T. cinnabarinus eggs per day, respectively. Larvae of F. acarisuga could consume an average of 175.4, T. cinnabarinus eggs, and female larvae consumed 14% more spider mite eggs (187.6 eggs) than male larvae (165.1 eggs). The significance of other life table parameters related to the population and the potential of using F. acarisuga as a biological control agent are discussed.     

Mother-infant spatial relationships in domestic goats

This study focused on spatial relationships between female domestic goats and their kids from birth to 15 weeks of age. Results indicate that goat mothers are primarily responsible for the initiation and maintenance of mother-infant contact only during the first week following parturition. A shift to infant responsibility for mother-infant proximity was seen during Week 2, and kids remained primarily responsible throughout all subsequent weeks of observation. Mothers and their young spent most of their time more than 10 mother-lengths from each other during the course of the study; this lack of close physical proximity was particularly evident during the infant's first 6–8 weeks following birth. Thereafter, kids exhibited significant increases in the amount of time spent in close proximity to their dams. This general trend in the development of mother-infant spatial relationships in domestic goats is similar to those reported for other “hider” ungulates, and confirms that the domestic goat has a “hider” rather than a “follower” type of mother-infant relationship.     

The relationship between reproductive success and demographic structure in remnant populations of Primula veris

Plants often suffer reductions in fecundity due to fragmentation, degradation and destruction of populations and their sites. Whether this decrease in seed production has population-level consequences is generally unknown. Here, we aimed to determine the current status of remnant populations in the perennial herb Primula veris in Belgium. Furthermore, we investigated the effects of reduced population size and morph bias on reproductive success and explored if changes in demographic structure could be associated with population fecundity. We studied 69 populations that differed in population size from three to nearly 1500 flowering plants. Three different population types could be distinguished: (a) “dynamic” populations, characterized by high densities of 1 year old juveniles, (b) “normal” populations with adult age-stages prevailing, but still a considerable number of juveniles, and (c) “regressive” populations, in which only flowering adults dominate and rejuvenation hardly occurs. The three population types differed with respect to population size and morph frequency. Dynamic populations were significantly larger and showed a weaker morph bias compared to the intermediate normal and the small regressive populations. Reproductive success, studied the previous year in 26 populations, decreased significantly with decreasing population size and was significantly associated with the demographic structure of the populations. Coefficients of variation for the proportion of flowers setting fruit, the number of seeds per fruit and the total number of seeds per plant decreased significantly with increasing population size. Hence, the observed variability in seed set may be one of the causal factors affecting the observed types of population demographic structure.     

Male hypofertility induced by Paraquat consumption in the non-target parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae)

The effects of a herbicide – Paraquat – on male development and reproduction were tested on the parasitoid wasp Anisopteromalus calandrae (Hymenoptera, Pteromalidae) by injecting host larvae with different concentrations of this substance. Data measured were: (1) developmental success, (2) sperm stock in seminal vesicles, (3) ability to copulate and transfer sperm, and (4) offspring production. Both developmental success and sperm in seminal vesicles were reduced in the “Paraquat” groups. However, neither sperm stored in the females’ spermatheca, nor offspring production (number of female offspring and sex ratio) differed from controls, whatever the host treatment. The decreased of male sperm reserve in ‘‘Paraquat” group is likely to reduce their reproductive success because they can succefully inseminated less female than control males. These males are thus hyporfertiles. Because Paraquat has non-negligible consequences on non-target parasitoid males, it is likely to affect natural and controlled insect populations.     

Cell cycle variation associated with feeder effects in cultures of Chinese hamster fibroblasts

Sub-confluent monolayer cultures of an established line of Chinese hamster fibroblast (Don) are shown to exhibit a density-dependent stimulation of growth. Evidence is presented that both long and short range ‘feeder effects’ are involved. Using the technique of autoradiography, cell cycle parameters have been studied in sub-confluent cultures seeded at different densities to identify the source of this density-dependent variation in growth rate. The durations of S phase, G2, and mitosis are constant as indicated by “percentage labelled mitoses” curves. A simple procedure has been developed for measurement of the fraction of a cell population in the G1 state, and this fraction is shown to be inversely related to the density of the culture. It is concluded that regulation of cell growth associated with feeder effects in cultured Don cells occurs within the G1 state. The data obtained from “percentage labelled mitoses” curves are shown to be highly consistent with the predictions of the Transition Probability model for cell cycle regulation.