Extending r/K selection with a maternal risk-management model that classifies animal species into divergent natural selection categories

Reproduction is a defining process of biological systems. Every generation, across all species, breeding females repopulate ecosystems with offspring. r/K selection was the first theory to classify animal species by linking the rates with which breeding females repopulated ecosystems, to the stability of ecosystems. Here, I introduce a species classification scheme that extends the reach of r-K selection and CSR selection by linking breeder investments in offspring quantity, quality, and diversity to specific natural selection pressures. The species classification scheme is predicated on the assumption that high rates of predation favor breeders that invest more in offspring quantity than quality; and that spatiotemporal scarcity favors breeders that investment more in offspring quality than quantity. I present equations that convert the species classification scheme into a maternal risk-management model. Thereafter, using the equations, I classify eighty-seven animal species into the model’s natural selection categories. Species of reptiles, fish, and marine invertebrates clustered in the predation selection category. Species of birds and mammals clustered in the scarcity selection category. Several species of apex predators clustered in the weak selection category. Several species of social insects and social mammals clustered in the convergent selectioncategory. In summary, by acknowledging breeding females as the individuals upon which natural selection acts to repopulate ecosystems with offspring, the proposed maternal risk-management model offers a testable, theoretical framework for the field of ecology

Skew Selection: Nature Favors a Trickle-Down Distribution of Resources in Ants

Synopsis: According to skew selection, ant queens are neither ruthlessly selfish nor blindly altruistic; they are shrewd investors. The goal of shrewd investors is not to win the game, but to continue play over evolutionary time. Skew selection describes a set of investment strategies employed by players such as ant queens to keep the game going. First, ant queens acquire excess resources—more than they need for immediate survival and reproduction. Second, queens invest a portion of their excess resources in personal capital to maintain dominant status. Third, queens also invest a portion of excess resources in low-quality offspring to gain group capital. Fourth, when investing in group capital, resources are distributed in a trickle-down fashion to maintain the largest number of diminishing-quality offspring possible. The trickle-down redistribution allows the shrewd queen to increase group size (safety in numbers) and, at the same time, maintain individual status (safety in position). According to skew selection, queens invest in low-quality offspring (sterile workers) to buffer hereself and her high-quality offspring from agents of death such as war, predation or disease. Copyright Kluwer Academic Publishers 2003Natural selection, group selection, cooperation, competition, altruism,

Sex ratio theory is a contradiction, not an extension, of kin selection.

Kin selection and sex ratio theory employ gene-centric models with coefficients of relatedness to explain the evolution of altruism in the social Hymenoptera. Central to both theories is the fact that Hymenoptera organisms are haplodiploid, a condition that creates an asymmetry in relatedness among siblings. This paper exposes the fact that sex ratio theory is a contradiction, not an extension, of kin selection. In kin selection, Hamilton developed the coefficient of relatedness as a probability fraction. Hamilton\u27s altruists must help a small number of close relatives or a large number of distant relatives to ensure that one copy of their altruistic genes are propagated into the next generation. In sex ratio theory, Trivers and Hare modeled the coefficient of relatedness as an arithmetic fraction rather than a probability fraction. As a result, their altruists help a large number of close relatives and a small number of distant relatives, the opposite of Hamilton\u27s altruists. Gene-centric modelers must clarify which relatedness coefficient, arithmetic or probability, they are using to frame their predictions

The flow of food and social organization in the fire ant Solenopsis invicta.

In social insects, the distribution of workers within and among tasks occurs without a central authority. To determine the mechanisms regulating worker labor, the flow of food from the environment to the larva was investigated using the fire ant, Solenopsis invicta. Replicated experiments were conducted on both laboratory- and field-reared colonies from Tallahassee, Florida, U.S.A. The frequency and duration of large numbers of individual food exchanges under experimental conditions were quantified using video-technology. Treatments included worker or larval food-deprivation (marked by food dyes), body size, age, food type, food concentration, food state, nest temperature, colony size and worker:larva ratio. During each worker-larva food exchange (trophallaxis), larvae were fed a discrete increment of food (- .5 ± 0.1 nl) regardless of larval attributes and conditions. Therefore, the total volume of food ingested by larvae was determined by the rates of trophallaxis. Larvae regulated their diet by soliciting feedings from workers via a hunger cue at a rate proportional to their size and in relation to food deprivation, food type and food concentration. Nutrients were homogenized and evenly distributed among larvae, over time, per unit of larval volume. Workers displayed considerable variation in their feeding response to larval hunger which affected the time required to fill larvae but not the even distribution of food among larvae. Within naturally occurring parameters, neither temperature, colony size, nor worker:larva ratios affected the rate of worker-larva trophallaxis. Foragers assessed food on site and recruited others in relation to food type and concentration. When offered two food types simultaneously, workers moved proteinaceous solutions to larvae and sugar solutions to workers, suggesting that the behavioral response of workers was based upon crop contents. The absence of protein in worker crops rather than the presence of larvae caused workers to forage for amino acids preferentially to sucrose. Food distribution among workers was uneven and may ensure that some workers will be empty enough to forage at all times. In summary, colony nutrition is regulated by two feedback cues: worker crop content, which determines the rate at which food moves from the environment into the colony, and larval hunger which determines the rate and direction at which food moves within the colony

Press release : 2003 : 11 : 12 : USF St. Petersburg Research Focuses on Fire Ant Control

Describes Deby Cassill\u27s research on fire ants

Skew selection: Nature favors a trickle-down distribution of resources in ants.

According to skew selection, ant queens are neither ruthlessly selfish nor blindly altruistic; they are shrewd investors. The goal of shrewd investors is not to win the game, but to continue play over evolutionary time. Skew selection describes a set of investment strategies employed by players such as ant queens to keep the game going. First, ant queens acquire excess resources-more than they need for immediate survival and reproduction. Second, queens invest a portion of their excess resources in personal capital to maintain dominant status. Third, queens also invest a portion of excess resources in low-quality offspring to gain group capital. Fourth, when investing in group capital, resources are distributed in a trickle-down fashion to maintain the largest number of diminishing-quality offspring possible. The trickle-down redistribution allows the shrewd queen to increase group size (safety in numbers) and, at the same time, maintain individual status (safety in position). According to skew selection, queens invest in low-quality offspring (sterile workers) to buffer herself and her high-quality offspring from agents of death such as war, predation or disease