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

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

The rich inner lives of fire ants

Video created as part of a TEDxUSF: A World Beyond Ourselves event, March 28, 2015. 9 minutes 29 seconds in duration

Why skew selection, a model of parental exploitation, should replace kin selection.

In his 1964 paper, William Hamilton wrote that inclusive fitness trumps direct fitness if, and only if, the effect of interactions among siblings on their parent’s fitness is ‘zero’. Kin selection models have succeeded only because they have ignored the fact that, if an altruist dies saving two siblings, the ‘zero impact on their parent’s fitness’ constraint is violated. Imagine a parent with three offspring. If two offspring drown, parental fitness is 1. On the other hand, if one altruistic offspring dies saving its two drowning siblings, parental fitness doubles to 2. Thus, direct fitness trumps inclusive fitness as an explanation for the evolution of altruism. In other words, parents that produce some portion of altruistic offspring willing to die to save some of their siblings (who would die without the intervention of the altruist) will realize greater fitness than parents producing no altruists. Skew selection, a bioeconomic extension of Michael Ghiselin’s (1974) parental exploitation model, is presented to explain the evolution of altruism from a direct fitness point of view

Rules of supply and demand regulate recruitment to food in an ant society.

The process by which ant scouts move a group of nestmates toward a newly discovered food site is called recruitment. In this paper, I report on the interactions between scouts and nestmates that result in a graded recruitment response to graded food quality in the fire ant, Solenopsis invicta. Twelve experimental groups composed of 100 fire ant workers and 50 fire ant larvae were established (three experimental groups per colony x four stock colonies). Each experimental group was placed in a shallow, artificial nest with a glass cover. After a 48-h period of food deprivation, experimental groups were exposed to one of three concentrations of sugar water. Behavioral interactions between scouts and nestmates in each group were videotaped at 10x magnification for 20 min. Detailed behavioral data on a total of 120 scouts (10 scouts per experimental group) and ~1,000 nestmates (~90 nestmates per experimental group) were transcribed from the videotapes using standard play and frame-by-frame techniques. Throughout the recruitment process, scouts employed six discrete behaviors to inform nestmates of the location and quality of a food site. Scouts laid incoming trails, waggled their heads, increased walking tempo, stroked nestmates with their antennae, advertised with a brief food display, and led groups of nestmates to the food site by laying outgoing trails. In turn, nestmates assessed the food sample with antennae, then responded to or resisted recruitment based on the quality of food advertised, their employment status and their level of hunger. In summary, recruitment was an emergent property based on competent supply and demand decisions made face-to-face inside the nest rather than on the trail or at the food site

Maternal risk management, a theory of reproductive diversity by means of natural selection

Maternal risk management extends Darwin\u27s theory of natural selection to explain, not only the fission of populations into diverse species via competition, but the fusion of parent and offspring into temporary family units via altruism and populations of family units into societies via cooperation