I. the origin of species by means of natural selection

Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

Citation classic - optimal foraging - a selective review of theory and tests

In his introduction to this detailed survey of knowledge of insect societies, the author points out that research on insect sociology has proceeded in three phases, the natural history phase, the physiological phase and the population-biology phase. Advances in the first two phases have permitted embarkation in the third phase on a more rigorous theory of social evolution based on population genetics and writing this book, the author wished to relate the three phases of research on insects and to express insect sociology as population biology. A glossary of terms, a considerable bibliography and a general index are included. Other CABI sites 

The Insect Societies

Multivariate analysis provides statistical methods for study of the joint rela­ tionships of variables in data that contain intercorrelations. Because several variables can be considered simultaneously, interpretations can be made that are not possible with univariate statistics. Applications are now common in medicine (117), agriculture (218), geology (50), the social sciences (7, 178, 193), and other disciplines. The opportunity for succinct summaries of large data sets, especially in the exploratory stages of an investigation, has contrib­ uted to an increasing interest in multivariate methods. The first applications of multivariate analysis in ecology and systematics were in plant ecology (54, 222) and numerical taxonomy (187) more than 30 years ago. In our survey of the literature, we found 20 major summaries of recent applications. Between 1978 and 1988, books, proceedings of sym­ posia, and reviews treated applications in ecology (73, 126, 155, 156), ordination and classification (13, 53, 67, 78,81,83,90,113,121,122,159), wildlife biology (33, 213), systematics (148), and morphometries (45, 164,

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Multivariate analysis in ecology and systematics: panacea or pandora's box?

1. What are Allee effects? 2. Mechanisms for Allee effects 3. Population dynamics: modelling demographic Allee effects 4. Genetics and evolution 5. Conservation and management 6. Conclusions and perspectives

Allee Effects in Ecology and Conservation

Differences in social organization and behaviour rank ant species into a competition hierarchy (starting with superior competitors): territorials (e.g., the Formica rufa -group red wood ants), encounterers (e.g. Camponotus, Lasius niger), and submissives (e.g., Formica fusca). Territorials and encounterers behave aggressively against individuals of alien colonies; these species are not expected to cooccur. Submissives behave recessively and may coexist with stronger species, but their forager numbers and nest densities should decrease. If such small-scale behavioural processes structure the ant community, predictable larger-scale nest-distribution pattern of the species is expected. We tested the expectations with bait experiments and nest mapping, and modelled the results by multiway contingency tables. Submissives showed complementary abundances with territorials in terms of forager numbers on the baits, and their nest densities within the territory increased toward its periphery. Pressure by territorial and encounter species on the baits caused the submissive species to shift from protein to carbohydrate. Territorials and encounterers had complementary occurrences on the baits. The nests of territorials were far apart, with only occasional nests of encounter species at the outskirts of the territory. In the late successional habitats of the boreal taiga biome superior territorial competitors, especially the polycalic red wood ant species, assume the role of organizing centers of ant species assemblages.

https://www.jstor.org/stable/pdfplus/3565636.pdf

A competition hierarchy among boreal ants: impact on resource partitioning and community structure

The question if dominant ant species affect habitat use of other ant species was studied around two mounds of the territorial Formica polyctena. We sampled foraging ants at 10, 30 and 60 m from the mounds in four vertical layers on rocky outcrop interspersed with small vegetation patches and in neighbouring forest. We tested expected interactions among ant species on the basis of a linear competition hierarchy concept consisting of three levels: territorial (top competitors), encounter (aggressive but nonterritorial) and submissive (nonaggressive) species. We focussed on resource partitioning by space (not by food) and shifts in use of vertical layers of the habitat in presence of the territorial species. F polyctena was present everywhere except in the litter. Its numbers decreased with distance from its mound, although its activity was substantially patchy within each distance zone. The encounter species occurred occasionally in places where F. polyctena was scarce. The submissive F. fusca, morphologically similar to the top dominant, did not respond by layer shifts; but its numbers decreased toward the mound of F polyctena. The submissive Myrmica shifted from surface of ground to litter and shrub layers at high densities of the dominant. Small colonies and short foraging distances of the submissive species allow coexistence within the territory in lowdensity patches of F polyctena. Our ant community consists of three functional guilds corresponding to taxonomic and morphological guilds: the larger above-ground Formicinae, the smaller and compacter Formicinae, and the small litter-inhabiting Myrmicinae. Interference competition is stronger and more effective among the Formicinae than among the Myrmicinae or between the subfamilies, but the top dominant affects all ant species of the community. Coexistence between the submissives and the top dominant is facilitated by niche differentiation and behavioural responses in the presence of the top dominant.

Niche differentiation of ant species within territories of the wood ant Formica polyctena

Sympatric speciation through intraspecific social parasitism has been proposed for the evolution of Hymenopteran workerless parasites. Such inquilines exploit related host taxa to produce their own sexual offspring. The relatedness of inquilines to their hosts has been generalized in Emery's rule, suggesting that social parasites are close or the closest relatives to their host species. If the closest relative of each parasite is its host, then multiple independent origins of the parasite species are implied even within a single genus, probably through sympatric speciation. To test the plausibility of sympatric speciation in inquilines, we conducted a mitochondrial DNA phylogenetic analysis in three inquiline–host pairs of Myrmica ant species. We show that congeneric inquilines have originated independently several times. We also show that two of the inqulines are more closely related to their hosts than to any other species. Our results suggest sympatric speciation of Myrmica inquilines. Sympatric speciation is probably facilitated by the social biology and ecology of Myrmica, with polygyny as a prerequisite for the evolution of intraspecific parasitism.

https://www.pnas.org/content/pnas/100/12/7169.full.pdf

Sympatric speciation through intraspecific social parasitism.

Ants were collected with sets of pitfall traps in four coniferous-forest habitats in southern Finland. A three-level competition hierarchy concept was used to generate predictions on ant community structure. The levels of the hierarchy, and the respective predictions, from top to bottom were: (1) The dominant territorial wood ants (Formica rufa-group species), expected to exclude each other. (2) The other aggressive species, likely to be excluded by the F. rufa-group. (3) The submissive species, non-aggressive and defending only their nest, and thus likely to coexist with the dominants but in reduced numbers. As expected, the species of the F. rufa-group excluded each other, and the species number of the other aggressive ants was significantly cut down in the presence of the F. rufa-group. The aggressive species F. sanguinea and Camponotus herculeanus showed complementary occurrences with the F. rufa-group, and Lasius niger reduced occurrences. The number of the submissive species was not significantly affected by the F. rufa-group. However, pairwise correlation coefficients were significantly more often negative than positive between presence of the F. rufa-group and average proportion of pitfalls per set with a submissive species, each analyzed in turn. The result indicates that the F. rufa-group also reduced the colony densities of the submissive species. We conclude that in the taiga biome territorial wood ants are, after adjusting for physical vicissitudes of the environment, the major structuring force of ant species assemblages.

Ant assemblages in the taiga biome: testing the role of territorial wood ants

Recherche de l'interaction entre plusieurs especes agressives de fourmis (dont certaines sont territoriales) et Myrmica auxquelles on presente des appâts concentres, simulant des resources stables en proteines et en glucides.

Riitta Savolainen

Papers

A competition hierarchy among boreal ants: impact on resource partitioning and community structure

Niche differentiation of ant species within territories of the wood ant Formica polyctena

Sympatric speciation through intraspecific social parasitism.

Ant assemblages in the taiga biome: testing the role of territorial wood ants

The effect of interference by formicine ants on the foraging of Myrmica.