Evolution of Protein Molecules

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

Bioindicators, as taxa or functional groups, are widely used as indicators of environmental change, specific ecological factors or taxonomic diversity. The use of ecological, environmental and biodiversity indicators, is reviewed here. Although indicator taxa are considered to be generally unreliable as broad indicators of biodiversity, they may serve a useful function in identifying ecological characteristics or monitoring the effects of habitat management. Use of only a narrow range of taxa may be unreliable, and is particularly vulnerable to distortion by a small number of invasive species. Taxa also need to be selected to reflect the specific ecosystem being studied. It is recommended that isopods be used for soil systems (if there is sufficient local diversity), in some areas earthworms or mites may be useable but are generally too difficult to identify to be practically useful. In the ground layer indicator sets could include ants, millipedes, molluscs (snails in particular), ground beetles, harvestmen and gnaphosid spiders. Foliage-inhabiting indicators could comprise ants, chrysomelid leaf beetles, theridiid spiders and arctiid moths. Ants, orthopterans and butterflies may be appropriate for use in open habitats. These basic sets should be supplemented by other taxa where appropriate resources and taxonomic expertise are available.

Terrestrial invertebrates as bioindicators: an overview of available taxonomic groups

The haplodiploid sex determining mechanism in Hymenoptera (males are haploid, females are diploid) has played an important role in the evolution of this insect order. In Hymenoptera sex is usually determined by a single locus, heterozygotes are female and hemizygotes are male. Under inbreeding, homozygous diploid and sterile males occur which form a genetic burden for a population. We review life history and genetical traits that may overcome the disadvantages of single locus complementary sex determination (sl-CSD). Behavioural adaptations to avoid matings between relatives include active dispersal from natal patches and mating preferences for non-relatives. In non-social species, temporal and spatial segregation of male and female offspring reduces the burden of sl-CSD. In social species, diploid males are produced at the expense of workers and female reproductives. In some social species, diploid males and diploid male producing queens are killed by workers. Diploid male production may have played a role in the evolution or maintenance of polygyny (multiple queens) and polyandry (multiple mating). Some forms of thelytoky (parthenogenetic female production) increase homozygosity and are therefore incompatible with sl-CSD. We discuss a number of hypothetical adaptations to sl-CSD which should be considered in future studies of this insect order.

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Single locus complementary sex determination in Hymenoptera: an "unintelligent" design?

Insect societies – colonies of ants, bees, wasps and termites – vary enormously in their social complexity. Social complexity is a broadly used term that encompasses many individual and colony-level traits and characteristics such as colony size, polymorphism and foraging strategy. A number of earlier studies have considered the relationships among various correlates of social complexity in insect societies; in this review, we build upon those studies by proposing additional correlates and show how all correlates can be integrated in a common explanatory framework. The various correlates are divided among four broad categories (sections). Under ‘polyphenism’ we consider the differences among individuals, in particular focusing upon ‘caste’ and specialization of individuals. This is followed by a section on ‘totipotency’ in which we consider the autonomy and subjugation of individuals. Under this heading we consider various aspects such as intracolony conflict, worker reproductive potential and physiological or morphological restrictions which limit individuals’ capacities to perform a range of tasks or functions. A section entitled ‘organization of work’ considers a variety of aspects, e.g. the ability to tackle group, team or partitioned tasks, foraging strategies and colony reliability and efficiency. A final section,‘communication and functional integration’, considers how individual activity is coordinated to produce an integrated and adaptive colony. Within each section we use illustrative examples drawn from the social insect literature (mostly from ants, for which there is the best data) to illustrate concepts or trends and make a number of predictions concerning how a particular trait is expected to correlate with other aspects of social complexity. Within each section we also expand the scope of the arguments to consider these relationships in a much broader sense of'sociality’ by drawing parallels with other ‘social’ entities such as multicellular individuals, which can be understood as ‘societies’ of cells. The aim is to draw out any parallels and common causal relationships among the correlates. Two themes run through the study. The first is the role of colony size as an important factor affecting social complexity. The second is the complexity of individual workers in relation to the complexity of the colony. Consequently, this is an ideal opportunity to test a previously proposed hypothesis that ‘individuals of highly social ant species are less complex than individuals from simple ant species’ in light of numerous social correlates. Our findings support this hypothesis. In summary, we conclude that, in general, complex societies are characterized by large colony size, worker polymorphism, strong behavioural specialization and loss of totipotency in its workers, low individual complexity, decentralized colony control and high system redundancy, low individual competence, a high degree of worker cooperation when tackling tasks, group foraging strategies, high tempo, multi-chambered tailor-made nests, high functional integration, relatively greater use of cues and modulatory signals to coordinate individuals and heterogeneous patterns of worker-worker interaction. Key words: Ants, insect societies, individual complexity, social complexity, polyphenism, totitpotency, work organization, functional integration, sociality.

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Individual versus social complexity, with particular reference to ant colonies

The presence and abundance of arthropods were compared in three olive orchards under organic, integrated and conventional management regimes. In each olive orchard, trees were sampled in the canopy by beating branches and soil arthropods by placing pitfall traps. Contrary to expectations, the highest abundance of arthropods occurred in the integrated management orchard. The most abundant groups were Formicidae and the species Euphyllura olivinae (Homoptera: Psyllidae). 2 Canopies and the soil under the tree canopy (interior soil) were selected as the most informative sites for sampling. The months with the strongest differences were May, June and July, especially June. In the canopy, Araneae, Coleoptera, Diptera, Heteroptera, Hymenoptera, Homoptera, Lepidoptera, Neuroptera and Thysanoptera were the most abundant, and showed significant differences in abundance among orchards with different management regimes. Moreover, in the canopies, Coleoptera and Lepidoptera showed a seasonal pattern of abund- ance and consistent significant differences between the organic orchard vs. the integrated and conventional ones in both years of study. In the soil, 12 orders showed significant differences in abundance among management regimes at some point of the sampling season. 3 In a search for biological indicators that could help to distinguish between management regimes, a discriminant analysis applied to the data indicated that only the samples from the canopy were classified according to their manage- ment regime in a consistent way over time. The groups selected by the analysis to establish differences among management regimes were Coleoptera, Diptera, Heteroptera, Lepidoptera and Thysanoptera. The analysis applied to compare organic vs. non-organic olive orchards, again identified Coleoptera and Lepi- doptera as suitable groups. The results suggest that these two orders are potential bioindicators to distinguish, in a simple way, organic olive orchards from non-organic ones.

Use of arthropods for the evaluation of the olive‐orchard management regimes

Natural selection favors signals, receptors, and signaling behavior that maximize the received signal relative to background noise and that minimize signal degradation. The physical properties of the environment affect rates of attenuation and degradation of the signal, and thus temperature may influence the evolution and maintenance of volatile chemical signals. We tested this hypothesis in ants, where nest mate recruitment to a food source by laying trail pheromones on a surface is a common phenomenon. We collected data on maximal soil surface temperatures during the ants’ activity and mode of foraging (recruitment or solitary). By using two different comparative methodologies, we demonstrated a relationship between maximal soil temperature at which species are active and recruitment behavior (which is hypothesized to be related to the presence or absence of chemical signals). The species that were active at lower temperatures proved to be those that used chemical signals to recruit nest mates during foraging. This is also the case when comparing sympatric species and thereby controlling for other environmental factors. Moreover, all seven nonrecruiter species developed from recruiter ancestries, which is consistent with our hypothesis because ample evidence suggests a forest and tropical origin for ants. Thus, contrary to previous hypotheses, species that forage individually cannot be categorically considered primitive, but rather appear to be derived from recruiter species. Therefore, we conclude that temperature influences the evolution and/or stability of chemical signals in ants by determining the recruitment of nest mates. Key words: ants, chemical-signal evolution, foraging systems, Formicidae, surface temperature, trail pheromones. [Behav Ecol 11:396–404 (2000)]

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High surface temperatures select for individual foraging in ants

The ant species Cardiocondyla batesii is unique in that, in contrast to all other ant species, both sexes are flightless. Female sexuals and wingless, ergatoid males mate in the nest in autumn and young queens disperse on foot to found their own colonies in spring. The close genetic relatedness between queens and their mates (rqm=0.76±SE 0.12) and the high inbreeding coefficient (F=0.55; 95%CI 0.45–0.65) suggest that 83% of all matings are between brothers and sisters. As expected from local mate competition theory, sex ratios were extremely female biased, with more than 85% of all sexuals produced being young queens. Despite the common occurrence of inbreeding, we could not detect any adult diploid males. Though the probability of not detecting multiple mating was relatively high, at least one-third of all queens in our sample had mated more than once. Multiple mating to some extent counteracts the effects of inbreeding on worker relatedness (rww=0.68±SE 0.05) and would also be beneficial through decreasing diploid male load, if sex was determined by a single locus complementary system.

Inbreeding and local mate competition in the ant Cardiocondyla batesii

Using mitochondrial cytochrome oxidase I gene (COI), we established the phylogenetic relationship between two slave-making genera of the tribe Formicini: Polyergus and Rossomyrmex. The resulting phylogenetic tree presentstwo well-defined groups: Formica + Polyergus, and Proformica + Cataglyphis + Rossomyrmex. Our result contradicts prior classifications which considered Polyergus and Rossomyrmex to be sister genera. These results imply that slave-making in the two taxa evolved independently.

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Molecular phylogeny of two slave-making ants: Rossomyrmex and Polyergus (Hymenoptera: Formicidae)

http://www.ugr.es/~zoologia/s_terrestres/RepelentRosso.pdf

Alberto Tinaut

Papers

Use of arthropods for the evaluation of the olive‐orchard management regimes

High surface temperatures select for individual foraging in ants

Inbreeding and local mate competition in the ant Cardiocondyla batesii

Molecular phylogeny of two slave-making ants: Rossomyrmex and Polyergus (Hymenoptera: Formicidae)

Dufour's gland secretion as a repellent used during usurpation by the slave-maker ant Rossomyrmex minuchae.