So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

I. the origin of species by means of natural selection

A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Effect of Temperature

Biological invasions are a global consequence of an increasingly connected world and the rise in human population size The numbers of invasive alien species – the subset of alien species that spread widely in areas where they are not native, affecting the environment or human livelihoods – are increasing Synergies with other global changes are exacerbating current invasions and facilitating new ones, thereby escalating the extent and impacts of invaders Invasions have complex and often immense long‐term direct and indirect impacts In many cases, such impacts become apparent or problematic only when invaders are well established and have large ranges Invasive alien species break down biogeographic realms, affect native species richness and abundance, increase the risk of native species extinction, affect the genetic composition of native populations, change native animal behaviour, alter phylogenetic diversity across communities, and modify trophic networks Many invasive alien species also change ecosystem functioning and the delivery of ecosystem services by altering nutrient and contaminant cycling, hydrology, habitat structure, and disturbance regimes These biodiversity and ecosystem impacts are accelerating and will increase further in the future Scientific evidence has identified policy strategies to reduce future invasions, but these strategies are often insufficiently implemented For some nations, notably Australia and New Zealand, biosecurity has become a national priority There have been long‐term successes, such as eradication of rats and cats on increasingly large islands and biological control of weeds across continental areas However, in many countries, invasions receive little attention Improved international cooperation is crucial to reduce the impacts of invasive alien species on biodiversity, ecosystem services, and human livelihoods Countries can strengthen their biosecurity regulations to implement and enforce more effective management strategies that should also address other global changes that interact with invasions

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Scientists' warning on invasive alien species.

Publisher Summary This chapter describes sterile insect techniques (SIT). It is a biologically based method for the control of key insect pests. Wild female insects inseminated by released, radiation-sterilized males do not reproduce, and repeated releases of the sterilized insects lead to a reduction in pest population numbers. Effective control using sterile insects is achieved when they are used systematically as part of area-wide integrated pest management (AW-IPM) programs. SIT is species-specific, nonpolluting, and resistance-free. Since the original concept was developed in the United States in the 1940s, SIT has been used successfully for screwworm flies, tsetse flies, fruit flies, and moths. Technical progress in behavioral ecology, mass rearing, strain improvement, global information, positioning and monitoring systems, and aerial release, combined with economies of scale and a growing demand for pest-free and low-pesticide agricultural products in local and international trade, have increased the use of SIT in AW-IPM programs. These programs, by decreasing insecticide use, have also facilitated the use of biological control agents against secondary insect pests.

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Sterile Insect Technique

The Sterile Insect Technique (SIT) is amongst the most non-disruptive pest control methods. Unlike some other biologically-based methods it is species specific, does not release exotic agents into new environments and does not even introduce new genetic material into existing populations as the released organisms are not self-replicating. However, the SIT is only effective when integrated on an areawide basis, addressing the total population of the pest, irrespective of its distribution. There has been considerable progress in the development and integrated application of the SIT against the Mediterranean fruit fly (medfly), Ceratitis capitata, as reflected by operational programs for prevention, suppression and eradication of this pest. There is however, considerable scope for improving the efficiency of medfly SIT, an indispensable requirement for increased involvement of the private sector in any future application. One way to achieve this has been the development of genetic sexing strains, making it possible to release only sterile males. Another is improving sterile male performance through a better understanding of the sexual behavior of this insect. Unlike other insects for which the SIT has been successfully applied, medfly has a complex lek-based mating system in which the females exert the mate choice selecting among aggregated and displaying wild and sterile males. With the objective of developing a better understanding of medfly mating behavior, an FAO/IAEA Coordinated Research Project was carried out from 1994 to 1999. Some of the resulting work conducted during this period with the participation of research teams from ten countries is reported in this issue.

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Medfly areawide sterile insect technique programmes for prevention, suppression or eradication: the importance of mating behavior studies

Area-wide control of insect pests: from research to field implementation.

One of the main obstacles for a wider use of the Sterile Insect Technique (SIT) against the Mediterranean fruit fly (medfly) is the damage commercial fruit suffers due to sterile female stings. To overcome this obstacle, the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture has played a leading role in sponsoring and carrying out research to develop medfly genetic sexing strains that allow male-only SIT releases.

Recently, as a result of this continued FAO/IAEA effort, genetic sexing strains based on a temperature sensitive lethal (tsl) mutation have been developed at the IAEA Laboratories at Seibersdorf. Unlike previous pupal color sexing strains, these ‘second generation’ sexing strains allow female killing at an early (embryonal) stage. In addition, they are essentially stable under mass rearing conditions. This represents an important breakthrough because both of these attributes were considered indispensable for genetic sexing strains with any potential to replace conventional strains with both sexes in large scale sterile medfly production facilities. Besides the considerable savings in the costs of release and field monitoring, genetic sexing strains in field tests have shown severalfold increases in the effectiveness of the SIT as compared with the standard strains involving males and females. When releasing both males and females, sterile males are apparently not used effectively, because they use their limited sperm mostly to mate with sterile females and because they do not disperse widely in the presence of these females. When males only are released, however, they disperse much further in search of wild females and compete more intensely with wild males for wild females.

As a result of the availability of usable male-only strains, and the demonstration of their increased effectiveness, the applicability of the SIT against medfly has increased in two different ways. Highly developed commercial fruit growing regions, that previously had excluded application of SIT because of the fruit damage due to sterile female stings, are now reconsidering such free area/exclusion programs. More-importantly, sterile male releases can now also be used for routine control purposes, rather than only for eradication programs, partially or fully replacing chemical bait-sprays during the fruiting seasons.

Increased effectiveness and applicability of the sterile insect technique through male‐only releases for control of Mediterranean fruit flies during fruiting seasons

We systematically observed the mating behavior of wild Ceratitis capitata (Wiedemann) flies released on a field-caged host tree (coffee) growing naturally in a plantation in Guatemala. The principal site of attempted copulation was the bottom surface of leaves. During late morning and early afternoon, males stationed themselves at this site, often forming leks, and released sex pheromone, thereby attracting virgin or otherwise receptive females. An additional important site of copulation attempts, particularly among already-mated females, and particularly during mid-morning and mid- to late afternoon, was the fruit, where males were arrested by oviposition-deterring pheromone deposited by females after egg laying. The principal strategy of males at this site appeared to be attempted seduction or rape of alreadymated or otherwise rather unreceptive females exhibiting oviposition behavior and little or no attraction to sex pheromone emitted by males on leaves. Possible selective advantages to males of each type of mate encounter pattern are discussed.

Jorge Hendrichs

Papers

Sterile Insect Technique

Medfly areawide sterile insect technique programmes for prevention, suppression or eradication: the importance of mating behavior studies

Area-wide control of insect pests: from research to field implementation.

Increased effectiveness and applicability of the sterile insect technique through male‐only releases for control of Mediterranean fruit flies during fruiting seasons

Mating Behavior of Ceratitis capitata on a Field-Caged Host Tree