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- Volume 47, 2002
Annual Review of Entomology - Volume 47, 2002
Volume 47, 2002
- Review Articles
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Arthropods on Islands: Colonization, Speciation, and Conservation
Vol. 47 (2002), pp. 595–632More Less▪ AbstractIslands have traditionally been considered to be any relatively small body of land completely surrounded by water. However, their primary biological characteristic, an extended period of isolation from a source of colonists, is common also to many situations on continents. Accordingly, theories and predictions developed for true islands have been applied to a huge array of systems, from rock pools, to single tree species in forests, to oceanic islands. Here, we examine the literature on islands in the broadest sense (i.e., whether surrounded by water or any other uninhabitable matrix) as it pertains to terrestrial arthropods. We categorize islands according to the features they share. The primary distinction between different island systems is “darwinian” islands (formed de novo) and “fragment” islands. In the former, the islands have never been in contact with the source of colonists and have abundant “empty” ecological niche space. On these islands, species numbers will initially increase through immigration, the rate depending on the degree of isolation. If isolation persists, over time species formation will result in “neo-endemics.” When isolation is extreme, the ecological space will gradually be filled through speciation (rather than immigration) and adaptive radiation of neo-endemics. Fragment islands are fundamentally different. In these islands, the ecological space will initially be filled as a consequence of connection to the source of colonists prior to insularization. Species numbers will decrease following fragmentation through the process of relaxation. If these islands become more isolated, species will eventually arise through relictualization with the formation of “paleo-endemics.” Given sufficient time, this process can result in generic level endemism on ancient fragment islands, a phenomenon well illustrated in Madagascar and New Zealand. Recognizing the distinction between the different kinds of islands is fundamental for understanding emerging patterns on each, in particular speciation, biodiversity (e.g., neo-endemics versus paleo-endemics), and conservation (e.g., naiveté in interactions with alien species).
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The Population Biology of Oak Gall Wasps (Hymenoptera: Cynipidae)
Vol. 47 (2002), pp. 633–668More Less▪ AbstractOak gall wasps (Hymenoptera: Cynipidae, Cynipini) are characterized by possession of complex cyclically parthenogenetic life cycles and the ability to induce a wide diversity of highly complex species- and generation-specific galls on oaks and other Fagaceae. The galls support species-rich, closed communities of inquilines and parasitoids that have become a model system in community ecology. We review recent advances in the ecology of oak cynipids, with particular emphasis on life cycle characteristics and the dynamics of the interactions between host plants, gall wasps, and natural enemies. We assess the importance of gall traits in structuring oak cynipid communities and summarize the evidence for bottom-up and top-down effects across trophic levels. We identify major unanswered questions and suggest approaches for the future.
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Short, Long, and Beyond: Molecular and Embryological Approaches to Insect Segmentation
Vol. 47 (2002), pp. 669–699More Less▪ AbstractOver the past dozen years, studies comparing the expression of orthologues of the Drosophila segmentation genes among various insects have served to broaden our view of the ways in which insects make segments. The molecular data suggest that, although the overall genetic mechanisms of segmentation during embryogenesis have been conserved, the details of this process vary both within and between various insect orders. Here we summarize comparative gene expression data relevant to segmentation with an emphasis on understanding the extent of molecular patterning prior to gastrulation. These results are discussed in embryological context with an eye toward understanding the evolution of segmentation within insects.
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Biology and Management of Economically Important Lepidopteran Cereal Stem Borers in Africa
Vol. 47 (2002), pp. 701–731More Less▪ AbstractCereals (maize, sorghum, millet, rice) are extremely important crops grown in Africa for human consumption. Of the various insect pests attacking cereal crops in Africa, lepidopteran stem borers are by far the most injurious. All 21 economically important stem borers of cultivated grasses in Africa are indigenous except Chilo partellus, which invaded the continent from India, and C. sacchariphagus, which has recently been found in sugarcane in Mozambique. C. partellus is competitively displacing indigenous stem borers in East and southern Africa. A parasitoid, Cotesia flavipes, was introduced from Pakistan for biological control of C. partellus and caused a 32–55% decrease in stem borer densities. This article is an attempt to summarize the status of knowledge about economically important cereal stem borers in Africa with emphasis on their distribution, pest status and yield losses, diapause, natural enemies, cultural control, host plant resistance, and biological control. Special attention is given to Busseola fusca and C. partellus, the most important pests of maize and grain sorghum.
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The Ecology and Evolution of Ant Association in the Lycaenidae (Lepidoptera)
Vol. 47 (2002), pp. 733–771More Less▪ AbstractThe estimated 6000 species of Lycaenidae account for about one third of all Papilionoidea. The majority of lycaenids have associations with ants that can be facultative or obligate and range from mutualism to parasitism. Lycaenid larvae and pupae employ complex chemical and acoustical signals to manipulate ants. Cost/benefit analyses have demonstrated multiple trade-offs involved in myrmecophily. Both demographic and phylogenetic evidence indicate that ant association has shaped the evolution of obligately associated groups. Parasitism typically arises from mutualism with ants, and entomophagous species are disproportionately common in the Lycaenidae compared with other Lepidoptera. Obligate associations are more common in the Southern Hemisphere, in part because highly ant-associated lineages make up a larger proportion of the fauna in these regions. Further research on phylogeny and natural history, particularly of the Neotropical fauna, will be necessary to understand the role ant association has played in the evolution of the Lycaenidae.
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Sympatric Speciation in Phytophagous Insects: Moving Beyond Controversy?
Vol. 47 (2002), pp. 773–815More Less▪ AbstractSympatric speciation is the splitting of one evolutionary lineage into two without the occurrence of geographic isolation. The concept has been intimately tied to entomology since the 1860s, when Benjamin Walsh proposed that many host-specific phytophagous insects originate by shifting and adapting to new host plant species. If true, sympatric speciation would have tremendous implications for our understanding of species and their origins, biodiversity (25–40% of all animals are thought to be phytophagous specialists), insect-plant coevolution, community ecology, phylogenetics, and systematics, as well as practical significance for the management of insect pests. During much of the twentieth century sympatric speciation was viewed as much less plausible than geographic (allopatric) speciation. However, empirical field studies, laboratory experiments, developments in population genetics theory, and phylogenetic and biogeographic data have all recently combined to shed a more favorable light on the process. We review the evidence for sympatric speciation via host shifting for phytophagous insects and propose a set of testable predictions for distinguishing geographic mode (allopatric versus sympatric) of divergence. Our conclusion is that sympatric speciation is a viable hypothesis. We highlight areas where more thorough testing is needed to move sympatric speciation into the realm of accepted scientific theory.
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Host Plant Quality and Fecundity in Herbivorous Insects
Vol. 47 (2002), pp. 817–844More Less▪ AbstractHost plant quality is a key determinant of the fecundity of herbivorous insects. Components of host plant quality (such as carbon, nitrogen, and defensive metabolites) directly affect potential and achieved herbivore fecundity. The responses of insect herbivores to changes in host plant quality vary within and between feeding guilds. Host plant quality also affects insect reproductive strategies: Egg size and quality, the allocation of resources to eggs, and the choice of oviposition sites may all be influenced by plant quality, as may egg or embryo resorption on poor-quality hosts. Many insect herbivores change the quality of their host plants, affecting both inter- and intraspecific interactions. Higher–trophic level interactions, such as the performance of predators and parasitoids, may also be affected by host plant quality. We conclude that host plant quality affects the fecundity of herbivorous insects at both the individual and the population scale.
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Economic, Ecological, Food Safety, and Social Consequences of the Deployment of Bt Transgenic Plants
Vol. 47 (2002), pp. 845–881More Less▪ AbstractTransgenic plants expressing insecticidal proteins from the bacterium, Bacillus thuringiensis (Bt), are revolutionizing agriculture. Bt, which had limited use as a foliar insecticide, has become a major insecticide because genes that produce Bt toxins have been engineered into major crops grown on 11.4 million ha worldwide in 2000. Based on the data collected to date, generally these crops have shown positive economic benefits to growers and reduced the use of other insecticides. The potential ecological and human health consequences of Bt plants, including effects on nontarget organisms, food safety, and the development of resistant insect populations, are being compared for Bt plants and alternative insect management strategies. Scientists do not have full knowledge of the risks and benefits of any insect management strategies. Bt plants were deployed with the expectation that the risks would be lower than current or alternative technologies and that the benefits would be greater. Based on the data to date, these expectations seem valid.
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Control and Biochemical Nature of the Ecdysteroidogenic Pathway
Vol. 47 (2002), pp. 883–916More Less▪ AbstractMolting is elicited by a critical titer of ecdysteroids that includes the principal molting hormone, 20-hydroxyecdysone (20E), and ecdysone (E), which is the precursor of 20E but also has morphogenetic roles of its own. The prothoracic glands are the predominate source of ecdysteroids, and the rate of synthesis of these polyhydroxylated sterols is critical for molting and metamorphosis. This review concerns three aspects of ecdysteroidogenesis: (a) how the brain neuropeptide prothoracicotropic hormone (PTTH) initiates a transductory cascade in cells of the prothoracic gland, which results in an increased rate of ecdysteroid biosynthesis (upregulation); (b) how the concentrations of 20E in the hemolymph feed back on the prothoracic gland to decrease rates of ecdysteroidogenesis (downregulation); and (c) how the prothoracic gland cells convert cholesterol to the precursor of E and then 20E, a series of reactions only now being understood because of the use of a combination of classical biochemistry and molecular genetics.
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The Biology of the Dance Language
Vol. 47 (2002), pp. 917–949More Less▪ AbstractHoney bee foragers dance to communicate the spatial location of food and other resources to their nestmates. This remarkable communication system has long served as an important model system for studying mechanisms and evolution of complex behavior. I provide a broad synthesis of recent research on dance communication, concentrating on the areas that are currently the focus of active research. Specific issues considered are as follows: (a) the sensory and integrative mechanisms underlying the processing of spatial information in dance communication, (b) the role of dance communication in regulating the recruitment of workers to resources in the environment, (c) the evolution of the dance language, and (d) the adaptive fine-tuning of the dance for efficient spatial communication.
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Previous Volumes
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Volume 70 (2025)
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Volume 69 (2024)
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Volume 68 (2023)
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Volume 67 (2022)
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Volume 66 (2021)
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Volume 65 (2020)
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Volume 64 (2019)
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Volume 63 (2018)
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Volume 62 (2017)
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Volume 61 (2016)
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Volume 60 (2015)
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Volume 59 (2014)
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Volume 58 (2013)
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Volume 57 (2012)
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Volume 56 (2011)
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Volume 55 (2010)
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Volume 54 (2009)
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Volume 53 (2008)
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Volume 52 (2007)
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Volume 51 (2006)
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Volume 50 (2005)
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Volume 49 (2004)
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Volume 48 (2003)
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Volume 47 (2002)
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Volume 46 (2001)
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Volume 45 (2000)
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Volume 44 (1999)
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Volume 43 (1998)
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Volume 42 (1997)
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Volume 41 (1996)
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Volume 40 (1995)
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Volume 39 (1994)
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Volume 38 (1993)
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Volume 37 (1992)
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Volume 36 (1991)
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Volume 35 (1990)
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Volume 34 (1989)
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Volume 33 (1988)
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Volume 32 (1987)
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Volume 31 (1986)
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Volume 30 (1985)
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Volume 29 (1984)
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Volume 28 (1983)
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Volume 27 (1982)
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Volume 26 (1981)
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Volume 25 (1980)
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Volume 24 (1979)
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Volume 23 (1978)
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Volume 22 (1977)
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Volume 21 (1976)
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Volume 20 (1975)
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Volume 19 (1974)
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Volume 18 (1973)
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Volume 17 (1972)
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Volume 16 (1971)
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Volume 15 (1970)
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Volume 14 (1969)
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Volume 13 (1968)
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Volume 12 (1967)
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Volume 11 (1966)
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Volume 10 (1965)
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Volume 9 (1964)
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Volume 8 (1963)
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Volume 7 (1962)
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Volume 6 (1961)
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Volume 5 (1960)
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Volume 4 (1959)
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Volume 3 (1958)
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Volume 2 (1957)
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Volume 1 (1956)
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Volume 0 (1932)