Dambroski HR, Feder JL. Host plant and latitude related diapause variation in Rhagoletis pomonella: a test for multifaceted life history adaptation on different stages of diapause development. Journal of Evolutionary Biology

Department of Biological Sciences, Galvin Life Science Center, University of Notre Dame, Notre Dame, IN 46556-0369, USA.
Journal of Evolutionary Biology (Impact Factor: 3.23). 12/2007; 20(6):2101-12. DOI: 10.1111/j.1420-9101.2007.01435.x
Source: PubMed


Variation in the overwintering pupal diapause of Rhagoletis pomonella appears to adapt sympatric populations of the fly to seasonal differences in the fruiting times of their host plants, generating ecological reproductive isolation. Here, we investigate what aspects of diapause development are differentially affected (1) by comparing the propensities of apple vs. hawthorn-infesting host races of R. pomonella to forgo an initially deep diapause and directly develop into adults, and (2) by determining the chronological order that R. pomonella races and sibling species break diapause and eclose when reared under standardized environmental conditions. The results imply that factors affecting initial diapause depth (and/or differential mortality during the prewintering period) and those determining the timing of diapause termination or rates of post-diapause development are both under differential selection and are to some degree genetically uncoupled in flies. The modular nature of diapause life history adaptation in Rhagoletis suggests that phenology may involve multiple genetic changes and represent a stronger ecological barrier separating phytophagous specialists than is generally appreciated.

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    • "Insect dormancy (diapause) is characterized by low metabolic activity and developmental arrest, with the timing of diapause determining the subsequent timing of metamorphosis and adult emergence (Tauber & Tauber, 1981; Tauber et al., 1986). Changes in diapause timing have often been linked to biotic factors such as host plant phenology (Feder et al., 1993; Dambroski & Feder, 2007). However , changes in diapause timing are also often correlated with latitudinal variation in abiotic factors such as photoperiod and temperature (reviewed in Hut et al., 2013). "
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    ABSTRACT: Many temperate insects take advantage of longer growing seasons at lower latitudes by increasing their generation number or voltinism. In some insects, development time abruptly decreases when additional generations are fit into the season. Consequently, latitudinal "sawtooth" clines associated with shifts in voltinism are seen for phenotypes correlated with development time, like body size. However, latitudinal variation in voltinism has not been linked to genetic variation at specific loci. Here we show a pattern in allele frequency among voltinism ecotypes of the European corn borer moth (Ostrinia nubilalis) that is reminiscent of a sawtooth cline. We characterized 145 autosomal and sex-linked SNPs and found that period, a circadian gene that is genetically linked to a major QTL determining variation in post-diapause development time, shows cyclical variation between voltinism ecotypes. Allele frequencies at an unlinked circadian clock gene cryptochrome1 were correlated with period. These results suggest that selection on development time to 'fit' complete life cycles into a latitudinally varying growing season produce oscillations in alleles associated with voltinism, primarily through changes at loci underlying the duration of transitions between diapause and other life history phases. Correlations among clock loci suggest possible coupling between the circadian clock and the circannual rhythms for synchronizing seasonal life history. We anticipate that latitudinal oscillations in allele frequency will represent signatures of adaptation to seasonal environments in other insects and may be critical to understanding the ecological and evolutionary consequences of variable environments, including response to global climate change. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Journal of Evolutionary Biology 11/2014; 28(1). DOI:10.1111/jeb.12562 · 3.23 Impact Factor
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    • "Thus, there is a well-defined series of populations that vary in their relative ages of divergence. Sources of host-related divergent selection are also known for Rhagoletis (Linn et al. 2003; Dambroski and Feder 2007; Powell et al. 2012), allowing for selection experiments. In this regard, all R. pomonella flies are host-plant specialists. "
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    ABSTRACT: Our current understanding of speciation is often based on considering a relatively small number of genes, sometimes in isolation of one another. Here, we describe a possible emergent genome process involving the aggregate effect of many genes contributing to the evolution of reproductive isolation across the speciation continuum. When a threshold number of divergently selected mutations of modest to low fitness effects accumulate between populations diverging with gene flow, nonlinear transitions can occur in which levels of adaptive differentiation, linkage disequilibrium, and reproductive isolation dramatically increase. In effect, the genomes of the populations start to “congeal” into distinct entities representing different species. At this stage, reproductive isolation changes from being a characteristic of specific, divergently selected genes to a property of the genome. We examine conditions conducive to such genome-wide congealing (GWC), describe how to empirically test for GWC, and highlight a putative empirical example involving Rhagoletis fruit flies. We conclude with cautious optimism that the models and concepts discussed here, once extended to large numbers of neutral markers, may provide a framework for integrating information from genome scans, selection experiments, quantitative trait loci mapping, association studies, and natural history to develop a deeper understanding of the genomics of speciation.
    Journal of Heredity 08/2014; 105(S1):810-820. DOI:10.1093/jhered/esu038 · 2.09 Impact Factor
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    • "The main characteristics of obligatory diapause in insects are 1) arrest of morphogenesis and growth, 2) hormonally mediated metabolic suppression, and 3) a duration that requires a period of time and accumulated environmental cues to be terminated, so that diapausing individuals emerge at the right time of year (Tauber et al. 1986). Although diapause is often thought of as a strategy for avoiding adverse conditions, it also plays a critical role in synchronizing life cycles with favorable times of the year (Dambroski and Feder 2007). The European cherry fruit fly, Rhagoletis cerasi (L.) (Diptera: Tephritidae), is a major pest for sweet and sour cherries in many European countries including Greece (Fimiani 1989). "
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    ABSTRACT: The European cherry fruit fly, Rhagoletis cerasi (L.) (Diptera: Tephritidae), is the key pest of sweet and sour cherries in many European countries and west Asia. It is a univoltine species of the west Palaearctic zone that undergoes obligatory pupal diapause. In this study, the development of R. cerasi pupae that were brought to an optimum temperature for postdiapause development following a long chilling period is described. The six most representative developmental stages within the puparium are illustrated, and the developmental progression among the stages after the end of the chilling period is quantified. Within 20 d postchilling, there was a gradual progress from stage I to pharate adult. However, ∼30% of the pupae remained at the transitional stage II, after 20 d at 25°C (optimum temperature for development). This suggests that a proportion of pupae remain at an intermediate developmental stage for an extended period of time that goes beyond 20 d postchilling. The pupal stage II might be related to diapause termination and responsiveness to environmental cues. It may also define the time before developmental progress to pharate adult. This finding agrees with previous studies proposing that a number of R. cerasi pupae undergo prolonged diapause, though the morphological characteristics of these pupae have never been described before.
    Journal of Insect Science 07/2014; 14(1). DOI:10.1093/jisesa/ieu018 · 1.03 Impact Factor
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