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1. Melanic pigmentation and light preference within and between two Drosophila species

   https://doi.org/10.1002/ece3.7998  

   Cooley, Arielle M.; Schmitz, Suzanne; Cabrera, Eduardo J.; Cutter, Mitchell; Sheffield, Maxwell; Gingerich, Ian; Thomas, Gabriella; Lincoln, Calvin N. M.; Moore, Virginia H.; Moore, Alexandra E.; et al (August 2021, Ecology and Evolution)

   Abstract Environmental adaptation and species divergence often involve suites of co‐evolving traits. Pigmentation in insects presents a variable, adaptive, and well‐characterized class of phenotypes for which correlations with multiple other traits have been demonstrated. InDrosophila, the pigmentation genesebonyandtanhave pleiotropic effects on flies' response to light, creating the potential for correlated evolution of pigmentation and vision. Here, we investigate differences in light preference within and between two sister species,Drosophila americanaandD. novamexicana, which differ in pigmentation in part because of evolution atebonyandtanand occupy environments that differ in many variables including solar radiation. We hypothesized that lighter pigmentation would be correlated with a greater preference for environmental light and tested this hypothesis using a habitat choice experiment. In a first set of experiments, using males ofD. novamexicanaline N14 andD. americanaline A00, the light‐bodiedD. novamexicanawas found slightly but significantly more often thanD. americanain the light habitat. A second experiment, which included additional lines and females as well as males, failed to find any significant difference betweenD. novamexicana‐N14 andD. americana‐A00. Additionally, the other dark line ofD. americana(A04) was found in the light habitat more often than the light‐bodiedD. novamexicana‐N14, in contrast to our predictions. However, the lightest line ofD. americana, A01, was found substantially and significantly more often in the light habitat than the two darker lines ofD. americana, thus providing partial support for our hypothesis. Finally, across all four lines, females were found more often in the light habitat than their more darkly pigmented male counterparts. Additional replication is needed to corroborate these findings and evaluate conflicting results, with the consistent effect of sex within and between species providing an especially intriguing avenue for further research. 

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2. Veiled preferences and cryptic female choice could underlie the origin of novel sexual traits

   https://doi.org/10.1098/rsbl.2018.0878  

   Moehring, Amanda J.; Boughman, Janette W. (February 2019, Biology Letters)

   Males in many species have elaborated sexual traits that females strongly prefer, and these traits often conspicuously differ among species. How novel preferences and traits originate, however, is a challenging evolutionary problem because the initial appearance of only the female preference or only the male trait should reduce the ability to find a suitable mate, which could reduce fitness for individuals possessing those novel alleles. Here, we present a hypothesis for how novel preferences, as well as the novel male traits that females prefer, can originate, be favoured and spread in polyandrous species. Novel preference mutations can arise as ‘veiled preferences’ that are not expressed when the corresponding male trait is not present in the population, allowing preferences to be hidden from selection, and thus persist. In those cases when a male trait is present, veiled preferences provide a selective advantage, and females disproportionately produce offspring from preferred males through either mate choice or cryptic female choice. This tips the fitness advantage for novel males, allowing both preference and trait to spread, and limiting selection against them in the absence of the corresponding trait or preference. 

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3. Changes in locus wide repression underlie the evolution of Drosophila abdominal pigmentation

   https://doi.org/10.1371/journal.pgen.1010722  

   Méndez-González, Iván D.; Williams, Thomas M.; Rebeiz, Mark (May 2023, PLOS Genetics)

   Kopp, Artyom (Ed.)

   Changes in gene regulation represent an important path to generate developmental differences affecting anatomical traits. Interspecific divergence in gene expression often results from changes in transcription-stimulating enhancer elements. While gene repression is crucial for precise spatiotemporal expression patterns, the relative contribution of repressive transcriptional silencers to regulatory evolution remains to be addressed. Here, we show that the Drosophila pigmentation gene ebony has mainly evolved through changes in the spatial domains of silencers patterning its abdominal expression. By precisely editing the endogenous ebony locus of D. melanogaster , we demonstrate the requirement of two redundant abdominal enhancers and three silencers that repress the redundant enhancers in a patterned manner. We observe a role for changes in these silencers in every case of ebony evolution observed to date. Our findings suggest that negative regulation by silencers likely has an under-appreciated role in gene regulatory evolution. 

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4. Consistent female preference for rare and unfamiliar male color patterns in wild guppy populations

   https://doi.org/10.1093/beheco/arz134  

   Valvo, Jennifer J.; Rodd, F. Helen; Hughes, Kimberly A.; Herberstein, ed., Marie (August 2019, Behavioral Ecology)

   Abstract How genetic variation is maintained in ecologically important traits is a central question in evolutionary biology. Male Trinidadian guppies, Poecilia reticulata, exhibit high genetic diversity in color patterns within populations, and field and laboratory studies implicate negative frequency-dependent selection in maintaining this variation. However, behavioral and ecological processes that mediate this selection in natural populations are poorly understood. We evaluated female mate preference in 11 natural guppy populations, including paired populations from high- and low-predation habitats, to determine if this behavior is responsible for negative frequency-dependent selection and to evaluate its prevalence in nature. Females directed significantly more attention to males with rare and unfamiliar color patterns than to males with common patterns. Female attention also increased with the area of male orange coloration, but this preference was independent of the preference for rare and unfamiliar patterns. We also found an overall effect of predation regime; females from high-predation populations directed more attention toward males than those from low-predation populations. Again, however, the habitat-linked preference was statistically independent from the preference for rare and unfamiliar patterns. Because previous research indicates that female attention to males predicts male mating success, we conclude that the prevalence of female preference for males with rare and unfamiliar color patterns across many natural populations supports the hypothesis that female preference is an important process underlying the maintenance of high genetic variation in guppy color patterns. 

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5. Evaluation of Additional Drosophila suzukii Male-Only Strains Generated Through Remobilization of an FL19 Transgene

   https://doi.org/10.3389/fbioe.2022.829620  

   Yamamoto, Akihiko; Yadav, Amarish K.; Scott, Maxwell J. (March 2022, Frontiers in Bioengineering and Biotechnology)

   Drosophila suzukii (D. suzukii) (Matsumura, 1931; Diptera: Drosophilidae), also known as spotted wing Drosophila , is a worldwide pest of fruits with soft skins such as blueberries and cherries. Originally from Asia, D. suzukii is now present in the Americas and Europe and has become a significant economic pest. Growers largely rely on insecticides for the control of D. suzukii . Genetic strategies offer a species-specific environmentally friendly way for suppression of D. suzukii populations. We previously developed a transgenic strain of D. suzukii that produced only males on a diet that did not contain tetracycline. The strain carried a single copy of the FL19 construct on chromosome 3. Repeated releases of an excess of FL19 males led to suppression of D. suzukii populations in laboratory cage trials. Females died as a consequence of overexpression of the tetracycline transactivator (tTA) and tTA-activated expression of the head involution defective proapoptotic gene. The aim of this study was to generate additional male-only strains that carried two copies of the FL19 transgene through crossing the original line with a piggyBac jumpstarter strain. Males that carried either two chromosome 3 or a singleX-linked transgene were identified through stronger expression of the red fluorescent protein marker gene. The brighter fluorescence of the X-linked lines was likely due to dosage compensation of the red fluorescent protein gene. In total, four X-linked lines and eleven lines with two copies on chromosome 3 were obtained, of which five were further examined. All but one of the strains produced only males on a diet without tetracycline. When crossed with wild type virgin females, all of the five two copy autosomal strains examined produced only males. However, the single copy X-linked lines did not show dominant female lethality. Five of the autosomal lines were further evaluated for productivity (egg to adult) and male competition. Based on these results, the most promising lines have been selected for future population suppression experiments with strains from different geographical locations. 

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