Conserved developmental processes and the formation of evolutionary novelties: examples from butterfly wings

The origin and diversification of evolutionary novelties—lineage-specific traits of new adaptive value—is one of the key issues in evolutionary developmental biology. However, comparative analysis of the genetic and developmental bases of such traits can be difficult when they have no obvious homologue in model organisms. The finding that the evolution of morphological novelties often involves the recruitment of pre-existing genes and/or gene networks offers the potential to overcome this challenge. Knowledge about shared developmental processes obtained from extensive studies in model organisms can then be used to understand the origin and diversification of lineage-specific structures. Here, we illustrate this approach in relation to eyespots on the wings of Bicyclus anynana butterflies. A number of spontaneous mutations isolated in the laboratory affect eyespots, lepidopteran-specific features, and also processes that are shared by most insects. We discuss how eyespot mutants with disturbed embryonic development may help elucidate the genetic pathways involved in eyespot formation, and how venation mutants with altered eyespot patterns might shed light on mechanisms of eyespot development

Involvement of the conserved Hox gene Antennapedia in the development and evolution of a novel trait

<p>Abstract</p> <p>Background</p> <p>Hox proteins specify segment identity during embryogenesis and have typical associated expression patterns. Changes in embryonic expression and activity of <it>Hox </it>genes were crucial in the evolution of animal body plans, but their role in the post-embryonic development of lineage-specific traits remains largely unexplored. Here, we focus on the insect <it>Hox </it>genes <it>Ultrabithorax </it>(<it>Ubx</it>) and <it>Antennapedia </it>(<it>Antp</it>), and implicate the latter in the formation and diversification of novel, butterfly-specific wing patterns.</p> <p>Results</p> <p>First, we describe a conserved pattern of <it>Ubx </it>expression and a novel pattern of <it>Antp </it>expression in wing discs of <it>Bicyclus anynana </it>butterflies. The discrete, reiterated domains of Antp contrast with the typical expression of Hox genes in single continuous regions in arthropod embryos. Second, we show that this pattern is associated with the establishment of the organizing centres of eyespots. <it>Antp </it>upregulation is the earliest event in organizer development described to date, and in contrast to all genes implicated in eyespot formation, is exclusive to those centres. Third, our comparative analysis of gene expression across nymphalids reveals unexpected differences in organizer determination.</p> <p>Conclusions</p> <p>We show that the Antp's recruitment for the formation of novel traits in butterfly wing discs involved the evolution of new expression domains, and is restricted to a particular lineage. This study contributes novel insights into the evolution of <it>Antp </it>expression, as well as into the genetic mechanisms underlying morphological diversification. Our results also underscore how a wider representation of morphological and phylogenetic diversity is essential in evolutionary developmental biology.</p

Deep structure, long-distance migration and admixture in the colour polymorphic land snail Cepaea nemoralis

Although snails of the genus Cepaea have historically been important in studying colour polymorphism, an ongoing issue is that there is a lack of knowledge of the underlying genetics of the polymorphism, as well as an absence of genomic data to put findings in context. We, therefore, used phylogenomic methods to begin to investigate the post-glacial history of Cepaea nemoralis, with a long-term aim to understand the roles that selection and drift have in determining both European-wide and local patterns of colour polymorphism. By combining prior and new mitochondrial DNA data from over 1500 individuals with ddRAD genomic data from representative individuals across Europe, we show that patterns of differentiation are primarily due to multiple deeply diverged populations of snails. Minimally, there is a widespread Central European population and additional diverged groups in Northern Spain, the Pyrenees, as well as likely Italy and South Eastern Europe. The genomic analysis showed that the present-day snails in Ireland and possibly some other locations are likely descendants of admixture between snails from the Pyrenees and the Central European group, an observation that is consistent with prior inferences from mitochondrial DNA alone. The interpretation is that C.nemoralis may have arrived in Ireland via long-distance migration from the Pyrenean region, subsequently admixing with arrivals from elsewhere. This work, therefore, provides a baseline expectation for future studies on the genetics of the colour polymorphism, as well as providing a comparator for similar species

Dangerous women of Hong Kong? Media construction of stigma in female sex workers

This study used a cultural model analysis to examine the Hong Kong print media’s social construction of stigma in respect to female sex workers. An analysis was conducted on captions and main headlines of two newspaper (Chinese and English) median in Hong Kong, 2003-2006. A total of 591 articles on sex workers were recruited in the analysis with 422 located from the Ming Pao and 169 articles the SCMP. A total of Sixty seven articles on health issues were identified. In Hong Kong, as in elsewhere, sex workers were commonly labeled as the sources of sexually transmitted diseases and as women who endangered the public safety through socially unacceptable occupations. They were also portrayed as “ugly”, “weak” and “powerless” in the articles identified. We conclude the Hong Kong print media plays a significant role in contributing to the stigmatization of sex workers, heightening health risk and vulnerability. Such social construction of public stigma then in turn, can be argued to contribute to a lessened propensity for female sex workers both seek and engage with formal health services.published_or_final_versio

Evolutionary history of the recruitment of conserved developmental genes in association to the formation and diversification of a novel trait.

BACKGROUND: The origin and modification of novel traits are important aspects of biological diversification. Studies combining concepts and approaches of developmental genetics and evolutionary biology have uncovered many examples of the recruitment, or co-option, of genes conserved across lineages for the formation of novel, lineage-restricted traits. However, little is known about the evolutionary history of the recruitment of those genes, and of the relationship between them -for example, whether the co-option involves whole or parts of existing networks, or whether it occurs by redeployment of individual genes with de novo rewiring. We use a model novel trait, color pattern elements on butterfly wings called eyespots, to explore these questions. Eyespots have greatly diversified under natural and sexual selection, and their formation involves genetic circuitries shared across insects. RESULTS: We investigated the evolutionary history of the recruitment and co-recruitment of four conserved transcription regulators to the larval wing disc region where circular pattern elements develop. The co-localization of Antennapedia, Notch, Distal-less, and Spalt with presumptive (eye)spot organizers was examined in 13 butterfly species, providing the largest comparative dataset available for the system. We found variation between families, between subfamilies, and between tribes. Phylogenetic reconstructions by parsimony and maximum likelihood methods revealed an unambiguous evolutionary history only for Antennapedia, with a resolved single origin of eyespot-associated expression, and many homoplastic events for Notch, Distal-less, and Spalt. The flexibility in the (co-)recruitment of the targeted genes includes cases where different gene combinations are associated with morphologically similar eyespots, as well as cases where identical protein combinations are associated with very different phenotypes. CONCLUSIONS: The evolutionary history of gene (co-)recruitment is consistent with both divergence from a recruited putative ancestral network, and with independent co-option of individual genes. The diversity in the combinations of genes expressed in association with eyespot formation does not parallel diversity in characteristics of the adult phenotype. We discuss these results in the context of inferring homology. Our study underscores the importance of widening the representation of phylogenetic, morphological, and genetic diversity in order to establish general principles about the mechanisms behind the evolution of novel traits.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

RNA interference in Lepidoptera: an overview of successful and unsuccessful studies and implications for experimental design

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Saenko_data archive

This file contains phenotypes and genotypes of Bicyclus anynana individuals used in the analysis of linkage between melanine and Ba_black, and Chocolate and Ba_CSAD loci

Data from: Genetic basis of stage-specific melanism: a putative role for a cysteine sulfinic acid decarboxylase in insect pigmentation

Melanism, the overall darkening of the body, is a widespread form of animal adaptation to particular environments, and includes bookcase examples of evolution by natural selection, such as industrial melanism in the peppered moth. The major components of the melanin biosynthesis pathway have been characterized in model insects, but little is known about the genetic basis of life-stage specific melanism such as cases described in some lepidopteran species. Here, we investigate two melanic mutations of Bicyclus anynana butterflies, called Chocolate and melanine, that exclusively affect pigmentation of the larval and adult stages, respectively. Our analysis of Mendelian segregation patterns reveals that the larval and adult melanic phenotypes are due to alleles at different, independently segregating loci. Our linkage mapping analysis excludes the pigmentation candidate gene black as the melanine locus, and implicates the gene encoding a putative PLP-dependant cysteine sulfinic acid decarboxylase as the Chocolate locus. We show variation in coding sequence and in expression levels for this candidate larval melanism locus. This is the first study that suggests a biological function for this gene in insects. Our findings open up exciting opportunities to study the role of this locus in the evolution of adaptive variation in pigmentation, and the uncoupling of regulation of pigment biosynthesis across developmental stages with different ecologies and pressures on body coloration