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Evolution & Development

Gavin Rice, Olga Barmina, Kevin Hu, Artyom Kopp
Male ornaments and other sex-specific traits present some of the most dramatic examples of evolutionary innovations. Comparative studies of similar but independently evolved traits are particularly important for identifying repeated patterns in the evolution of these traits. Male-specific modifications of the front legs have evolved repeatedly in Drosophilidae and other Diptera. The best understood of these novel structures is the sex comb of Drosophila melanogaster and its close relatives. Here, we examine the evolution of another male foreleg modification, the sex brush, found in the distantly related Drosophila immigrans species group...
January 25, 2018: Evolution & Development
Theresa M Grieco, Joy M Richman
We performed a test of how function impacts a genetically programmed process that continues into postnatal life. Using the dentition of the polyphyodont gecko as our model, tooth shedding was recorded longitudinally across the jaw. We compared two time periods: one in which teeth were patterned symmetrically in ovo and a later period when teeth were initiated post-hatching. By pairing shedding events on the right and left sides, we found the patterns of tooth loss are symmetrical and stable between periods, with only subtle deviations...
January 10, 2018: Evolution & Development
Marina Micaela Strelin, Santiago Benitez-Vieyra, Juan Fornoni, Christian Peter Klingenberg, Andrea Cocucci
The astounding variety of angiosperm flower morphologies has evolved in response to many selective forces. Flower development is highly coordinated and involves developmental associations between size and shape, ontogenetic allometry, which in turn affect the morphology of mature flowers. Although ontogenetic allometries can act as a developmental constraint and may influence adaptive evolution, allometries can evolve themselves and may change rapidly in response to selection. We explored the evolution of ontogenetic allometry in the flowers of 11 species of Loasoideae...
December 15, 2017: Evolution & Development
Emanuel Redl, Maik Scherholz, Tim Wollesen, Christiane Todt, Andreas Wanninger
The homeodomain transcription factors six3 and otx are involved in patterning the anterior body and parts of the central nervous system (CNS) in bilaterians. Their similar expression patterns have been used as an argument for homology of heads, brains, segmentation, and ciliated larvae. We investigated the developmental expression of six3 and otx in the aplacophoran mollusk Wirenia argentea. Six3 is expressed in subepithelial cells delimiting the apical organ of the solenogaster pericalymma larva. Otx is expressed in cells of the prototroch and adjacent regions as well as in posterior extensions of the prototrochal expression domain...
December 15, 2017: Evolution & Development
Gerardo A Cordero, Rory S Telemeco, Eric J Gangloff
Reptile embryos have recently been observed moving within the egg in response to temperature, raising the exciting possibility that embryos might behaviorally thermoregulate analogous to adults. However, the conjecture that reptile embryos have ample opportunity and capacity to adaptively control their body temperature warrants further discussion. Using turtles as a model, we discuss the spatiotemporal constraints to movement in reptile embryos. We demonstrate that, as embryos grow, the internal egg space rapidly diminishes such that the temporal window for appreciable displacement is confined to stages that feature incomplete neuromuscular differentiation...
December 1, 2017: Evolution & Development
Tian Wu, Gurpreet K Dhami, Graham J Thompson
In a termite colony, reproduction is typically monopolized by a small number of sexuals that are supported by reproductively altruistic soldiers and workers. We expect caste differentiation to be associated with clear-cut differences in gene expression, and for these differences to reflect caste function and development. Here, we use RNA-Sequencing to compare the gene expression profiles of sexual nymphs and two non-reproductive helper castes (i.e., workers and soldiers) of the Eastern subterranean termite Reticulitermes flavipes...
November 23, 2017: Evolution & Development
David M Linz, Armin P Moczek
No abstract text is available yet for this article.
November 2017: Evolution & Development
Mark C Currey, Susan Bassham, Stephen Perry, William A Cresko
Comparing ontogenetic patterns within a well-described evolutionary context aids in inferring mechanisms of change, including heterochronies or deletion of developmental pathways. Because selection acts on phenotypes throughout ontogeny, any within-taxon developmental variation has implications for evolvability. We compare ontogenetic order and timing of locomotion and defensive traits in three populations of threespine stickleback that have evolutionarily divergent adult forms. This analysis adds to the growing understanding of developmental genetic mechanisms of adaptive change in this evolutionary model species by delineating when chondrogenesis and osteogenesis in two derived populations begin to deviate from the developmental pattern in their immediate ancestors...
November 2017: Evolution & Development
Simon Hellemans, Denis Fournier, Robert Hanus, Yves Roisin
In termite species with asexual queen succession (AQS), parthenogenetically produced immatures mostly differentiate into secondary queens, called "neotenics." In order to elucidate the ontogenetic origin of neotenics in Cavitermes tuberosus (Termitidae: Termitinae), a neotropical termite with AQS, we investigated developmental pathways of offspring according to their sex and genetic origin using both morphometric and genetic tools. The caste system of C. tuberosus follows the classical pathway of Termitidae...
November 2017: Evolution & Development
Benjamin Naumann, Peter Warth, Lennart Olsson, Peter Konstantinidis
The vertebrate head/trunk interface is the region of the body where the different developmental programs of the head and trunk come in contact. Many anatomical structures that develop in this transition zone differ from similar structures in the head or the trunk. This is best exemplified by the cucullaris/trapezius muscle, spanning the head/trunk interface by connecting the head to the pectoral girdle. The source of this muscle has been claimed to be either the unsegmented head mesoderm or the somites of the trunk...
October 13, 2017: Evolution & Development
Marko M Lazić, Dennis Rödder, Antigoni Kaliontzopoulou
Canalization and developmental stability (DS) are important organismal properties involved in determining the level of phenotypic variation. Ontogenetic patterns of phenotypic variance components can shed light on the mechanistic basis of developmental buffering (DB). Here, we analyze how individual FA and among-individual variation in head shape change in ontogenetic series of three lizard species raised in laboratory. The degree of asymmetry increased slightly with size, suggesting that developmental mechanisms hypothesized to correct for deviations either do not exist, or that their efficiency is truncated with increasing size...
September 19, 2017: Evolution & Development
Xiaohong Su, Xiaojuan Yang, Jing Li, Lianxi Xing, He Liu, Jiaoling Chen
Termite workers are characterized by unique flexibility in that a worker can develop in one of three ways: remain a worker, become a soldier within two successive moults, or become a neotenic reproductive (NR) within a single moult. However, is it true that workers can transform into NRs within a single moult? Actually, the developmental pathways of workers turning into NRs remains unclear. In this study, we show for the first time that the female workers of Reticulitermes labralis develop into NRs after a pre-NRs stage...
July 2017: Evolution & Development
Liisa K Heikkinen, Jenni E Kesäniemi, K Emily Knott
Species with multiple different larval developmental modes are interesting models for the study of mechanisms underlying developmental mode transitions and life history evolution. Pygospio elegans, a small, tube-dwelling polychaete worm commonly found in estuarine and marine habitats around the northern hemisphere, is one species with variable developmental modes. To provide new genomic resources for studying P. elegans and to address the differences in gene expression between individuals producing offspring with different larval developmental modes, we performed whole transcriptome Illumina RNA sequencing of adult worms from two populations and prepared a de novo assembly of the P...
July 2017: Evolution & Development
Elena N Temereva
Nervous system organization differs greatly in larvae and adults of many species, but has nevertheless been traditionally used for phylogenetic studies. In phoronids, the organization of the larval nervous system depends on the type of development. With the goal of understanding the ground plan of the nervous system in phoronid larvae, the development and organization of the larval nervous system were studied in a viviparous phoronid species. The ground plan of the phoronid larval nervous system includes an apical organ, a continuous nerve tract under the preoral and postoral ciliated bands, and two lateral nerves extending between the apical organ and the nerve tract...
July 2017: Evolution & Development
Emily A Buchholtz, Jessica K Gee
Axial morphology was dramatically transformed during the transition from terrestrial to aquatic environments by archaeocete cetaceans, and again during the subsequent odontocete radiation. Here, we reconstruct the sequence of developmental events that underlie these phenotypic transitions. Archaeocete innovations include the loss of primaxial/abaxial interaction at the sacral/pelvic articulation and the modular dissociation of the fluke from the remainder of the tail. Odontocetes subsequently integrated lumbar, sacral, and anterior caudal vertebrae into a single torso module, and underwent multiple series-specific changes in vertebral count...
July 2017: Evolution & Development
Patrick T Rohner, Wolf U Blanckenhorn, Martin A Schäfer
Ultimate factors driving insect body size are rather well understood, while-apart from a few model species-the underlying physiological and developmental mechanisms received less attention. We investigate the physiological basis of adaptive size variation in the yellow dung fly Scathophaga stercoraria, which shows pronounced male-biased sexual size dimorphism and strong body size plasticity. We estimate variation of a major physiological threshold, the critical weight, which is the mass at which a larva initiates pupariation...
May 2017: Evolution & Development
Aude G M Caromel, Daniela N Schmidt, Emily J Rayfield
Developmental processes represent one of the main constraints on the generation of adult form. Determining how constructional and energetic demands operate throughout growth is es-sential to understanding fundamental growth rules and trade-offs that define the framework within which new species originate. In organisms producing spiral shells, coiling patterns can inform on the constructional constraints acting throughout development that dictated the diversification of forms within a group. Here, we use Synchrotron radiation X-Ray tomographic microscopy (SRXTM) reconstructions of eight planktic foraminifera repre-sentative of the major morphotypic groups to determine disparity of coiling patterns by measuring Raupian parameters...
May 2017: Evolution & Development
Claudia Gabriela Montes-Cartas, Pablo Padilla, Julieta A Rosell, César A Domínguez, Juan Fornoni, Mark E Olson
The study of modularity allows recognition of suites of character covariation that potentially diagnose units of evolutionary change. One prominent perspective predicts that natural selection should forge developmental units that maximize mutual functional independence. We examined the module-function relation using secondary xylem (wood) in a clade of tropical trees as a study system. Traditionally, the three main cell types in wood (vessels, fibers, and parenchyma) have respectively been associated with three functions (conduction, mechanical support, and storage)...
May 2017: Evolution & Development
Robin M Andrews, Sable A Skewes
In many respects, reptile hatchlings are fully functional, albeit miniature, adults. This means that the adult morphology must emerge during embryonic development. This insight emphasizes the connection between the mechanisms that generate phenotypic variation during embryonic development and the action of selection on post-hatching individuals. To determine when species-specific differences in limb and tail lengths emerge during embryonic development, we compared allometric patterns of early limb growth of four distantly related species of lizards...
May 2017: Evolution & Development
Ralf Janssen
Evolution of segmented limbs is one of the key innovations of Arthropoda, allowing development of functionally specific specialized head and trunk appendages, a major factor behind their unmatched evolutionary success. Proximodistal limb patterning is controlled by two regulatory networks in the vinegar fly Drosophila melanogaster, and other insects. The first is represented by the function of the morphogens Wingless (Wg) and Decapentaplegic (Dpp); the second by the EGFR-signaling cascade. While the role of Wg and Dpp has been studied in a wide range of arthropods representing all main branches, that is, Pancrustacea (= Hexapoda + Crustacea), Myriapoda and Chelicerata, investigation of the potential role of EGFR-signaling is restricted to insects (Hexapoda)...
May 2017: Evolution & Development
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