LAUSR

One of the questions that is at the forefront of every evodevo's researcher's mind is “How?” We are always seeking to know more about how extremely unusual traits come in to being, or how subtle variations in form between animal breeds are achieved. We look to uncover mysteries from the bottom-up by delving into the molecular mechanisms and intricate timing of morphogenesis. We also take a perspective from the outside-in by exploring how the environment and behavior effects the processes of development and how these effects may be inherited. The research in In Part Two of this Special Issue on Advances in Evolutionary and Developmental Biology, exemplifies this curiosity by providing beautiful case-studies of how evo-devo seeks to understand the mechanisms behind the incredible variety of phenotypes present in the flora and fauna of our planet. When investigating the natural world, often the more extreme morphologies tend to catch our attention first. In this issue, authors investigate a variety of fascinating anatomical and life-history adaptations from niches below the earth's surface to the night sky. Montoya-Sanhueza et al explore the post-natal development of the highly specialized limbs of the Cape dune mole rat, a fully-subterranean mammal that is endemic to the Western Cape Province of South Africa. By analyzing bones on a detailed micro-anatomical level and relating developmental changes to the external anatomy, limb function and changes in animal behavior as maturation commences, Montoya-Sanhueza et al reveal how a combination of both genetic and behavioral factors related to digging likely impact the process of mole rat limb maturation. Similarly, Camacho et al use 3D geometric morphometrics to interrogate skull diversity amongst phyllostomid bats, which are adapted to suit a variety of nocturnal dietary habits. By analyzing the timing of skull shape change over the course of embryonic and post-embryonic development, they show how accelerated growth changes and extended gestation periods contributes to the diversity of bat skull morphologies. This theme of developmental timing is continued by Hu et al who investigate the molecular mechanisms behind peadomophosis in the diminutive Danionella, a relative of zebrafish that resembles the larval form of this common model organism. They show that while thyroid hormone is important for metamorphosis in a variety of vertebrates, it is not responsible for the delayed development observed in Danionella. Staying with the Danioninae subfamily, Nelson et al explore another intriguing teleost adaptation as they delve into the development of the cement gland in a giant danio species, Devario malabaricus. They conduct a thorough and, it must be noted, incredibly beautiful analysis of the morphogenesis of this adhesive structure, including brightfield, SEM, SBF-SEM, TEM, and immunofluorescence imaging. Finally, topping the charts of intriguing life-history phenotypes, Griffing et al introduce a new squamate model for obligate parthenogenesis in the mourning gecko. They provide a detailed staging series, showing that hemipenis-like structures persist in this allfemale species throughout embryonic development. In addition, μCT scans provide exquisite detail of brain development. Finally, they present an embryonic transcriptome for this model that is likely to greatly expand our understanding of the evolution of parthenogenesis in vertebrates. The topic of how developmental and genetic differences shape phenotypic variation between and within species is also discussed in this Special Issue, one study deals with chicken breeds (Núñez-León et al) and the another with flowering plants (Larter et al). Integumentary structures develop via epithelial-mesenchymal interactions and comparisons of the timing of when these structures develop in embryos of five chicken breeds is discussed in Núñez-León et al. These authors suggest that changes in epithelial-mesenchymal interactions likely drive the highly diverse integument of chicken breeds, increasing our understanding of domestication in this species. In the flowering plant lineage Iochrominae, convergent phenotypic evolution at different time scales (populations, species, lineages) is explored. Larter and colleagues show that while white-flowered lineages and white morphs of a pigmented species are biochemically convergent, they differ in gene expression levels. This study shows that developmental mechanisms causing intra-species variation (ie, within a population) vs inter-species variation within a clade can differ, even though the phenotypes are convergent. The developmental and evolutionary conservation of non-protein coding genes is discussed in a review article by Murillo-Maldonado et al. The authors review criteria for identifying and characterizing long-non-coding-RNAs (IncRNAs) and the importance of dosage compensation and DOI: 10.1002/dvdy.123