Timothy B. Sackton, Phil Grayson, Alison Cloutier, Zhirui Hu, Jun S. Liu, Nicole E. Wheeler, Paul P. Gardner, Julia A. Clarke, Allan J. Baker, Michele Clamp & Scott V. Edwards (2019)
Convergent regulatory evolution and loss of flight in paleognathous birds
Science 364(6435): 74-78
DOI: 10.1126/science.aat7244
All roads lead to regulation
Species from widely divergent taxa can experience similar changes in traits. What underlying genetic drivers cause these parallel changes remains an open question. Sackton et al. looked across groups of birds that have repeatedly lost flight, the ratites and tinamous, and found that there is convergence in the regulatory regions associated with genes related to flight, but not within the protein coding regions. Changes within these regulatory regions influenced limb development and may represent quick paths toward convergent change across taxa.
Abstract
A core question in evolutionary biology is whether convergent phenotypic evolution is driven by convergent molecular changes in proteins or regulatory regions. We combined phylogenomic, developmental, and epigenomic analysis of 11 new genomes of paleognathous birds, including an extinct moa, to show that convergent evolution of regulatory regions, more so than protein-coding genes, is prevalent among developmental pathways associated with independent losses of flight. A Bayesian analysis of 284,001 conserved noncoding elements, 60,665 of which are corroborated as enhancers by open chromatin states during development, identified 2355 independent accelerations along lineages of flightless paleognaths, with functional consequences for driving gene _expression_ in the developing forelimb. Our results suggest that the genomic landscape associated with morphological convergence in ratites has a substantial shared regulatory component.
News:
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Dasyornis walterbolesi, sp. nov.ÂÂÂ
Jacqueline M. T. Nguyen (2019)
A new species of bristlebird (Passeriformes, Dasyornithidae) from the early Miocene of Australia.
Journal of Vertebrate Paleontology Article: e1575838 |
The bristlebird family (Passeriformes, Dasyornithidae) constitutes one of the earliest branches in the oscine (songbird) tree. A new bristlebird, Dasyornis walterbolesi, sp. nov., is described from lower Miocene deposits of the Riversleigh World Heritage Area, Australia. This new species is based on a femur, a tibiotarsus, and a tarsometatarsus of one individual, the first known instance of associated passerine bones in the pre-Pleistocene record of Australia, as well as a distal part of a femur of a second individual. Dasyornis walterbolesi is smaller in size than the extant eastern bristlebird, D. brachypterus, and extends the known fossil record for Dasyornithidae by 18 million years. The new fossils considerably increase the geographic range of Dasyornithidae and indicate that the bristlebird family was once more widespread in Australia. A phylogenetic analysis of 91 morphological characters strongly supports the placement of the new fossil species in Dasyornithidae, although its intrafamilial relationships will only be better informed by discovery and study of additional material. Dasyornis walterbolesi meets five criteria for consideration as a well-justified fossil calibration and can be used to calibrate molecular estimates of the passerine evolutionary timescale.
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