Ben Creisler
Some recent avian papers:
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Free pdf:
Niche expansion is a critical step in the speciation process. Large brains linked to improved cognitive ability may enable species to expand their niches and forage in new ways, thereby promoting speciation. Despite considerable work on ecological divergence in brain size and its importance in speciation, relatively little is known about how brain shape relates to behavioral, ecological, and taxonomic diversity at macroevolutionary scales. This is due, in part, to inherent challenges with quantifying brain shape across many species. Here, we present a novel, semiautomated approach for rapidly phenotyping brain shape using semilandmarks derived from X-ray computed micro-tomography (microCT) scans.
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We then test its utility by parsing evolutionary trends within a diverse radiation of birds, kingfishers (Aves: Alcedinidae). Multivariate comparative analyses reveal that rates of brain shape evolution, but not beak shape, are positively correlated with lineage diversification rates. Distinct brain shapes are further associated with changes in body size and foraging behavior, suggesting both allometric and ecological constraints on brain shape evolution. These results are in line with the idea of brains acting as a "master regulator" of critical processes governing speciation, such as dispersal, foraging behavior, and dietary niche.
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Highlights
The first record of a fossil avian egg from Uruguay (Late Pleistocene).
The first complete fossil avian egg from the Quaternary of South America.
The morphology of the fossil egg indicate affinities with fossil tinamid species.
Abstract
In this contribution we report a fossil avian egg with an exceptional preservation. This material was recovered from sediments assigned to the Late Pleistocene-Early Holocene of Uruguay and it could be included as one of the few Cenozoic cases of complete preservation of fossil avian eggs. The micro and macrostructural analysis of the egg and its eggshell allow us to assign it to Family Tinamidae.
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Apteryx is a genus of flightless birds endemic to New Zealand known to lay very large eggs in proportion to body weight. The eggshell of Apteryx is unusually thin and less porous than allometrically expected possibly as a compensation for a very long incubation period. Past studies have been carried out on Apteryx australis, a species which once comprised all kiwi with brown plumage, now separated into three distinct species. These species use different habitats and live at different latitudes and altitudes, therefore generating a need to revise our knowledge of the attributes of their eggshells. In this study, we measured the physical characteristics and water conductance on eggshell fragments of these three species and Greatâspotted Kiwi and relate them to the environmental conditions of their respective environments; we also measured the water vapor conductance of Brown Kiwi eggs of late stages of incubation. We found that several tradeâoffs exist between incubation behavior, environmental conditions, and eggshell structure. We found differences between species in eggshell water vapor conductance seemingly related to altitude; Brown Kiwi and Rowi generally inhabiting lower altitudes had the highest conductance and Tokoeka, generally living in montane environments, the lowest. This is achieved by an increased eggshell thickness rather than a pore area reduction. Finally, the water vapor conductance late in incubation was 58% higher than infertile unincubated eggs, suggesting a drastic increase in conductance throughout the long incubation period. Using the values previously reported, we calculated the embryonic eggshell thinning to be 32.5% at the equatorial region of the eggshell. We describe several new features, such as triangular mineral particles in the cuticle, reported for the extinct Trigonoolithus amoeiÂ[dinosaur egg], and confirmed the existence of plugged pores. We suggest that these structures provide microbial protection needed by a burrow nesting species with a long incubation period.
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Background
The naturally occurring chicken mutant talpid2 (ta2), best known for its limb and craniofacial defects, has long served as a valuable tool for developmental biologists studying growth and patterning of craniofacial structures and the limb. The mutant provides a unique tool to examine the molecular and cellular processes regulating limb development. This mutant also provides unique insights into the evolution of developmental genetic programs.
Results
Previous work defined the appearance of atavistic dentition in ta2 embryos. Herein we describe the appearance of ancestral characters of the hindlimb in embryonic ta2 chicken embryos.
Conclusion
As the ta2 phenotype arises as a result of mutation in C2CD3 and disrupted cilia function, this mutant provides genetic and developmental insight into the causes of asymmetry in the limb and also a model for the evolution of the avian hindlimb.