Ben Creisler
Some mainly avian-related papers:
Yan Zhao, Yi-Bo Yang, Ying Guo, Guang-Ying Ren & Fu-Cheng Zhang (2021)
Stable carbon isotope composition of bone hydroxylapatite: significance in paleodietary analysis.
Palaeoworld (advance online publication)
DOI: Â
https://doi.org/10.1016/j.palwor.2021.02.004https://www.sciencedirect.com/science/article/abs/pii/S1871174X21000214The stable carbon isotope composition of the structural carbonate derived from animal bone hydroxylapatite (Î13CB-HA) could record an animalâs diet. These records provide critical evidence for different paleontological disciplines, e.g., paleodiet analyses, and paleoclimate reconstructions. Compared to those of other body tissues, such as bone collagen or teeth enamel hydroxylapatite, Î13CB-HA values record information on the whole diet of an animal in its last years. Î13CB-HA can be applied to fossil animals of various body sizes. The Î13C analytical instruments available only require that prepared bone samples be approximately 2â5 mg for precise measurement, allowing Î13CB-HA analysis to be feasible on most vertebrate fossils without destructive sampling, especially on small mammals or birds whose teeth are not large enough for sampling or are lost. Moreover, Î13CB-HA can be used from different times or under less than ideal burial environments. For fossils dating back to Devonian or buried in hot and humid regions, dietary information has been completely lost in bone collagen during post-depositional processes but still remained in the Î13CB-HA values because hydroxylapatite is less influenced by diagenetic effects after deposition. In addition, systematic methods such as X-ray diffraction and Fourier transform infrared spectroscopy have been developed to qualitatively or semiquantitatively assess the influence of diagenesis on bone hydroxylapatite to ensure the credibility of the Î13CB-HA values. With the above merits, Î13CB-HA analysis is therefore becoming an increasingly important method in paleodiet-related research. Currently, applications of the Î13CB-HA method on fossil animals are primarily focused on two aspects, namely, paleodietary reconstruction of fossil animals with uncertain diets and paleoenvironmental reconstruction based on the Î13CB-HA values of fossil herbivores. The published researches, combined with our new results from early birds, demonstrate the considerable significance of the Î13CB-HA method in paleontological and paleoenvironmental research. Notably, the Î13CB-HA-based paleodietary analysis of early vertebrates, especially the large number of small birds or mammals discovered in the past decades would be an important work in the near future.
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Highlights
First high-density sampling survey of pneumaticity in a non-aquatic avian group
Cuckoos exhibit relatively pneumatic skeletons, with low variation across species
Results support hypotheses relating pneumaticity and biomechanical loading regimes
Abstract
Postcranial skeletal pneumaticity (i.e., epithelial-lined, air-filled bones) is a condition unique to birds among extant tetrapods. Previous research reveals extensive variation in the _expression_ of this trait in different bird species, from taxa that pneumatize nearly the entire skeleton to others that do not pneumatize a single bone. These studies, however, have primarily focused on aquatic/semi-aquatic birds, specifically Anseriformes (screamers, ducks, geese, swans) and Aequorlitornithes (loons, gulls, penguins, storks, etc.). This is the first clade-centric study of pneumaticity in an exclusively terrestrial clade (i.e., a group without any proclivities for water), Cuculidae. Given the variation in body size and ecology exhibited by cuckoos, they represent an ideal group for evaluating previously established trends in pneumaticity patterns. Similar to previous studies, our results indicate that cuckoos do exhibit extensive postcranial skeletal pneumaticity but with much more limited variation in _expression_. Of the surveyed species, 30 of 41 display an identical _expression_ pattern, pneumatizing all postaxial vertebrae, the humerus, sternum and pelvic girdle. The remaining species (11/41) deviate from this pattern by no more than two elements (i.e., the femur or the scapula/coracoid). All variable species expand upon the basic cuckoo pattern, with five species pneumatizing the femur and the remaining six taxa pneumatizing both the scapula and coracoid. Furthermore, most variation occurs in early diverging clades, with distinct subclades associated with specific anatomical expansions in pneumaticity (e.g. pneumatic femora in Neomorphinae and pneumatic scapulae/coracoids in select members of Couinae and Centropodinae). Limited variation noted in Cuculidae may be the result of the relatively high base level of pneumaticity when compared with previously sampled groups of water-oriented birds. Additional analyses indicate a positive relationship between body mass and pneumaticity, with possible (i.e., non-quantifiable) relationships noted between the limited expansions from the basic cuckoo pattern and specific locomotor behaviors (e.g., pneumatic femora present in species with enhanced cursorial behavior). These basic trends have also been observed in other densely sampled neognath clades. Taken together, the data herein supports the hypothesis that changes in pneumaticity _expression_ may be correlated with shifts in biomechanical loading regimes rather than solely as a weight saving (i.e., density-altering) mechanism.
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First total-evidence phylogeny of 158 extant and extinct species of rails.
Doubling geographic distance decrease dispersal rates to 31% in rails.
Flightlessness influence dispersal rates but dispersal parameter in this state was not 0.0.
Flight is lost approximately 22 times independently in the evolutionary history of rails.
Abstract
The ability of lineages to disperse over evolutionary timescales may be influenced by the gain or loss of traits after adaptation to new ecological conditions. For example, rails (Aves: Rallidae) have many cases of flightless insular endemic species that presumably evolved after flying ancestors dispersed over large ocean barriers and became isolated. Nonetheless, the details of how flying and its loss have influenced the cladeâs historical biogeography are unknown, as is the importance of other predictors of dispersal such as the geographic distance between regions. Here, we used a dated phylogeny of 158 species of rails to compare trait-dependent and trait-independent biogeography models in BioGeoBEARS. We evaluated a probabilistic historical biogeographical model that allows geographic range and flight to co-evolve and influence dispersal ability on a phylogeny. The best-fitting dispersal model was a trait-dependent dispersal model (DEC+j +x+t21+m1) that accrued 85.2% of the corrected Akaike Information Criterion (AICc) model weight. The distance-dependence parameter, x was estimated at -0.54, ranging from -0.49 to -0.65 across models, suggesting that a doubling of dispersal distance results in an approximately 31% decrease in dispersal rate (2-0.54 = 0.69). The estimated rate of loss of flight (t21) was similar across all models (â0.029 loss events per lineage per million years). The multiplier on dispersal rate when a lineage is non-flying, m1, is estimated to be 0.38 under this model. Surprisingly, the estimate of m1 was not 0.0, probably because the loss of flight is so common in the rails that entire clades of flightless species are found in the data, forcing the model to attribute some dispersal to flightless lineages. These results indicate that long-distance dispersal over macroevolutionary timespans can be modelled, rather than simply attributed to chance, allowing support for different hypotheses to be quantified and model limitations to be identified. Overall, by combining new analytical methods with a comprehensive phylogenomic dataset, we use a quantitative framework to show how traits influence dispersal capacity and eventually shape geographical distributions at a macroevolutionary scale.
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