Biology subjects
Publications and source records attributed to Steell, E. M..
Wilken et al. (1) investigate the evolution of avian palatal kinesis using comparative morphology and biomechanical modelling. While the studys topic and approach are timely, its conclusions are marred by inadequate taxon sampling and morphological misinterpretations.
Phylogenetic analyses of phenotypic characters in crown-group birds often recover results that are strongly incongruous with the findings of recent phylogenomic analyses. Furthermore, existing morphological datasets for crown birds are frequently limited by restricted taxon or character sampling, inconsistent character construction, incorrect scoring, or a combination of several of these factors. As part of an effort to address these limitations, in this study we focus on identifying phylogenetically informative characters of the avian pectoral girdle and forelimb skeleton, elements of which are commonly preserved as avian fossils. We assembled and vetted a dataset of 204 characters, which were then scored for a phylogenetically diverse range of 75 extant avian taxa and incorporated into phylogenetic analyses. Analyses run without topological constraints exhibited notable conflicts with the results of recent phylogenomic studies, possibly due to functional convergence and rapid cladogenesis in the early evolutionary history of crown birds. Qualitative anatomical comparisons and quantitative metrics of homoplasy further highlighted the fact that similar morphologies in pectoral girdle and forelimb elements have evolved repeatedly in distantly related groups of birds, representing a major confounding factor in avian morphological phylogenetics. However, the implementation of molecular scaffolds allowed identification of diagnostic character combinations for numerous avian clades previously only recognized through molecular data, such as Phaethontimorphae, Aequornithes, and Telluraves. Although large morphological datasets may not guarantee increased congruence with molecular phylogenetic studies, they can nonetheless be valuable tools for identifying anatomical synapomorphies of key clades, placing fossils into phylogenetic context, and studying macroevolutionary patterns within major groups of organisms.
AimBiodiversity is distributed unevenly among lineages and regions, and understanding the processes generating these global patterns is a central goal in evolutionary research, particularly in light of the current biodiversity crisis. Here, we integrate phylogenetic relatedness with species diversity patterns in four major clades of living tetrapods (amphibians, squamates, birds, and mammals) to approach this challenge. LocationGlobal. Time period300 million years ago - Present. Major taxa studiedTetrapods. MethodsWe studied geographic patterns of richness-corrected phylogenetic diversity (residual PD), identifying regions where species are phylogenetically more closely or distantly related than expected by richness. We explored the effect of different factors in residual PD: recent speciation rates, temporal trends of lineage accumulation, and environmental variables. Specifically, we searched for evolutionary and ecological differences between regions of high and low residual PD. ResultsOur results show heterogeneous spatial patterns of diversity dynamics across tetrapods. They reveal an overall negative relationship between recent speciation rates and residual PD, underscoring the role of recent speciation events in structuring current biogeographic patterns. Furthermore, we found differences between endothermic and ectothermic tetrapods in response to temperature and precipitation, highlighting the pivotal role of thermal physiology in shaping diversity dynamics. Main conclusionsGeographic patterns of diversity dynamics are heterogeneous across tetrapod clades and help us disentangle the evolutionary and ecological processes underlying them. By illuminating the multifaceted factors underpinning global diversity patterns, our study represents a significant advancement towards better understanding of how the present-day diversity of tetrapods was formed and how speciation rates influenced their species and phylogenetic diversity across clades and regions.
Homoplasy is among the main hinderances to phylogenetic inference. However, investigating patterns of homoplasy can also improve our understanding of macroevolution, for instance by revealing evolutionary constraints on morphology, or highlighting convergent form-function relationships. Several methods have been proposed to quantify the extent of homoplasy in discrete character matrices, but the consistency index (CI) and retention index (RI) have remained the most widely used for decades, with little recent scrutiny of their function. Here, we test the performance of CI and RI using simulated and empirical datasets and investigate patterns of homoplasy with different matrix scenarios. In addition, we describe and test a new scaled metric, the relative homoplasy index (RHI), implemented in the R statistical environment. The results suggest that, unlike the RI, the CI does not constitute a direct measure of homoplasy. However, the RI consistently underestimates the extent of homoplasy in phylogenetic character-taxon matrices, particularly in datasets characterised by high levels of homoplasy. By contrast, RHI--the newly proposed metric--outperforms both methods in sensitivity to homoplasy levels, and is scaled between zero and one for comparison of values between different datasets. Using both simulated and empirical phylogenetic datasets, we show that relative levels of homoplasy remain constant with the addition of novel characters, and, in contrast to earlier work, decrease with the addition of taxa. Our results help illuminate the inherent properties of homoplasy in cladistic matrices, opening new potential avenues of research for investigating patterns of homoplasy in macroevolutionary studies.