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  1. Gene tree discordance is expected in phylogenomic trees and biological processes are often invoked to explain it. However, heterogeneous levels of phylogenetic signal among individuals within datasets may cause artifactual sources of topological discordance. We examined how the information content in tips and subclades impacts topological discordance in the parrots (Order: Psittaciformes), a diverse and highly threatened clade of nearly 400 species. Using ultraconserved elements from 96% of the clade's species-level diversity, we estimated concatenated and species trees for 382 ingroup taxa. We found that discordance among tree topologies was most common at nodes dating between the late Miocene and Pliocene, and often at the taxonomic level of genus. Accordingly, we used two metrics to characterize information content in tips and assess the degree to which conflict between trees was being driven by lower quality samples. Most instances of topological conflict and non-monophyletic genera in the species tree could be objectively identified using these metrics. For subclades still discordant after tip-based filtering, we used a machine learning approach to determine whether phylogenetic signal or noise was the more important predictor of metrics supporting the alternative topologies. We found that when signal favored one of the topologies, noise was the mostmore »important variable in poorly performing models that favored the alternative topology. In sum, we show that artifactual sources of gene tree discordance, which are likely a common phenomenon in many datasets, can be distinguished from biological sources by quantifying the information content in each tip and modeling which factors support each topology.« less
    Free, publicly-accessible full text available August 2, 2023
  2. This symposium will focus on five projects’ professional development efforts to enhance educators’ understanding and use of the Next Generation Science Standards (NGSS). Involving educators from preschool to middle school levels in diverse contexts, each project has worked in this problem space in different ways. Of central importance to all the projects is how the NGSS necessitate productive classroom discourse, but the projects differ on how to support educators to achieve “rich science talk.” For example, an “assessment for learning” lens guides one group’s work, while recognizing language and argument as epistemic tools is the driving conceptual framework for another. In this symposium, project leaders discuss the decisions and dilemmas of, and the lessons learned from, their work. This highly interactive session includes brief introductions from each project followed by time for interaction with the projects’ researchers and materials. Projects will bring materials such as scaffolds for collaborative instructional planning, a formative classroom observation tool to support teachers’ use of productive classroom discourse, and examples of instructional units with 7 curricular features designed to support the vision of the NGSS. The session will culminate with time for crosstalk and discussion.