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Abstract Nitrogen (N)-fixing symbiosis is critical to terrestrial ecosystems, yet possession of this trait is known for few plant species. Broader presence of the symbiosis is often indirectly determined by phylogenetic relatedness to taxa investigated via manipulative experiments. This data gap may ultimately underestimate phylogenetic, spatial, and temporal variation in N-fixing symbiosis. Still needed are simpler field or collections-based approaches for inferring symbiotic status. N-fixing plants differ from non-N-fixing plants in elemental and isotopic composition, but previous investigations have not tested predictive accuracy using such proxies. Here we develop a regional field study and demonstrate a simple classification model for fixer status using nitrogen and carbon content measurements, and stable isotope ratios (δ¹⁵N and δ¹³C), from field-collected leaves. We used mixed models and classification approaches to demonstrate that N-fixing phenotypes can be used to predict symbiotic status; the best model required all predictors and was 80–94% accurate. Predictions were robust to environmental context variation, but we identified significant variation due to native vs. non-native (exotic) status and phylogenetic affinity. Surprisingly, N content—not δ¹⁵N—was the strongest predictor, suggesting that future efforts combine elemental and isotopic information. These results are valuable for understudied taxa and ecosystems, potentially allowing higher-throughput field-based N-fixer assessments. 

Abstract PremiseEndophytic plant‐microbe interactions range from mutualistic relationships that confer important ecological and agricultural traits to neutral or quasi‐parasitic relationships. In contrast to root‐associated endophytes, the role of environmental and host‐related factors in the acquisition of leaf endophyte communities at broad spatial and phylogenetic scales remains sparsely studied. We assessed endofoliar diversity to test the hypothesis that membership in these microbial communities is driven primarily by abiotic environment and host phylogeny. MethodsWe used a broad geographic coverage of North America in the genusHeucheraL. (Saxifragaceae), representing 32 species and varieties across 161 populations. Bacterial and fungal communities were characterized using 16S and ITS amplicon sequencing, respectively, and standard diversity metrics were calculated. We assembled environmental predictors for microbial diversity at collection sites, including latitude, elevation, temperature, precipitation, and soil parameters. ResultsAssembly patterns differed between bacterial and fungal endophytes. Host phylogeny was significantly associated with bacteria, while geographic distance was the best predictor of fungal community composition. Species richness and phylogenetic diversity were consistent across sites and species, with only fungi showing a response to aridity and precipitation for some metrics. Unlike what has been observed with root‐associated microbial communities, in this system microbes show no relationship with pH or other soil factors. ConclusionsOverall, this work improves our understanding of the large‐scale patterns of diversity and community composition in leaf endophytes and highlights the relative significance of environmental and host‐related factors in driving different microbial communities within the leaf microbiome. 

ABSTRACT Although the frequency of ancient hybridization across the Tree of Life is greater than previously thought, little work has been devoted to uncovering the extent, timeline, and geographic and ecological context of ancient hybridization. Using an expansive new dataset of nuclear and chloroplast DNA sequences, we conducted a multifaceted phylogenomic investigation to identify ancient reticulation in the early evolution of oaks (Quercus). We document extensive nuclear gene tree and cytonuclear discordance among major lineages ofQuercusand relatives in Quercoideae. Our analyses recovered clear signatures of gene flow against a backdrop of rampant incomplete lineage sorting, with gene flow most prevalent among major lineages ofQuercusand relatives in Quercoideae during their initial radiation, dated to the Early‐Middle Eocene. Ancestral reconstructions including fossils suggest ancestors ofCastanea + Castanopsis,Lithocarpus, and the Old World oak clade probably co‐occurred in North America and Eurasia, while the ancestors ofChrysolepis, Notholithocarpus, and the New World oak clade co‐occurred in North America, offering ample opportunity for hybridization in each region. Our study shows that hybridization—perhaps in the form of ancient syngameons like those seen today—has been a common and important process throughout the evolutionary history of oaks and their relatives. Concomitantly, this study provides a methodological framework for detecting ancient hybridization in other groups. 

Abstract PremiseAstragalus(Fabaceae), with more than 3000 species, represents a globally successful radiation of morphologically highly similar species predominant across the northern hemisphere. It has attracted attention from systematists and biogeographers, who have asked what factors might be behind the extraordinary diversity of this important arid‐adapted clade and what sets it apart from close relatives with far less species richness. MethodsHere, for the first time using extensive phylogenetic sampling, we asked whether (1)Astragalusis uniquely characterized by bursts of radiation or whether diversification instead is uniform and no different from closely related taxa. Then we tested whether the species diversity ofAstragalusis attributable specifically to its predilection for (2) cold and arid habitats, (3) particular soils, or to (4) chromosome evolution. Finally, we tested (5) whetherAstragalusoriginated in central Asia as proposed and (6) whether niche evolutionary shifts were subsequently associated with the colonization of other continents. ResultsOur results point to the importance of heterogeneity in the diversification ofAstragalus, with upshifts associated with the earliest divergences but not strongly tied to any abiotic factor or biogeographic regionalization tested here. The only potential correlate with diversification we identified was chromosome number. Biogeographic shifts have a strong association with the abiotic environment and highlight the importance of central Asia as a biogeographic gateway. ConclusionsOur investigation shows the importance of phylogenetic and evolutionary studies of logistically challenging “mega‐radiations.” Our findings reject any simple key innovation behind high diversity and underline the often nuanced, multifactorial processes leading to species‐rich clades. 

Studies on the perception of animals and plants often report that students prefer to learn more about animals than plants and usually have more difficultly noticing plants in the environment. This could impact conservation programs and initiatives, as animals are often considered more important and may be deemed worthier of conservation efforts. Providing students an opportunity to connect to plants and understand how they affect their lives is one step toward raising awareness around this issue. Compositae, also known as Asteraceae or the sunflower family, is the largest family of flowering plants, accounting for ~10% of flowering plant diversity in the world. They are present in virtually all biomes and environments and fulfill multiple ecological niches. Some members of the family are widely cultivated as crops, such as sunflower, lettuce, artichoke, and chicory; several species are grown as ornamental plants; and others are used in the pharmaceutical and chemical industry. Compositae’s presence in so many contexts make the family a good candidate for activities aiming to increase plant awareness, as several Compositae species are already present in our everyday lives. Here we present Compositae in a Crate, a teacher-guided outreach activity aimed at the 4th and 5th school grades. This crate of activities contains four different modules focusing on different aspects of the sunflower family: biodiversity, morphology, society, and genomics. Each module has different learning objectives and can be used independently from each other. A guide and different activities, such as flash cards, puzzles, and 3D models, are provided in each module. The activities will be prepared to meet the national and state of Tennessee education standards for the 4th and 5th grades. The produced crates will be available at different institutions and all materials will be made available online so other interested parties can produce their own crates. 

The sunflower family, Asteraceae, comprises 10% of all flowering plant species and displays an incredible diversity of form. Asteraceae are clearly monophyletic, yet resolving phylogenetic relationships within the family has proven difficult, hindering our ability to understand its origin and diversification. Recent molecular clock dating has suggested a Cretaceous origin, but the lack of deep sampling of many genes and representative taxa from across the family has impeded the resolution of migration routes and diversifications that led to its global distribution and tremendous diversity. Here we use genomic data from 256 terminals to estimate evolutionary relationships, timing of diversification(s), and biogeographic patterns. Our study places the origin of Asteraceae at ∼83 MYA in the late Cretaceous and reveals that the family underwent a series of explosive radiations during the Eocene which were accompanied by accelerations in diversification rates. The lineages that gave rise to nearly 95% of extant species originated and began diversifying during the middle Eocene, coincident with the ensuing marked cooling during this period. Phylogenetic and biogeographic analyses support a South American origin of the family with subsequent dispersals into North America and then to Asia and Africa, later followed by multiple worldwide dispersals in many directions. The rapid mid-Eocene diversification is aligned with the biogeographic range shift to Africa where many of the modern-day tribes appear to have originated. Our robust phylogeny provides a framework for future studies aimed at understanding the role of the macroevolutionary patterns and processes that generated the enormous species diversity of Asteraceae.