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Premise: The true blueberries (Vaccinium sect. Cyanococcus; Ericaceae), endemic to North America, have been intensively studied for over a century. However, with species estimates ranging from nine to 24 and much confusion regarding species boundaries, this ecologically and economically valuable group remains inadequately understood at a basic evolutionary and taxonomic level. As a first step toward understanding the evolutionary history and taxonomy of this species complex, we present the first phylogenomic hypothesis of the known diploid blueberries. Methods: We used flow cytometry to verify the ploidy of putative diploid taxa and a target‐enrichment approach to obtain a genomic data set for phylogenetic analyses. Results: Despite evidence of gene flow, we found that a primary phylogenetic signal is present. Monophyly for all morphospecies was recovered, with two notable exceptions: one sample of V. boreale was consistently nested in the V. myrtilloides clade and V. caesariense was nested in the V. fuscatum clade. One diploid taxon, Vaccinium pallidum, is implicated as having a homoploid hybrid origin. Conclusions: This foundational study represents the first attempt to elucidate evolutionary relationships of the true blueberries of North America with a phylogenomic approach and sets the stage for multiple avenues of future study such as a taxonomic revision of the group, the verification of a homoploid hybrid taxon, and the study of polyploid lineages within the context of a diploid phylogeny. [ABSTRACT FROM AUTHOR]

The true blueberries (Vaccinium sect. Cyanococcus; Ericaceae) comprise a clade of about nine to 24 species distributed mainly in eastern temperate North America, with one species reaching farther west. Despite extensive study, the systematics and evolution of the group are still poorly understood. Limited morphological variation, multiple ploidy levels of uncertain origin, and natural hybridization all contribute to the challenge. Questionable analytical methods, such as the use of phenetics and an overemphasis on crossing experiments, have further impeded progress. Here we review the history of research on the systematics and evolution of V. sect. Cyanococcus with the aim of clarifying and summarizing hypotheses of species origins and diversification, especially in relation to polyploidy. We also present recent progress from our own work and, on that basis, offer promising lines of investigation with morphological and molecular data. We anticipate that these avenues of research will ultimately clarify patterns of natural species diversity in V. sect. Cyanococcus with benefits for biodiversity studies, conservation, and crop breeding. [ABSTRACT FROM AUTHOR]

Premise of the Study: The North American Cercis clade spans dry to mesic climates and exhibits complex morphological variation. We tested various proposed species classifications of this group and whether aspects of leaf morphology, particularly the "drip-tip" in some regional populations, are adaptive and/or linked with phylogeny., Methods: We made measurements on over 1100 herbarium specimens from throughout North America and analyzed the data with univariate and multivariate approaches. We analyzed phylogenetically DNA sequence data from nuclear ITS and three plastid regions from 40 samples, and estimated divergence times with a relaxed-clock Bayesian analysis. We used climate and geographic position data to predict the variation observed in leaf size and shape by using stepwise multiple linear regressions., Key Results: Morphometric analyses yielded a pattern of continuous and often clinal character variation across North America, without correlated gaps in character states. Conversely, phylogenetic and divergence time analyses yielded distinct clades from California, the interior west, and eastern North America separated by between ~12 and 16 million years. Multiple regressions yielded highly significant correlations between leaf apex shape and precipitation of the warmest quarter., Conclusions: Despite a pattern of continuous morphological character variation, the long period of geographic and presumably genetic isolation warrants the delimitation of three species. Predictive modeling supports the adaptive value of acuminate apices or "drip-tips" in mesic habitats. This suggests that Cercis leaves change more rapidly than inferred from parsimony reconstruction, which has implications for the evolution of the dry floras of North America and Eurasia., (© 2018 Botanical Society of America.)