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  1. Free, publicly-accessible full text available January 1, 2024
  2. Abstract

    We have previously suggested that a shift from bee to hummingbird pollination, in concert with floral architecture modifications, occurred at the crown of Salvia subgenus Calosphace in North America ca. 20 mya (Kriebel et al. 2020 and references therein). Sazatornil et al. (2022), using a hidden states model, challenged these assertions, arguing that bees were the ancestral pollinator of subg. Calosphace and claiming that hummingbirds could not have been the ancestral pollinator of subg. Calosphace because hummingbirds were not contemporaneous with crown subg. Calosphace in North America. Here, using a variety of models, we demonstrate that most analyses support hummingbirds as ancestral pollinators of subg. Calosphace and show that Sazatornil et al. (2022) erroneously concluded that hummingbirds were absent from North America ca. 20 mya. We contend that “biological realism” – based on timing and placement of hummingbirds in Mexico ca. 20 mya and the correlative evolution of hummingbird associated floral traits – must be considered when comparing models based on fit and complexity, including hidden states models.

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  3. Abstract Lamiaceae are one of the largest and most economically important families of flowering plants. Despite focused study on relationships within subclades, higher-level relationships have been under-studied. Moreover, the herbaceous habit of much of the family has resulted in a poor fossil record and has hampered estimates of divergence times. Using a new dataset of five plastid loci from 178 members of Lamiaceae representing all subfamilies and nearly all tribes, we clarify major infrafamilial relationships and present a robust set of divergence times. We use this phylogenetic hypothesis as a platform to test previous hypotheses regarding the historical biogeography and evolution of major traits in the family. We confirm the placement of subfamily Nepetoideae, show continued uncertainty in the placement of subfamilies Ajugoideae and Premnoideae and highlight extreme discordance with recent results from nuclear data. Lamiaceae originated during the Late Cretaceous as woody plants with nutlet fruits and four stamens, probably in South-East Asia. Most subfamilies diverged during the Eocene, perhaps facilitated by climatic cooling. Our results provide a valuable set of secondary dates for Lamiaceae and highlight the need for focused study of subfamilies Callicarpoideae and Viticoideae. Our results also provide several hypotheses regarding trait or range-dependent diversification. 
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  4. The genus Salvia is comprised of about 1000 species and has diversity hotspots in the Americas, East Asia, southwest Asia and the Mediterranean region. Central Asia also possesses considerable Salvia species diversity but is understudied relative to the aforementioned diversity hotspots. To help remedy this deficiency, we present a synopsis of Central Asian Salvia species based on extensive fieldwork, herbarium consultation, and literature surveys focusing on Uzbekistan, Kyrgyzstan, Tajikistan, Kazakhstan, and Turkmenistan (i.e., Central Asia). According to our final taxonomic revision, there are 41 species of native Salvia in the flora of Central Asia, 24 of which are endemic. Salvia ariana from Tajikistan and S. spinosa from Kazakhstan are documented from the respective countries for the first time, and the presence of S. tianschanica from Tajikistan and S. verticillata from Kazakhstan has been confirmed. In addition, the neotypification of S. deserta and three lectotypifications (Perovskia abrotanoides, S. bucharica and S. trautvetterii) are provided. Furthermore, we synonymized six species of Salvia that were previously reported from Central Asia, including S. intercedens, S. kopetdaghensis, S. linczevskii, S. lipskyi, S. semilanata and S. stepposa. Finally, a new species identification key for Central Asian Salvia is presented based on the new nomenclature changes and our taxonomic revision. 
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  5. Abstract Winter annuals comprise a large fraction of warm-desert plant species, but the drivers of their diversity are little understood. One factor that has generally been overlooked is the lack of obvious means of long-distance seed dispersal in many desert-annual lineages, which could lead to genetic differentiation at small spatial scales and, ultimately, to speciation and narrow endemism. If our gene-flow hypothesis is correct, individual winter-annual species should have populations with genetic spatial structures implying short distances of gene flow. To test this idea, we sampled six populations of Eschscholzia parishii (Papaveraceae) in three pairs of watersheds within a 28-km radius in southern California. We quantified genetic diversity and structure and inferred the distance of gene flow in these populations using single nucleotide polymorphisms derived from genotyping-by-sequencing. Estimated distances of gene flow were quite small (σ = 10.4–14.9 m), with strong genetic structure observed within and between populations. Kinship declined steeply with ln distance (r2 = 0.85). Petal size and shape differed significantly between the northernmost and southernmost populations. These findings support the hypothesis that the high diversity of warm-desert winter annuals might result, in part, from genetic differentiation within species at small spatial scales driven by poor seed dispersal. 
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  6. Abstract A fundamental question in evolutionary biology is how clades of organisms exert influence on one another. The evolution of the flower and subsequent plant/pollinator coevolution are major innovations that have operated in flowering plants to promote species radiations at a variety of taxonomic levels in the Neotropics. Here we test the hypothesis that pollination by Neotropical endemic hummingbirds drove the evolution of two unique stigma traits in correlation with other floral traits in New World Salvia (Lamiaceae). We examined morphometric shapes of stigma lobing across 400 Salvia spp., scored presence and absence of a stigma brush across Salvia, and used a suite of phylogenetic comparative methods to detect shape regime shifts, correlation of trait shifts with BayesTraits and phylogenetic generalized least square regressions, and the influence of scored pollinators on trait evolution using OUwie. We found that a major Neotropical clade of Salvia evolved a correlated set of stigma features, with a longer upper stigma lobe and stigmatic brush, following an early shift to hummingbird pollination. Evolutionary constraint is evident as subsequent shifts to bee pollination largely retained these two features. Our results support the hypothesis that hummingbirds guided the correlative shifts in corolla, anther connective, style and stigma shape in Neotropical Salvia, despite repeated shifts back to bee pollination. 
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  7. Next-generation sequencing technologies have facilitated new phylogenomic approaches to help clarify previously intractable relationships while simultaneously highlighting the pervasive nature of incongruence within and among genomes that can complicate definitive taxonomic conclusions. Salvia L., with ∼1,000 species, makes up nearly 15% of the species diversity in the mint family and has attracted great interest from biologists across subdisciplines. Despite the great progress that has been achieved in discerning the placement of Salvia within Lamiaceae and in clarifying its infrageneric relationships through plastid, nuclear ribosomal, and nuclear single-copy genes, the incomplete resolution has left open major questions regarding the phylogenetic relationships among and within the subgenera, as well as to what extent the infrageneric relationships differ across genomes. We expanded a previously published anchored hybrid enrichment dataset of 35 exemplars of Salvia to 179 terminals. We also reconstructed nearly complete plastomes for these samples from off-target reads. We used these data to examine the concordance and discordance among the nuclear loci and between the nuclear and plastid genomes in detail, elucidating both broad-scale and species-level relationships within Salvia . We found that despite the widespread gene tree discordance, nuclear phylogenies reconstructed using concatenated, coalescent, and network-based approaches recover a common backbone topology. Moreover, all subgenera, except for Audibertia , are strongly supported as monophyletic in all analyses. The plastome genealogy is largely resolved and is congruent with the nuclear backbone. However, multiple analyses suggest that incomplete lineage sorting does not fully explain the gene tree discordance. Instead, horizontal gene flow has been important in both the deep and more recent history of Salvia . Our results provide a robust species tree of Salvia across phylogenetic scales and genomes. Future comparative analyses in the genus will need to account for the impacts of hybridization/introgression and incomplete lineage sorting in topology and divergence time estimation. 
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  8. null (Ed.)
    Abstract Background A robust molecular phylogeny is fundamental for developing a stable classification and providing a solid framework to understand patterns of diversification, historical biogeography, and character evolution. As the sixth largest angiosperm family, Lamiaceae, or the mint family, consitutes a major source of aromatic oil, wood, ornamentals, and culinary and medicinal herbs, making it an exceptionally important group ecologically, ethnobotanically, and floristically. The lack of a reliable phylogenetic framework for this family has thus far hindered broad-scale biogeographic studies and our comprehension of diversification. Although significant progress has been made towards clarifying Lamiaceae relationships during the past three decades, the resolution of a phylogenetic backbone at the tribal level has remained one of the greatest challenges due to limited availability of genetic data. Results We performed phylogenetic analyses of Lamiaceae to infer relationships at the tribal level using 79 protein-coding plastid genes from 175 accessions representing 170 taxa, 79 genera, and all 12 subfamilies. Both maximum likelihood and Bayesian analyses yielded a more robust phylogenetic hypothesis relative to previous studies and supported the monophyly of all 12 subfamilies, and a classification for 22 tribes, three of which are newly recognized in this study. As a consequence, we propose an updated phylogenetically informed tribal classification for Lamiaceae that is supplemented with a detailed summary of taxonomic history, generic and species diversity, morphology, synapomorphies, and distribution for each subfamily and tribe. Conclusions Increased taxon sampling conjoined with phylogenetic analyses based on plastome sequences has provided robust support at both deep and shallow nodes and offers new insights into the phylogenetic relationships among tribes and subfamilies of Lamiaceae. This robust phylogenetic backbone of Lamiaceae will serve as a framework for future studies on mint classification, biogeography, character evolution, and diversification. Graphical abstract 
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