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  1. Abstract Background and Aims

    Few studies of angiosperms have focused on androecial evolution in conjunction with evolutionary shifts in corolla morphology and pollinator relationships. The Western Hemisphere clade of Justiciinae (Acanthaceae) presents the rare opportunity to examine remarkable diversity in staminal morphology. We took a phylogenetically informed approach to examine staminal diversity in this hypervariable group and asked whether differences in anther thecae separation is associated with phylogenetically informed patterns of variation in corolla morphology. We further discuss evidence for associations between anther diversity and pollinators in this lineage.


    For the Dianthera/Sarotheca/Plagiacanthus (DSP) clade of Western Hemisphere Justiciinae, we characterized floral diversity based on a series of corolla measurements and using a model-based clustering approach. We then tested for correlations between anther thecae separation and corolla traits, and for shifts in trait evolution, including evidence for convergence.

    Key Results

    There is evolutionary vagility in corolla and anther traits across the DSP clade with little signal of phylogenetic constraint. Floral morphology clusters into four distinct groups that are, in turn, strongly associated with anther thecae separation, a novel result in Acanthaceae and, to our knowledge, across flowering plants. These cluster groups are marked by floral traits that strongly point to associations with pollinating animals. Specifically, species that are known or likely to be hummingbird pollinated have stamens with parallel thecae, whereas those that are likely bee or fly pollinated have stamens with offset, divergent thecae.


    Our results suggest that anther thecae separation is likely under selection in concert with other corolla characters. Significant morphological shifts detected by our analyses corresponded to putative shifts from insect to hummingbird pollination. Results from this study support the hypothesis that floral structures function in an integrated manner and are likely subject to selection as a suite. Further, these changes can be hypothesized to represent adaptive evolution.

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  2. Abstract— Acanthaceae is a family of tropical flowering plants with approximately 4900 species. Despite remarkable variation in morphological traits, research on patterns of character evolution has been limited by uncertain relationships among some of the major lineages. We sampled 16 taxa from these major lineages to estimate a phylogenomic framework using a combination of five newly sequenced shotgun genome skims plus seven new and four publicly available transcriptomes. We used OrthoFinder2 to infer a species tree with strong branch support. Except for the placement of Crabbea , our results corroborate the most recent chloroplast and nrITS sequence-based topology. Of 587 single copy loci, 10 were recovered for all 16 species; a RAxML tree estimated from these 10 loci resulted in the same topology as other datasets assembled in this study, with the exception of relationships among three sampled species of Barleria ; however, branch support was lower compared to the tree reconstructed using more data. ABBA-BABA tests were conducted to investigate patterns of introgression involving Crabbea ; few nucleotides supported alternative topologies. SplitsTree networks of the 587 loci and 6136 orthogroup trees revealed conflict among the branches leading to Andrographideae, Whitfieldieae, and Neuracanthus . A principal components analysis in treespace found no distinct clusters of trees. Our results based on combined genome skim and transcriptome sequences strongly corroborate the previously published chloroplast and nr-ITS-based phylogeny of Acanthaceae with increased resolution among Barlerieae, Andrographideae, Whitfieldieae, and Neuracanthus . This advance in our knowledge of Acanthaceae relationships will allow us to investigate character evolution and other phenomena within this diverse group of plants in studies with increased taxon sampling. 
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  3. Summary Recent molecular phylogenetic results have demonstrated that Monechma s.l., a group of plants with ecological importance in the savanna and succulent biomes of sub-Saharan Africa, is polyphyletic with two discrete lineages recognisable. In the present work, we recognise Monechma Groups I and II at the generic rank, which can be distinguished by differences in inflorescence characteristics and seed morphology. The nomenclatural implications of these findings are investigated. The lectotype of Monechma , M. bracteatum Hochst., is a part of a small lineage of plants closely allied to Justicia L. sect. Harnieria (Solms) Benth. for which the earliest valid name is found to be Meiosperma Raf. Hence, Monechma is synonymised within Meiosperma , which comprises six accepted species and two undescribed taxa. The majority of species of former Monechma s.l. are resolved within the second lineage for which the only validly published generic name is Pogonospermum Hochst. This resurrected genus comprises 34 accepted species plus two undescribed taxa. Pogonospermum displays considerable morphological variation and is here subdivided into six sections based primarily on differences in plant habit, inflorescence form, calyx, bract and bracteole venation, and seed indumentum. The new combinations and new sections are validated, and seven accepted species names are lectotypified. 
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  4. Abstract

    Carbon‐concentrating mechanisms (CCMs) are a widespread phenomenon in photosynthetic organisms. In vascular plants, the evolution of CCMs ([C44‐carbon compound] and crassulacean acid metabolism [CAM]) is associated with significant shifts, most often to hot, dry and bright, or aquatic environments. If and how CCMs drive distributions of other terrestrial photosynthetic organisms, remains little studied. Lichens are ecologically important obligate symbioses between fungi and photosynthetic organisms. The primary photosynthetic partner in these symbioses can include CCM‐presenting cyanobacteria (as carboxysomes), CCM‐presenting green algae (as pyrenoids) or green algae lacking any CCM. We use an extensive dataset of lichen communities from eastern North America, spanning a wide climatic range, to test the importance of CCMs as predictors of lichen ecology and distribution. We show that the presence or absence of CCMs leads to opposite responses to temperature and precipitation in green algal lichens, and different responses in cyanobacterial lichens. These responses contrast with our understanding of lichen physiology, whereby CCMs mitigate carbon limitation by water saturation at the cost of efficient use of vapor hydration. This study demonstrates that CCM status is a key functional trait in obligate lichen symbioses, equivalent in importance to its role in vascular plants, and central for studying present and future climate responses.

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  5. Premise

    Apetaly is widespread across distantly related lineages of flowering plants and is associated with abiotic (or self‐) pollination. It is particularly prevalent in the carnation family, and the cosmopolitan genusStellariacontains many lineages that are hypothesized to have lost petals from showy petalous ancestors. But the pollination biology of apetalous species ofStellariaremains unclear.


    Using a substantial species‐level sampling (~92% of known taxonomic diversity), we describe the pattern of petal evolution withinStellariausing ancestral character state reconstructions. To help shed light on the reproductive biology of apetalousStellaria, we conducted a field experiment at an alpine tundra site in the southern Rocky Mountains to test whether an apetalous species (S. irrigua) exhibits higher levels of selfing than a sympatric, showy petalous congener (S. longipes).


    Analyses indicated that the ancestor ofStellariawas likely showy petalous and that repeated, parallel reductions of petals occurred in clades across much of the world, with uncommon reversal back to showy petals. Field experiments supported high rates of selfing in the apetalous species and high rates of outcrossing in the petalous species.


    Petal loss is rampant across major clades ofStellariaand is potentially linked with self‐pollination worldwide. Self‐pollination occurs within the buds inS. irrigua, and high propensities for this and other forms of selfing known in many other taxa of arctic‐alpine habitats may reflect erratic availability of pollinators.

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