Our analyses confirm that with large amounts of sequence data, most deep-level relationships within the angiosperms can be resolved. We anticipate that this well-resolved angiosperm tree will be of broad utility for many areas of biology, including physiology, ecology, paleobiology, and genomics.
Based on these results the following are characterized: (1) the independent origin of the staminal lever mechanism on at least three different occasions in Salvia, (2) that Salvia is clearly polyphyletic, with five other genera intercalated within it, and (3) staminal evolution has proceeded in different ways in each of the three lineages of Salvia but has resulted in remarkably similar staminal morphologies.
Salvia, with over 900 species from both the Old and New World, is the largest genus in the Lamiaceae. Unlike most members of the subfamily Nepetoideae to which it belongs, only two stamens are expressed in Salvia. Although the structure of these stamens is remarkably variable across the genus, generally each stamen has an elongate connective and divergent anther thecae, which form a lever mechanism important in pollination. In a preliminary investigation of infrageneric relationships within Salvia, the monophyly of the genus and its relationship to other members of the tribe Mentheae were investigated using the chloroplast DNA regions rbcL and trnL-F. Significant conclusions drawn from the data include: Salvia is not monophyletic, Rosmarinus and Perovskia together are sister to an Old World clade of Salvia, the section Audibertia is sister to subgenus Calosphace or the monotypic Asian genus Dorystaechas, and the New World members of section Heterosphace are sister to section Salviastrum. Owing to the non-monophyly of Salvia, relationships at the next clearly monophyletic level, tribe Mentheae, were investigated.
Previous molecular phylogenetic research, based on chloroplast and nuclear ribosomal DNA data, has demonstrated that the large genus Salvia (Lamiaceae) is paraphyletic as traditionally circumscribed. However, neither relationships within Salvia s.l. nor within subtribe Salviinae have been evaluated using low‐copy nuclear gene regions. Here, we use two low‐copy nuclear gene regions (PPR‐AT3G09060, GBSSI) to further assess relationships of Salvia and related genera within Salviinae. Our results largely confirm results from previous studies based on chloroplast and nuclear ribosomal DNA. Based upon the phylogenetic results presented here, previous phylogenetic studies, and taxonomic, morphological, and practical considerations, we conclude that the botanical community would be best served by maintaining a broadly defined Salvia, including the five small embedded genera Dorystaechas, Meriandra, Perovskia, Rosmarinus, and Zhumeria as Salvia species. We subsequently present an updated circumscription of Salvia.
Some of the most interesting but still most contentious disjunct biogeographical distributions involve Southern Hemisphere tropical and warm temperate families. The PHMV clade of Myrtales includes four families (Psiloxylaceae, Heteropyxidaceae, Myrtaceae, and Vochysiaceae) that exhibit a number of these biogeographical patterns. The related Psiloxylaceae and Heteropyxidaceae are small families restricted in distribution to the recent volcanic Mascarene Islands to the east of Madagascar and to southeast Africa, respectively. Myrtaceae are found on three major Gondwanan regions (South America, Australasia, and Africa). Because the New World taxa are almost exclusively fleshy fruited, it is unclear whether the family distribution is a classic Gondwanan vicariance pattern or results from one or more long-distance dispersal events over ocean barriers. The Vochysiaceae represent one of a handful of families with amphi-Atlantic distributions vigorously argued to support both long-distance dispersal over the Atlantic and vicariance of western Gondwanan biota by Atlantic seafloor spreading. Molecular phylogenetic relationships, fossil dating of nodes, and penalized likelihood rate smoothing of maximum likelihood trees were employed for a Myrtaleswide analysis using rbcL and ndhF and an analysis of the PHMV analysis using ndhF and matK. The results indicate that the PHMV differentiated during the late Cretaceous. The African lineage of Vochysiaceae is nested within a South American clade and probably arose via long-distance dispersal in the Oligocene at a time when the Atlantic had already rifted 80 m.yr. at the equatorial region. The African/Mascarene Island families, most closely related to Myrtaceae, differentiated during the late Eocene, with subsequent but recent longdistance dispersal from Africa to the Mascarenes. Myrtaceae show a rapid differentiation of a basal, paraphyletic subf. Leptospermoideae in Australasia. Fleshy-fruited taxa (subf. Myrtoideae) are not monophyletic. Vicariance of a widespread warm temperate Southern Hemisphere distribution is likely in explaining the South American-Australasian disjunction, with subsequent dispersal events between the two and to Africa and the Mediterranean basin.
Premise of the StudyA key question in evolutionary biology is why some clades are more successful by being widespread geographically, biome diverse, or species‐rich. To extend understanding of how shifts in area, biomes, and pollinators impact diversification in plants, we examined the relationships of these shifts to diversification across the mega‐genus Salvia.MethodsA chronogram was developed from a supermatrix of anchored hybrid enrichment genomic data and targeted sequence data for over 500 of the nearly 1000 Salvia species. Ancestral areas and biomes were reconstructed using BioGeoBEARS. Pollinator guilds were scored, ancestral pollinators determined, shifts in pollinator guilds identified, and rates of pollinator switches compared.Key ResultsA well‐resolved phylogenetic backbone of Salvia and updated subgeneric designations are presented. Salvia originated in Southwest Asia in the Oligocene and subsequently dispersed worldwide. Biome shifts are frequent from a likely ancestral lineage utilizing broadleaf and/or coniferous forests and/or arid shrublands. None of the four species diversification shifts are correlated to shifts in biomes. Shifts in pollination system are not correlated to species diversification shifts, except for one hummingbird shift that precedes a major shift in diversification near the crown of New World subgen. Calosphace. Multiple reversals back to bee pollination occurred within this hummingbird clade.Conclusions Salvia diversified extensively in different continents, biomes, and with both bee and bird pollinators. The lack of tight correlation of area, biome, and most pollinator shifts to the four documented species diversification shifts points to other important drivers of speciation in Salvia.
Salvia subgenus Calosphace (Lamiaceae) is economically and ethnomedicinally significant and comprised of more than 500 species. Although strongly supported as monophyletic, it has received no comprehensive systematic research since the initial establishment of 91 taxonomic sections in 1939. Representative taxa of 73 sections of Calosphace were sampled to investigate the phylogenetic relationships and identify major lineages using chloroplast (intergenic spacer psbA-trnH) and nuclear ribosomal DNA (internal transcribed spacer). Phylogenetic analysis of the combined data sets established monophyly of seven sections (Blakea, Corrugatae, Erythrostachys, Hastatae, Incarnatae, Microsphace, and Sigmoideae) and four major lineages (S. axillaris, "Hastatae clade", "Uliginosae clade", and "core Calosphace"). Sections spanning two or more centers of diversity are not supported by our results; rather, supported relationships exhibit significant geographic structure. Mexico is supported as the geographic origin of Calosphace, and no more than seven dispersal events to South America are required to account for current disjunct distributions.
The pollen morphology and ultrastructure of the subtribe Salviinae were investigated with light, scanning electron, and transmission electron microscopy. In addition, cladistic analyses of the obtained morphological data, supplemented with rbcL data from GenBank, were conducted in order to assess the phylogenetic signal of palynological characters. Salviinae pollen is small to large, oblate to prolate in shape, with a circular to slightly elliptic amb, and mostly hexacolpate. Perovskia abrotanoides appears to be distylous and shows a significant pollen dimorphism between pin and thrum flowers. The sexine ornamentation of the genera Lepechinia and Chaunostoma is perforate, while the ornamentation of other genera is bireticulate. Perovskia expresses a unique type of sexine ornamentation. The sexine ornamentation variation in Salvia has systematic importance but only partly corresponds with current phylogenetic hypotheses. Unbranched columellae and a continuous, granular endexine are hypothesized to be a symplesiomorphic condition in the tribe Mentheae. Our combined phylogenetic analyses show that the addition of palynological characters contributes to improved resolution and also increases bootstrap support values in comparison with molecular phylogenetic analyses.
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