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Staminal evolution in the genus Salvia (Lamiaceae): molecular phylogenetic evidence for multiple origins of the staminal lever.

ABSTRACT: BACKGROUND AND AIMS:The genus Salvia has traditionally included any member of the tribe Mentheae (Lamiaceae) with only two stamens and with each stamen expressing an elongate connective. The recent demonstration of the non-monophyly of the genus presents interesting implications for staminal evolution in the tribe Mentheae. In the context of a molecular phylogeny, the staminal morphology of the various lineages of Salvia and related genera is characterized and an evolutionary interpretation of staminal variation within the tribe Mentheae is presented. METHODS:Two molecular analyses are presented in order to investigate phylogenetic relationships in the tribe Mentheae and the genus Salvia. The first presents a tribal survey of the Mentheae and the second concentrates on Salvia and related genera. Schematic sketches are presented for the staminal morphology of each major lineage of Salvia and related genera. KEY RESULTS:These analyses suggest an independent origin of the staminal elongate connective on at least three different occasions within the tribe Mentheae, each time with a distinct morphology. Each independent origin of the lever mechanism shows a similar progression of staminal change from slight elongation of the connective tissue separating two fertile thecae to abortion of the posterior thecae and fusion of adjacent posterior thecae. A monophyletic lineage within the Mentheae is characterized consisting of the genera Lepechinia, Melissa, Salvia, Dorystaechas, Meriandra, Zhumeria, Perovskia and Rosmarinus. CONCLUSIONS: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.

SUBMITTER: Walker JB

PROVIDER: S-EPMC2735309 | biostudies-literature | 2007 Aug

REPOSITORIES: biostudies-literature

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Staminal evolution in the genus Salvia (Lamiaceae): molecular phylogenetic evidence for multiple origins of the staminal lever.

Walker Jay B JB Sytsma Kenneth J KJ

Annals of botany 20060822 2

<h4>Background and aims</h4>The genus Salvia has traditionally included any member of the tribe Mentheae (Lamiaceae) with only two stamens and with each stamen expressing an elongate connective. The recent demonstration of the non-monophyly of the genus presents interesting implications for staminal evolution in the tribe Mentheae. In the context of a molecular phylogeny, the staminal morphology of the various lineages of Salvia and related genera is characterized and an evolutionary interpretat ...[more]

PMID: 16926227

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Project description:Background and Aims:Salvia is the largest genus within Lamiaceae, with about 980 species currently recognized. East Asia, with approx. 100 species, is one of the three major biodiversity centres of Salvia. However, relationships within this lineage remain unclear, and the staminal lever mechanism, which may represent a key innovation within the genus, has been understudied. By using six genetic markers and nearly comprehensive taxon sampling, this study attempts to elucidate relationships and examine evolutionary trends of staminal development within the East Asia (EA) Salvia clade. Methods:Ninety-one taxa of EA Salvia were sampled and 34 taxa representing all other major lineages of Salvia were included for analysis. Two nuclear [internal transcribed spacer (ITS) and external transcribed spacer (ETS)] and four chloroplast (psbA-trnH, ycf1-rps15, trnL-trnF and rbcL) DNA markers were used for phylogenetic analysis employing maximum parsimony (MP), maximum likelihood (ML) and BEAST, with the latter also used to estimate divergence times. Key Results:All Salvia species native to East Asia form a clade, and eight major subclades (A-G) were recognized. Subclade A, comprising two limestone endemics (S. sonchifolia and S. petrophila), is sister to the remainder of EA Salvia. Six distinct stamen types were observed within the EA clade. Stamen type A, with two fully fertile posterior thecae, only occurs in S. sonchifolia and may represent the ancestral stamen type within EA Salvia. Divergence time estimates showed that the crown of EA Salvia began to diversify approx. 17.4 million years ago. Conclusions:This study supports the adoption of a broadly defined Salvia and treats EA Salvia as a subgenus, Glutinaria, recognizing eight sections within this subgenus. Stamen type A is ostensibly plesiomorphic within EA Salvia, and the other five types may have been derived from it. Staminal morphology has evolved in parallel within the EA Salvia, and staminal structure alone is inadequate to delimit infrageneric categories.

Project description:Glechoma L. (Lamiaceae) is distributed in eastern Asia and Europe. Understanding chromosome evolution in Glechoma has been strongly hampered by its small chromosomes, constant karyotype and polyploidy. Here phylogenetic patterns and chromosomal variation in Glechoma species are considered, using genome sizes, chromosome mapping of 5S and 35S rDNAs by fluorescence in situ hybridisation (FISH), and phylogenetic analyses of internal transcribed spacers (nrITS) of 35S rDNA and 5S rDNA NTS sequences. Species and populations of Glechoma are tetraploid (2n = 36) with base chromosome number of x = 9. Four chromosomes carry pericentric 5S rDNA sites in their short arms in all the species. Two to four of these chromosomes also carry 35S rDNA in subterminal regions of the same arms. Two to four other chromosomes have 35S rDNA sites, all located subterminally within short arms; one individual possessed additional weak pericentric 35S rDNA signals on three other chromosomes. Five types of rDNA locus distribution have been defined on the basis of 35S rDNA variation, but none is species-specific, and most species have more than one type. Glechoma hederacea has four types. Genome size in Glechoma ranges from 0.80 to 0.94 pg (1C), with low levels of intrapopulational variation in all species. Phylogenetic analyses of ITS and NTS sequences distinguish three main clades coinciding with geographical distribution: European (G. hederacea-G. hirsuta), Chinese and Korean (G. longituba), and Japanese (G. grandis). The paper presents the first comparative cytogenetic analyses of Glechoma species including karyotype structure, rDNA location and number, and genome size interpreted in a phylogenetic context. The observed variation suggests that the genus is still in genomic flux. Genome size, but not rDNA loci number and distribution, provides a character for species delimitation which allows better inferences of interspecific relationships to be made, in the absence of well-defined morphological differentiation.

Project description:The evolutionary relationships of Salvia have been difficult to estimate. In this study, we used the Next Generation Sequencing method Hyb-Seq to evaluate relationships among 90 Lamiaceae samples, including representatives of Mentheae, Ocimeae, Salvia subgenera Audibertia, Leonia, Salvia, and 69 species of subgenus Calosphace, representing 32 of Epling's sections. A bait set was designed in MarkerMiner using available transcriptome data to enrich 119 variable nuclear loci. Nuclear and chloroplast loci were assembled with hybphylomaker (HPM), followed by coalescent approach analyses for nuclear data (ASTRAL, BEAST) and a concatenated Maximum Likelihood analysis of chloroplast loci. The HPM assembly had an average of 1,314,368 mapped reads for the sample and 527 putative exons. Phylogenetic inferences resolved strongly supported relationships for the deep-level nodes, agreeing with previous hypotheses which assumed that subgenus Audibertia is sister to subgenus Calosphace. Within subgenus Calosphace, we recovered eight monophyletic sections sensu Epling, Cardinalis, Hastatae, Incarnatae, and Uricae in all the analyses (nDNA and cpDNA), Biflorae, Lavanduloideae, and Sigmoideae in nuclear analyses (ASTRAL, BEAST) and Curtiflorae in ASTRAL trees. Network analysis supports deep node relationships, some of the main clades, and recovers reticulation within the core Calosphace. The chloroplast phylogeny resolved deep nodes and four monophyletic Calosphace sections. Placement of S. axillaris is distinct in nuclear evidence and chloroplast, as sister to the rest of the S. subg. Calosphace in chloroplast and a clade with “Hastatae clade” sister to the rest of the subgenus in nuclear evidence. We also tested the monophyly of S. hispanica, S. polystachia, S. purpurea, and S. tiliifolia, including two samples of each, and found that S. hispanica and S. purpurea are monophyletic. Our baits can be used in future studies of Lamiaceae phylogeny to estimate relationships between genera and among species. In this study, we presented a Hyb-Seq phylogeny for complex, recently diverged Salvia, which could be implemented in other Lamiaceae.

Dataset Information

Staminal evolution in the genus Salvia (Lamiaceae): molecular phylogenetic evidence for multiple origins of the staminal lever.

Publications

Staminal evolution in the genus Salvia (Lamiaceae): molecular phylogenetic evidence for multiple origins of the staminal lever.

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