Topic
Micranthes
About: Micranthes is a research topic. Over the lifetime, 17 publications have been published within this topic receiving 361 citations.
Papers
TL;DR: Deep-level relationships within both Saxifraga s.
Abstract: To elucidate relationships at deep levels within Saxifragaceae we analyzed phylogenetically a data set of sequences for six DNA regions, four representing the chloroplast genome (rbcL, matK, trnL-trnF, psbA-trnH) and two from the nuclear genome (ITS and expansion segments of the 26S rDNA). A total of 6676 bp was aligned per taxon, 4559 bp and 1878 bp from the chloroplast and nuclear genomes, respectively. Chloroplast and nuclear trees agreed closely, prompting analysis of a combined, six-gene data set. Application of both parsimony and maximum likelihood methods yielded similar topologies. The use of different ITS alignments and the exclusion of hard-to-align ITS regions had little impact on either the final nuclear-based topology, or the shortest trees from the analysis of six genes. The affinities of two monotypic genera (Saxifragella and Saxifragodes) endemic to Tierra del Fuego were elucidated. Saxifragella is an early branching member of the North Temperate genus Saxifraga s. str.; Saxifragodes is sister to Cascadia, a genus endemic to Oregon and Washington. Long-distance dispersal from east Asia or western North America to South America may have played an important role in forming these and other similar disjunctions in the family. A number of well-supported clades are present, including Saxifraga s. str., Micranthes, Saxifragopsis/Astilbe, Chrysosplenium/Peltoboykinia, and the Boykinia and Heuchera groups. The use of additional characters has provided greatly increased resolution and internal support at deep levels. Saxifragaceae comprise two major lineages: Saxifraga s. str. (including Saxifragella) and all other genera of the family (the heucheroids). This major split is accompanied by general biogeographical and morpihological differences. Whereas Saxifraga s. str. is largely arctic to alpine in occurrence, the heucheroid clade is largely temperate in distribution, Saxifraga s. str. has a relatively uniform floral morphology (generally actinomorphic; 5 sepals, 5 petals, 10 stamens, 2 carpels), whereas the heucheroid clade encompasses actinomorphic and zygomorphic forms, as well as variation in the number of sepals, petals, stamens, and carpels. Deep-level relationships within both Saxifraga s. str. and the heucheroid clade are well resolved and supported. A phylogenetic classification of the family is provided.
108 citations
TL;DR: The molecular phylogenetic tree from the combined dataset revealed eight well-supported clades of Micranthes, and it is suggested that these eight groups should be recognized as sections ofMicranthes.
25 citations
TL;DR: The distribution of trichome types generally supports Engler's classification of the genus Saxifraga, and is compatible with other evidence from palynology, embryology and seed morphology.
Abstract: Trichomes on flower pedicels and leaves were examined in 213 species of Saxifraga L. and in the monotypic, segregate genera Zahlbrucknera Reichenb., Saxifragella Engl., Saxifragodes D. M. Moore and Saxifragopsis Small. Pedicel trichomes were found to be better taxonomic characters than foliar ones. Six main trichome types were identified: i) multiseriate, glandular; ii) uniseriate, glandular; iii) sessile, multicellular, glandular; iv) multiseriate, eglandular; v) uniseriate, eglandular; vi) unicellular, eglandular. The different types were distributed (except in certain species) on pedicels as follows. Multiseriate, glandular types occur in four series of Saxifraga sect. Micranthes (Haw.) D. Don, part of sect. Gymnopera D. Don, and in sects Ciliatae Haw., Trachyphyllum Gaudin, Xanthizoon Griseb., Ligulatae Haw., Porophyllum Gaudin, Porphyrion Tausch and Irregulares Haw. They also occur in the genus Saxifragopsis. Uniseriate, glandular types occur in five series of Saxifraga sect. Micranthes, part of sect. Gymnopera and Irregulares, and in sects. Miscopetalum (Haw.) Sternb., Cymbalaria, Griseb. Tridactylites (Haw.) Engl., Saxifraga and Stoloniferae Haw. They also occur in the genus Zahlbrucknera. Eglandular, multicellular trichomes occur occasionally in Saxifraga sects Micranthes and Gymnopera, more frequently in sects Ciliatae and Ligulatae, and are ubiquitous in sects Xanthizoon, Porophyllum and Porphyrion. Eglandular, unicellular trichomes occur only in Saxifragopsis and Saxifragodes. Sessile, glandular trichomes occur in a group of species from Saxifraga sect. Stoloniferae. Saxifragella is glabrous. This taxonomic distribution of trichome types generally supports Engler's classification of the genus, and is compatible with other evidence from palynology, embryology and seed morphology. The taxonomic disposition of the few exceptional species is discussed.
24 citations
TL;DR: Molecular data confirmed the monophyly of the genus Micranthes and the consistency of the existing systematic treatments based on morphological criteria and added weight to the view that Micranthe species native from the Iberian Peninsula should be included into Micanthes sect.
Abstract: Recent phylogenetic studies have shown that Saxifraga, as currently understood, must be divided into two genera: Saxifraga L. sensu stricto and Micranthes Haw. To better understand the evolutionary history of these two genera, we performed phylogenetic analyses inferred from the nuclear ribosomal sequences from the internal transcribed spacer and the sequences of the plastid DNA (rbcL). Our molecular data confirmed the monophyly of the genus Micranthes and the consistency of the existing systematic treatments based on morphological criteria. Moreover, Micranthes species native from the Iberian Peninsula (i.e. M. clusii, M. lepismigena and M. stellaris) should be included into Micranthes sect. Arabisa.
24 citations
TL;DR: It is demonstrated that superior ovaries, although widely reported for various members of the family, are unusual and limited to a few species of Micranthes and Saxifraga and to male flowers of the dioecious Tanakaea among investigated genera.
Abstract: We discuss the structural homology of the gynoecium and the developmental variations associated with ovary diversity in Saxifragaceae. Diverse ovary positions are present within most of the major clades in the family. We demonstrate that superior ovaries, although widely reported for various members of the family, are unusual and limited to a few species of Micranthes and Saxifraga and to male flowers of the dioecious Tanakaea among investigated genera. Most species reported to have superior ovaries actually have developmentally epigynous flowers in which the ovary has a small portion below the insertion of the perianth and androecium. Such ovaries of epigynous flowers that mimic superior ovaries are termed “pseudosuperior.” Labile shifts in proportioned growth of that part of the ovary above the insertion of the perianth and androecium to that below their insertion have created extensive variation in ovary position among closely related taxa, e.g., in both Saxifraga and Micranthes. The heterostylous Jeps...
23 citations
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| Year | Papers |
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| 2016 | 1 |
| 2015 | 2 |
| 2013 | 1 |
| 2011 | 1 |
| 2009 | 1 |
| 2008 | 1 |