Person:

Davis, Charles

Species of Taxus, particularly Taxus baccata, have long been cultivated as ornamentals in Europe and North America. Ten species of Taxus are generally recognized, but phylogenetic relationships among these species remain unclear. We used sequences of the nuclear ribosomal DNA ITS region to infer phylogenetic relationships. Three of the four New World species form a well-supported clade, within which the Pacific coastal species. T. brevifolia is sister to a clade containing T. floridana and T. globosa of northwestern Florida and northern Mexico, respectively. Taxus canadensis, which is more widely distributed in eastern North America, appears to be more closely related to Old World taxa than to other New World species. This relationship, though weakly supported in our analysis, is consistent with leaf anatomical features. Taxus chinensis and T. mairei of southeast Asia form a clade, which is sister to a clade containing T. cuspidata of Japan and northeastern China, and T. baccata of Europe and North Africa. Our ITS phylogeny implies that intercontinental disjunctions in Taxus entailed at least two vicariance events: an initial split between the New World T. floridana-T. brevifolia-T. globosa clade and the rest, and a later split separating T. canadensis from the Old World species.

Torreya, composed of five to seven species, is distributed disjunctly in easten Asia and the eastern and western United States. In this study, interspecific relationships of Torreya were examined on the basis of sequences of the nrDNA ITS region. Torreya taxifolia and T. californica of the New World form a clade, as do the Old World species. This result suggests that the previous division of Torreya into two sections does not reflect phylogenetic relationships and that the diagnostic character for the two sections, namely rumination of albumen, is homoplastic. It is possible that the present distribution of species of Torreya resulted from a single vicariance event separating the Old World and New World. However, the modern species are apparently young in age, and it will be necessary to integrate older fossils to ascertain the deeper biogeographic history of the genus.

The evolution of floral zygomorphy is an important innovation in flowering plants and is thought to arise principally from specialization on various insect pollinators. Floral morphology of neotropical Malpighiaceae is distinctive and highly conserved, especially with regard to symmetry, and is thought to be caused by selection by its oil-bee pollinators. We sought to characterize the genetic basis of floral zygomorphy in Malpighiaceae by investigating CYCLOIDEA2-like (CYC2-like) genes, which are required for establishing symmetry in diverse core eudicots. We identified two copies of CYC2-like genes in Malpighiaceae, which resulted from a gene duplication in the common ancestor of the family. A likely role for these loci in the development of floral zygomorphy in Malpighiaceae is demonstrated by the conserved pattern of dorsal gene expression in two distantly related neotropical species, Byrsonima crassifolia and Janusia guaranitica. Further evidence for this function is observed in a Malpighiaceae species that has moved to the paleotropics and experienced coincident shifts in pollinators, floral symmetry, and CYC2-like gene expression. The dorsal expression pat-tern observed in Malpighiaceae contrasts dramatically with their actinomorphic-flowered relatives, Centroplacaceae (Bhesa paniculata) and Elatinaceae (Bergia texana). In particular, B. texana exhibits a previously undescribed pattern of uniform CYC2 expression, suggesting that CYC2 expression among the actinomorphic ancestors of zygomorphic lineages may be much more complex than previously thought. We consider three evolutionary models that may have given rise to this patterning, including the hypothesis that floral zygomorphy in Malpighiaceae arose earlier than standard morphology-based character reconstructions suggest.

Premise of the study: The Malpighiaceae include ∼1300 tropical flowering plant species in which generic definitions and intergeneric relationships have long been problematic. The goals of our study were to resolve relationships among the 11 generic segregates from the New World genus Mascagnia, test the monophyly of the largest remaining Malpighiaceae genera, and clarify the placement of Old World Malpighiaceae.

Methods: We combined DNA sequence data for four genes (plastid ndhF, matK, and rbcL and nuclear PHYC) from 338 ingroup accessions that represented all 77 currently recognized genera with morphological data from 144 ingroup species to produce a complete generic phylogeny of the family.

Key results and conclusions: The genera are distributed among 14 mostly well-supported clades. The interrelationships of these major subclades have strong support, except for the clade comprising the wing-fruited genera (i.e., the malpighioid+Amorimia, Ectopopterys, hiraeoid, stigmaphylloid, and tetrapteroid clades). These results resolve numerous systematic problems, while others have emerged and constitute opportunities for future study. Malpighiaceae migrated from the New to Old World nine times, with two of those migrants being very recent arrivals from the New World. The seven other Old World clades dispersed much earlier, likely during the Tertiary. Comparison of floral morphology in Old World Malpighiaceae with their closest New World relatives suggests that morphological stasis in the New World likely results from selection by neotropical oil-bee pollinators and that the morphological diversity found in Old World flowers has evolved following their release from selection by those bees.

DNA sequences of nine genes (plastid: atpB, matK, and rbcL; mitochondrial: atp1, matR, mtSSU, and mtLSU; nuclear: 18S and 26S rDNAs) from 100 species of basal angiosperms and gymnosperms were analyzed using parsimony, Bayesian, and maximum likelihood methods. All of these analyses support the following consensus of relationships among basal angiosperms. First, Amborella, Nymphaeaceae, and Austrobaileyales are strongly supported as a basal grade in the angiosperm phylogeny, with either Amborella or Amborella and Nymphaeales as sister to all other angiosperms. An examination of nucleotide substitution patterns of all nine genes ruled out any possibility of analytical artifacts because of RNA editing and GC-content bias in placing these taxa at the base of the angiosperm phylogeny. Second, Magnoliales are sister to Laurales and Piperales are sister to Canellales. These four orders together constitute the magnoliid clade. Finally, the relationships among Ceratophyllum, Chloranthaceae, monocots, magnoliids, and eudicots are resolved in different ways in various analyses, mostly with low support. Our study indicates caution in total evidence approaches in that some of the genes employed ( e. g., mtSSU, mtLSU, and nuclear 26S rDNA) added signal that conflicted with the other genes in resolving certain parts of the phylogenetic tree.

The Malpighiaceae are a family of similar to ~1250 species of predominantly New World tropical flowering plants. Infrafamilial classification has long been based on fruit characters. Phylogenetic analyses of chloroplast DNA nucleotide sequences were analyzed to help resolve the phylogeny of Malpighiaceae. A total of 79 species. representing 58 of the 65 currently recognized genera. were studied. The 3' region of the gene ndhF was sequenced for 77 species and the noncoding intergenic spacer region trnL-F was sequenced for 65 species' both sequences were obtained for the outgroup, Humiria (Humiriaceae), Phylogenetic relationships inferred from these data,ets are largely congruent with one another and with results from combined analyses. The family is divided into two major clades, recognized here as the subfamilies Byrsonimoideae (New World only) and Malpighioideae (New World and Old World). Niedenzu's tribes are all polyphyletic, suggesting extensive convergence on similar fruit types; only de Jussieu's tribe Gaudichaudieae and Anderson's tribes Acmanthereae and Galphimieae are monophyletic. Fleshy fruits evolved three times in the family and bristly fruits at least three times. Among the wing-fruited vines, which constitute more than half the diversity in the family, genera with dorsal-winged samaras are fairly well resolved, while the resolution of taxa with lateral-winged samaras is poor. The trees suggest a shift from radially symmetrical pollen arrangement to globally symmetrical pollen at the base of one of the clades within the Malpighioideae. The Old World taxa fall into at least six and as many as nine clades.

Climate change has led to major changes in the phenology (the timing of seasonal activities, such as flowering) of some species but not others. The extent to which flowering-time response to temperature is shared among closely related species might have important consequences for community-wide patterns of species loss under rapid climate change. Henry David Thoreau initiated a dataset of the Concord, Massachusetts, flora that spans ≈150 years and provides information on changes in species abundance and flowering time. When these data are analyzed in a phylogenetic context, they indicate that change in abundance is strongly correlated with flowering-time response. Species that do not respond to temperature have decreased greatly in abundance, and include among others anemones and buttercups [Ranunculaceae pro parte (p.p.)], asters and campanulas (Asterales), bluets (Rubiaceae p.p.), bladderworts (Lentibulariaceae), dogwoods (Cornaceae), lilies (Liliales), mints (Lamiaceae p.p.), orchids (Orchidaceae), roses (Rosaceae p.p.), saxifrages (Saxifragales), and violets (Malpighiales). Because flowering-time response traits are shared among closely related species, our findings suggest that climate change has affected and will likely continue to shape the phylogenetically biased pattern of species loss in Thoreau's woods.

Madagasikaria andersonii is described here as a new genus and species of Malpighiaceae from Madagascar. The phylogenetic placement of Madagasikaria was estimated by using combined data from ndhF and trnL-F chloroplast sequences and phytochrome (PHYC) and ITS nuclear sequences. It forms a strongly supported clade with the Malagasy endemic genera Rhynchophora and Microsteira. Despite nearly identical floral morphology among species in this elude (here called the madagasikarioid clade), these genera are easily distinguishable on the basis of their fruits, The schizocarpic fruits of Madagasikaria have distinctive mericarps. Each mericarp has a lateral wing, which completely encircles the nut, and a peculiar dorsal wing, which folds over on itself. The morphology of this fruit suggests that the homology of the unusual wing in Rhyncnophora is lateral in nature and represents a reduced wing similar to the lateral wing in Madagasikaria. Taxa in the madagasikarioid clade all appear to be morphologically androdioecious and functionally dioecious, producing both staminate and "bisexual" (i.e., functionally carpeliate) individuals. This condition appears to be exceedingly rare in flowering plants and has important implications for floral evolution within Malpighiaccae. Neotropical Malpighiaceae are pollinated by specialized oil-collecting anthophorine bees of the tribe Centridini and exhibit highly conserved floral morphology despite tremendous diversity in fruit morphology and habit. These oil-collecting bees are absent from the paleotropics, where most members of the Malpighiaceae lack both the oil glands and the typical floral orientation crucial to pollination by neotropical oil-collecting bees. The madagasikarioids represent one shift from the neotropical pollination syndrome among Old World Malpighiaceae.