02387nas a2200181 4500008004100000245011600041210006900157300001200226490000800238520171900246653008501965100001902050700002402069700002402093700002202117700001902139856004702158 2003 eng d00aBiogeography of discontinuously distributed hydrophytes: a molecular appraisal of intercontinental disjunctions0 aBiogeography of discontinuously distributed hydrophytes a molecu a917-9320 v1643 a

The extraordinarily wide distributional ranges of aquatic flowering plants have long stimulated phytogeographical discussion. Although aquatic plants occur rarely among the angiosperms, they represent a disproportionately large number of taxa with broad distributions including various intercontinental disjunctions that are manifest even at the species level. Throughout the nineteenth and early twentieth centuries, long-range dispersal by waterfowl was the prevailing explanation for widespread aquatic plant distributions. This explanation gradually fell into disfavor as biologists raised doubts as to the ability of waterfowl to transport propagules across the extensive transoceanic distances between the continents on which an assortment of aquatic taxa now reside. During the twentieth century, the development of biogeographical displacement theory, i.e., “continental drift,” steadily began to supplant dispersal as the preferred explanation for discontinuous angiosperm distributions. Our study assesses the dispersal/displacement hypotheses from a temporal standpoint using molecular estimates of divergence time for a diverse sample of phylogenetically related aquatic taxa that exhibit discontinuous intercontinental distributions. With few exceptions, we found divergence times that are far too recent to implicate continental drift as a major determinant of discontinuous distributions in aquatic plants. We suggest that long-distance dispersal by birds should continue to be regarded as a viable explanation for widely disjunct aquatic plant distributions, although such dispersal is likely to have involved a combination of overland as well as transoceanic migratory routes.

10abiogeography, hydrophyte, aquatic plant, intercontinental disjunction, dispersal1 aLes, Donald, H1 aCrawford, Daniel, J1 aKimball, Rebecca, T1 aMoody, Michael, L1 aLandolt, Elias uhttp://www.jstor.org/stable/10.1086/37865001980nas a2200205 4500008004100000245010600041210006900147300001000216490000800226520135500234653001401589653001901603653002301622653001301645653001501658653001401673100001801687700002201705856004701727 2000 eng d00aFloral structure and development of Acoraceae and its systematic relationships with basal angiosperms0 aFloral structure and development of Acoraceae and its systematic a23-410 v1613 a

Flower development and anatomy of Acorus calamus and flower anatomy of A. gramineus were studied. Findings were compared with published reports on paleoherbs. Important developmental features include an abaxially median tepal that is initiated first and is similar to a flower-subtending bract and unidirectional flower development with an inversion of organ initiation sequence in the second tepal whorl. The mature gynoecium is largely synascidiate, but early development of carpels is plicate, and the apocarpous portion persists up to anthesis. The carpels form dorsal bulges on the style, enclosing longitudinal intercarpellary slits. The dominance of the synascidiate portion and the apical position of the placenta result from a late and distinct basal elongation of the gynoecium. Stigma, pollen transmitting tract, and ovary are filled with secretion. Secretory papillae are present from the stigma to the placenta; papillae also occur on the rims of the integuments of the ovules. In the uppermost part of the inflorescence, the adaxial floral sectors are reduced in number and structure, and at the apex of the inflorescence, a peloria-like structure is formed. Developmental and morphological similarities seem to be closer between Acorus and Piperales than between Acorus and other magnoliids.

10aAcoraceae10acomplex organs10aflower development10amonocots10apaleoherbs10aPiperales1 aBuzgo, Matyas1 aEndress, Peter, K uhttp://www.jstor.org/stable/10.1086/314241