02733nas a2200157   4500008004100000245017900041210006900220300001200289490000800301520204500309653010502354100002402459700002102483700002102504856005002525       2005                        eng d00aEvolutionary transitions among flowers of perianthless Piperales: inferences from inflorescence and flower development in the anomalous species Peperomia fraseri (Piperaceae)0 aEvolutionary transitions among flowers of perianthless Piperales  a925-9430 v1663 aFloral and inflorescence structure and ontogeny are described in detail in Peperomia fraseri, an anomalous species of Piperaceae that differs in several respects from other species of Peperomia and other perianthless Piperales (Piperaceae and Saururaceae). Inflorescence structure is atypical in this species, with numerous spikes arranged spirally on a long raceme. There is a gender distribution of flowers along each spike, with the proximal (lower) part bearing bisexual flowers and the distal (upper) region bearing female flowers. Furthermore, there is a high degree of polymorphism in the structure (including presence or absence) of flower-subtending bracts in the same inflorescence. Bract suppression at the basalmost abaxial position in P. fraseri could be explained by a strong inhibitory activity of the spike-subtending bract or its primordium. Bract suppression among scattered flowers in the lower (bisexual) region is interpreted as an example of somatic instability. By contrast, more distal bract and stamen suppression seems to be part of a general tendency to flower reduction toward the spike apex in P. fraseri, where spatial constraints in the inflorescence control the size and shape of the bract and floral primordia, resulting in stamen suppression in smaller primordia. However, it is difficult to understand why an abracteate flower is formed in P. fraseri rather than a sterile bract, as in Peperomia hispidula. Furthermore, in contrast with most other Piperaceae, P. fraseri has no apical residuum on mature spikes; at least some partial inflorescences bear a terminal flowerlike structure, although this more closely resembles those of some Saururaceae than the "true" terminal flower of perianth-bearing Piperales, such as Aristolochiaceae. Peperomia fraseri and other atypical members of Piperaceae represent potentially useful models for examination of patterns of bract and stamen loss in perianthless Piperales, in which spatial constraints in the developing spike are important for floral construction.10abasal angiosperms, bract, floral evolution, ontogeny, Piperales, stamen suppression, terminal flower1 aRemizowa, Margarita1 aRudall, Paula, J1 aSokoloff, Dmitry  uhttps://juncaginaceae.myspecies.info/node/30002203nas a2200157   4500008004100000245006500041210006500106300001200171490000800183520165000191653009301841100002501934700002101959700001601980856004901996       2001                        eng d00aPhylogenetic patterns in Northern Hemisphere plant geography0 aPhylogenetic patterns in Northern Hemisphere plant geography  aS41-S520 v1623 aGeological and climatological processes that have impacted the biota of the Northern Hemisphere during the Tertiary are expected to yield little resolution when are cladograms are compared without taking the timing of diversification into account. In an attempt to establish a set of appropriate phylogenetic comparisons, we distinguish between a Pacific track involving (minimally) China, Japan, and eastern North America but not Europe, and an Atlantic track involving China, Europe, and eastern North America but not Japan (or, in most cases, western North America). Within the two Atlantic-track taxa considered here - Liquidambar and Cercis - European and North American species are more closely related to one another than they are to the Asian species. Within a set of five Pacific-track taxa - Hamamelis, Weigela-Diervilla, Triosteum, Buckleya, and Torreya - we see all possible relationships involving China, Japan, and eastern North America. Estimates of minimum divergence times between Old World and New World lineages, based on molecular and fossil evidence, differ markedly between the two Atlantic-track clades. Among the Pacific-track taxa, we find no correlation between pattern of area relationships and estimated divergence times of the Old World-New World disjuncts. Instead, we see a wide range in the timing of these splitting events among and within phylogenetic patterns. Despite the existence of a variety of patterns, inferred ancestral areas and divergence times can be explained by assuming initial diversificiation within Asia in a number of lineages, followed by iterative trans-Beringian dispersion and vicariance.10abiogeography, dispersal, vicariance, phylogeny, Northern Hemisphere, North America, Asia1 aDonoghue, Michael, J1 aBell, Charles, D1 aLi, Jianhua  uhttps://juncaginaceae.myspecies.info/node/92