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Judd W.S.,University of Florida | Majure L.C.,Conservation and Collections | Skean J.D.,Albion College | Neubig K.M.,Southern Illinois University Carbondale
Rhodora | Year: 2015

In the course of a taxonomic revision of several clades of Greater Antillean Melastomataceae, we discovered a previously undescribed species, Miconia abscondita, from the Massif de la Hotte, Haiti. Miconia abscondita is based on a vegetative collection by Swedish botanist, E. L. Ekman, which was made in 1926. This new species is a member of the Mecranium clade, a group well supported on the basis of both morphological and molecular data, but which is highly embedded within the phylogenetic structure of the genus Miconia. Miconia abscondita is clearly placed within the Mecranium clade on the basis of DNA sequence data, and this placement also is supported by the form of its hairs and, especially, the pattern of stem indumentum; however, it matches no currently described species. Miconia abscondita is thus described, illustrated, and compared with putatively related and/or phenetically similar species. The discovery of M. abscondita brings to 25 the number of recognized species within the Mecranium clade and to 11 the number of species occurring in the Massif de la Hotte, Haiti, a region of exceptional biodiversity that is under continuous threat from anthropogenic pressure. © 2015 by the New England Botanical Club.

Judd W.S.,University of Florida | Clase T.,Jardin Botanico National Dr. Rafael M. Moscoso | Majure L.C.,Conservation and Collections
Journal of the Botanical Research Institute of Texas | Year: 2015

Miconia alainii, a species previously known only from specimens in vegetative condition or with immature fruits, is now known from flowering material collected by the second author in the Sierra de Baoruco, Dominican Republic. A revised description of this species, including previously unknown floral characters, is presented. © Copyright 2015 Botanical Research Institute of Texas.

Hultine K.R.,Conservation and Collections | Burtch K.G.,University of Utah | Ehleringer J.R.,University of Utah
Global Change Biology | Year: 2013

Air temperatures in the arid western United States are predicted to increase over the next century. These increases will likely impact the distribution of plant species, particularly dioecious species that show a spatial segregation of the sexes across broad resource gradients. On the basis of spatial segregation patterns, we hypothesized that temperature increases will have a greater negative impact on female plants compared with co-occurring male plants of dioecious species. This hypothesis was tested by examining the whole-plant carbon and water relations of 10-year-old female (n = 18) and male (n = 13) Acer negundo Sarg. trees grown in a common garden in Salt Lake City, UT. The trees were established from cuttings collected where the growing season temperature averaged about 6.5 °C cooler than at the common garden. During May and June, stem sap flux (Js) was similar between genders, but averaged 25% higher in males during the warmer months of July and August. Daytime canopy stomatal conductance (gs) per unit leaf area was 12% higher in females in May : June, but was 11% higher in males in July : August. We combined measurements of sap flux-scaled transpiration with measurements of tree allometry and δ13C of leaf soluble sugars to estimate whole-tree carbon assimilation (Atree) and water use efficiency (WUE) (Atree : Etree). Atree was similar between genders until late August when Atree was 32% higher in male trees. Atree : Etree was on average 7% higher in females than in males during the growing season. Patterns of Js, gs, Atree and Atree : Etree in the present study were in contrast to those previously reported for A. negundo genders under native growing season temperatures. Results suggest that the spatial segregation of the sexes could shift under global warming such that female plants lose their dominance in high-resource habitats, and males increase their dominance in relatively lower-resource habitats. © 2013 John Wiley & Sons Ltd.

Majure L.C.,Conservation and Collections | Majure L.C.,University of Florida | Neubig K.M.,University of Florida | Neubig K.M.,Southern Illinois University Carbondale | And 3 more authors.
International Journal of Plant Sciences | Year: 2015

Premise of research. The Sandpaper clade comprises a group of taxa endemic to the Greater Antilles and forms a subgroup of a larger Caribbean assemblage of Miconieae. Numerous species within this monophyletic group share striking morphological characters and thus traditionally have been considered close relatives. Recent phylogenetic work has shown that not all of these species are each other’s closest relatives, and they actually form three distinct clades: the Lima, Paralima, and Pseudolima clades. We reconstructed a phylogeny of these poorly known species to test patterns of morphological evolution and the biogeographic history of the clade. Methodology. We reconstructed a phylogeny of the Sandpaper clade using two plastid intergenic spacers (accD-psaI, psbK-psbL) and two nuclear ribosomal spacers (ITS, ETS) and then sequenced three more plastid spacers for the Lima clade (rpl32-trnL, trnV-ndhC, trnH-psbA) to provide better resolution among those species. The biogeographic history and the evolution of morphological traits were tested using maximum parsimony based on 12 mountain ranges in the Greater Antilles and 48 morphological characters, respectively. Pivotal results. The Sandpaper clade most likely originated in eastern Cuba, with subsequent dispersals to other parts of the island, as well as to Jamaica, Hispaniola, and Puerto Rico. In general, morphological characters shared by the Lima, Paralima, and Pseudolima clades evolved independently. All subclades of the Sandpaper clade can be recognized by suites of characters; however, unique synapomorphies for clades are rare. Conclusions. Eastern Cuba formed the starting point for the diversification of the Sandpaper clade, likely as a result of the diverse topography and associated ecological diversity (e.g., serpentine soils). This clade represents only a moderate-sized radiation of the Caribbean clade; however, the convergent nature of character evolution and the lack of unique synapomorphies for subclades underscore the lability of morphological characters in this group and the difficulty in recognizing these clades from a purely morphological standpoint. © 2015, by The University of Chicago. All rights reserved.

Williams D.G.,University of Wyoming | Hultine K.R.,Conservation and Collections | Dettman D.L.,University of Arizona
Journal of Experimental Botany | Year: 2014

Columnar cacti occur naturally in many habitats and environments in the Americas but are conspicuously dominant in very dry desert regions. These majestic plants are widely regarded for their cultural, economic, and ecological value and, in many ecosystems, support highly diverse communities of pollinators, seed dispersers, and frugivores. Massive amounts of water and other resources stored in the succulent photosynthetic stems of these species confer a remarkable ability to grow and reproduce during intensely hot and dry periods. Yet many columnar cacti are potentially under severe threat from environmental global changes, including climate change and loss of habitat. Stems in columnar cacti and other cylindrical-stemmed cacti are morphologically diverse; stem volume-to-surface area ratio (V:S) across these taxa varies by almost two orders of magnitude. Intrinsic functional trade-offs are examined here across a broad range of V:S in species of columnar cacti. It is proposed that variation in photosynthetic gas exchange, growth, and response to stress is highly constrained by stem V:S, establishing a mechanistic framework for understanding the sensitivity of columnar cacti to climate change and drought. Specifically, species that develop stems with low V:S, and thus have little storage capacity, are expected to express high mass specific photosynthesis and growth rates under favourable conditions compared with species with high V:S. But the trade-off of having little storage capacity is that low V:S species are likely to be less tolerant of intense or long-duration drought compared with high V:S species. The application of stable isotope measurements of cactus spines as recorders of growth, water relations, and metabolic responses to the environment across species of columnar cacti that vary in V:S is also reviewed. Taken together, our approach provides a coherent theory and required set of observations needed for predicting the responses of columnar cacti to climate change. © 2014 The Author.

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