Epiphytes are one of the most ubiquitous elements of tropical forest canopies, including seasonally dry tropical forests. Given the temporal variation in weather conditions in the latter, epiphyte populations may be subject to wide temporal variation in seedling recruitment, reproductive success, vegetative propagation and mortality rate. In this study, we use a 3-y demographic data set for Tillandsia brachycaulos to project its long-term population dynamics through the use of average and periodic matrices, as well as stochastic simulations. The results show that demographic behaviour varied over the 3 years of study, apparently in relation to rainfall. The first 2 years yielded a low λ value (0.79 and 0.80 – although only the former was significantly lower than unity), while the third year resulted in a λ = 1.08 (not significantly different from 1.0). When incorporating this demographic variation in an average matrix, a periodic matrix and stochastic simulations, the resulting overall λ was below unity in all three cases. The projections of the stochastic simulations suggest that the population would be able to persist in the long run only if the frequency of “good” years (defined here as those with an August rainfall above 200 mm) was above 0.6, which appears unlikely given that global warming might result in a lower frequency of rainy years in tropical dry forests.
There are 26 phylogenetic studies for Bromeliaceae based on different sources of evidence. Despite this broad phylogenetic coverage of Bromeliaceae, however, the available phylogenetic data display a scattered sampling, with little overlap among different types of evidence. The aim of this study is to integrate the available phylogenetic information of the Bromeliaceae in one hypothesis using a supertree. To test which of them integrates best the information for Bromeliaceae, nine supertree methods were employed: Avcon, MSS, MinFlip, MMC, MRP, PhySIC_IST, Robinson-Foulds Supertree, Sfit, and SuperFine. Supertrees were compared with a reference tree, generated from the maximum likelihood (ML) analysis of a supermatrix integrated by 120 taxa of Bromeliaceae and seven cpDNA regions. In order to select which method best reconstructs the most robust phylogeny, two different sets of source trees were used: (i) those generated from the analysis of each individual DNA regions; and (ii) four selected phylogenies (from the 26 published works). We used the consensus fork index, normalized partition metric, patristic distance coefficient, and the Shimodaira-Hasegawa test to compare supertrees with the reference tree. The best performing methods were used to construct a supertree using all phylogenies of Bromeliaceae. The SuperFine method generated the best supertree. The lack of overlapping among phylogenies was the major limiting factor for the integration of the phylogenetic information of Bromeliaceae. Nonetheless, supertree methods helped in the identification of poorly sampled groups, as well as to explore levels of agreement among published phylogenetic studies for Bromeliaceae.
Two new Maxillaria species from the Venezuelan Guayana, M. foldatsiana and M. santanae, are described and illustrated. One highly variable species, M. auyantepuiensis, is discussed, and a new subspecific taxon is proposed. Maxillaria tenuis is noted as a new record for the Venezuelan flora.Maxillaria Ruiz & Pavon is the largest genus itary flowers originating from the pseudobulb has of the subtribe Maxillarinae, with about 400-450 or from the internodes of the rhizome (the Camaspecies ranging from Mexico and the West Indies ridium alliance). The flowers may be minute to to southern Brazil. The genus reaches its highest very large and showy and are variable in many development in the Andes, but Middle America, respects, although the column is always basally southern Brazil, the Amazonian Basin, and the produced into a more or less well-developed col-Guayanas are well represented. The species of umn-foot to which the labellum is hinged. Orni-Maxillaria usually grow in places of heavy rainfall thidium Salisb. has a rigidly attached, unhinged but often can be found in places with a marked labellum, and thus we feel it should be recognized, dry season. They grow in almost every vegetation even though many authors do not do so. As a association and at any elevation from sea level to member of the subtribe Maxillarinae, all Maxilnear the snow line but are especially common in laria species have four dorsiventrally flattened polrainforest or cloud forests at 500-2,000 m. Most linia in two unequal pairs, more or less well-demembers of the genus are epiphytic, but it is not veloped, usually semilunate viscidium, and variously unusual to find lithophy tic or even terrestrial species, sized and shaped stipites or no stipe at all. particularly in open, humid places. The vegetative In Venezuela there have been recorded about morphology is very variable, ranging from tiny 75 species of Maxillaria, of which 47 are known plants less than 1 cm high to plants 2 m long. in the Venezuelan Guayana. All major groups with-They are usually pseudobulbous, sympodial plants, in the genus are represented in southern Venezuela, but pseudobulbless, almost monopodial species are In terms of numbers of species, Maxillaria is only not unknown. Rhizomes may be short, making surpassed in the Venezuelan Guayana by Fleucaespitose plants, but many species have long rothallis R. Br. (ca. 57 species) and Epidendrum creeping primary stems; these may be appressed L. (ca. 51 species). The next-largest genus is Octo substrate for their entire lengths or only attached tomeria R. Br. (ca. 29 species). at their bases to the host, making erect, ascendent, or pendulous plants.A survey of Maxillaria species, associated with the Orchidaceae treatment for Steyermark's Flora Maxillaria is characterized generically by sol-of the Venezuelan Guayana (Carnevali et al., in 1 We are grateful to Lie. Bruno Manara for the drawings and criticisms of the Latin diagnoses and to Dr. Julian Steyermark for permitting us to use drawings originally intended for publication in hi...
Three new species of Hechtia from the Mexican State of Oaxaca are herein proposed as new: Hechtia flexilifolia, H. huamelulaensis, and H. nivea, from the physiogeographical provinces of Mixteca Alta, Costas del Sur, and Sierras Centrales de Oaxaca respectively. All three species are described and illustrated. Iconography provided features plants in habitat and under cultivation. An assessment of their conservation status sensu IUCN criteria is presented as well. We also discuss and illustrate the three growth patterns identified at this time in the genus.
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