534 research outputs found
Three new rarely collected or endangered species of Annonaceae from Venezuela
No full textThree new species of Annonaceae from Venezuela are described here: Cremastosperma venezuelanum Pirie, Klarobelia subglobosa Chatrou, and Pseudomalmea wingfieldii Chatrou. All three are represented by few collections (in comparison to those of other Neotropical species of Annonaceae). Klarobelia subglobosa and P. wingfieldii in particular are only known from a few individual specimens collected in areas vulnerable to habitat destruction. IUCN threat categories are assigned to these specie
Phylogeny reconstruction and molecular dating in four Neotropical genera of Annonaceae: the effect of taxon sampling in age estimations
No full textPreliminary results are presented comparing the timing of diversification in four predominantly Neotropical genera of Annonaceae: Cremastosperma, Duguetia, Guatteria and Mosannona. With the exception of a few basal lineages, the majority of the ca. 2500 species of the Annonaceae diverge into two major sister clades. One comprises relatively few, larger, genera (including Duguetia and Guatteria) representing roughly twice as many species in total and with an apparent rate of molecular divergence (revealed by branch lengths in most parsimonious trees) around three times as high as the other (including Cremastosperma and Mosannona), in which more genera each comprise fewer species. Explanations for the disparity in numbers of species in these four genera are explored from the perspective of phylogeny reconstruction and molecular dating techniques (using nonparametric rate smoothing), aiming to assess monophyly and to arrive at preliminary estimates of the relative ages of their most recent common ancestors (MRCAs). The effects, in particular, of taxon and character sampling on date estimates in these genera is assessed and compared. Results in the species rich genus Guatteria show higher sampling of crown group taxa resulting in significantly older age estimation for the MRCA
From morphological nightmare to molecular conundrum : phylogenetic evolutionary and taxonomic studies on Guatteria (Annonaceae)
No full textThe Neotropics (Mexico to South Brazil) contains c. 30% of the world's plant diversity, but the origin of this diversity remains unclear. Several recent studies have suggested that a substantial portion of this diversity has resulted from the dispersal of taxa into that region. However, more data are needed to substantiate this claim. Guatteria (Annonaceae) is with c. 290 species the third largest genus of Neotropical trees. Its widespread distribution and frequent occurrence makes the genus an excellent model taxon to study diversification patterns. This dissertation reconstructed the evolutionary history of Guatteria and inferred three major events in the history of this genus: 1) A migration across the ocean from Central into South America before the closing of the Isthmus of Panama; 2) a major diversification of the lineage within South America; and 3) several migrations of South American lineages back into Central America via the closed Panamanian land bridge. Therefore, most of the species of Guatteria resulted from a major radiation that followed its dispersal into South America over 6 million years ago. This study provides further evidence that migration into the Neotropics was an important factor in the historical assembly of its biodiversity.
Next to this, the accepted classification of the species within Guatteria as well as the relationship between Guatteria and its small satellite genera (Guatteriopsis, Guatteriella and Heteropetalum) was investigated. Current classification of Guatteria is based on morphology and species are often difficult to tell apart. Because of this morphological complexity researchers have been reluctant to study these plants. Therefore, the last thorough study of this genus as a whole dates back to 1939. In this dissertation, an evolutionary tree containing c. 40% of the species of Guatteria was constructed. This was done on the basis of chloroplast DNA. Unfortunately, clear insight in most of the evolutionary relationships between species was not achieved. Therefore, a completely new classification of Guatteria would be premature. However, it is clear that the largest part of the currently accepted classification should be abandoned. Notwithstanding this, conclusions could be drawn on the morphological evolution of the genus. Furthermore, the closest relative of Guatteria could not be determined with certainty. This knowledge is necessary in order to understand the origin of the genus. A morphological nightmare for taxonomists in the past decades proves to some extent to be a mystery for molecular biologists, even today.
The Central American species of Guatteria are in general easier to tell apart than the South American representatives. In order to study these species, field work in Costa Rica and Panama was carried out. During this fieldwork five new species of Guatteria were discovered and named. These species were studied together with all the already known Central American species of Guatteria and the resulting Flora treatment is included in this dissertation. The descriptions of the species, accompanied by photographs, can be used by specialists and non-specialists to identify herbarium material of Central American Guatteria's.
Finally, the use of herbarium specimens in this molecular phylogenetic study was evaluated
Insights into the influence of priors in posterior mapping of discrete morphological characters: a case study in Annonaceae
No full textBackground - Posterior mapping is an increasingly popular hierarchical Bayesian based method used to infer character histories and reconstruct ancestral states at nodes of molecular phylogenies, notably of morphological characters. As for all Bayesian analyses specification of prior values is an integrative and important part of the analysis. He we provide an example of how alternative prior choices can seriously influence results and mislead interpretations. Methods/Principal Findings - For two contrasting discrete morphological characters, namely a slow and a fast evolving character found in the plant family Annonaceae, we specified a total of eight different prior distributions per character. We investigated how these prior settings affected important summary statistics. Our analyses showed that the different prior distributions had marked effects on the results in terms of average number of character state changes. These differences arise because priors play a crucial role in determining which areas of parameter space the values of the simulation will be drawn from, independent of the data at hand. However, priors seemed to fit the data better if they would result in a more even sampling of parameter space (normal posterior distribution), in which case alternative standard deviation values had little effect on the results. The most probable character history for each character was affected differently by the prior. For the slower evolving character, the same character history always had the highest posterior probability independent of the priors used. In contrast, the faster evolving character showed different most probable character histories depending on the prior. These differences could be related to the level of homoplasy exhibited by each character. Conclusions - Although our analyses were restricted to two morphological characters within a single family, our results underline the importance of carefully choosing prior values for posterior mapping. Prior specification will be of crucial importance when interpreting the results in a meaningful way. It is hard to suggest a statistically sound method for prior specification without more detailed studies. Meanwhile, we propose that the data could be used to estimate the prior value of the gamma distribution placed on the transformation rate in posterior mappin
The Miliuseae revisited : phylogenetic, taxonomic, and palynological studies in a major clade of Annonaceae
No full textThis thesis presented eight studies in the field of systematic botany, with a focus on the molecular phylogenetics, taxonomy, and pollen morphology of the tribe Miliuseae (formerly known as the miliusoid clade) of the pantropical flowering plant family Annonaceae. The general aims were: (1) to investigate intertribal relationships of the tribe Miliuseae, (2) to clarify generic delimitations by investigating the intergeneric relationships within the tribe Miliuseae, and (3) to understand patterns of character evolution within the tribe Miliuseae. To achieve these aims, a molecular phylogeny of a subclade of the subfamily Malmeoideae consisting of the tribes Maasieae, Malmeeae, Fenerivieae, Dendroking- stonieae (sampled for the first time), Monocarpieae, and Miliuseae was reconstructed using a much expanded taxon and chloroplast DNA marker sampling in comparison to previous studies. In addition, detailed taxonomic and/or palynological studies of the monogeneric tribes Dendrokingstonieae and Monocarpieae, and several genera in Miliuseae have been presented. The evolution of selected macromorphological and palynological characters was investigated using ancestral character-state reconstructions. Generic delimitations within Miliuseae, in light of the results of the molecular phylogenetic studies, were discussed, and two new genera, Hubera and Winitia, have been characterized based on macromorphology and pollen morphology.The Royal Thai GovernmentUBL - phd migration 201
A taxonomic revision of the Neotropical genus Cremastosperma (Annonaceae), including five new species
No full textWe present a taxonomic revision of Cremastosperma, a genus of Neotropical Annonaceae occurring in lowland to premontane wet forest, mostly in areas surrounding the Andean mountain chain. We recognise 34 species, describing five as new here: from east of the Andes, C. brachypodum Pirie & Chatrou, sp. nov. and C. dolichopodum Pirie & Maas, sp. nov., endemic to Peru; C. confusum Pirie, sp. nov., from southern Peru and adjacent Bolivia and Brazil; and C. alticola Pirie & Chatrou, sp. nov., at higher elevations in northern Peru and Ecuador; and from west of the Andes, C. osicola Pirie & Chatrou, sp. nov. endemic to Costa Rica, the most northerly distributed species of the genus. We provide an identification key, document diagnostic characters and distributions and provide illustrations and extensive lists of specimens, also presenting the latter in the form of mapping data with embedded links to images available online. Of the 34 species, 22 are regional endemics. On the basis of the extent of occurrence and area of occupancy of species estimated from the distribution data, we designate IUCN threat categries for all species. Fourteen species proved to be endangered (EN) and a further one critically endangered (CR), reflecting their rarity and narrow known distributions
Little ecological divergence associated with speciation in two African rain forest tree genera
No full textAbstract Background The tropical rain forests (TRF) of Africa are the second largest block of this biome after the Amazon and exhibit high levels of plant endemism and diversity. Two main hypotheses have been advanced to explain speciation processes that have led to this high level of biodiversity: allopatric speciation linked to geographic isolation and ecological speciation linked to ecological gradients. Both these hypotheses rely on ecology: in the former conservation of ecological niches through time is implied, while in the latter adaptation via selection to alternative ecological niches would be a prerequisite. Here, we investigate the role of ecology in explaining present day species diversity in African TRF using a species level phylogeny and ecological niche modeling of two predominantly restricted TRF tree genera, Isolona and Monodora (Annonaceae). Both these genera, with 20 and 14 species, respectively, are widely distributed in African TRFs, with a few species occurring in slightly less humid regions such as in East Africa. Results A total of 11 sister species pairs were identified most of them occurring in allopatry or with little geographical overlap. Our results provide a mixed answer on the role of ecology in speciation. Although no sister species have identical niches, just under half of the tests suggest that sister species do have more similar niches than expected by chance. PCA analyses also support little ecological differences between sister species. Most speciation events within both genera predate the Pleistocene, occurring during the Late Miocene and Pliocene periods. Conclusions Ecology is almost always involved in speciation, however, it would seem to have had a little role in species generation within Isolona and Monodora at the scale analyzed here. This is consistent with the geographical speciation model for TRF diversification. These results contrast to other studies for non-TRF plant species where ecological speciation was found to be an important factor of diversification. The Pliocene period appears to be a vital time in the generation of African TRF diversity, whereas Pleistocene climatic fluctuations have had a smaller role on speciation than previously thought. Ecological niche modeling, species level phylogeny, ecological speciation, African tropics, Isolona, Monodora, Annonaceae</p
Studies in Annonaceae XXVIII. Macromorphological variation of recent invaders in northern Central America: the case of Malmea (annonaceae)
No full textCluster analysis is used to reveal patterns of macromorphological variation in a species complex of Malmea (Annonaceae) distributed in eastern Mexico, Guatemala, Belize, and Honduras. Of 53 characters, 24 are important for the clustering of 238 herbarium specimens into 12 clusters. No cluster is exclusively specified by any character or combination of characters. Neither can any geographical pattern be detected, except for the clustering of specimens from Los Tuxtlas Tropical Biological Station, Veracruz. A new subspecies from this area, M. depressa subsp. abscondita, is described. Malmea gaumeri and M. leiophylla are brought into synonymy with M. depressa. Distribution patterns of Mexican and Central American taxa of Malmea are largely concordant with those of South American taxa, which spread into Cental America after the Pliocene closure of the Isthmus of Panama. A phytogeographical novelty is presented, however, as the distribution of M. depressa subsp. abscondita within the Sierra de los Tuxtlas shows an hitherto unknown pattern: the new subspecies is distributed only on the northeastern slopes of this mountain range, and is geographically separated from M. depressa subsp. depressa, which occurs only on the southwestern slope
The Annonaceae and the Annonaceae Project: a brief overview of the state of affairs
No full textThe large tropical family Annonaceae is subject to systematic research by a group of scientists, who are collaborating within the framework of the Annonaceae Project. The significance of the Annonaceae is outlined briefly, and the achievements of the Annonaceae Project are summarize
Myristicineae, a new suborder within Magnoliales
No full textMyristicaceae are sister group to the remaining five families of Magnoliales, which make up the suborder Magnoliineae. Both with regard to morphological and DNA sequence data, Myristicaceae have diverged substantially from Magnoliineae, whereas at the same time monophyly of Magnoliales is conclusive. This relationship between Myristicaceae and Magnoliineae is affirmed by describing the suborder Myristicineae
- …
