32 research outputs found
SKEWNESS AND PERMUTATION
The skewness criterion of phylogenetic structure in data is too sensitive to character state frequencies, is not sensitive enough to number of characters (degree of corroboration) and relies on counts of arbitrarily-resolved bifurcating trees. For these reasons it can give misleading results. Permutation tests lack those drawbacks and can be performed quickly by using approximate parsimony calculations, but the test based on minimal tree length can imply strong structure in ambiguous data. A more satisfactory test is obtained by using a support measure which takes multiple trees into account.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73640/1/j.1096-0031.1992.tb00071.x.pd
Phylogenetic diversity and the conservation biogeography of African primates
Aim Phylogenetics has an important role in conservation biogeography.
However, there are few data on the phylogenetic diversity of African primates.
The phylogenetic diversity (PD) of a species is a measure of its taxonomic
distinctness and can be estimated by looking at the phylogenetic relationships
among taxa. Species-specific metrics on PD can then be used to determine
conservation priorities at various biogeographical scales. We used PD metrics to
rank 55 African primate species according to their conservation priorities at the
country level and within six African biogeographical regions. We also addressed
the following question: are there differences in conservation rankings between the
IUCN Red List and our PD metrics?
Location Africa.
Methods We created a consensus phylogeny for all African primate clades based
on genetic studies. Analyses of species distributions were determined using
presence/absence scores at two levels: country and biogeographical region.
A node-based method that standardizes for widespread taxa and endemicity was
used to calculate PD indices. Hierarchical cluster analysis was used to convert one
of the standardized, phylogenetic indices into three clusters that could be ranked
and compared with the main IUCN conservation rankings of endangered,
vulnerable, and lower risk.
Results At the country and region levels, the top-priority species in terms of PD are
Pan paniscus, Macaca sylvanus, Arctocebus calabarensis, Gorilla beringei, Arctocebus
aureus, Allenopithecus nigroviridis, Gorilla gorilla, Procolobus verus, Cercopithecus
solatus, Cercocebus galeritus, Colobus angolensis, Theropithecus gelada, Galagoides
zanzibaricus, Galagoides granti, and Procolobus (Piliocolobus) badius. Geographic
rankings were highest for the Democratic Republic of the Congo (country level) and
Central Africa (region level). Although there were no overall differences between
IUCN conservation ranks and the PD rankings, there were significant differences
between the two systems for vulnerable and endangered primate taxa.
Main conclusions There are few ecological and behavioural data on populations
of some of the African primates that represent the highest levels of phylogenetic
diversity. Studies of primate taxa with high PD rankings should focus on
identifying sites suitable for intensive studies of population densities, feeding
ecology, and reproductive behaviour. We suggest that PD metrics can serve as an
important, complementary data set in the IUCN ranking system for primates
Capitulum compartmentalization in Leucheria (Nassauvieae): Insights into the evolution of Asteraceae inflorescence
An unusual feature occurs in the capitula of Leucheria (Nassauvieae, Asteraceae), some phyllaries of the involucre are twisted and/or rotated. The different spatial orientations of these phyllaries, called here paleaceous phyllaries, divide the capitulum into compartments enclosing florets and fruits. Because the internal morphology of the phyllaries could play a role in the compartmentalization, the anatomy of the phyllaries together with their different spatial arrangements was analyzed in the 49 species of Leucheria. We found differences between the abaxial and adaxial epidermis, bulliform-like cells in the epidermis, and a callus at the base of the phyllaries. Cohesion, swelling, and turgor mechanisms in tissues are proposed to play a role in the positional changes of the phyllaries. The phyllaries bend, twist, rotate, and spread down and, excepting the latter, all are involved in capitula compartmentalization. The paleaceous phyllaries are already present in buds and continue during the whole plant life. Our results support previous phylogenetic hypotheses that suggest that Leucheria achieved a regular capitulum but maintained the remnants of an ancestor's pseudocephalium.Fil: Katinas, Liliana. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División de Plantas Vasculares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Forte, Noelia Beatriz. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División de Plantas Vasculares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin