Michael J. Sanderson

Learn More
Rates of molecular evolution vary widely between lineages, but quantification of how rates change has proven difficult. Recently proposed estimation procedures have mainly adopted highly parametric approaches that model rate evolution explicitly. In this study, a semiparametric smoothing method is developed using penalized likelihood. A saturated model in(More)
SUMMARY Estimating divergence times and rates of substitution from sequence data is plagued by the problem of rate variation between lineages. R8s version 1.5 is a program which uses parametric, nonparametric and semiparametric methods to relax the assumption of constant rates of evolution to obtain better estimates of rates and times. Unlike most programs(More)
A new method for estimating divergence times when evolutionary rates are variable across lineages is proposed. The method, called nonparametric rate smoothing (NPRS), relies on minimization of ancestor-descendant local rate changes and is motivated by the likelihood that evolutionary rates are autocorrelated in time. Fossil information pertaining to minimum(More)
The extraordinary contemporary species richness and ecological predominance of flowering plants (angiosperms) are even more remarkable when considering the relatively recent onset of their evolutionary diversification. We examine the evolutionary diversification of angiosperms and the observed differential distribution of species in angiosperm clades by(More)
Phylogenetic analysis of 330 plastid matK gene sequences, representing 235 genera from 37 of 39 tribes, and four outgroup taxa from eurosids I supports many well-resolved subclades within the Leguminosae. These results are generally consistent with those derived from other plastid sequence data (rbcL and trnL), but show greater resolution and clade support(More)
Comparisons between insular and continental radiations have been hindered by a lack of reliable estimates of absolute diversification rates in island lineages. We took advantage of rate-constant rDNA sequence evolution and an "external" calibration using paleoclimatic and fossil data to determine the maximum age and minimum diversification rate of the(More)
Rates of phenotypic evolution have changed throughout the history of life, producing variation in levels of morphological, functional, and ecological diversity among groups. Testing for the presence of these rate shifts is a key component of evaluating hypotheses about what causes them. In this paper, general predictions regarding changes in phenotypic(More)
We assess the phylogenetic potential of approximately 300,000 protein sequences sampled from Swiss-Prot and GenBank. Although only a small subset of these data was potentially phylogenetically informative, this subset retained a substantial fraction of the original taxonomic diversity. Sampling biases in the databases necessitate building phylogenetic data(More)
Intercellular Ca2+ signaling in primary cultures of glial cells was investigated with digital fluorescence video imaging. Mechanical stimulation of a single cell induced a wave of increased [Ca2+]i that was communicated to surrounding cells. This was followed by asynchronous Ca2+ oscillations in some cells. Similar communicated Ca2+ responses occurred in(More)
In response to mechanical stimulation of a single cell, airway epithelial cells in culture exhibit a wave of increased intracellular free Ca2+ concentration that spreads from cell to cell over a limited distance through the culture. We present a detailed analysis of the intercellular wave in a two-dimensional sheet of cells. The model is based on the(More)