The 500-1000 cichlid species endemic to Lake Malawi constitute one of the most rapid and extensive radiations of vertebrates known. There is a growing debate over the role natural and sexual selection have played in creating this remarkable assemblage of species. Phylogenetic analysis of the Lake Malawi species flock has been confounded by the lack of appropriate morphological characters and an...

Title of Document: THE EFFECT OF SUNLIGHT ON DECORATION PLACEMENT AND MATING SUCCESS IN MALE SATIN BOWERBIRDS Archer Freni Larned, Master of Science 2012 Directed By: Dr. Gerald Borgia, Professor, Department of Biology Males of some bird species choose sunlit display sites to enhance their visual signal. Satin bowerbird (Ptilonorhynchus violaceus) males place colored decorations on their bower ...

Sexual selection driving display trait divergence has been suggested as a cause of rapid speciation, but there is limited supporting evidence for this from natural populations. Where speciation by sexual selection has occurred in newly diverged populations, we expect that there will be significant differences in female preferences and corresponding male display traits in the absence of substant...

We present optical long-slit spectroscopy of the nucleus of the nearby radio galaxy M84 (NGC 4374 = 3C 272.1) obtained with STIS aboard HST. Our spectra reveal that the nuclear gas disk seen in WFPC2 imaging by Bower et al. (1997, ApJ, 483, L33) is rotating rapidly. The velocity curve has an S-shape with a peak amplitude of 400 km s−1 at 0. ′′1 = 8 pc from the nucleus. To model the observed gas...

In many animals, sexual selection on male traits results from female mate choice decisions made during a sequence of courtship behaviors. We use a bower-building cichlid fish, Nyassachromis cf. microcephalus, to show how applying standard selection analysis to data on sequential female assessment provides new insights into sexual selection by mate choice. We first show that the cumulative selec...

Previous electrophysiological studies and computational modeling suggest the hypothesis that cholinergic neuromodulation may reduce olfactory associative interference during learning (M. E. Hasselmo, B. P. Anderson, & J. M. Bower, 1992; M. E. Hasselmo & J. M. Bower, 1993). These results provide behavioral evidence supporting this hypothesis. A simultaneous discrimination task required learning ...

The behavior of focus samples central to the multiple-look model of Trabasso and Bower (1968) is examined by three methods. First, exact probabilities of success conditional upon, a certain brief history of stimulation are determined. Second, possible states of the organism during the experiment are defined awl a transition matrix for those states determined, permitting prediction over all poss...