We investigate the relationship between housing wealth, property taxes, and elderly labor supply. Using twenty years of restricted access data from the Health and Retirement Study (HRS) containing plausibly exogenous variation in housing wealth from the recent boom/bust cycle and MSA-specific housing price indexes, we estimate longitudinal and difference-in-difference models. Our findings sugge...

We remark that hyperbolic conservation laws are a class of nonlinear evolution equations. As such, it would be natural to study them also from the point of view of dynamical systems. In particular, this would mean looking at periodic orbits, bifurcations, attractors, chaotic dynamics, etc. . . At present, however, very little of this is seen, within hyperbolic theory. Apparently, the main reaso...

A set of fundamental principles for the cybernetics domain is sketched, based on the spontaneous emergence of systems through variation and selection. The (mostly self-evident) principles are: selective retention, autocatalytic growth, asymmetric transitions, blind variation, recursive systems construction, selective variety, requisite knowledge and incomplete knowledge. Existing systems princi...

This essay assesses the two most significant changes in psychology over the past century: the attempt to localize psychological phenomena in restricted brain sites and the search for genetic contributions to behavior and psychopathology. Although there are advantages to these new developments, they are accompanied by some questionable assumptions. Because the investigators in these domains ofte...

The pied flycatcher is one of the most phenotypically variable bird species in Europe. The geographic variation in phenotypes has often been attributed to spatial variation in selection regimes that is associated with the presence or absence of the congeneric collared flycatcher. Spatial variation in phenotypes could however also be generated by spatially restricted gene flow and genetic drift....

We investigated cpDNA sequence and nuclear microsatellite variation among populations of the wild daffodil Narcissus triandrus to examine the role of historical vs. contemporary forces in shaping population structure, morphological differentiation and sexual-system evolution. This wide-ranging heterostylous species of the Iberian Peninsula is largely composed of two allopatric varieties (vars. ...

Detailed information about the geographic distribution of genetic and genomic variation is necessary to better understand the organization and structure of biological diversity. In particular, spatial isolation within species and hybridization between them can blur species boundaries and create evolutionary relationships that are inconsistent with a strictly bifurcating tree model. Here, we ana...

Although pairs of species often interact over broad geographic ranges, few studies have explored how interactions vary across these large spatial scales. Surveys along 1500 kilometers of the Pacific coast of North America documented marked variation in the frequency of predation by the snail Nucella canaliculata on the intertidal mussel Mytilus californianus. Laboratory rearing experiments sugg...

Large-scale patterns of spatial variation in species geographic range size are central to many fundamental questions in macroecology and conservation biology. However, the global nature of these patterns has remained contentious, since previous studies have been geographically restricted and/or based on small taxonomic groups. Here, using a database on the breeding distributions of birds, we re...

Although salamanders are characteristic amphibians in Holarctic temperate habitats, in tropical regions they have diversified evolutionarily only in tropical America. An adaptive radiation centered in Middle America occurred late in the history of a single clade, the supergenus Bolitoglossa (Plethodontidae), and large numbers of species now occur in diverse habitats. Sublineages within this cla...