Do Start-Ups Pay Less?

The authors analyze Danish registry data from 1991 to 2006 to determine how firm age and firm size influence wages. Unadjusted statistics suggest that smaller firms paid less than larger firms paid, and that firm age had little or no bearing on wages. After adjusting for differences in the characteristics of employees hired by these firms, however, they observe both firm age and firm size effects. Larger firms paid more than did smaller firms for observationally equivalent individuals but, contrary to conventional wisdom, younger firms paid more than older firms. The size effect, however, dominates the age effect. Thus, although the typical start-up — being both young and small — paid less than a more established employer, the largest start-ups paid a wage premium

A phylogenomic perspective on the radiation of ray-finned fishes based upon targeted sequencing of ultraconserved elements

Ray-finned fishes constitute the dominant radiation of vertebrates with over 30,000 species. Although molecular phylogenetics has begun to disentangle major evolutionary relationships within this vast section of the Tree of Life, there is no widely available approach for efficiently collecting phylogenomic data within fishes, leaving much of the enormous potential of massively parallel sequencing technologies for resolving major radiations in ray-finned fishes unrealized. Here, we provide a genomic perspective on longstanding questions regarding the diversification of major groups of ray-finned fishes through targeted enrichment of ultraconserved nuclear DNA elements (UCEs) and their flanking sequence. Our workflow efficiently and economically generates data sets that are orders of magnitude larger than those produced by traditional approaches and is well-suited to working with museum specimens. Analysis of the UCE data set recovers a well-supported phylogeny at both shallow and deep time-scales that supports a monophyletic relationship between Amia and Lepisosteus (Holostei) and reveals elopomorphs and then osteoglossomorphs to be the earliest diverging teleost lineages. Divergence time estimation based upon 14 fossil calibrations reveals that crown teleosts appeared ~270 Ma at the end of the Permian and that elopomorphs, osteoglossomorphs, ostarioclupeomorphs, and euteleosts diverged from one another by 205 Ma during the Triassic. Our approach additionally reveals that sequence capture of UCE regions and their flanking sequence offers enormous potential for resolving phylogenetic relationships within ray-finned fishes

The Social Attachment to Place

Many theories either implicitly or explicitly assume that individuals readily move to places that improve their financial well-being. Other forces, however, offset these tendencies; for example, people often wish to remain close to family and friends. We introduce a methodology for determining how individuals weigh these countervail-ing forces, and estimate how both financial and social factors influence geographic mobility in the Danish population. Our results suggest that individuals respond to opportunities for higher pay elsewhere, but that their sensitivity to this factor pales in comparison to their preferences for living near family and friends

A SINGLE ANCIENT ORIGIN OF BROOD PARASITISM IN AFRICAN FINCHES: IMPLICATIONS FOR HOST-PARASITE COEVOLUTION

. Robust phylogenies for brood-parasitic birds, their hosts, and nearest nesting relatives provide the framework to address historical questions about host-parasite coevolution and the origins of parasitic behavior. We tested phylogenetic hypotheses for the two genera of African brood-parasitic finches, Anomalospiza and Vidua , using mitochondrial DNA sequence data from 43 passeriform species. Our analyses strongly support a sister relationship between Vidua and Anomalospiza , leading to the conclusion that obligate brood parasitism evolved only once in African finches rather than twice, as has been the conventional view. In addition, the parasitic finches (Viduidae) are not recently derived from either weavers (Ploceidae) or grassfinches (Estrildidae), but represent a third distinct lineage. Among these three groups, the parasitic finches and estrildids, which includes the hosts of all 19 Vidua species, are sister taxa in all analyses of our full dataset. Many characters shared by Vidua and estrildids, including elaborate mouth markings in nestlings, unusual begging behavior, and immaculate white eggs, can therefore be attributed to common ancestry rather than convergent evolution. The host-specificity of mouth mimicry in Vidua species, however, is clearly the product of subsequent host-parasite coevolution. The lineage leading to Anomalospiza switched to parasitizing more distantly related Old World warblers (Sylviidae) and subsequently lost these characteristics. Substantial sequence divergence between Vidua and Anomalospiza indicates that the origin of parasitic behavior in this clade is ancient (∼20 million years ago), a striking contrast to the recent radiation of extant Vidua . We suggest that the parasitic finch lineage has experienced repeated cycles of host colonization, speciation, and extinction through their long history as brood parasites and that extant Vidua species represent only the latest iterations of this process. This dynamic process may account for a significantly faster rate of DNA sequence evolution in parasitic finches as compared to estrildids and other passerines. Our study reduces by one the tally of avian lineages in which obligate brood parasitism has evolved and suggests an origin of parasitism that involved relatively closely related species likely to accept and provide appropriate care to parasitic young. Given the ancient origin of parasitism in African finches, ancestral estrildids must have been parasitized well before the diversification of extant Vidua , suggesting a long history of coevolution between these lineages preceding more recent interactions between specific hosts and parasites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72018/1/j.0014-3820.2001.tb00768.x.pd