The future of the national laboratories

The end of the Cold War has called into question the activities of the national laboratories and, more generally, the level of support now given to federal intramural research in the United States. This paper seeks to analyze the potential role of the laboratories, with particular attention to the possibility, on the one hand, of integrating private technology development into the laboratory’s menu of activities and, on the other hand, of outsourcing traditional mission activities. We review the economic efficiency arguments for intramural research and the political conditions that are likely to constrain the activities of the laboratories, and analyze the early history of programs intended to promote new technology via cooperative agreements between the laboratories and private industry. Our analysis suggests that the laboratories are likely to shrink considerably in size, and that the federal government faces a significant problem in deciding how to organize a downsizing of the federal research establishment.

Testing ancient RNA–protein interactions

The past decade in molecular biology has seen remarkable advances in the study of the origin and early evolution of life. The mathematical tools for analyzing DNA and protein sequences, coupled with the availability of complete microbial genome sequences, provide insight almost as far back as the age of the nucleic acids themselves. Experimental evolution in the laboratory and especially in vitro evolution of RNA provide insight into a hypothetical world where RNA, or a close relative, may have debuted as a primary functional and informational molecule. The ability to isolate new functional RNAs from random sequences now ultimately makes the world of possible primitive chemical interactions accessible even when the molecules or reactions are no longer present in modern species. Thus we can at last form direct experimental tests of specific models for the origin of RNA–protein associations, such as those that influenced the genetic code. This marks a turning point for probing the origin and early history of life at the molecular level.

A Carboniferous insect gall: insight into early ecologic history of the Holometabola.

Although the prevalence or even occurrence of insect herbivory during the Late Carboniferous (Pennsylvanian) has been questioned, we present the earliest-known ecologic evidence showing that by Late Pennsylvanian times (302 million years ago) a larva of the Holometabola was galling the internal tissue of Psaronius tree-fern fronds. Several diagnostic cellular and histological features of these petiole galls have been preserved in exquisite detail, including an excavated axial lumen filled with fecal pellets and comminuted frass, plant-produced response tissue surrounding the lumen, and specificity by the larval herbivore for a particular host species and tissue type. Whereas most suggestions over-whelmingly support the evolution of such intimate and reciprocal plant-insect interactions 175 million years later, we provide documentation that before the demise of Pennsylvanian age coal-swamp forests, a highly stereotyped life cycle was already established between an insect that was consuming internal plant tissue and a vascular plant host responding to that herbivory. This and related discoveries of insect herbivore consumption of Psaronius tissues indicate that modern-style herbivores were established in Late Pennsylvanian coal-swamp forests.

Spontaneous heterosis in larval life-history traits of hemiclonal frog hybrids

European water frog hybrids Rana esculenta (Rana ridibunda × Rana lessonae) reproduce hemiclonally, transmitting only their ridibunda genome to gametes. We compared fitness-related larval life-history traits of natural R. esculenta from Poland with those of the two sympatric parental species and of newly generated F1 hybrids. Compared with either parental species, F1 hybrid offspring had higher survival, higher early growth rates, a more advanced developmental stage by day 49, and earlier metamorphosis, but similar mass at metamorphosis. R. esculenta from natural lineages had trait values intermediate between those of F1 offspring and of the two parental species. The data support earlier observations on natural R. esculenta that had faster larval growth, earlier metamorphosis, and higher resistance to hypoxic conditions compared with either parental species. Observing larval heterosis in F1 hybrids in survival, growth rate, and time to metamorphosis, however, at an even higher degree than in hybrids from natural lineages, demonstrates that heterosis is spontaneous and results from hybridity per se rather than from subsequent interclonal selection; in natural lineages the effects of hybridity and of clonal history are confounded. This is compelling evidence for spontaneous heterosis in hybrid clonals. Results on hemiclonal fish hybrids (Poeciliopsis) showed no spontaneous heterosis; thus, our frog data are not applicable to all hybrid clonals. Our data do show, however, that heterosis is an important potential source for the extensively observed ecological success of hybrid clonals. We suggest that heterosis and interclonal selection together shape fitness of natural R. esculenta lineages.

Genetics and the population history of Europe

Analysis of genetic variation among modern individuals is providing insight into prehistoric events. Comparisons of levels and patterns of genetic diversity with the predictions of models based on archeological evidence suggest that the spread of early farmers from the Levant was probably the main episode in the European population history, but that both older and more recent processes have left recognizable traces in the current gene pool.

A pre-Columbian Y chromosome-specific transition and its implications for human evolutionary history.

A polymorphic C-->T transition located on the human Y chromosome was found by the systematic comparative sequencing of Y-specific sequence-tagged sites by denaturing high-performance liquid chromatography. The results of genotyping representative global indigenous populations indicate that the locus is polymorphic exclusively within the Western Hemisphere. The pre-Columbian T allele occurs at > 90% frequency within the native South and Central American populations examined, while its occurrence in North America is approximately 50%. Concomitant genotyping at the polymorphic tetranucleotide microsatellite DYS19 locus revealed that the C-->T mutation displayed significant linkage disequilibrium with the 186-bp allele. The data suggest a single origin of linguistically diverse native Americans with subsequent haplotype differentiation within radiating indigenous populations as well as post-Columbian European and African gene flow. The mutation may have originated either in North America at a very early time during the expansion or before it, in the ancestral population(s) from which all Americans may have originated. The analysis of linkage of the DYS199 and the DYS19 tetranucleotide loci suggests that the C-->T mutation may have occurred around 30,000 years ago. We estimate the nucleotide diversity over 4.2 kb of the nonrecombining portion of the Y chromosome to be 0.00014. compared to autosomes, the majority of variation is due to the smaller effective population size of the Y chromosome rather than selective sweeps. There begins to emerge a pattern of pronounced geographical localization of Y-specific nucleotide substitution polymorphisms.