Boden als ausschöpfbarer Naturvorrat

The Science of Nature -     

NaU2Cl6, a reduced metallic chloride of uranium

This work has been supported by a NATO Research Grant and by the Fonds der Chemischen Industrie.     

Reproductive isolation among morphotypes of the Atlantic seastar species<Emphasis Type="Italic"> Zoroaster fulgens</Emphasis> (Asteroidea: Echinodermata)

Zoroaster fulgens is a slope-dwelling seastar species that is distributed throughout the Atlantic Ocean. Studies into the population structure and systematics of marine animals have increasingly found that species with a reported cosmopolitan distribution are, in fact, collections of closely related cryptic or sibling species. In the Porcupine Seabight, three morphotypes of Z. fulgens can be found that have a distribution that is stratified by depth. This study investigates the genetic divergence between these morphotypes using sections of the cytochrome oxidase 1 (COI) and 16S regions of the mitochondrial genome. Bathymetrically separated morphotypes of Z. fulgens are reproductively isolated over distances of approximately 1 km while gene flow occurs among morphotypes, along isobaths, over distances of approximately 900 km. Reproductive isolation on the continental slope may have occurred as a result of selection exerted by gradients of depth-correlated physical factors, such as pressure and temperature. However, allopatric speciation with subsequent range expansion may also explain the observed patterns of genetic divergence. Further investigation of radiation within this group may provide important information on the evolution of slope species. Taxonomic revision of the genus is required.Communicated by J.P. Thorpe, Port Erin     

Extra-pair paternity uncommon in the cooperatively breeding bicolored wren

We investigated parentage using multilocus DNA fingerprinting for 222 juveniles produced during 99 group-years in the bicolored wren Campylorhynchus griseus, a cooperatively breeding bird of the Venezuelan savanna. Young adult bicolored wrens (auxiliaries) remain in their natal territories and substantially enhance the production of young there. We have previously used behavioral indicators of dominance by a single male/female pair (principals) to infer breeding status, resulting in the commonly applied model of helping in which current fitness accrues to auxiliaries only indirectly, in proportion to their relatedness to the principals and the effect of their assistance on breeding success. Our parentage analysis has demonstrated that 8.6% of the juveniles found on territories were not produced by the principal pair. Parentage of 4.1% of the juveniles was completely outside the social group; these appear to result from early dispersal of juveniles rather than from brood parasitism, most likely resulting from breakup of nearby groups. Principal females mated outside of their group (2.3%), or with an auxiliary male (2.3%), in the remaining cases of parentage outside the principal pair. No matings were detected between close relatives (e.g. mother-son); matings detected between the principal female and an auxiliary male followed a typical replacement of the principal female by an unrelated immigrant female. Our finger-printing results indicate that: (1) current fitness benefits accruing to most auxiliaries do not exceed their likely reproductive success had they dispersed successfully to a breeding position; (2) nearly all wren mating is monogamous and (3) behavioral dominants (especially females) can monopolize breeding. Received: 23 September 1994/Accepted after revision: 10 June 1995