Phenotypic variation along a cline in allozyme and karyotype frequencies, and its relationship with habitat, in the dog-whelk Nucella lapillus, L.

The dog-whelk Nucella lapillus exhibits a number of phenotypic variations and genetic polymorphisms which correlate with habitat-specific environmental pressures, especially those associated with wave action and temperature. This study investigates the relationship between genetic composition (karyotypic and electrophoretic variation) and phenotypic differentiation in N. lapillus sampled at 15 points along an 8 km stretch of coastline. Coincident clinal variation in gene frequencies and shell shape is described; they covary with differences in karyotype and also with growth. Laboratory-reared young show that differences in phenotype (shell shape and growth) are inherited. Experimental evidence is presented that specific shell shapes are adaptive under conditions of thermal stress. Together with the well-established correlations between shell shape and shore exposure, this association provides an argument for a relationship between genetic composition, phenotype and habitat in this species.     

Sexual-Selection Models for Exaggerated Traits are Useful but Constraining

SYNOPSIS. Science is driven by productive hypotheses and technology,but these may sometimes limit the questions posed. For instance,Fisherian runaway sexual selection and related hypotheses havehelped us understand the evolution of exaggerated visual sexualdimorphism. Species with indistinguishable sexes, however, mayuse different behavioral mechanisms when pairing and thus possessdifferent adaptations. In the monomorphic Midas cichlid (Amphilophuscitrinellum), females chose large aggressive males in a restrainedsituation, as sexual selection predicts, but males did not choose.The nuchal hump of males swells coincidently with pair formation.However, overly large humps were shunned by females while thenormal— size hump facilitated sex recognition. This speciesis polychromatic, and pairs mate assortatively by color in Nicaragua.Some have suggested the Midas cichlid might therefore show howsexual selection produces explosive speciation of cichlids inAfrica. All females, however, are biased toward normal—colormales. The color of gold morphs modulates aggressive responsesof the other fish. All else equal, the benefit to gold in afight equals 15% more weight than the opponent. Pair formationsucceeds best when the typically smaller female of a pair isrelatively more aggressive than the male. The pair combination,gold male with normal female, is difficult to produce; makingthe female the same size as the male removes the disability.Pair formation is a negotiated process in which the male teststhe aggressiveness of the female relative to self. That putsthe behavioral mechanisms of the male and female in conflict.     

First insights into the genes that control plant–bacterial interactions

The events leading up to the cloning of the first bacterial avirulence gene, avrA , from Pseudomonas syringae pv. glycinea are described. The cloning of this gene marked the beginning of the molecular analyses of bacterial effectors and has paved the way for determining of the role of bacterial effectors in pathogen virulence and the triggering of plant innate immunity.     

Late Devonian marine ecology and zoogeography of the central Appalachians and New York

Ecological and statistical analyses of the Late Frasnian (Late Devonian) fauna of the Java Group of New York reveals the presence of three benthic marine communities. Using sedimentological and stratigraphic criteria, the Java Group may be divided into five physical-environmental zones: nearshore marine, platform, prodelta, open shelf, and slope and basin. The Ambocoelia- Cariniferella, Tylothyris-Schizophoria . and C yrtospirifer-Douvillina Communities inhabited open shelf, outer platform - prodelta, and inner platform - nearshore habitats. respectively. Java species gradient curves overlap each other continuously, and species optima replace each other in a regular fashion along the onshore-offshore environmental gradient. No evidence for competitive exclusion between species or sharp habitat discontinuities (ecotones) is seen for Java ecosystems. The same three-fold division of communities, in equivalent habitats, can be seen in central Appalachian marine environments located approximately 500 km away along the ancient shoreline. The distribution of communities in this region appears to be directly related to the position and relative size of fluviodeltaic systems along the 500 km of ancient coastline. Palacoecology. communities, Braschiopoda. palaegeography. Devonian. Frasnian, Appalachians, New. York .     

The Metabolic Fate of Phenoxyacetic Acids in Higher Plants

The metabolism of phenoxyacetie acid (POA) was followed overshort periods in segments of Auena and Pisum using a vacuuminfiltration technique. Both species form 4-hydroxyphenoxy-aceticacid (4-OH-POA) and its phenolic glucoside (OGlu-POA) but Pisumincorporates much of the substrate into an insoluble wall component.This insoluble material appears to be formed from 4-OH-POA.Preliminary kinetic experiments show that the overall conversionof POA is linearly related to concentration up to 2µmolPOA g^-1 fresh tissue and can be completed in a few hours. Themethod provides a very useful means of preparing sufficientquantities of ¹⁴C-labelled 4 OH POA and O-Glu-POA in a pureform for subsequent use as substrates for the enzymes involvedin glucosylation and formation of the insoluble material. Althoughlight has relatively little effect on hydroxylation, the capacityformation of both the glucoside and the insoluble material isincreased by continuous fluorescent, red, and far red light.The results so far obtained suggest that phytochromeis involvedin the transformations. The chlorinated derivatives of phenoxyaceticacid with high herbicidal activity e.g. 2, 4-dichlorophenoxyaceticacid (2, 4-D) are also metabolized by analogous reactions andthe formation of hydroxylated and glycosylated derivatives maycontribute to the detoxification of such herbicides in resistantspecies.