Bromeliads affect the interactions and composition of invertebrates on their support tree

Individual species can have profound effects on ecological communities, but, in hyperdiverse systems, it can be challenging to determine the underlying eco     

Ontogenetic scaling of scansorial surface area and setal dimensions of Chondrodactylus bibronii (Gekkota: Gekkonidae): testing predictions derived from cross‐species comparisons of gekkotans

Little is known of how the adhesive apparatus of gekkotans scales with growth. Cross‐species comparisons of certain characteristics, using size as a comparator to investigate scaling relationships, suggest certain relationships between subdigital pad area and body size. The manner in which the adhesive apparatus grows and scales within any one species, however, remains unknown, and it is unclear whether interspecific and intraspecific patterns are similar. To address this, we examined a post‐hatching ontogenetic series of the southern African gecko Chondrodactylus bibronii and demonstrate that setal density, setal basal diameter and setal spacing remain relatively constant in relation to size, indicating conserved subdigital pad assembly rules that are independent of size. Conversely, however, average and maximal setal lengths increase slightly and isometrically with size, an outcome that is probably explained by setal row recruitment, and the surface area of the subdigital pads scales close to, but below, isometry with respect to body mass and snout–vent length, it therefore does not increase sufficiently with size to compensate for the increase in mass. As a result, relative adhesive capacity decreases with growth with a regression slope of –0.45.     

Tests for heritable genetic damage and for evidence of gonadal exposure in mammals

Tests for the induction of genetic damage in mammalian germ cells provide the data needed for human genetic risk assessment and are used as standards for judging the ability of shorter-term tests to predict genetic hazard. In this review, 15 mammalian germ-cell tests and their variants are described. These tests are of two general types: (a) those designed to detect certain classes of genetic damage (gene mutations, chromosome breakage and/or rearrangement, and chromosome mis-segregation), regardless of whether or not the endpoint scored has any significance to human health, and (b) those designed to detect phenotypes that have human health implications, while the nature of the genetic damage is not usually known. Exposure to a mutagenic agent presents no genetic hazard if the chemical or its metabolites fail to reach the reproductive cells. Tests for gonadal exposure are, therefore, important, as preliminaries or components of studies on germ-cell mutagenicity. Seven of these tests and their variants are briefly described in the second part of the paper.     

Kin structure and shoal composition dynamics in the guppy, Poecilia reticulata

Although kin associations between fish can develop in the laboratory, the importance of kin structure in natural social groups remains uncertain. Guppies ( Poecilia reticulata ) possess many behavioural and life-history traits that promote kin structure, and so constitute ideal candidates for testing its general significance amongst fish. We collected 25 adult only shoals from ∼150 m stretches along two Trinidadian rivers. The 272 sampled fish were genotyped from a pool of seven hypervariable microsatellite loci. Although mark-recapture experiments have previously detected male-biased dispersal, which is predicted from the guppy mating system and which may have important implications for population differentiation, we found no sex-biases in dispersal between shoals. Because sex-biased dispersal was not evident, males and females were pooled in analyses of kin structure. Relatedness levels within each shoal did not differ significantly from zero, indicating that kin selection does not contribute to gross structure. Instead, our data is more consistent with the hypothesis that individual-level selection underlies shoal composition dynamics. These dynamics have important implications for the evolution of cooperative behaviour in guppies.     

The Anthropology of Economy: Community, Market, and Culture.

The Anthropology of Economy: Community, Market, and Culture. Stephen Gudeman. Williston, VT: Blackwell Publishers, 2001.189 pp.     

MEASUREMENTS OF SELECTION IN A HERMAPHRODITIC PLANT: VARIATION IN MALE AND FEMALE POLLINATION SUCCESS

I measured phenotypic selection of floral traits through both male and female functions of the hermaphroditic flowers of Ipomopsis aggregata (Pursh) V. Grant subsp. aggregata (Polemoniaceae). Fluorescent powdered dyes were used to track movement of pollen by hummingbirds and to measure pollen delivery to individual plants as well as pollen receipt. A phenotypic selection analysis revealed that selection due to male-male competition during pollination was capable of delaying flowering date and widening corolla tubes by 0.22 and 0.24 standard-deviation units, respectively, in a single generation. Several floral traits were highly correlated with each other. Multivariate selection analysis suggested that selection through male function directly favored late flowering as well as a sexual expression characterized by a short pistillate phase and long corollas. Selection intensities through male and female functions were of similar overall magnitude during the pollination stage of the life cycle, but different traits were favored, and selection sometimes acted in opposing directions. In 1985, selection through female function favored increased time spent in the pistillate phase and exserted stigmas (unlike selection through male function). As a result, individual plants varied greatly in functional gender. Plants that had exserted stigmas and narrow corollas and that spent a disproportionately long time in the pistillate phase achieved greater pollination success as females, while plants with the opposite traits achieved greater success as males. Moreover, female pollination success tended to increase, and male pollination success to decrease, with time spent in the pistillate phase, supporting a critical assumption of sex-allocation theory. Selection in the populations studied fluctuated from year to year and was highly sex-specific.     

Dexfenfluramine protects against pulmonary hypertension in rats.

Dexfenfluramine (Dex), an appetite suppressant and serotonin reuptake inhibitor, is associated with pulmonary vascular disease (PVD) in some patients. The variability might be related to undetermined genetic abnormalities interacting with factors such as gender, weight loss, and vascular injury. We, therefore, assessed the effect of Dex (5 mg. kg(-1). day(-1)) in female obese rats, designated JCR:LA-cp or cp/cp; in lean rats, designated (+/?); and in normal Sprague-Dawley (S-D) rats under control conditions or after endothelial injury induced by monocrotaline (60 mg/kg). Pulmonary arterial pressure, right ventricular hypertrophy, percent medial wall thickness of muscular arteries, and muscularization of peripheral arteries were assessed as indexes of PVD. Although Dex reduced weight gain in cp/cp and S-D rats (P < 0.05 for both), it did not cause PVD. Moreover, PVD in S-D rats after monocrotaline injection was paradoxically ameliorated by Dex (P < 0.05) despite induction of pulmonary artery elastase (P < 0.05), which we showed is critical in inducing experimental PVD. Thus it is possible that Dex is concomitantly offsetting the sequelae of elastase activity.     

Environmental constraints on microevolution in Prasiola stipitata s. lat. (Prasiolales: Chlorophyta)

Three cultured strains of Prasiola stripitata were established from populations on shores of NW England (Hilbre), N Norway (Vardö) and SW Finland (Ören). Experiments were carried out on the effects of seawater salinity (6, 34, 68, 102%o) on these strains. All isolates showed significant differences in plantlet density in response to salinity, and density maxima at 34%o. The Ören culture density was least reduced at 6%.
Growth of these isolates was also significantly affected by salinity and their patterns of response also differed significantly. The Hilbre strain proved to be the most vigorous in 68 and 102%o. The Ören strain performed best in 6 and 34%o and grew very poorly in 102%o. The responses of the Vardö isolate proved to be somewhat intermediate in character. Microevolutionary divergence can therefore occur in this taxon but the constraints imposed by the harsh conditions at high shore levels in all localities ensure that differences in salt tolerance between ecotypes will be small.