Macro-alga population shows low but significant heterogeneity in developmental instability with no detectable association with individual fitness

We studied among-individual variation in developmental instability (DI) and fitness-related parameters in 80 individual plants of Fucus vesiculosus (Phaeophyta). To minimize differential environmental effects, plants were sampled from one environmentally homogenous population. DI was measured as fluctuating asymmetry (FA) of four bilaterally symmetric traits (branch length, receptacle length and width, and bladder width) for an average total of 30 structures per individual. FA levels varied significantly among individual plants, consistent with a coefficient of variation of 0.12 for organism-wide DI or 0.13–0.21 for trait-specific DI. These values are lower than estimates for other organisms, suggesting that the genetic heterogeneity in DI was low. The data provide some evidence for organism-wide DI, but simulations show that organism-wide and trait-specific variation cannot be conclusively separated. Growth rate of branch tips was determined experimentally, demonstrating significant variation among individuals. FA was not significantly correlated with growth rate or with morphological variables associated with fecundity, age, size, and health. At the same time, the signs of all the correlation coefficients were consistent with the expectation of a negative relationship between DI and fitness. The simulations indicated that the correlation between FA and the underlying DI was comparatively strong (high hypothetical repeatability), implying that the lack of significant associations between FA and fitness variables reflected a weak relationship between DI and these fitness parameters. This weak relationship may be related to the low amount of DI variation in the study population.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 277–286.     

Endogenous Growth Substances in Normal and Dwarf Mutants of Cortland and Golden Delicious Apple Shoots

Endogenous growth substances in the shoots of dwarf mutants of Cortland (Cortland 65–6 and Cortland 65–7) and Golden Delicious (Golden Auvil Spur and Yellow Spur) were investigated in relation to dwarfism. The shoots were extracted at three stages of growth, namely: 1) rapid elongation growth, 2) formation of terminal bud, and 3) cessation of cambial growth. The growth substances were partially separated by thin layer chromatography and bioassayed using the Avena first internode and Lepidium seed germination tests. Shoot extracts from the normal Cortland and Golden Delicious plants contained higher levels of auxins at all stages of growth than those from dwarf mutants. Growth-promoting activity was found in two zones on chromatograms developed with isopropanol: ammonia: water (10:1:1 v/v/v):R_f 0.4 to 0.5 and R_f 0.8 to 0.9. The Lepidium seed germination test showed the presence of a highly inhibitory zone between R_f 0.3 and 0.4 in the extracts of dwarf and normal plants. However, the peak of germination inhibition activity was sharp for dwarf mutants and less for extracts of normal growing plants at 3 stages of growth. The inhibitory substance(s) was further purified on TLC plates by successive separations in different solvent systems. Two substances which inhibited the Lepidium seed germination were found, one close to the R_f value of synthetic abscisic acid and the other appeared to be similar to xanthoxin in R_f value, biological activity and UV absorption spectra.     

Sexual and reproductive traits of Hypania invalida (Polychaeta,Ampharetidae): a remarkable invasive species in Central European waterways

1. The Ponto‐Caspian polychaete Hypania invalida (Archiv für Naturgeschichte, 1860, 26, 109) is undergoing rapid range expansion in the Rhine and other central European waterways. We examined its reproductive traits in an attempt to account for its remarkable invasive success. 2. For the first time in this species, we found males, dioecy (gonochorism) and an exclusively sexual mode of reproduction; no indication for hermaphroditism or (unisexual) parthenogenesis, that could explain the rapid range expansion of H. invalida, was found. 3. Our experimental evidence shows that H. invalida reproduces by males discharging their sperm into the water column while eggs are retained and fertilised in the female dwelling tubes. This mode of ‘spermcast’ reproduction is common in sessile benthic animals on wave‐washed shores. 4. Fecundity of H. invalida ranged between 60 and 260 eggs per clutch and is increased by iteroparity (i.e. multiple cycles of oogenesis and egg‐laying per specimen). Offspring are brooded for about 2 weeks before they leave the maternal dwelling tubes and disperse in the water column. 5. After connection to a supply of Rhine water, sediments in flumes were rapidly colonised up to a density of 12 000 ind. m^?2 via the settlement of small larvae (<300 μm) from the water column; these reached sexual maturity approximately 12 weeks after settlement. 6. The reproductive traits of H. invalida give the species a high rate of dispersal. The capacity of its larvae to survive passage through pumps before settlement enables them to travel in the ballast water of ships. This might explain the upstream expansion of H. invalida in rivers. We conclude that further range expansion, and especially intercontinental transport of this polychaete, can only be prevented by improved ballast water treatment.     

Drought effect on isoprene production and consumption in Biosphere 2 tropical rainforest

Isoprene is the most abundant of the hydrocarbon compounds emitted from vegetation and plays a major role in tropospheric chemistry. Models predict that future climate change scenarios may lead to an increase in global isoprene emissions as a consequence of higher temperatures and extended drought periods. Tropical rainforests are responsible for more than 80% of global isoprene emissions, so it is important to obtain experimental data on isoprene production and consumption in these ecosystems under control of environmental variables. We explored isoprene emission and consumption in the tropical rainforest model ecosystem of Biosphere 2 laboratory during a mild water stress, and the relationship with light and temperature. Gross isoprene production (GIP) was not significantly affected by mild water stress in this experiment because the isoprene emitters were mainly distributed among the large, canopy layer trees with deep roots in the lower soil profile where water content decreased much less than the top 30 cm. However, as found in previous leaf level and whole canopy studies, the ecosystem gross primary production was reduced by (32%) during drought, and as a consequence the percentage of fixed C lost as isoprene tended to increase during drought, from ca. 1% in wet conditions to ca. 2% when soil water content reached its minimum. GIP correlated very well with both light and temperature. Notably, soil isoprene uptake decreased dramatically during the drought, leading to a large increase in daytime net isoprene fluxes.     

Efficiency of Filter Feeding in Two Species of Tetrahymena*

SYNOPSIS. Rates of removal of suspended India ink particles from the surrounding medium by 2 ciliates, Tetrahymena pyriformis strain GL and Tetrahymena vorax strain V₂S, have been measured. It is evident from the results that the food vacuoles concentrate the suspended particles, clearing a volume of the surrounding suspension fluid 500 × greater than the total volume of food vacuoles made during the same period of time.