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Reproductive Adults (reproductive + adult)
Selected AbstractsLipophilic regulator of a developmental switch in Caenorhabditis elegansAGING CELL, Issue 6 2004Matthew S. Gill In Caenorhabditis elegans, the decision to develop into a reproductive adult or arrest as a dauer larva is influenced by multiple pathways including insulin-like and transforming growth factor , (TGF,)-like signalling pathways. It has been proposed that lipophilic hormones act downstream of these pathways to regulate dauer formation. One likely target for such a hormone is DAF-12, an orphan nuclear hormone receptor that mediates these developmental decisions and also influences adult lifespan. In order to find lipophilic hormones we have generated lipophilic extracts from mass cultures of C. elegans and shown that they rescue the dauer constitutive phenotype of class 1 daf-2 insulin signalling mutants and the TGF, signalling mutant daf-7. These extracts are also able to rescue the lethal dauer phenotype of daf-9 mutants, which lack a P450 steroid hydroxylase thought to be involved in the synthesis of the DAF-12 ligand; extracts, however, have no effect on a DAF-12 ligand binding domain mutant that is predicted to be ligand insensitive. The production of this hormone appears to be DAF-9 dependent as extracts from a daf-9;daf-12 double mutant do not exhibit this activity. Preliminary fractionation of the lipophilic extracts shows that the activity is hydrophobic with some polar properties, consistent with a small lipophilic hormone. We propose that the dauer rescuing activity is a hormone synthesized by DAF-9 that acts through DAF-12. [source] Insects in a warmer world: ecological, physiological and life-history responses of true bugs (Heteroptera) to climate changeGLOBAL CHANGE BIOLOGY, Issue 8 2007DMITRY L. MUSOLIN Abstract Focusing on the southern green stink bug, Nezara viridula (Pentatomidae), in central Japan the effects of climate change on true bugs (Insecta: Heteroptera) are reviewed. In the early 1960s, the northern edge of the species's distribution was in Wakayama Prefecture (34.1°N) and distribution was limited by the +5°C coldest month (January) mean temperature isothermal line. By 2000, N. viridula was recorded 70 km further north (in Osaka, 34.7°N). Historical climate data were used to reveal possible causes of the northward range expansion. The increase of mean and lowest winter month temperatures by 1,2°C in Osaka from the 1950s to the 1990s improved potential overwintering conditions for N. viridula. This promoted northward range expansion of the species. In Osaka, adult diapause in N. viridula is induced after mid-September, much later than in other local seed-feeding heteropterans. This late diapause induction results in late-season ineffective reproduction: some females start oviposition in autumn when the progeny have no chance of attaining adulthood and surviving winter. Both reproductive adults and the progeny die. A period from mid-September to early November represents a phenological mismatch: diapause is not yet induced in all adults, but it is already too late to start reproduction. Females that do not start reproduction but enter diapause in September have reduced postdiapause reproductive performance: they live for a shorter period, have a shorter period of oviposition and produce fewer eggs in smaller egg masses compared with females that emerge and enter diapause later in autumn. To some extent, N. viridula remains maladapted to Osaka environmental conditions. Ecological perspectives on establishment in recently colonized areas are discussed. A review of available data suggests that terrestrial and aquatic Heteroptera species respond to climate change by shifting their distribution ranges, changing abundance, phenology, voltinism, physiology, behaviour, and community structure. Expected responses of Heteroptera to further climate warming are discussed under scenarios of slight (<2°C) and substantial (>2°C) temperature increase. [source] Restriction of the upper distribution of New England cobble beach plants by wave-related disturbanceJOURNAL OF ECOLOGY, Issue 5 2000Coleman W. Kennedy Summary 1,The New England cobble beach plant community is an intertidal assemblage of halophytic forbs found exclusively behind fringing beds of the grass Spartina alterniflora. The purpose of this study was to determine the life stage and factors that limit the upper (landward) distribution of cobble beach plants in Narragansett Bay, Rhode Island, USA. 2,Seed traps and soil samples above the community border contained large numbers of seeds and buried seedlings of three cobble beach species, indicating that seed supply and germination do not limit vertical plant distribution. Experimentally added seeds of four species germinated above the community border, but seedlings did not emerge suggesting that seedling emergence is the proximate life stage limiting population and community distribution. 3,Measures of wave disturbance (cobble movement and change in cobble depth) indicated that substrate instability is substantially greater above than within the community, probably due to the lack of buffering by the S. alterniflora bed at higher tidal heights. 4,A second seed addition experiment demonstrated that seedlings of Suaeda linearis, a common cobble beach forb, are only able to emerge and grow into reproductive adults above the community border when the substrate there is artificially stabilized. Seedling transplants and glasshouse manipulations demonstrated that neither herbivores nor soil quality limited seedling emergence. 5,Overall, the vertical restriction of habitat modification by S. alterniflora appears to result in substrate instability at higher tidal elevations sufficient to prevent seedling emergence and limit the vertical distribution of cobble beach plants. [source] Inferring colonization history from analyses of spatial genetic structure within populations of Pinus strobus and Quercus rubraMOLECULAR ECOLOGY, Issue 3 2006F. A. JONES Abstract Many factors interact to determine genetic structure within populations including adult density, the mating system, colonization history, natural selection, and the mechanism and spatial patterns of gene dispersal. We examined spatial genetic structure within colonizing populations of Quercus rubra seedlings and Pinus strobus juveniles and adults in an aspen,white pine forest in northern Michigan, USA. A 20-year spatially explicit demographic study of the forest enables us to interpret the results in light of recent colonization of the site for both species. We assayed 217 Q. rubra seedlings and 171 P. strobus individuals at 11 polymorphic loci using nine allozyme systems. Plant genotypes and locations were used in an analysis of spatial genetic structure. Q. rubra and P. strobus showed similar observed levels of heterozygosity, but Q. rubra seedlings have less heterozygosity than expected. Q. rubra seedlings show spatial genetic clumping of individuals on a scale to 25 m and levels of genetic relatedness expected from the clumped dispersion of half-siblings. In contrast, P. strobus has low levels of genetic relatedness at the smallest distance class and positive spatial genetic structure at scales < 10 m within the plot. The low density of adult Q. rubra outside the study plot and limited, spatially clumped rodent dispersal of acorns is likely responsible for the observed pattern of spatial genetic structure and the observed heterozygote deficit (i.e. a Wahlund effect). We attribute weaker patterns observed in P. strobus to the longer dispersal distance of seeds and the historical overlap of seed shadows from adults outside of the plot coupled with the overlap of seed shadows from younger, more recently established reproductive adults. The study demonstrates the utility of long-term demographic data in interpreting mechanisms responsible for generating contemporary patterns of genetic structure within populations. [source] Reestablishment of the Southern California Rocky Intertidal Brown Alga, Silvetia compressa: An Experimental Investigation of Techniques and Abiotic and Biotic Factors That Affect Restoration SuccessRESTORATION ECOLOGY, Issue 2010Stephen G. Whitaker Previous research has indicated that many rocky intertidal macrophyte communities in southern California, and other locations around the world, have shifted from larger, highly productive, fleshy seaweeds toward a smaller, less productive, disturbance-tolerant flora. In widespread decline are ecologically important, canopy-forming, brown seaweeds, such as the southern California rockweed species Silvetia compressa. Restoration efforts are common for depleted biogenic species in other habitats, but restoration within rocky intertidal zones, particularly on wave-exposed coasts, has been largely unexplored. In two phases, we attempted to restore Silvetia populations on a southern California shore by transplanting live plants and experimentally investigating factors that affect their survival. In Phase I, we implemented a three-way factorial design where juvenile Silvetia thalli were transplanted at four sites with a combination of simulated canopy and herbivore exclusion treatments. Transplant survival was low, although enhanced by the presence of a canopy; site and herbivore presence did not affect survival. In Phase II, we used a two-way factorial design, transplanting two size classes of rockweeds (juveniles and reproductive adults) on horizontal and partially shaded, north-facing vertical surfaces at a target location where this rockweed has been missing since at least the 1970s. Transplant survival was moderate but lower than natural survival rates. Larger thalli exhibited significantly higher survival rates than smaller thalli in both the transplanted and naturally occurring populations, particularly on vertical surfaces. Higher mortality on horizontal surfaces may have been due to differences in desiccation stress and human trampling. Transplanting reproductive adults resulted in the subsequent recruitment of new individuals. [source] Biological and biochemical characteristics for quality control of Harmonia axyridis (Pallas) (Coleoptera, Coccinellidae) reared on a liver-based dietARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 1 2008Luca Sighinolfi Abstract Biological and biochemical parameters of a flightless strain of Harmonia axyridis, fed on a pork liver,based artificial diet and on Ephestia kuehniella eggs as controls, were compared. The diet-grown larvae showed a significantly longer developmental time and a lower adult emergence rate compared to control larvae. The weights of the newly emerged adults were significantly higher for adults fed E. kuehniella eggs during their larval stages than fed the artificial diet. In contrast, larval food source had no effect on the duration of the pre-oviposition period or adult longevity. For adults fed on E. kuehniella eggs as larvae, a significantly longer pre-oviposition period, lower daily weight gain and fecundity were found for the diet-fed females compared to those fed on E. kuehniella eggs throughout the life span. The adult food source had no significant effect on longevity and fertility. Lower amino acid and fatty acid contents (in particular C16:1 and C18:3n-3) were found for the prepupae and newly emerged females obtained from diet-reared larvae compared to controls. Deficiencies in fatty acids C16:1 and C18:3n-3 were also observed in females obtained from E. kuehniella egg-reared larvae and fed on diet from adult emergence. The analyses of the foods showed deficiencies in artificial diet, especially for some amino and fatty acids. The results suggest a non-optimal composition of the artificial diet and some possibilities for its improvement. However, this polyphagous predator could be reared from first instar larvae to fully reproductive adults on a pork liver,based artificial diet. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley-Liss, Inc. [source] | ||||||||||