Biotic and abiotic drivers of intraspecific trait variation within plant populations of three herbaceous plant species along a latitudinal gradient

Background

The importance of intraspecific trait variation (ITV) is increasingly acknowledged among plant ecologists. However, our understanding of what drives ITV between individual plants (ITV_BI) at the population level is still limited. Contrasting theoretical hypotheses state that ITV_BI can be either suppressed (stress-reduced plasticity hypothesis) or enhanced (stress-induced variability hypothesis) under high abiotic stress. Similarly, other hypotheses predict either suppressed (niche packing hypothesis) or enhanced ITV_BI (individual variation hypothesis) under high niche packing in species rich communities. In this study we assess the relative effects of both abiotic and biotic niche effects on ITV_BI of four functional traits (leaf area, specific leaf area, plant height and seed mass), for three herbaceous plant species across a 2300 km long gradient in Europe. The study species were the slow colonizing Anemone nemorosa, a species with intermediate colonization rates, Milium effusum, and the fast colonizing, non-native Impatiens glandulifera.

Results

Climatic stress consistently increased ITV_BI across species and traits. Soil nutrient stress, on the other hand, reduced ITV_BI for A. nemorosa and I. glandulifera, but had a reversed effect for M. effusum. We furthermore observed a reversed effect of high niche packing on ITV_BI for the fast colonizing non-native I. glandulifera (increased ITV_BI), as compared to the slow colonizing native A. nemorosa and M. effusum (reduced ITV_BI). Additionally, ITV_BI in the fast colonizing species tended to be highest for the vegetative traits plant height and leaf area, but lowest for the measured generative trait seed mass.

Conclusions

This study shows that stress can both reduce and increase ITV_BI, seemingly supporting both the stress-reduced plasticity and stress-induced variability hypotheses. Similarly, niche packing effects on ITV_BI supported both the niche packing hypothesis and the individual variation hypothesis. These results clearly illustrates the importance of simultaneously evaluating both abiotic and biotic factors on ITV_BI. This study adds to the growing realization that within-population trait variation should not be ignored and can provide valuable ecological insights.

     

Accumulation of zinc in egg yolk, ovarian follicles and organs after forced resting by high dietary zinc

1. Eighteen Warren SSL hens of 71 weeks of age were forced-moulted by ad libitum feeding of a high-zinc diet (10,000 ppm zinc for 2 days followed by 5,000 ppm zinc-supplement diet for 4 days). From the start of the treatment, eggs were collected and 3 hens were slaughtered on days 0, 2, 3, 4, 5 and 6 of the study. 2. Zinc analyses were carried out on the different components of the eggs and on liver, pancreas, kidney, different yolky follicles of the ovary and various segments of the oviduct. 3. Seven-, six- and threefold increases in zinc concentration were found in pancreas, liver and kidney, respectively. 4. The shell gland and isthmus, but not the magnum, also showed slight but significant increases in Zn content. 5. Zinc accumulation was also high and almost identical in ovarian follicles F1 to F4 but slightly less in F5 and F6 follicles. 6. In the egg, a significant increase in zinc concentration was only observed in the yolk.     

Sensitivity to habitat fragmentation across European landscapes in three temperate forest herbs

Landscape Ecology - Evidence for effects of habitat loss and fragmentation on the viability of temperate forest herb populations in agricultural landscapes is so far based on population genetic...     

The autumn leafroller: Phenology,damage and parasitoids in a Dutch apple orchard

The phenology of the autumn leafroller,Syndemis musculana, a local pest of apple, was studied in order to forecast larval emergence. From 1983–1986, peak flight as determined with sexpheromone traps was always between 13–18 May. The duration of embryonic development was determined at various constant temperatures and used to estimate the periods of egg hatch in these four years. Each year, most eggs should have hatched in the second decade of June.Differences in attack rates between apple cultivars seem to be explained largely by the variation in picking time. Larvae are only half grown at the beginning of harvest (cv. James Grieve), and have gone into hibernation when the latest variety (cv. Golden Delicious) is picked. Moreover, the varieties Cox's Orange Pippin and Belle de Boskoop, picked about half time, are liable to receive additional damage by caterpillars brought with the picked fruits into storage.Various hymenopterous parasites were reared from caterpillars. As the only leafroller in the orchard which hibernates as mature larva,S. musculana may promote winter survival of some parasitoids, like the eulophidColpyclypeus florus.Samenvatting De fenologie van de herfstbladroller (Syndemis musculana Hübner), een incidentele plaag op appel, werd nader bepaald met het doel het uitkomen van de eieren te kunnen voorspellen. In 1983–1986 viel de piekvlucht, bepaald met behulp van feromoonvallen, steeds tussen 13 en 18 mei.De ontwikkelingsduur van de eieren bij verschillende constante temperaturen werd gebruikt om de periode van uitkomen te schatten. De meeste eieren zullen ieder jaar in de eerste helft van juni uitkomen.Geconstateerde verschillen in schade tussen appelrassen blijken goeddeels terug te voeren op verschillen in pluktijdstip. De rupsen van de herfstbladroller zijn pas half-was als de eerste appels eind augustus geplukt worden, terwijl tegen het einde van de oogst begin oktober de meeste al in winterslaap zijn. Met name tussentijdse rassen, als Cox's Orange Pippin and Schone van Boskoop, lopen extra schade op doordat grotere rupsen met de geplukte vruchten in de kist terecht komen.Uit de rupsen werden negen, al van andere boomgaardbladrollers bekende, sluipwespen gekweekt, Omdat deze bladrollersoort, als enige in de boomgaard, als volgroeide rups overwintert, lijkt zij bij uitstek geschikt als winterwaard.This study was carried out at the Experimental Orchard De Schuilenburg, Schuilenburg 3, 4041 BK Kesteren, the Netherlands, to which address correspondence should be addressed.     

Elevation changes in Antarctica mainly determined by accumulation variability

Antarctic Ice Sheet elevation changes, which are used to estimate changes in the mass of the interior regions, are caused by variations in the depth of the firn layer. We quantified the effects of temperature and accumulation variability on firn layer thickness by simulating the 1980-2004 Antarctic firn depth variability. For most of Antarctica, the magnitudes of firn depth changes were comparable to those of observed ice sheet elevation changes. The current satellite observational period ( approximately 15 years) is too short to neglect these fluctuations in firn depth when computing recent ice sheet mass changes. The amount of surface lowering in the Amundsen Sea Embayment revealed by satellite radar altimetry (1995-2003) was increased by including firn depth fluctuations, while a large area of the East Antarctic Ice Sheet slowly grew as a result of increased accumulation.     

Phenology of the common earwig Forficula auricularia L. (Dermaptera: Forficulidae) in an apple orchard

Abstract

Observational data taken over 13 years, on the phenology and the abundance of the first brood of the common earwig, Forficula auricularia L., in a Dutch apple orchard were analysed. The results are used to indicate a fixed sampling moment for this predator. The fourth instar nymphs emerged between 12 June and 10 July, and the adult stage was reached between 8 and 30 July. The observed phenology, and the number of earwigs in shelter traps, correlated well with the temperature sum in day-degrees above a thermal threshold of 6 C, accumulated from 1 January. Maximum numbers of earwigs could be trapped in the trees when the nymphs of the first brood entered the fourth instar, generally between 600 and 750 day-degrees.