Temperature effects on forest herbs assessed by warming and transplant experiments along a latitudinal gradient

Slow‐colonizing forest understorey plants are probably not able to rapidly adjust their distribution range following large‐scale climate change. Therefore, the acclimation potential to climate change within their actual occupied habitats will likely be key for their short‐ and long‐term persistence. We combined transplant experiments along a latitudinal gradient with open‐top chambers to assess the effects of temperature on phenology, growth and reproductive performance of multiple populations of slow‐colonizing understorey plants, using the spring flowering geophytic forb Anemone nemorosa and the early summer flowering grass Milium effusum as study species. In both species, emergence time and start of flowering clearly advanced with increasing temperatures. Vegetative growth (plant height, aboveground biomass) and reproductive success (seed mass, seed germination and germinable seed output) of A. nemorosa benefited from higher temperatures. Climate warming may thus increase future competitive ability and colonization rates of this species. Apart from the effects on phenology, growth and reproductive performance of M. effusum generally decreased when transplanted southwards (e.g., plant size and number of individuals decreased towards the south) and was probably more limited by light availability in the south. Specific leaf area of both species increased when transplanted southwards, but decreased with open‐top chamber installation in A. nemorosa. In general, individuals of both species transplanted at the home site performed best, suggesting local adaptation. We conclude that contrasting understorey plants may display divergent plasticity in response to changing temperatures which may alter future understorey community dynamics.     

Spider cues stimulate feeding,weight gain and survival of crickets

1. To avoid predation, prey often change their behaviour upon encountering cues of predator presence. Such behavioural changes should enhance individual survival, but are likely to be energy‐demanding. This should deplete energy reserves of the prey, unless it increases food intake. 2. These hypotheses were studied by conducting two microcosm experiments. In the first, crickets were kept on plants previously occupied by a spider or on control plants. After 3 days leaf consumption and weight gain of the crickets were quantified. In the second experiment, crickets were kept in the presence or absence of spider cues for 3 days. Spiders were then added and predation of the crickets was recorded during 24 h. 3. Crickets that had previously experienced spider cues were more successful in avoiding predation. Moreover, crickets under predation risk tended to increase foraging in the first microcosm experiment and gained more weight in the second microcosm experiment. 4. The results demonstrate that previous experience of predator cues decreases predation rate. Furthermore, they suggest that crickets are able to compensate for increased energy demands caused by antipredator behaviour. In more natural situations, moving to cue‐free plants may play an addition role.     

The colonization of squares of plastic suspended in midwater

(1) A flat substratum hung in midwater is colonized rapidly by a number of species normally found in vegetation. Some have been recorded consistently, a greater number occasionally, but only a few have not been recorded at all. Evidently most species are moving round frequently, even those, such as snails and case-building caddis-larvae, that cannot swim. (2) It seems likely from this that the identity of the plant cover has less influence on the structure of a community than some have thought. (3) A comparison of flat sheet, pleated sheet and artificial Littorella suspended in midwater makes possible certain statements and deductions. (i) Leptophlebia, Enallagma and chironomid larvae are more numerous on artificial Littorella; their natural habitat is within the vegetation cover. (ii) Cloeon, Cyrnus and Holocentropus are as numerous on the sheets or more numerous than in the artificial vegetation; they inhabit the surface of the plant cover where Cloeon is protected by its speed, and where the polycentropopids, protected by their nets, can trap both the true plankton and the Cladocera which feed in the vegetation. (iii) The foot of a snail and the suckers of a leech are most effective on a flat surface, which also provides a good feeding place for a snail. The higher numbers of Lymnaea and Erpobdella on the pleated compared with the flat sheets indicates the importance of cover for these two animals. (4) Flat plastic sheets hanging in the illuminated zone would improve the production of fish a little, pleating the sheets would improve it a little more, and best results would come from hanging something with a greater resemblance to natural vegetation.     

Impact of Clutch Relocation on Green Turtle Offspring

ABSTRACT For species with temperature-dependent sex determination, such as marine turtles, global climate change poses numerous threats. At the nesting beach, rising temperatures are predicted to further skew already female-biased sex ratios and increase embryonic mortality; sea-level rise and resultant coastal squeeze may leave few alternative breeding habitats in developed regions. As a result, clutch relocation, a commonly used management tool to reduce egg loss, may become necessary for safeguarding populations. Although studies have examined the impact of relocation on clutch success, few have examined the impact of this practice on the sex or phenotypic characteristics of hatchlings produced. We used a randomized block design experiment to examine effects of relocation on green turtle (Chelonia mydas) clutches. We compared hatching success, thermal conditions, and size (length and mass) of hatchlings from in situ control clutches with those subjected to 2 relocation methods, while controlling for maternal and other environmental effects. Relocated clutches did not vary significantly from control clutches in incubation temperature or inferred sex ratios during the critical middle third of incubation when sex is thought to be determined. Hatchling size was also unaffected by relocation. Both relocation methods, however, resulted in a 20% reduction in hatching success in comparison to in situ clutches. Clutch relocation is, however, likely to affect the population primary sex ratio, when clutches are relocated from sites in proximity to the sea where tidal inundation is a threat. Here, cooler conditions are likely to produce more males than are the warmer female-producing temperatures higher up the beach. For clutches at risk, relocation is a viable process and does not appear to affect hatchling size or predicted sex ratios if relocation sites are selected in areas utilized by other females. We urge caution, however, when moving clutches from potentially male-producing sites, particularly given predicted impacts of climate change on already female-biased sex ratios.     

Elevation and experimental snowmelt manipulation affect emergence phenology and abundance of soil‐hibernating arthropods

1. Effects of climate change, such as higher average temperatures and earlier snowmelt, are already apparent, especially in alpine regions. However, community responses of functionally important arthropod taxa to changing climatic conditions are mostly unknown. 2. In this study, an earlier snowmelt was simulated at 15 plots along an elevational gradient in the German Alps. At each study site, soil emergence traps were established for sampling soil‐hibernating arthropods on earlier and control snowmelt treatments during the growing season. The abundance and emergence phenology of the five most common arthropod orders (Araneae, Coleoptera, Diptera, Hemiptera, Hymenoptera) were analysed, as well as the species richness of Coleoptera. 3. There was increasing abundance and species richness of Coleoptera along the elevational gradient, indicating that at higher altitudes more individuals and species hibernate in the soil. Abundances of Diptera also increased with elevation. By contrast, abundances of Hemiptera declined with increasing elevation, while abundances of Araneae and Hymenoptera did not show significant elevational patterns. Arthropods at higher elevations emerged, on average, 5 weeks later than arthropods at lower elevations, because of a longer‐lasting snow cover. The earlier snowmelt treatment resulted in higher abundances of Araneae and Hymenoptera compared with the control plots, indicating that the time of snowmelt influenced the abundance of predators, such as spiders or parasitic wasps, more than that of herbivores. 4. An earlier emergence of certain arthropod guilds and a change in relative abundance of guilds might desynchronise species interactions, leading to a possible loss of biodiversity.     

Isolation and characterization of microsatellite loci from the truffle‐like ectomycorrhizal fungi Rhizopogon occidentalis and Rhizopogon vulgaris

We have isolated and characterized five microsatellite loci from Rhizopogon occidentalis and six loci from Rhizopogon vulgaris (Boletales, Basidiomycota). Microsatellite variation was assessed using 32 R. occidentalis and 48 R. vulgaris individuals from four populations in California. The number of alleles across populations ranged from two to 10 for R. occidentalis and three to eight for R. vulgaris. Expected heterozygosity values within populations ranged from 0.00 to 0.85 for R. occidentalis and 0.00 to 0.75 for R. vulgaris. These are the first microsatellite loci isolated for R. occidentalis and R. vulgaris and will be useful in the examination of their population genetic structure.     

Impact of tropical land‐use change on soil organic carbon stocks – a meta‐analysis

Land‐use changes are the second largest source of human‐induced greenhouse gas emission, mainly due to deforestation in the tropics and subtropics. CO₂ emissions result from biomass and soil organic carbon (SOC) losses and may be offset with afforestation programs. However, the effect of land‐use changes on SOC is poorly quantified due to insufficient data quality (only SOC concentrations and no SOC stocks, shallow sampling depth) and representativeness. In a global meta‐analysis, 385 studies on land‐use change in the tropics were explored to estimate the SOC stock changes for all major land‐use change types. The highest SOC losses were caused by conversion of primary forest into cropland (?25%) and perennial crops (?30%) but forest conversion into grassland also reduced SOC stocks by 12%. Secondary forests stored less SOC than primary forests (?9%) underlining the importance of primary forests for C stores. SOC losses are partly reversible if agricultural land is afforested (+29%) or under cropland fallow (+32%) and with cropland conversion into grassland (+26%). Data on soil bulk density are critical in order to estimate SOC stock changes because (i) the bulk density changes with land‐use and needs to be accounted for when calculating SOC stocks and (ii) soil sample mass has to be corrected for bulk density changes in order to compare land‐use types on the same basis of soil mass. Without soil mass correction, land‐use change effects would have been underestimated by 28%. Land‐use change impact on SOC was not restricted to the surface soil, but relative changes were equally high in the subsoil, stressing the importance of sufficiently deep sampling.     

Effects of stream flooding on the distribution and diversity of groundwater‐dependent vegetation in riparian areas

1. Effects of the frequency and duration of flooding on the structural and functional characteristics of riparian vegetation were studied at four sites (n = 80, 50 × 50 cm, plots) along medium‐sized naturally meandering lowland streams. Special focus was on rich fens, which – due to their high species richness – are of high priority in nature conservation. 2. Reed beds, rich fens and meadows were all regularly flooded during the 20‐year study period, with a higher frequency in reed bed areas than in rich fen and meadow areas. In rich fens, species richness was higher in low frequency flooded areas (≤3 year^?1) than in areas with a high frequency of flooding (>3 year^?1) or no flooding, whereas species richness in reed beds and meadows was unaffected by flood frequency. 3. The percentage of stress‐tolerant species was higher in low intensity flooded rich fen areas than in high intensity and non‐flooded areas, indicating that the higher species richness in low frequency flooded rich fens was caused by competitive release. We found no indication that increased productivity was associated with high flooding frequencies. 4. We conclude that the restoration of morphological features in stream channels to increase the flooding regime can be beneficial for protected vegetation within riparian areas, but also that groundwater discharge thresholds and critical levels for protected vegetation should be identified and considered when introducing stream ecosystem restoration plans.     

Comparative Binding of 125I-and 99mTc-Labeled Native and Glycated Low-Density Lipoprotein to Human Microvascular Endothelial Cells-Potential for Atherosclerosis Imaging?

Native (n), glycated (g), and glycoxidated (go) low-density lipoproteins (LDL) were labeled with ¹²⁵I or ^99mTc, and the labeling efficiency and binding were assessed for potential use of these LDL compounds in imaging analysis of atherosclerotic lesions (PPAR-γ receptors) by determining the number of specific receptors for nLDL, gLDL or goLDL on human microvascular endothelial cells as well as the K_D s using either ¹²⁵I-or ^99mTc-labeled LDLs. The specific activity of labeled gLDL and goLDL was much higher (for goLDL 20 times higher) than that of nLDL. Gel filtration of labeled LDLs revealed, however, that ^99mTc–g/goLDL is significantly degraded by the labeling reaction. No fragmentation was observed for ^99mTc-nLDL and all the ¹²⁵I-labeled LDL forms. Binding studies using both ¹²⁵I-and ^99mTc-nLDL indicated a weak binding affinity (K_D 10^{? 7}mol/L) to human microvascular endothelial cells. The binding affinity of ¹²⁵I-g/goLDL to these cells was significantly higher (K_D 10^{? 9}mol/L) and could be increased further by preactivation of the endothelial cells using TNFα. Incubation with ^99mTc-goLDL, however, did not result in specific binding of the ligand, possibly as a consequence of the fragmentation of the lipoprotein during the labeling. Scatchard transformation of the binding data with ^99mTc-gLDL revealed the presence of only a few binding sites. This was in contrast to the results obtained with ¹²⁵I-labeled gLDL, which revealed a much higher membrane density of scavenger receptors for this ligand. We conclude that for in vitro binding studies as well as for potential in vivo imaging, only ¹²⁵I-labeled goLDL should be used, whereas nLDL may be applied as ¹²⁵I-or ^99mTc-labeled ligand.     

Differentiation in morphology and habitat partitioning of genetically characterized Gammarus fossarum forms (Amphipoda) across a contact zone

Evolutionary processes do not affect all character types equally. Depending on environmental effects, morphological and ecological evolution may be uncoupled from molecular evolution. A natural contact zone between two forms of the amphipod Gammarus fossarum was used to assess the levels of differentiation in genetic, morphological and habitat characters. About 50 individuals per population were analysed for six enzyme loci in 72 populations and four size-standardized morphometric traits in a subset of 32 populations. Nine environmental parameters per population were used to characterize the habitat. All three character sets revealed significant divergences between G. fossarum forms. The eastern form A of G. fossarum differs from the western form B by longer setae at the second antennae (males) and longer exopodits at die third uropods (males and females). The variance partitioning within populations, among populations and between forms, was compared within the three character sets. The relative variance component between forms in genetic characters appeared to be 10-fold greater in comparison to morphological traits, indicating morphological stasis during speciation. The inter-form environmental differentiation was shown to be low, but consistent between pure populations. The eastern form A seems to prefer higher altitudes, a substrate type of gravel, stones and leaves, shading, and water with higher conductivity and pH man the western form B.