Lizards as a plant's 'hired help': letting pollinators in and seeds out

It is well-known that plants utilize many different kinds of animals for pollination and dispersal of their seeds, but an alternative kind of evolutionary relationship has attracted less attention: animals can facilitate pollen and seed transport without acting as a vector. We studied interactions between an epacridaceous plant (the honey bush, Richea scoparid) and a lizard (the snow skink, .Niveoscincus microtepidotus) near the summit of Mount Wellington, Tasmania. The lizards gain access to the plant's nectar by tearing the fused petals (the calyptra) from the flower, thus exposing the plant's reproductive organs. Snow skinks forage selectively on flowers with higher-than-average nectar content, suggesting that this behaviour has evolved in response to plant characteristics. Lizard foraging may benefit R. scoparia , because calyptra remain attached unless a lizard tears the flower open. Our experiments demonstrated that the lizard's calyptra removal dramatically increased the plant's seed release. In 60 fruits from flowers with their calyptra intact, no seeds at all were released. However, 57 out of 60 (87%) fruits from flowers with their calyptra removed by the lizards successfully released their seeds. This system appears to involve reciprocal evolutionary changes in the interacting species (behaviour in the lizards and reproductive morphology in the plant). Thus the system seems to provide an unusual case of coevolution.     

Enzymes of the Ornithine-Arginine Metabolism of Trypanosomatids of the Genus Crithidia*

SYNOPSIS. Twelve strains of Crithidia, which fall into 8 species, were tested for occurrence of enzymes of ornithine-arginine metabolism. The following enzymes were investigated: arginase, ornithine carbamoyltransferase, argininosuccinate lyase, citrulline hydrolase, arginine deiminase and urease. Arginase and argininosuccinate lyase were found in all species. Citrulline hydrolase was also found in all but the 2 strains carrying endosymbiotes C. deanei and C. oncopelti. On the other hand, ornithine carbamoyltransferase was found only in these 2 strains. Arginine deiminase and urease were absent in all strains. The existence of a common enzymatic pattern for species of the genus Crithidia is thus reported.     

Annual growth of Cassiope tetragona as a proxy for Arctic climate: developing correlative and experimental transfer functions to reconstruct past summer temperature on a millennial time scale

Annual growth of the polar evergreen shrub Cassiope tetragona on Svalbard was evaluated as a proxy for Arctic summer temperatures. Transfer functions were derived from temperature‐growth correlations of shoots and from a temperature‐growth response, obtained from experimental warming using open top chambers (OTC) in high Arctic tundra vegetation at Isdammen approximately 1.5 km southeast of Longyearbyen, Svalbard (78°N, 15 E) and in Longyeardalen, 3 km west of Isdammen from 2004 to 2006. Air temperatures, monitored throughout the summer months, were 1.3 °C higher inside the OTCs than in the control plots. Annual stem growth was measured by tagging stems and leaves, and in the lab with shoots harvested from OTCs and control plots. Annual growth parameters assessed were leaf production, sum of length and weight of individual leaves, and stem length increment derived from leaf scar distances and the distances between wintermarksepta in the stem. Wintermarksepta are formed at the end of the summer growth period when the pith is narrowing and consist of dense and dark tissue ( Fig. 1b ). The variation of annual growth in a 34‐year site chronology (based on Cassiope shoots from the surroundings of the OTCs and control plots) correlated strongly with the mean summer temperature on Svalbard. The number of leaf pairs, leaf length and stem length also increased in the OTC warmed plots in the second and third year of warming. Transfer functions were derived from the temperature‐annual growth correlations from a single shoot from Longyeardalen, from the cross‐dated Isdammen site chronology and from the growth response to experimental warming. Based on leaf scar distances and distances between wintermarksepta of well‐preserved subfossil shoots in arctic tundra soil, annual stem length increase was assessed for the layers of a soil core collected at the Isdammen site. Based on the derived transfer functions summer temperature of the period relating to the 15 cm deep tundra soil core layer, radiocarbon dated at 4230±40 bp , may have been 3.0 °C lower than the present‐day 6.2 °C value. These results indicate that the transfer functions can be used to reconstruct past temperatures, beyond the time range of instrumental temperature and ice core records of Svalbard.

Figure 1 Open in figure viewer PowerPoint (a) Morphology of shoot of Cassiope tetragona collected May 26, 2007, Longyeardalen. Removal of the front row of leaves shows four leaf pairs of the 2006 summer, the leaf primordium for the 2007 growing season and the stem length increase summer 2006. (b) Wintermarksepta, darker colored than the pith tissue, indicating the winterperiod in a longitudinal section of an air‐dried shoot collected August 26, 2006, Longyeardalen.     

Characteristics of woods used recently and historically by Lesser Spotted Woodpeckers Dendrocopos minor in England

Lesser Spotted Woodpecker Dendrocopos minor numbers have declined greatly in England since the early 1980s for reasons that are not yet fully understood. It has been suggested that the species’ decline may be linked to the increase in Great Spotted Woodpeckers Dendrocopos major, changes in woodland habitat quality (such as deadwood abundance) and landscape‐scale changes in tree abundance. We tested some of these hypotheses by comparing the characteristics of woods in southern England where the species is still relatively numerous with those of woods used in the 1980s before the major decline. In each time period, habitat, predator and landscape information from woods known to be occupied by Lesser Spotted Woodpeckers was compared with those found to be unoccupied during surveys. Before the main period of decline, Lesser Spotted Woodpeckers used oak‐dominated, mature, open woods with a large amount of standing deadwood. Habitat use assessed from recent data was very similar, the species being present in mature, open, oak‐dominated woodlands. There was a strong relationship between wood use probability and the extent of woodland within a 3‐km radius, suggesting selection for more heavily wooded landscapes. In recent surveys, there was no difference in deadwood abundance or potential predator densities between occupied and unoccupied woods. Habitat management should focus on creating and maintaining networks of connected woodlands in areas of mature, open woods. Finer‐scale habitat selection by Lesser Spotted Woodpecker within woodlands should be assessed to aid development of beneficial management actions.     

Connectivity counts: disentangling effects of vegetation structure elements on the searching movement of a parasitoid

1. A heterogeneous habitat structure can have a profound impact on foraging carnivorous arthropods. In the present study, we examined which elements of complex vegetation structure influence the searching movement of a parasitoid model organism. 2. Previous field work showed that tall and dense vegetation reduces the parasitism success of the eulophid egg parasitoid Oomyzus galerucivorus while the probability of host egg deposition increased close to plant tips. 3. In laboratory bioassays, dried grass stems were arranged according to the natural situation in different setups. The wasps' walking time on stems increased with increasing stem height and density. High stem density decreased the walking time of the parasitoids on the ground and an increased stem height reduced the propensity to fly to the ground. Connectivity had a minor positive effect on the number of stem contacts, but considerably reduced the number of wasps reaching the upper part of grass stems by two‐thirds. 4. Thus, although enhanced vegetation complexity enhances walking activity of the parasitoids in the vegetation, laying eggs at the tip of long grass stems in dense vegetation can be an adaptive strategy for the host, as it maximises the number of connections between plant parts to cross by parasitoids before reaching the host. The connection points disorient the wasps, which lose time, reverse their direction or fly away.     

Short‐term effects of CO2 and O2 on citrate metabolism in illuminated leaves

Although there is now a considerable literature on the inhibition of leaf respiration (CO₂ evolution) by light, little is known about the effect of other environmental conditions on day respiratory metabolism. In particular, CO₂ and O₂ mole fractions are assumed to cause changes in the tricarboxylic acid pathway (TCAP) but the amplitude and even the direction of such changes are still a matter of debate. Here, we took advantage of isotopic techniques, new simple equations and instant freeze sampling to follow respiratory metabolism in illuminated cocklebur leaves (Xanthium strumarium L.) under different CO₂/O₂ conditions. Gas exchange coupled to online isotopic analysis showed that CO₂ evolved by leaves in the light came from ‘old’ carbon skeletons and there was a slight decrease in ¹³C natural abundance when [CO₂] increased. This suggested the involvement of enzymatic steps fractionating more strongly against ¹³C and thus increasingly limiting for the metabolic respiratory flux as [CO₂] increased. Isotopic labelling with ¹³C₂‐2,4‐citrate lead to ¹³C‐enriched Glu and 2‐oxoglutarate (2OG), clearly demonstrating poor metabolism of citrate by the TCAP. There was a clear relationship between the ribulose‐1,5‐bisphosphate oxygenation‐to‐carboxylation ratio (v_o/v_c) and the ¹³C commitment to 2OG, demonstrating that 2OG and Glu synthesis via the TCAP is positively influenced by photorespiration.     

Polyoma Virus Mutants as Probes of Variety Among Mouse Embryonal Carcinoma Cell Lines

The tumor promoter 12–0-tetradecanoylphorbol-13-acetate (TPA) dramatically modifies the differentiative program of myotubes, developed in culture from chick embryo skeletal myogenic cells. In fact TPA selectively decreases the expression of differentiative parameters with a lag of 8–10 h from its administration to the cultures. We have tested whether the reported effect of TPA depends on the synthesis of specific products during the lag phase of TPA action. The data presented indicate that inhibition of protein synthesis by the use of cycloheximide prevents the appearance of TPA induced inhibition of the expression of differentiative products, such as creatine phosphokinase (CPK) activity and acetylcholine receptors (AChR). Following removal of cycloheximide and reinitiation of normal protein synthesis, the TPA induced inhibitory effect on CPK and AChR appears after a delay of about the same length as the time lag of TPA action. Our results indicate that inhibition of protein synthesis during the lag phase of TPA action prevents the effect of this tumor promoter on myotube differentiative parameters, and suggest that the expression of differentiative traits in cultured myotubes is affected by TPA via a regulatory step implying protein synthesis.     

Pronounced genetic diversity in tropical epiphyllous lichen fungi

Lowland tropical habitats harbour an unexplored genetic diversity of epiphyllous fungi. In the shade of rainforest understoreys, lichenized fungi are specialized to an ephemeral habitat where they produce little vegetative biomass and develop reproductive structures early. In a first population genetic study of epiphyllous lichen fungi, we analysed the intraspecific genetic diversity of five leaf-colonizing lichen mycobiont species. Sampling focused on a lowland perhumid forest plot in Costa Rica, with additional collections from other localities throughout the country. In all species we detected sympatric occurrence of highly diverged haplotypes. Haplotypes belonging to distinct clades in networks were also found on the same leaf, clearly indicating multiple independent colonization events on single leaves. Despite the unusually high genetic diversity of these leaf-colonizing tropical fungi, we did not detect pronounced spatial structure of the haplotype distribution between geographical regions. The observed patterns suggest that the diversity of foliicolous lichens could be much higher than expected, with several cryptic genetic lineages within each morphologically characterized species.     

Stone-curlews Burhinus oedicnemus and recreational disturbance: developing a management tool for access

Stone-curlews Burhinus oedicnemus have a vulnerable population status in the UK after a large population decline and range contraction since the 1930s. Much Stone-curlew breeding habitat is open-access land designated under the Countryside and Rights of Way Act 2000. In order to guide the conservation and habitat management for this species whilst allowing recreational access, a tool known as the Stone-Curlew Access Response Evaluator (SCARE) has been developed. SCARE offers a method to assess the effects of scenarios for future changes in disturbance type, routes and frequency and will be valuable in making informed decisions about the management of public access to Stone-curlew breeding sites and the deployment of habitat creation measures.