The Apoplastic Pathway of Transport to Salt Glands

The availability of the apoplastic route for ion transport tosalt glands was assessed by electron microscope examinationsand by the use of lanthanum as an electron-dense tracer to demarcatethe apoplast. The results show that this solute can reach thesalt glands via the apoplast and this observation is discussedin relation to current ideas concerning salt gland function.     

Correlation between spermathecal morphology and mating systems in spiders

This study tested predictions regarding male mating preferences which were based on some aspects of female reproductive morphology which may influence sperm precedence patterns in six species of spiders. Males of two species, whose 'conduit' spermathecal design has been associated in previous studies with first male sperm precedence, showed the predicted preference for associating with immature females about to moult to maturity rather than mature females. Those of a third species, however, associated indiscriminately with mature and penultimate instar females. As predicted, males of three other species with 'cul-de-sac' spermathecal morphology did not associate preferentially with immature females. Immature females were avoided in two of the species, but not in the third. One of the species with cul-de-sac spermathecae showed, as predicted, lack of a strong first male advantage in sperm precedence. These data give only limited confirmation of the predictions.     

Isolation of microsatellite loci from the common buzzard,Buteo buteo (Aves: Accipitridae)

We isolated 56 common buzzard (Buteo buteo) microsatellite loci from (AC)_n‐ and (AAAG)_n‐enriched genomic libraries. Eleven loci were tested on 90 individuals from Eastern Westphalia in Germany, yielding two to 17 alleles per locus (average 5.7) and expected heterozygosities ranging from 0.11 to 0.93 (average 0.53). These highly variable microsatellite markers provide a powerful means for investigating population genetic diversity in the common buzzard, a little‐understood aspect of this widespread species.     

Behavioral Thermoregulation and the "Final Preferendum" Paradigm

Wider attention to Fry's (1947) "final preferendum" paradigmwould facilitate comparative studies of temperature preference(behavioral thermoregulation) among different animal groups.According to Fry's bipartite definition, the final preferendumis that temperature at which preference and acclimation areequal, and to which an animal in a thermal gradient will finallygravitate regardless of its prior thermal experience (acclimation).This paradigm is helpful in distinguishing between acute thermalpreferenda (measured within 2 hr or less after placing an animalin a thermal gradient), which are influenced by acclimationtemperature, and the species-specific final preferendum (measured24–96 hr after placement in the gradient), which is essentiallyindependent of prior acclimation because reacclimation occursduring the gravitation process. The paradigm does not take intoaccount non-thermal acclimatization influences (e.g., season,photoperiod, age, light intensity, salinity, disease, nutrition,pollutants, biotic interactions) which can also affect temperaturepreference. However, a graph of acutely preferred temperaturesversus acclimation temperatures can be employed to determinean equivalent acclimation temperature for any given acclimatizationstate, as a simple means of quantifying acclimatization statesresulting from interactions of many influences. This paradigm,developed for use with fishes, can also be applied to otherectothermic taxa, although it is most easily employed with aquaticorganisms because of the simplicity of specifying aquatic thermalenvironments in terms of water temperature alone. Methodologiesused in studies of behavioral thermoregulation should take theparadigm into account (especially with respect to length oftests) to enhance the comparative value of data across taxa.     

Effects of nutrient loading and extreme rainfall events on coastal tallgrass prairies: invasion intensity, vegetation responses, and carbon and nitrogen distribution

Soil fertility and precipitation are major factors regulating transitions from grasslands to forests. Biotic regulation may influence the effects of these abiotic drivers. In this study, we examined the effects of extreme rainfall events, anthropogenic nutrient loading and insect herbivory on the ability of Chinese tallow tree ( Sapium sebiferum ) to invade coastal prairie to determine how these factors may influence woody invasion of a grassland. We manipulated soil fertility (NPK addition) and simulated variation in frequency of extreme rainfall events in a three growing season, full factorial field experiment. Adding water to or pumping water out of plots simulated increased and decreased rainfall frequencies. We added Sapium seeds and seedlings to each plot and manipulated insect herbivory on transplanted Sapium seedlings with insecticide. We measured soil moisture, Sapium performance, vegetation mass, and carbon and nitrogen in vegetation and soils (0–10 cm deep, 10–20 cm deep). Fertilization increased Sapium invasion intensity by increasing seedling survival, height growth and biomass. Insect damage was low and insect suppression had little effect in all conditions. Recruitment of Sapium from seed was very low and independent of treatments. Vegetation mass was increased by fertilization in both rainfall treatments but not in the ambient moisture treatment. The amount of carbon and nitrogen in plants was increased by fertilization, especially in modified moisture plots. Soil carbon and nitrogen were independent of all treatments. These results suggest that coastal tallgrass prairies are more likely to be impacted by nutrient loading, in terms of invasion severity and nutrient cycling, than by changes in the frequency of extreme rainfall events.     

Comparative seed germination ecology of Austrostipa compressa and Ehrharta calycina (Poaceae) in a Western Australian Banksia woodland

Austrostipa compressa, a native ephemeral of southwest Western Australia was stimulated to germinate under a range of temperatures, in the presence of light, and exposure to smoke-water. This combination of environmental cues results in winter-maximum germination in immediate postfire and disturbed-soil environments of this Mediterranean-type climate. In contrast, Ehrharta calycina, an introduced perennial grass from southern Africa that has invaded Banksia woodlands, germinated under a wide range of temperature and light conditions, but showed no promotive response to smoke-water. Although A. compressa seeds tolerated heat shock better than E. calycina, the self-burial mechanism of A. compressa seeds ensures protection from fire. High-intensity fire could have a greater impact on E. calycina, as the seeds of this species tend to accumulate in the top of the soil profile where they are more susceptible to high temperatures. Although seeds of E. calycina are more susceptible to high temperatures, survival of mature individuals by postfire resprouting ensures continued survival in native woodlands. Estimates of soil seed bank densities showed extreme variability, but some recently burnt areas of the Yule Brook Botany Reserve contained up to 8000 seed m^?2 of A. compressa and nearly 75 000 seeds m^?2 of E. calycina. Viable soil seed bank densities of A. compressa are reduced with time-since-last fire, but areas of greater than 45 years since the last fire, still contained up to 119 seeds m^?2. In both species, only about half their soil seed bank germinates following fire, thus ensuring the potential for later recruitment. Massive soil seed populations of E. calycina in native Banksia woodlands pose a major problem to management of this plant community type.     

Mitochondrial phylogeny of Arvicolinae using comprehensive taxonomic sampling yields new insights

Comprehensive taxonomic sampling can vastly improve the accuracy of phylogenetic reconstruction. Here, we present the most inclusive phylogenetic analysis of Arvicolinae (Mammalia, Rodentia) to date, combining all published cytochrome  b gene sequences of greater than 1097 bp and new sequences from two monotypic genera. Overall, the phylogenetic relationships between 69 species of voles and lemmings, representing 18 genera and 10 tribes, were studied. By applying powerful modern approaches to phylogenetic reconstruction, such as maximum likelihood and Bayesian analysis, we provide new information on the early pulse of evolution within the Arvicolinae. While the position of two highly divergent lineages, Phenacomys and Ondatra , could not be resolved, the tribe Lemmini, appeared as the most basal group of voles. The collared lemmings (Dicrostonychini) grouped together with all of the remaining tribes. The two previously unstudied monotypic genera Dinaromys and Prometheomys form a moderately well-supported monophyletic clade, possibly a sister group to Ellobius (Ellobiusini). Furthermore, with one exception, all tribes ( sensu Musser & Carleton, 2005) proved to be monophyletic and can thus be regarded as meaningful evolutionary entities. Only the tribe Arvicolini emerged as paraphyletic in both analyses because of the unresolved phylogenetic position of Arvicola terrestris . Steppe voles of the genus Lagurus were solidly supported as a sister group to the Microtus and allies clade.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 825–835.     

Cold-Inhibited Phloem Translocation in Sugar Beet: II. CHARACTERIZATION AND LOCALIZATION OF THE SLOW-COOLING RESPONSE

Experiments were undertaken on a simplified sugar beet systemto characterize the phloem translocation response to slow coolingtreatments that were applied to the source leaf petiole. Inthese experiments the temperature was decreased by 4°C every16 min, such that the tissue temperature was lowered from 25°Cto 1°C over a period of 80 min. Our results indicated thatan initial slow cooling treatment, on a given test plant, causedno change in the rate of translocation. However, all subsequentslow cooling regimes that were applied to the same petiole positionelicited a characteristic step-type inhibition. This inhibitionaveraged about 10% of the original translocation rate in allcases with no recovery being observed. The data suggest thatthe initial cooling treatment induced an alteration in the petioletissue which facilitated the inhibition phenomenon during subsequentslow coolings. This alteration was shown to be localized withinthe upstream region of the chilled petiole segment, followingan initial slow cooling, or throughout the chilled petiole segmentafter an initial quick cooling from 25°C to 1°C. Resultsalso show that the alteration is a long-lived phenomenon thathas no detectable influence on the quick-cooling induced transientinhibition of translocation. Key words: Phloem, Translocation, Cooling response, Petiole