Algicidal Sesquiterpene Hydroquinones from the Brown Alga Dictyopteris undulata

Flavoglaucin, its derivatives, and pyranonigrins, which are antioxidants produced by the molds used in fermented foods, were examined for their inhibition of tumor promotion by the Epstein-Barr virus early antigen activation test. Flavoglaucin and its derivatives exhibited high activity. Flavoglaucin and such a derivative as isodihydroauroglaucin inhibited mouse skin tumor promotion in a two-stage carcinogenesis test and appear to be antitumor promoters.     

Immune function, parasitization and extended phenotypes in colour polymorphic pygmy grasshoppers

Ecological and evolutionary consequences of host–parasite interactions have attracted considerable attention from evolutionary biologists. Previous studies have suggested that immune responsiveness may be genetically or developmentally linked with colour pattern, such that the evolution of animal colour patterns may be influenced by correlated responses to selection for parasite resistance. We studied interactions between the endoparasitic fly Leiophora innoxia (Meigen) (Diptera: Tachinidae) and its colour polymorphic pygmy grasshopper host Tetrix undulata (Sow.) (Orthoptera: Tetrigidae) to test for morph‐specific differences in parasitization and immune defence, and host‐induced variation in parasite phenotypes. Our results revealed that c. 2 and 30% of adult grasshoppers collected from the same natural population in two subsequent years, respectively were parasitized. Parasite prevalence was independent of host sex and colour morph. Pupae were larger if the parasite had developed in a female than in a male host, possibly reflecting host resource value or a physical constraint on larval growth imposed by host body size. Pupal size was also associated with host colour morph, with individuals that had developed in dark morphs being smaller at pupation compared to those that developed in paler morphs. However, immune defence, measured as the encapsulation response to a novel antigen, did not differ among individuals belonging to alternative colour morphs or sexes. Darker morphs warm up more quickly and prefer higher body temperatures than paler ones. Encapsulation was not influenced by maintenance temperature (15 vs. 30 °C), however, suggesting that indirect effects of coloration on parasite resistance mediated via differential body temperature are unlikely. The dependence of parasite body size on host colour morph may thus reflect plasticity of growth and development of the larvae in response to differential host body temperature, rather than variable host immune defence. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 373–383.     

Minimal evidence of interspecific hybridisation between the Yellow-billed Duck and introduced Mallard in central and northwestern South Africa

Hybridisation is the interbreeding of genetically distinct groups that can lead to introgression – an exchange of genetic material between species. Hybridisation is of conservation concern when an alien invasive species is involved, as it can lead to a loss of local genetic adaptations and genetic diversity. Hybridisation is a significant threat for many dabbling ducks where interbreeding with the closely related invasive Mallard Anas platyrhynchos is extremely common. Phenotypic evidence suggests that Mallard populations in South Africa hybridise with the indigenous Yellow-billed Duck Anas undulata. The aim of this study was to determine the incidence of hybridisation between Yellow-billed Ducks, occurring in central and northwestern South Africa, and introduced Mallards. Genetic variation between Mallards, Yellow-billed Ducks, and their inferred hybrids was assessed using mitochondrial and microsatellite DNA markers. All samples inferred to be hybrids based on the phenotype were found to have Yellowbilled Duck mitochondrial DNA and showed minimal evidence of admixture across the microsatellite markers. Thus, these results do not support the notion that hybridisation between Mallards and Yellow-billed Ducks is prevalent in central and northwestern South Africa. However, hybridisation could be occurring where Mallards are found in higher abundance, such as in the Western Cape Province. Therefore, continued monitoring of this potential hybridisation should be performed frequently and throughout South Africa.     

NaCl胁迫对滨藜生长及其根和叶中无机离子含量的影响

用不同浓度的NaCl溶液处理滨藜（Atriplex undulata）植株后发现：100mmol/L NaCl促进滨藜地上部及根部生物量积累,高于100mmol/l NaCl,抑制其生长。各部位的Na^ 和Cl^-含量随着NaCl浓度的升高明显增加。NaCl处理下,叶片的Na^ 和Cl^-含量高于根部,幼叶高于老叶,且叶片的K^ （除500mmol/L NaCl处理的老叶外）,根部的K^ 、Ca^2 和NO3^-无显著变化。叶片的Na/K比随NaCl浓度的升高而增加,但较高浓度时下降（在老叶中）或维持稳定（在幼叶中）。随着处理浓度的增加,各部位对K^ 的选择性（相对于Na^ ）增加,渗透调节能力增强,渗透势降低。另外,还讨论了滨藜对盐渍生境的适应特征。     

三肋果莎属(莎草科)、中国一新记录的属

<正> 三肋果莎属(新拟) Tricostularia Nees in Lehm. Pugillus 8: 50. 1844; in Lehm. P1. Preiss. 2:83. 1846—1847; Benth. F1. Austr. 7: 382. 1878; Benth. & Hook. Gen.P1. 3: 1064. 1883; Pax in Engl. et Prantl. Pflanzenr. Fam. 2 ed. 2: 115.1887; Kukenth. in Fedde, Repert. 53: 212. 1944.     

Reverse evolution: selection against costly resistance in disease-free microcosm populations of Paramecium caudatum

Evolutionary costs of parasite resistance arise if genes conferring resistance reduce fitness in the absence of parasites. Thus, parasite-mediated selection may lead to increased resistance and a correlated decrease in fitness, whereas relaxed parasite-mediated selection may lead to reverse evolution of increased fitness and a correlated decrease in resistance. We tested this idea in experimental populations of the protozoan Paramecium caudatum and the parasitic bacterium Holospora undulata. After eight years, resistance to infection and asexual reproduction were compared among paramecia from (1) "infected" populations, (2) uninfected "naive" populations, and (3) previously infected, parasite-free "recovered" populations. Paramecia from "infected" populations were more resistant (+12%), but had lower reproduction (-15%) than "naive" paramecia, indicating an evolutionary trade-off between resistance and fitness. Recovered populations showed similar reproduction to naive populations; however, resistance of recently (<3 years) recovered populations was similar to paramecia from infected populations, whereas longer (>3 years) recovered populations were as susceptible as naive populations. This suggests a weak, convex trade-off between resistance and fitness, allowing recovery of fitness, without complete loss of resistance, favoring the maintenance of a generalist strategy of intermediate fitness and resistance. Our results indicate that (co)evolution with parasites can leave a genetic signature in disease-free populations.     

Genome evolution in allotetraploid Nicotiana

The nuclear cytoplasmic interaction (NCI) hypothesis of genome evolution and speciation in plants states that newly formed allopolyploids pass through a bottleneck of sterility and the fertile plants that emerge are fixed for species‐specific chromosome translocations. These translocations restore fertility and reduce negative effects of the maternal cytoplasm on an alien paternal genome. Using fluorescent in situ hybridization and genomic in situ hybridization and by reviewing published data, we test the NCI hypothesis using three natural Nicotiana allotetraploids (all 2n = 4x = 48, N. arentsii, N. rustica and several genotypes, including a feral plant and cultivars, of N. tabacum (tobacco)). We compare these data with three synthetic tobacco plants (Th37) that are F3 descendent progeny of an allotetraploid formed from ♀N. sylvestris (2n = 24) ×♂N. tomentosiformis (2n = 24). No intergenomic translocations were observed in N. arentsii and N. rustica. An analysis of subtelomeric tandem repeats in these allotetraploids and their putative parents shows minimal genetic changes; those that do occur may reflect evolution in the diploids or the polyploids subsequent to allopolyploidy. All natural N. tabacum genotypes have intergenomic translocations. This may reflect a large ‘genomic‐shock’ generated by allopolyploidy involving widely diverged parental species. Two of three synthetic tobacco plants had a translocation similar to that found in all cultivars of tobacco. This translocation may be significant in tobacco fertility and may have been fixed early in tobacco's evolution. But it is lacking in the feral tobacco, which might indicate a polyphyletic origin or early divergence from all cultivars examined. Overall, only in tobacco is there any evidence that NCI may have influenced genome evolution, and here further data are required to verify chromosome identity. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 599–606.     

新疆准噶尔盆地东部波斑鸨炫耀栖息地选择

2000年4－7月,通过野餐直接观察采样的方法,对准噶尔盆地东部波斑鸨炫耀栖息地进行了研究。结果表明：条块状高灌丛随机散布在视野开阔、地势平坦的小半灌木群落中是波斑鸨炫耀栖息地的景观特征;影响波斑鸨炫耀栖息地选择的主要环境因子是植物种数、植被盖度、密度和蹁高灌丛距离;炫耀地内的植物种数、植被盖度、植被密度和草本植物种数显著低于对照样方内的相应成分;绝大多数炫耀地位于低矮稀疏的半灌木群落中,同时又总是靠近条块状高灌丛。这种灌嵌景观的炫耀地植物群落结构为波斑鸨的生存、炫耀提供了理想场所。