太白山巴山冷杉林主要树种与开花秦岭箭竹的空间点格局分析

采用单变量和双变量O-ring函数对太白山大熊猫栖息地巴山冷杉林主要树种的空间分布格局、种间关联性及其与林下开花箭竹的空间关联性进行了多尺度分析.结果表明: 巴山冷杉林中,巴山冷杉数量最多,但种群结构衰退,白桦种群相对年轻,种群结构稳定,红桦种群也呈衰退趋势;3个主要树种在小尺度上呈聚集分布,随尺度增加,逐渐表现为随机分布.3个树种的空间关联性主要表现在小尺度范围内,随尺度增加,空间分布格局逐渐表现为不关联;巴山冷杉和白桦与开花秦岭箭竹在大、中尺度内呈现正相关,而红桦与开花秦岭箭竹在大、中尺度上表现出负相关.大熊猫栖息地内乔木和林下秦岭箭竹共同推动森林的动态演替和发展,进而影响秦岭大熊猫栖息地的环境变化.     

Relative effects of elevated grazing pressure and competition from a red algal turf on two post-settlement stages of Fucusevanescens C. Ag.

In Nova Scotia, Canada, the lower shore of wave-exposed and semi-sheltered portions of the coast is dominated by a dense turf of the red alga Chondrus crispus C. Ag. The mid shore is dominated by three species of rockweed belonging to the genus Fucus, which are also physiologically competent in the low zone, but may be inhibited by pre-emptive competitive exclusion by red algal turf and/or increased grazing pressure from abundant mesoherbivores. A grazer assay showed that herbivore pressure is >50% higher in the Chondrus zone than in the rockweed zone. Fucus can colonize the low shore only through microrecruits which develop from planktonic zygotes. A main objective of this study was to test the hypothesis that early post-settlement stages represent a critical phase for successful recruitment. We, therefore, tested the relative effects of competitive pressure from Chondrus and grazing on small (2 mm) and larger (6 cm) Fucus evanescens plants in a three-way factorial experiment. Red algal turf and grazers independently depressed F. evanescens growth, but only a combination of factors resulted in a significant weight loss in the rockweeds. The effect size of grazing was more than double that of competition from the turf. Small and larger individuals of F. evanescens were equally affected by grazing and competition. The results showed that colonization by rockweeds may only occur where there are gaps in the Chondrus canopy. We hypothesized that grazer effects may decrease with increasing gap size. However, a controlled experiment showed no differences in Fucus recruitment among the range of naturally occurring gap sizes. That is, larger gaps do not promote rockweed recruitment. In concordance with this observation, we found that grazer abundances were similar among gap sizes. Chondrus was shown to be highly resistant to intense physical and herbivore-induced disturbance. This combination ensures the persistence of a dense canopy which largely excludes rockweed recruitment from zygotes. Competitive dominance of Chondrus on the low shore is not obviously related to individual growth rates or canopy height. A positive correlation between growth rate and competitive ability may be expressed only in morphologically similar species which are likely to compete as germlings.     

Ontogenetic succession and the ant mosaic: An empirical approach using pioneer trees

Arboreal ant mosaics have been intensively investigated, but what generates these mosaics remains poorly understood. In this paper, we hypothesize that the dynamics of arboreal ant mosaics could be better understood by examining the ontogenetic succession of ants in tropical trees. We used three African pioneer tree species as biological models. Lophira alata (Ochnaceae) is a long-lived species that does not furnish any reward (i.e., extra-floral nectaries [EFNs], shelter) to ants, Anthocleista vogelii (Gentianaceae) bears extremely well-developed EFNs, and Barteria fistulosa (Passifloraceae) is a long-lived myrmecophyte providing both EFNs and domatia. For both L. alata and A. vogelii, we noted a succession of different associated ants as the plants grew and aged. Ground-nesting, arboreal-foraging ant species were the first associates, followed by arboreal species that build nests with the leaves of their host trees, together with some species nesting opportunistically in pre-existing cavities. Carton-building Crematogaster species were the last in this succession. The presence of EFNs on A. vogelii slows species turnover, demonstrating that the plant exerts some control over its ant associates. The comparison with B. fistulosa, which generally remains associated with the same plant-ant species during its entire ontogeny, highlights the importance of the selective attractiveness of the trees for their associated ants – or, perhaps, the existence of plant filters that screen arriving ants.     

中国裂隙衣属地衣（文字衣科）的初步研究

在中国文衣科地衣系统研究中,对裂隙衣属Fissurina地衣进行了订正,报道了16种,其中中国新记录种3个,即连绵裂隙衣F. consentanea、球孢裂隙衣F. globulifica和皱体裂隙衣F. insidiosa。建议4个异名,即Fissurina isidiata Z.F. Jia 为Platythecium dimorphodes (Nyl.) Staiger的异名;Fissurina marginata Staiger为Fissurina elaocarpa (A.W. Archer) A.W. Archer的异名;Graphis canlaonensis Vain.为Fissurina consentanea Nyl.的异名;Graphis glauca Müll. Arg.为Fissurina dumastii Müll. Arg.的异名。本文提供了中国裂隙衣属每个种的描述和分布,并提供了鉴定检索表。     

人工覆盖地表对北京典型绿化树光合特性的影响

地表硬化影响城市绿化树生长及生态服务功能的发挥,研究人工覆盖地表下城市绿化树关键生理过程具有重要意义.采用田间模拟试验方法,布设对照(自然地表)、透水硬化和不透水硬化3种覆盖地表,栽植北京2种典型绿化树白蜡和元宝枫,栽植后第4年野外测定其叶片光合及相关生理生态参数,分析人工覆盖地表对北京典型绿化树光合特性的影响.结果表明:白蜡和元宝枫光合作用对不同人工覆盖地表的响应存在差异,对于白蜡而言,透水硬化和不透水硬化地表均使其净光合速率显著降低,对于元宝枫而言,仅不透水硬化地表导致其净光合速率显著降低,透水硬化地表并未对其造成显著影响.透水硬化和不透水硬化地表的空气相对湿度和土壤体积含水率低于对照,植物可利用水分减少,叶片气孔导度下降是白蜡和元宝枫净光合速率降低的主要原因.透水硬化和不透水硬化地表使白蜡PSⅡ有效光化学量子产量(F_v′/F_m′)下降,不透水硬化地表使元宝枫PSⅡ实际光化学量子效率(Φ_PSⅡ)和表观电子传递速率(ETR)升高.     

Induction of tannin acyl hydrolase (EC 3.1.1.20) activity in some members of fungi imperfecti

The potential of gallotannin, methyl gallate, gallic acid, and pyrogallol to induce tannin acyl hydrolase (EC 3.1.1.20) activity in Aspergillus niger, Aspergillus fischerii, Fusarium solani, and Trichoderma viride has been investigated. The maximum induction ratios recorded were A. fischerii (26.7), F. solani (26.1), and T. viride (40.7) when the fungi were induced with gallotannin, gallic acid, and methyl gallate, respectively. A. niger was devoid of basal enzyme activity. The gallotannin tolerance limits for A. niger, A. fischerii, F. solani, and T. viride were determined by progressively increasing the gallotannin concentration and were found to be 20, 4, 3, and 3%, respectively. F. solanii induced with 3% gallotannin has been recommended for the production of tannase enzyme.     

亚高山暗针叶林林缘华西箭竹对岷江冷杉幼苗更新的影响

大量研究表明在箭竹-冷云杉林下,竹类对冷杉的影响大于其它树种。在卧龙自然保护区岷江冷杉(Abies faxoniana)林下,华西箭竹(Fargesia nitida)为灌木层优势种。为了进一步了解箭竹对岷江冷杉幼苗更新的影响,该文采用样带法在四川省卧龙自然保护区亚高山岷江冷杉林林缘,针对华西箭竹和岷江冷杉幼苗展开调查研究。以竹丛覆盖区域为边界,分别向竹丛外2 m (带1)、1 m (带2),向竹丛内1 m (带3)、2 m (带4)、3 m (带5)做5条长30 m的相邻样带,每条样带划分为30个连续的1 m×1 m小样方。对岷江冷杉幼苗数量动态、种群结构、生长与生物量的研究表明: 1)离竹丛越远,大年龄岷江冷杉幼苗数量越多;岷江冷杉幼苗转化率(下一径级苗木数量与前一径级苗木数量之比)随年龄增加而减小,随离竹丛距离增大而增大。2)苗木高度与径级结构相似,随深入竹丛,幼苗数量峰值的径级和高度级分布从较大径级(Ⅲ)向小径级(Ⅰ)变化。3)华西箭竹的存在抑制了岷江冷杉小径级幼苗(Ⅰ)的高生长,基径与高度的回归也表明离竹丛越远,高生长相对更大;但一定密度华西箭竹(带4)增大了大径级(Ⅲ)岷江冷杉幼苗冠幅的扩展。4)岷江冷杉幼苗总生物量随华西箭竹密度的增高而减小,华西箭竹的大量存在抑制岷江冷杉幼苗对地下生物量的分配。总的看来,一定密度华西箭竹环境下岷江冷杉幼苗的生长和更新较好,华西箭竹大量分布的区域,岷江冷杉幼苗的更新和生长受到抑制,可能会影响岷江冷杉种群的扩散以及群落的发展。     

湛江特呈岛红树植物群落结构特征

2008年6月,采用样方调查法对湛江特呈岛红树植物群落结构及白骨壤(Avicennia marina)的种群特征进行了全面调查.结果表明:该地区红树林是白骨壤纯林以及白骨壤为主,有红海榄(Rhizophora stylosa)、木榄(Bruguieragymnorrhiza)和桐花树(Aegiceras corniculatum)的混交林.白骨壤在潮滩上连续分布,红海榄、木榄和桐花树生长于近陆林缘及潮滩的中部,物种多样性指数由陆缘向海缘呈降低趋势.通过分析白骨壤种群的株高、地径在潮滩上的变化规律得出年幼的个体聚集于近陆林缘,近海林缘较少.白骨壤种群的年龄结构为增长型,但是根据生境条件及白骨壤种群在海滩上的分布格局,分析得出该红树林资源处于退化的状态.     

黄顶菊凋落物分解对节肢动物群落结构的影响

选择黄顶菊(Flaveria bidentis)入侵的林地、农田、荒地、沟渠等4种生境作为调查样地, 比较黄顶菊与本地植物凋落物的分解速率及凋落物分解对节肢动物群落结构的影响。于2014年10月凋落物高峰期在各样地内分别搜集黄顶菊与本地植物的凋落物, 每种凋落物称取20 g装入尼龙网分解袋中, 放入各生境。2015年的每个月将不同生境不同处理凋落袋各取回10袋, 用Tullgren法分离节肢动物。 4种生境共捕获17,466头, 隶属8纲18目, 4种生境的优势类群皆为蜱螨目和啮目。其中, 林地、农田、荒地、沟渠4种生境处理组中节肢动物数量分别为1,698头, 1,838头, 2,631头, 3,413头, 分别比对照组高18%, 53%, 22%, 11%。多数月份黄顶菊凋落物中的节肢动物丰富度及多样性指数高于同生境对照组, 并且在黄顶菊生长盛期差异显著; 黄顶菊凋落物的分解速率高于对照植物分解速率, 且各月份凋落物分解速率动态与节肢动物数量变化动态呈显著相关。黄顶菊凋落物对节肢动物的影响与人为干扰程度有关, 这种影响在人为干扰较小的荒地与沟渠生境中更为明显。综上所述, 黄顶菊凋落物的分解改变了节肢动物群落结构, 并引起节肢动物多样性的升高。     

茄病镰刀菌单克隆抗体的制备及胶体金免疫层析试纸条的研发*

Objective: The cell lines secreting specific monoclonal antibodies (McAbs) were prepared by using Fusarium solani, one of the pathogenic fungi causing root rot of Fritillaria thunbergii, and the colloidal gold immunochromatographic test strip based on McAbs was developed to provide scientific basis for detecting root rot of F. thunbergii. Methods: Hybridoma technology was used to obtain cell lines that could secrete specific McAbs against F. solani using the whole protein extract of F. solani as the antigen. The specificity, titer, sensitivity and binding protein of McAbs were detected by indirect ELISA and Western blot. Colloidal gold particles were prepared by trisodium citrate reduction method and McAbs were labeled to prepare colloidal gold immunochromatographic strip. Results: Three cell lines secreting specific McAbs against F. solani were obtained, which were named as FsA3, FsG6 and FsD4. The detection sensitivity of FsA3 was 24.41 ng / mL, and that of both FsG6 and FsD4 was 12.21 ng / mL. FsA3, FsG6 and FsD4 had strong reactions to F. solani, and had no cross-reaction to Alternaria tenuissima, A. alternata, Botrytis cinerea, F. equiseti, F. incarnatum, F. oxysporum, Phoma sp., and Phomopsis oblonga. The colloidal gold immunochromatographic strip based on FsG6 showed only a quality control line when detecting the tissue culture seedlings of F. thunbergii. When 100 ng F. solani antigen or the samples of F. thunbergii infested with root rot disease were detected, there were visible quality control lines and test lines. Conclusion: The specificity and sensitivity of the McAbs and test strip are sufficient to detect F. solani isolated from diseased strains of F. thunbergii, which provides the technical support for the rapid detection of root rot of F. thunbergii in the field.     

Daily Rhythms of Body Temperature in Acornys russatus: The Response to Chemical Signals Released by Acomys cahirinus

Two species of spiny mice of the genus Acomys—the golden spiny A. russaturs and the common spiny A. cuhirinus—are syrnpatnc in the and and hot parts of the Rift Valley in Israel. The coexistence of these two species is due to exclusion of A. russatus mice by A. cuhirinus mice from nocturnal activity. The aim of this research was to study if odor signals released by A. cahirinus mice can play a role in the exclusion of A. russatus mice. A. russatus mice with an implanted transmitter recording body temperature (T_b) were kept alone in a metabolic chamber under constant conditions of ambient temperature (27°C) and photoperiod (12 h light: 12 h dark). After 5 days of recording, chemical signals from an A. cuhirinus mouse were added through the air tube going into the metabolic chamber of the A. russatus mice. This treatment caused a shift of ∼ 2 h inT_b daily rhythm of the naive tested A. russutus mice, whereas no shift was observed in A. russatus mice that had been kept in the same room with the A. cahirinus mouse before measurements. These results strongly support the idea that chemical signals released by A. cahirinus mice can entrain the T_b rhythms of A. russatus mice. Therefore, it may be assumed that the exclusion of A. russatus mice from nocturnal activity by A. cuhirinus mice could be achieved through the odor released by the latter.     

Species richness in macroalgae and macrofauna assemblages on Fucus serratus L. (Phaeophyceae) and Zostera marina L. (Angiospermae) in Skagerrak, Norway

The macrophytes Fucus serratus and Zostera marina form similar substrates for associated flora and fauna in shallow waters in Norway. While F. serratus forms a more or less continuous belt on rocky substrate along the coast, Z. marina forms disjunct populations on sandy or muddy bottoms. This study focused on the organisms associated with these two macrophytes in two localities in the Skagerrak region. In total, 130 taxa of epiphytic organisms were identified: 22 green algae, 41 red algae, 32 brown algae, eight diatoms and 27 sessile animals. One hundred and twenty-seven taxa of mobile macrofauna were registered. The dominant group was crustaceans, with amphipods as the order containing most species. Many species of both plants and animals preferred one or the other habitat. It is concluded that coastal macrophyte systems have high species diversity.     

Interspecific variation in chemical defenses in the sea hares (Opisthobranchia: Anaspidea)

Most species of sea hares (Opisthobranchia: Anaspidea) sequester secondary metabolites from their algal diets in their digestive glands. Aplysia Juliana Quoy and Gaimard, 1832, a sea hare that feeds on Ulva spp. and Enteromorpha spp., algae with few or no secondary metabolites, were compared with the sympatric sea hares A. oculifera Adams and Reeve, 1850, A. kurodai (Baba, 1937), and Dolabella auricularia (Solander, 1786), all of which eat chemically rich algae, to see if sequestered secondary metabolites afford protection to sea hares from potential predators. Organic extracts of whole A. Juliana stimulated, and organic extracts of whole D. auricularia deterred feeding by crabs. However, tests with organic extracts of individual body parts indicated that this pattern was due almost exclusively to unpalatability of extracts of D. auricularia digestive glands. Tests with pieces of tissue from the exterior of the animals, or with extracts of such tissues, showed no consistent patterns indicating that A. Juliana were more palatable than other sea hares. Sea hare egg masses do not appear to contain diet-derived secondary metabolites. However, pieces of egg masses of A. Juliana and D. auricularia were universally rejected by crabs and reef fish, and extracts of A. Juliana egg masses deterred feeding by some reef fish. Finally, both opaline secretion of A. Juliana and ink of A. kurodai, but not ink of D. auricularia, none of which appear to contain diet-derived secondary metabolites, deterred feeding by crabs. Opaline secretion from A. Juliana, but not ink from A. kurodai, induced avoidance behavior in crabs. Although sequestered secondary metabolites clearly can affect the palatability of the digestive gland, there is little evidence that they affect the palatibility of the ink, opaline secretion, eggs, or skin, suggesting that sequestered secondary metabolites may not play a key role in anti-predator defense of sea hares.     

Phenotypic analysis of adults of Fasciola hepatica, Fasciola gigantica and intermediate forms from the endemic region of Gilan, Iran

Fascioliasis is an important human and animal disease caused by Fasciola hepatica and Fasciola gigantica. In Iran, the distribution of these two species overlaps in most areas, including the northern human endemic province of Gilan where both fasciolids are simultaneously found in individual cattle and buffaloes. A phenotypic study of fasciolid adult flukes from naturally infected bovines from Gilan was carried out by means of an exhaustive morphometric analysis using traditional microscopic measurements and an allometric model. The Iranian fasciolids were compared to F. hepatica and F. gigantica standard populations, i.e. from geographical areas where both species do not co-exist (Bolivia and Burkina Faso, respectively). Although morphometric values somewhat overlapped, there were clear differences in allometric growth. The allometric function was adjusted to 25 pairs of variables. Results obtained revealed that Iranian F. hepatica-like specimens are larger than the F. hepatica standard and Iranian F. gigantica-like specimens are longer and narrower than the F. gigantica standard, but with smaller body area. Measurements which permit a specific differentiation in allopatric populations (distance between ventral sucker and posterior end of the body; ratio between body length and body width) overlap in the specimens from Gilan, thus proving the presence of intermediate forms. When compared to the standard populations, the different Iranian fasciolid morphs show greater differences in F. gigantica-like specimens than in F. hepatica-like specimens. This study shows that simple, traditional microscopic measurements may be sufficient for the morphometric characterisation of fasciolids, even in areas where intermediate forms are present.     

The effects of brown alga proteins and polysaccharides on egg fertilization and the development of embryos of the sea urchin Strongylocentrotus intermedius A. Agassiz, 1863

The toxic effects of a water–ethanol extract of the brown alga Saccharina (= Laminaria) cichorioides and the isolated I₁ and I₂ proteins on egg fertilization and the development of embryos of the sea urchin Strongylocentrotus intermedius were revealed and studied. The protective effects of fucoidans and 1,3;1,6-β-D-glucans (laminarans, translam, and glucan II) that were isolated from the brown algae S. cichorioides and Fucus evanescens against the toxic impacts of the I₁ and I₂ proteins were examined. It was found that the lifespan of sea urchin embryos increased from 1.5 to 3 times in the presence of 1,3;1,6-β-D-glucans and fucoidans, whereas the I₁ and I₂ proteins decreased embryo viability by 2 times. Preadministration of polysaccharides completely neutralized the inhibitory effects of the proteins on developing embryos. It was also shown that a water–ethanol extract of S. cichorioides, derived I₁ and I₂ proteins, and fucoidans has a contraceptive effect.     

In vitro evaluation of antagonistic properties of Pseudomonas corrugata

Pseudomonas corrugata, a soil bacterium originally isolated from a temperate site of Indian Himalayan Region (IHR) is examined for its antagonistic activities against two phytopathogenic fungi, Alternaria alternata and Fusarium oxysporum. Although the bacterium did not show inhibition zones due to production of diffusible antifungal metabolites, a reduction in growth between 58% and 49% in both test fungi, A. alternata and F. oxysporum, was observed in sealed Petri plates after 120 h of incubation due to production of volatile antifungal metabolites. Reduction in biomass of A. alternata (93.8%) and F. oxysporum (76.9%) in Kings B broth was recorded after 48 h of incubation in dual culture. The antagonism was observed to be affected by growth medium, pH and temperature. The reduction in fungal biomass due to antagonism of bacteria was recorded maximum in the middle of the stationary phase after 21 h of inoculation. The production of siderophore, ammonia, lipase and chitinase in growth medium by P. corrugata were considered contributing to the antagonistic activities of the bacterium.     

Feeding on dinoflagellates by intermediate and late stage crab zoeae raised in the laboratory and collected from the field

Hatching stage crab larvae will ingest algae, including non-toxic and toxic dinoflagellates. We determined that later zoeal stages, obtained from both laboratory-raised larvae and natural assemblages, also ingest dinoflagellates and we measured the effects of prey density, prior feeding history and time of exposure to prey on incidence of ingestion. Both stage 1 and later stage larvae exposed to algal prey were examined using epifluorescence for the presence of chl a. Both stage 1 and stage 3 laboratory-raised Cancer oregonensis (Dana) and Hemigrapsus nudus (Dana) ingested both the non-toxic dinoflagellate Prorocentrum micans Ehrenberg and the toxic Alexandrium andersoni Balech, with no difference between the stages. Both species showed higher ingestion of P. micans than A. andersoni. Ingestion of both prey types occurred at prey densities as low as 200 cell ml^− 1 in C. oregonensis and 50 cells ml^− 1 in H. nudus. Samples collected in summer, 2004, provided both stage 1 and late stage Lophopanopeus bellus (Stimpson); stage 1, intermediate, and late stage Fabia subquadrata Dana; and an unidentified porcellanid. Stage 1 L. bellus ingested both prey, while late stage zoeae did not, although the latter apparently were not actively feeding. F. subquadrata fed on both prey, with no difference between early and late larvae. Both stages ingested P. micans more readily than A. andersoni. First evidence of ingestion of P. micans at 600 cells ml^− 1 occurred after only 0.5 h, while it took 2 h for ingestion at 50 cells ml^− 1. The model of larval feeding involving both omnivory and prey discrimination described previously for the hatching stage is sustained throughout zoeal development and is, perhaps, an adaptation to an uncertain prey environment, one that trades opportunism for inefficiency.     

Population genetic structure of the giant panda staple food bamboo (Fargesia spathacea complex) and its taxonomic implications

The taxonomy of woody bamboo presents many difficulties due to its long blooming interval and complex morphological variation. Whether the current taxonomy reflects genuine species divergence within woody bamboo is an intriguing question. The Fargesia spathacea Franch. complex comprises 15 closely related species with a sympatric distribution in China. Their classification has long been controversial because only a handful of vegetative traits are available, providing a good opportunity to explore the evolutionary relationships and genetic differentiation in woody bamboo. Here, we present a study involving 750 individuals from 39 representative populations in the F. spathacea complex using 14 simple sequence repeat markers. We found varying degrees of genetic diversity across populations of the F. spathacea complex (He = 0.07–0.81) and largely negative F-values at the population level, implying an excess of heterozygotes in the populations. Phylogenetic analyses revealed that all populations were divided into two major groups (clusters A and B), with the majority of the 15 species representing distinct genetic lineages. Based on population genetic analysis along with morphological evidence, we confirmed the identity of three species (F. decurvata J. L. Lu, F. spathacea, and F. murielae Gamble) and suggested the invalidation of four other species (F. scabrida T. P. Yi, F. robusta T. P. Yi, F. denudata T. P. Yi F. murielae (Gamble) T. P. Yi, and F. nitida (Mitford) Keng f. ex T. P. Yi). The delimitation of the remaining eight species has yet to be explored. The analysis of ecological factors and spatial autocorrelation suggested that altitudinal differences might account for the distinct genetic divergence between the two major groups.     

Loss of innovative traits underlies multiple origins of Aquilegia ecalcarata

Traits are basic attributes of organisms that form the basis for speciation and diversity. The floral nectar spur is a classic example of a key innovative trait. Differences in nectar spur morphology can lead to pollinator specialization and thereby promote reproductive isolation between species. Despite its importance, the nectar spur has been lost in some members of the columbine genus (Aquilegia), resulting in a new spurless trait, and the evolutionary influence of this trait has become a topic of scientific interest. Aquilegia ecalcarata is an important representative columbine species that lacks spurs. Here, we resequenced the genomes of 324 individuals from A. ecalcarata and four related species. We found that A. ecalcarata was divided into three groups based on the phylogenetic relationships and population genetic structures. Topology weighting analysis revealed that A. ecalcarata has multiple origins, and Patterson′s D statistic showed that the spurless trait may have one origin. Floral morphological analysis revealed significant differences between A. ecalcarata and its spurred sister groups, and the floral phenotypes of the three A. ecalcarata groups have identical or similar floral phenotypes. Our results confirmed that the spurless trait not only produced the phenotype of A. ecalcarata but also contributed to the emergence of the A. rockii phenotype. Moreover, the spurless trait promoted the divergence between A. ecalcarata and its close, spurred relatives. Our research shows that the loss of key innovative traits can play a very important role in speciation and species diversity.     

Interaction between algae and seed germination in tropical dune slack species: a facilitation process

The importance of algae dune slack stabilisation has been extensively analysed, but little has been done regarding their potentially favourable role in germination and establishment of phanerogams. Dune slack is a seasonal freshwater habitat that depends on water table level fluctuation. Our hypothesis is that in these highly unpredictable systems, algae maintain a certain degree of humidity in the soil and, thus, permit phanerogam germination and establishment. The objective of this study was to compare the germination of four species characteristic of tropical dune systems: Cyperus articulatus L., Fimbristylis cymosa R. Br., Fuirena simplex Vahl and Rhynchospora colorata (L.) Pfeiffer, in different substrates and degrees of humidity. For germination trials, seeds of the four species were placed each on three substrates: in sand (control), filamentous algae on sand and cotton on sand. Two irrigation protocols were followed: continual watering (wet treatment) and weekly watering (dry treatment). Each week during a 21-week period, the number of germinated seeds from each species was recorded. The highest percentage of germination for the four species was observed during wet treatment. C. articulatus had the highest germination rate of the four species in algae (70%), and cotton (51%) on sand. Highest germination for F. simplex, F. cymosa and R. colorata took place in algae, although the percentages were very low. Differences in germination between the three substrates for these species were statistically significant (P<0.05). During dry treatment, C. articulatus was the only species that exhibited a significant germination, principally in algae and cotton. The results suggest that algae maintain substrate humidity and favour germination of the four species. This could be important in sand dune slacks where marked fluctuations in temperature and humidity occur.