Documenting the Effect of Foundress Number in a Dioecious Fig, Ficus fistulosa, in Malaysia

We studied foundress number and its effect on seed production in a dioecious fig Ficus fistulosa in Sarawak, Malaysia. The effects of flowering time and the two-way interaction of flowering time and tree location on foundress number were statistically significant. A multiple regression indicated seed production increased significantly with the number of foundresses. Our results indicate that phenology and local ecological factors generate a large variance in foundress number, which in turn affects the reproductive success of F. fistulosa.     

Variation in Gender and Flower‐Size Dimorphism in the Dioecious Tree Dombeya ciliata,an Endemic to La Reunion Island1

The genus Dombeya is an important component of tropical forests in west Africa, Madagascar, and the Mascarene islands, but little is known about the reproductive biology of its members. In this study, we quantified gender variation and flower‐size variation in three populations of the dioecious tree Dombeya ciliata, an endemic of La Reunion Island (Indian Ocean). Variation among the three populations was observed for three characters. First, the high elevation population had strict males and females, whereas in the two low elevation populations, males were inconstant, with > 50 percent of the males set a small number of fruit. Second, females showed greater seed production at high elevation. Third, flower‐size dimorphism was greater at high elevation because male flowers were larger than female flowers.     

Parasitoid and inquiline attack in the galls of four alien, cynipid gall wasps: host switches and the effect on parasitoid sex ratios

1. Four alien cynipid gall wasps of the genus Andricus are established and still spreading in the British Isles. The order, according to the northerliness of their distribution boundary, is: A. corruptrix→A. quercuscalicis→A. lignicola→A. kollari. All four aliens have a sexual generation in spring on Quercus cerris (introduced to Britain) and an agamic generation in autumn on native oak species. 2. For 2 years 1994 and 1995, galls of both generations of the four alien species were sampled at eight sites from the south of England to the north of Scotland to determine the parasitoid and inquiline species that attack the new galls. The spring generations of the invading species shared a parasitoid complex of four pteromalid species. Five species of inquilines and 11 species of parasitoids emerged from the autumn galls. 3. Two colonisation events were recorded for A. lignicola and A. corruptrix. On both occasions, the spring generations were found first at the new sites, indicating that the agamic generation provides the colonisers for these invading species. After colonisation, the galls of both species were attacked by parasitoids in their first season. 4. In spring, the invading species were among the most abundant cynipids at all eight sites. By sampling the whole local community of cynipid galls, it was found that the parasitoid species attacking the spring galls of the invaders seemed to have shifted their attack to the new hosts. 5. The secondary sex ratios of the parasitoid species emerging from the sexual galls of A. quercuscalicis (the smallest of the four) showed a strong and significant male bias at all sites and in both years. Parasitoid emergence from the galls of the sexual generations of the other three species (all about equal in size) was between 60 and 70% male, and variable among sites and between years.     

Effects of Host Size and Parasite Burden on Sex Ratio in the Mosquito Parasite Octomyomermis muspratti

The ratio of Octomyomermis muspratti to the host mosquito at the time of exposure had little effect on the ratio of male to female parasites that resulted. However, the ratio of males to females increased as the number of parasites/host increased. Hosts with a single nematode produced fewer than 1% males in comparison with hosts with 8 parasites which produced about 40% males; hosts with 10 or more nematodes generally produced more male than female nematodes. Males of O. muspratti usually emerged before females because of the earlier death of multiply-infected mosquitoes. The size of the host at the time of invasion bad no significant influence on nematode sex ratios. Since mating is apparently necessary for reproduction in O. muspratti, the low male to female ratios that occur will be important in developing successful mass production techniques.     

On the possible role of nonreproductive traits for the evolution of unisexuality: Life‐history variation among males,females, and hermaphrodites in Opuntia robusta (Cactaceae)

In angiosperms, dioecy has arisen in 871–5,000 independent events, distributed in approximately 43% of the flowering families. The reproductive superiority of unisexuals has been the favorite explanation for the evolution of separate sexes. However, in several instances, the observed reproductive performance of unisexuals, if any, does not seem to compensate for the loss of one of the sex functions. The involvement of fitness components not directly associated with reproduction is a plausible hypothesis that has received little attention. Life‐history traits recently recognized as predictors of plant performance were compared among males, females, and hermaphrodites of a rare trioecious Opuntia robusta population in the field, using the cladode as the study unit. Cladode mortality by domestic herbivores was common and higher in females and hermaphrodites than in males. Males, females, or both displayed lower shrinkage and higher rates of survival, growth, and reproductive frequency than hermaphrodites. Unisexuals simultaneously outperformed hermaphrodites in demographic traits known to compete for common limiting resources, such as the acceleration of reproductive maturation (progenesis) and survival. A meta‐analysis combining the outcomes of each of the analyzed life‐history traits revealed a tendency of males (d₊₊ = 1.03) and females (d₊₊ = 0.93) to outperform hermaphrodites in presumably costly demographic options. Clonality is induced by human or domestic animal plant sectioning; and males and females highly exceeded hermaphrodites in their clonality potential by a factor of 8.3 and 5.3, respectively. The performances of unisexuals in the analyzed life‐history traits may enhance their reproductive potential in the long run and their clonality potential and could explain the observed increase of unisexuality in the population. Life‐history traits can be crucial for the evolution of unisexuality, but their impact appears to be habitat specific and may involve broad ontogenetic changes.     

Herbivory in the tilapia Oreochromis niloticus: a comparison of feeding rates on phytoplankton and periphyton

A quantitative comparison of the grazing behaviour of young Oreochromis niloticus feeding on the planktonic cyanobacterium Microcystis aeruginosa and a periphytic community dominated by the cyanobacterium Oscillatoria sp., determined that biomass ingestion rates of fish filter-feeding on planktonic cyanobacteria were significantly lower than those surface-grazing on periphyton. Comparisons of published laboratory data on filter-feeding with field data on algal ingestion rates suggest that filter-feeding may be a relatively unimportant method of ingesting algae.     

Differential stratification, movement and parasitism of sexes of the bagworm, Thyridopteryx ephemeraeformis on redcedar

Abstract. 1. Male and female bagworm larvae develop and pupate at different heights on redcedar trees.
2. Habitat segregation by height of male and female bagworms is apparent by the third instar, and results in part from differential movement of male and female larvae on redcedar foliage during their development. Females gradually ascend the crown, whereas males remain at the same height on the tree.
3. Parasitism of male bagworm pupae was greater than for female pupae. Pupal parasitism is heaviest in the bottom of redcedar trees, where most male bagworms pupate.
4. Several hypotheses are offered concerning the origin and maintenance of differential habitat utilization by male and female bagworms, despite apparently strong selection against males pupating low in the crowns of redcedar.     

The cost of realized sexual reproduction: assessing patterns of reproductive allocation and sporophyte abortion in a desert moss

The desert moss Syntrichia caninervis exhibits one of the most skewed sex ratios in the plant kingdom, with female individuals far outnumbering male individuals (exceeding 14♀:1♂). The "cost of sex hypothesis" derives from allocational theory and predicts that the sex which is most expensive should be the rarer sex. This hypothesis, which, as considered here represents the realized cost of sexual reproduction, is contingent upon two assumptions that are explored: (1) that male sex expression is more expensive than female sex expression, and (2) that sexual reproduction is resource limited. Using inflorescence biomass and discounting sperm, male sex expression was found to be in the neighborhood of one order of magnitude more expensive than female sex expression, and this difference is reflected in higher numbers of gametangia per male inflorescence, presence of paraphyses in male inflorescences, and a much longer developmental time for male inflorescences. The realized cost of female reproduction from two communities dominated by S. caninervis was found to be lower than the realized cost of male sexual reproduction. Resource-limited reproduction was assessed by determining the frequency of sporophyte abortion, the age distribution of sporophyte abortions, and patterns of sporophyte abortion that may be density dependent. Among ten sexually reproducing populations, abortive sporophytes occurred at a frequency of 0.64. Abortive sporophytes averaged 8% the mass of mature sporophytes, and cohort sporophytes from the same individual female were found to abort in a density-dependent pattern. We conclude that the two assumptions, upon which the cost of sex hypothesis depends, are supported.     

Direct and indirect effects of two herbivore species on resource allocation in their shared host plant: the rhizome galler Eurosta comma, the folivore Trirhabda canadensis and Solidago missouriensis

We examined the effects of the rhizome galling fly, Eurosta comma (Wiedemann), on rhizome mass and nitrogen allocation in a clone of its goldenrod host plant, Solidago missouriensis Nutt. In comparison to ungalled ramets, galled ramets initiated significantly fewer new rhizomes, and allocated less mass to leaves and stems and more to roots. Galled ramets had lower concentrations of nitrogen in roots and rhizomes but leaf and stem nitrogen concentrations were not affected. In the second year of our study, outbreaks of the leaf-eating beetle, Trirhabda canadensis (Kirby), occurred in three of our four study clones, removing ∼20%, ∼50%, and 100% of leaf area from clones 2–4, respectively. In the most heavily grazed clones, the influence of rhizome galls on plant resource allocation was least pronounced. Despite the overwhelming immediate impact of grazing, the presence of a gall population may be important because they decrease the ability of S. missouriensis clones to initiate new rhizomes and hence to recover from defoliation. Received: 28 December 1997 / Accepted: 28 December 1998     

Effects of Patch Size and Floral Herbivory on Seed Set in Trichogoniopsis adenantha (Asteraceae) in Southeastern Brazil1

The effects of patch size and floral herbivory on reproductive success of Trichogoniopsis adenantha (Asteraceae) were studied in a semideciduous forest in southeastern Brazil. Plants in large patches and capitula not attacked by endophagous insects had higher seed set. The consequences of living in large or small patches for plant reproductive success are discussed.     

Herbivory and plant competition effects on the population dynamics of Naufraga balearica,a threatened narrow endemic species of the Balearic Islands

Naufraga balearica is a caespitose member of the Umbelliferae and is endemic to Majorca. We conducted a 12-year study in which permanent plots were monitored (each plot was divided into 100 cells) to assess (1) the natural population dynamics, (2) goat herbivory (1998–2003) and (3) plant competition. Using photographs and a G-test of independence, we analysed the frequency of cells in which a species was present and, for each annual transition, the frequency of cells where the species was stable, decreased or increased for each species and treatment (plots open to herbivores vs. closed plots). The natural dynamics of this threatened species showed a clear decline at the study site. Dactylis glomerata and Erodium reichardii were the species that appeared to have the greatest effect on the presence of N. balearica, especially in the closed plots. The competition effect of neighbouring species was not homogeneous throughout the 11 annual transitions analysed, suggesting that other factors affect the dynamics of the threatened species. Some herbivory pressure is beneficial to N. balearica because the species fluctuates more in the opened plots and the behaviour of the goats helps to control competing species, permitting the establishment of N. balearica.     

Studies on Formation of Flower Bud and Prerequisite of Flowering in Vitro in Gentiana manshurica Kitag

Large amounts of plantlets of Gentiana manshurica Kitag. from germinated seeds in vitro can be obtained by micropropagation. Flower buds differentiate on shoot tip and leaf axil when ptantlets are transferred into MS medium supplemented with 0.4 mg/l zeatin, 0.2 mg/l NAA, 0.4 mg/l kinetin and 2 mg/l succinic acid-2, 2-dimethyl hydrazide under the cultural conditions of 28±2℃, 1,300 lx and 8 hours per day. The anthesis of blue-purple flower can prolong to 4 weeks. The development of pollen and ovule is normal and is similar to that of Gentiaceae described in the monograph"Systematic embryology of the angiosperms", by Davis (1966). Flowers in vitro are utilized expectantly for breeding or for commerical use directly.     

Effects of Herbivory,Fire and N<Subscript>2</Subscript>-fixation on Nutrient Limitation in a Humid African Savanna

The quantities and spatial distribution of nutrients in savanna ecosystems are affected by many factors, of which fire, herbivory and symbiotic N₂-fixation are particularly important. We measured soil nitrogen (N) pools and the relative abundance of N and phosphorus (P) in herbaceous vegetation in five vegetation types in a humid savanna in Tanzania. We also performed a factorial fertilization experiment to investigate which nutrients most limit herbaceous production. N pools in the top 10 cm of soil were low at sites where fires were frequent, and higher in areas with woody legume encroachment, or high herbivore excretion. Biomass production was co-limited by N and P at sites that were frequently burnt or heavily grazed by native herbivores. In contrast, aboveground production was limited by N in areas receiving large amounts of excreta from livestock. N₂-fixation by woody legumes did not lead to P-limitation, but did increase the availability of N relative to P. We conclude that the effects of fire, herbivory and N₂-fixation upon soil N pools and N:P-stoichiometry in savanna ecosystems are, to a large extent, predictable. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author Contributions  P.C., H.O.V. and P.E. designed the study and wrote the paper. P.C. and T.K. performed the research and analyzed the data.     

化学调控四季花龙眼成花座果的初步研究

不同化学试剂组合对四季花龙眼枝梢生长和成花座果研究表明,不同时期成熟的枝梢对四季花龙眼成花座果无重大的影响;乙烯利、多效唑和赤霉素三者共同作用可促进成花座果;当枝梢充分成熟时,树冠喷施乙烯利250mg·L-1+多效唑450mg·L-1,谢花3/4时再喷施赤霉素50mg·L-1,可以有效抑制四季花龙眼植株新梢的萌发,促使植株100%成花,并且花穗和果穗性状的综合表现最好。     

南瓜茎、叶、花的营养成分分析

对南瓜茎、叶、花等部位进行了粗脂肪、粗蛋白、粗纤维、总糖、Vc等主要营养成分和K、Na、Ca、Mg、Zn等矿质元素的测定。结果表明,南瓜茎、叶、花营养丰富,各种营养成分较为全面。南瓜叶中粗脂肪、粗蛋白、Vc、K、Ca、Mg、Mn、Fe、Zn等成分含量均高于南瓜茎和南瓜花。与其他8种常见蔬菜相比,主要营养成分和矿质元素含量也远远高于这8种蔬菜。为南瓜茎、叶、花的菜用价值提供了科学依据,也为增加人们的膳食营养、改变餐桌食品花样、开发蔬菜资源及其利用价值提供了参考。     

Sex expression, sex-specific traits, and the effects of salinity on growth and reproduction of Amaranthus cannabinus (Amaranthaceae), a dioecious annual

Amaranthus cannabinus was studied to investigate some of the ecological factors thought to be involved in the evolution of dioecy and to investigate the effects of salinity on sex expression and sex-specific selection. In the field portion of this study, sex ratios, stability of sex expression, spatial distribution, allocation strategies, and phenologies of the sexes were investigated in New Jersey freshwater and salt marsh populations of water hemp. To examine the effects of salinity on vegetative and reproductive development of males and females, plants were grown in the greenhouse at three salinity levels. Adult sex ratios were found to be 1:1. Temporal deviations from a 1:1 sex ratio varied by population and were due to differences in flowering phenology and mortality between the sexes. No plants were observed to change sex expression, and there was no evidence of spatial segregation of the sexes in the field. In both the field and the greenhouse, females allocated more resources to vegetative tissues and had a longer growing period than males. The results of this study suggest that increased reproductive efficiency through sex-specific growth patterns may have been an important selective factor involved in the evolution of dioecy in A. cannabinus.     

枇杷花茶水提物的镇咳、抗炎与抗氧化作用研究

采用小鼠氨水致咳法研究枇杷花茶水提物镇咳效果,以二甲苯致小鼠耳肿胀法研究其抗炎效果,并从枇杷花茶的还原能力及对超氧阴离子和羟自由基的清除作用分析枇杷花茶水提物的抗氧化效果。结果表明,枇杷花茶的水提物高剂量组(3000 mg·kg-1)、低剂量组(700 mg·kg-1)均有镇咳抗炎效果,水提物的浓度越高,效果越好。各浓度枇杷花茶水提物均表现出一定的还原能力,对于羟基自由基和超氧阴离子都有一定的清除效果。其中,20 mg·mL-1水提物还原效果最好(吸光值0.903),超过0.2 mg·mL-1抗坏血酸(吸光值0.814);10 mg·mL-1的水提物对超氧阴离子的清除率为47.32%;20 mg·mL-1水提物对于羟基自由基的清除效果非常明显,清除率为91.62%。枇杷花茶水提物镇咳、抗炎、抗氧化效果明显。     

Effects of Mycorrhizae and Nontarget Organisms on Restoration of a Seasonal Tropical Forest in Quintana Roo, Mexico: Factors Limiting Tree Establishment

We initiated a study of the effects of mycorrhizal fungal community composition on the restoration of tropical dry seasonal forest trees. Tree seedlings were planted in a severely burned experimental site (1995 fire) during the growing season of 1998 at the El Edén Ecological Reserve, in north Quintana Roo, Mexico. Seedlings of Leucaena leucocephala, Guazuma ulmifolia, Caesalpinia violacea, Piscidia piscipula, Gliricidia sepium, and Cochlospermum vitifolium were germinated in steam‐sterilized soil and either remained uninoculated (nonmycorrhizal at transplanting) or were inoculated with mycorrhizal fungi in soils from early‐seral (recently burned) or late‐seral (mature forest) inoculum. Inoculum from the early‐seral soil was largely Glomus spp., whereas a diverse community of arbuscular mycorrhizal fungi were reintroduced from the mature forest including species of Scutellospora, Gigaspora, Glomus, Sclerocystis, and Acaulospora. Plants grew better when associated with the mature forest inoculum, unlike a previous experiment in which plants grew taller with the early‐seral inoculum. Reasons for the different responses include a less‐intense burn resulting in more residual organic matter. In addition to mycorrhizal responses, plants were severely affected by deer browsing. One tree species, C. vitifolium found in the region but not in the reserve, was eliminated by a resident fungal facultative pathogen. Several practical conclusions for restoration can be made. The common nursery practice of soil sterilization may be detrimental because it eliminates beneficial mycorrhizal fungi; species not native to the site may not survive because they may not be adapted to the local pathogens; and herbivory can be severe depending on the landscape context of the restoration.     

Colony structure of a slavemaking ant. I. Intracolony relatedness, worker reproduction, and polydomy

Colony and population structure of the obligate slavemaker ant Protomognathus americanus was analyzed via four nuclear microsatellite loci and mitochondrial DNA (mtDNA) markers. Colonies of P. americanus usually contain a single queen, and here we show that she is singly inseminated. Nestmate workers are generally full sisters and their relatedness does not deviate from the expected value of 0.75. Even though colonies were strictly monogynous, we were able to infer that colony takeover by related queens was common and queen replacement by unrelated queens was rare. Polydomy is widespread, with neighboring nests having the same genetic composition. Although we found no evidence of population viscosity or inbreeding from nuclear markers, mtDNA markers provided evidence for small-scale genetic structuring. Haplotype structuring and takeover by related queens suggest philopatry of newly mated queens. In this species, workers reproduce in queenright and queenless nests and worker reproduction accounts for more than 70% of all males. Although sex-ratio theory points to slavemaking ants as important systems for studying queen-worker conflict, our results indicate no basis for such conflict in P. americanus, because extensive worker reproduction generates shifts in relatedness values. Rather, the dual effects of independent polydomous nest units and local resource competition among queens produce male-biased allocation ratios in this species.     

Abundance and Flower Visits of Bees in a Cerrado of Bahia,Tropical Brazil

Abundance, seasonal phenology and flower visits of eusocial bees were studied in Diamantina, a national park with cerrado vegetation in Bahia, tropical Brazil. About 700 bees were collected, mainly native stingless bees and the introduced Africanized honey bee. Sampling along a transect was most effective March through September during the dry season. The foraging worker bees were observed on flowers of over 60 angiosperm species of which a few were visited with high frequency. Foraging activity concentrated on flowering plants of the families Leguminosae and Asteraceae. The results are discussed under aspects of nutritional resource partitioning by bee communities in neotropical habitats and the specific composition of a cerrado apifauna.