Number of conspecifics and reproduction in the invasive plant Eschscholzia californica (Papaveraceae): is there a pollinator‐mediated Allee effect?

The component Allee effect has been defined as ‘a positive relationship between any measure of individual fitness and the number or density of conspecifics’. Larger plant populations or large patches have shown a higher pollinator visitation rate, which may give rise to an Allee effect in reproduction of the plants. We experimentally tested the effect of number of conspecifics on reproduction and pollinator visitation in Eschscholzia californica Cham., an invasive plant in Chile. We then built patches with two, eight and 16 flowering individuals of E. californica (11 replicates per treatment) in an area characterised by dominance of the study species. We found that E. californica exhibits a component Allee effect, as the number of individuals of this species has a positive effect on individual seed set. However, individual fruit production was not affected by the number of plants examined. Pollinator visitation rate was also independent of the number of plants, so this factor would not explain the Allee effect. This rate was positively correlated with the total number of flowers in the patches. We also found that the number of plants did not affect the seed mass or proportion of germinated seeds in the patches. Higher pollen availability in patches with 16 plants and pollination by wind could explain the Allee effect. The component Allee effect identified could lead to a weak demographic Allee effect that might reduce the rate of spread of E. californica. Knowledge of this would be useful for management of this invasive plant in Chile.     

Pollinator‐mediated phenotypic selection does not always modulate flower size and number in the large‐flowered Mediterranean shrub Cistus ladanifer (Cistaceae)

Flower size and number usually evolve under pollinator‐mediated selection. However, hot, dry environments can also modulate display, counteracting pollinator attraction. Increased pollen deposition on larger flower displays may not involve higher female fitness. Consequently, stressful conditions may constrain flower size, favouring smaller‐sized flowers. The large‐flowered, self‐incompatible Mediterranean shrub Cistus ladanifer was used to test that: (1) this species suffers pollen limitation; (2) pollinators are spatially–temporally variable and differentially visit plants with more/larger flowers; (3) increased visits enhance reproduction under pollen limitation; (4) stressful conditions reduce female fitness of larger displays; and (5) phenotypic selection on floral display is not just pollinator‐mediated. We evaluated pollen limitation, related floral display to pollinator visits and fruit and seed production and estimated phenotypic selection. Flower size was 7.2–10.5 cm and varied spatially–temporally. Visitation rates (total visits/50 min) ranged from 0.26 to 0.43 and increased with flower size. Fruit set averaged 80% and seed number averaged 855, but only fruit set varied between populations and years. Selection towards larger flowers was detected under conditions of pollen limitation. Otherwise, we detected stabilizing selection on flower size and negative selection on flower number. Our results suggest that selection on floral display is not only pollinator‐dependent through female fitness in C. ladanifer. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 540–555.     

福建梅花山17种常绿阔叶植物叶片虫食状况

从福建梅花山自然保护区海拔450m和1 200m的常绿阔叶林中选取17种常绿乔、灌木,对其叶片虫食状和取食强度进行分析,结果如下:(1)17种植物叶片共有15种虫食状类型,每种叶片虫食状类型为8~14;虫食状出现频率0.02%~37.01%,其中缘食状出现频率最高(37.01%),叶中脉食状出现频率最低(0.02%)。(2)木荷(Schima superba)的取食强度最大(9.60%),栲树(Castanopsis fargesii)次之(6.61%),油茶(Camellia Oleifera)最小(0.34%)。(3)15种虫食状类型中有6对虫食状呈显著正相关,2对呈显著负相关。(4)海拔1 200m处的甜槠(Castanopsis eyrei)、木荷、栲树和连蕊茶(Camellia fraterna)比海拔450m处的同种植物叶片的虫食强度高,其中木荷差异最大,从13.81%降至2.93%。     

The effects of foraging ants on arboreal insect herbivores in an undisturbed woodland savanna

ABSTRACT.

• 1 A comparison was made of the insect fauna on paired Terminalia sericea, Burkea africana and Ochna pulchra trees; one tree in each pair was treated with Formex® to exclude ants from the canopy, and the other was designated the control.
• 2 Treatment with Formex banding to exclude ants did not influence plant phenology.
• 3 Pyrethrum knockdown samples from control trees had generally more insect individuals and insect species than samples from trees where ants were excluded.
• 4 Formex-treated trees had significantly less homopterous individuals and species than the control trees.
• 5 With the exception of ants and Homoptera, there was no difference in the insect guild composition and dominance ranking of various insect taxa, sampled by pyrethrum knockdown, between the control and Formex-treated trees.
• 6 T.sericea had significantly greater populations of both sessile and mobile Homoptera on the control trees than on the Formex-treated trees. A similar trend could be seen on B.africana. There were significantly more sessile homopterans on the control trees of O.pulchra than on the Formex-treated trees. Low numbers of mobile Homoptera were recorded on both control and Formex-treated O.pulchra trees, and numbers on control trees were fewer in comparison to numbers of mobile Homoptera on control T.sericea and B.africana trees.
• 7 It is concluded that the ants have similar effects on the insect communities of trees in a natural, undisturbed savanna as has been demonstrated on trees in agro-ecosystems, and on plants that are structurally adapted for mutualistic associations with ants.
• 8 Although slight, leaf damage by some leaf-feeding insects was greater on trees where ants had been excluded than on control trees that supported foraging ant populations.

     

Which food‐mimic floral traits and environmental factors influence fecundity in a rare orchid,Calanthe yaoshanensis?

Orchid species that are food mimics produce fewer fruits than species offering rewards, but few studies have shown the impact of environmental factors (e.g. anthropogenic activity, frost and herbivores) on their reproductive success over several seasons. In this study, we focused on the sole population of the endangered Calanthe yaoshanensis as it secretes no nectar. We investigated its floral biology, fruit set rates and prevailing environmental factors over three seasons (2008–2010). Mechanical self‐pollination did not occur in C. yaoshanensis, but hand‐selfed and crossed flowers produced equal numbers of fruit. However, seed viability and embryo size were significantly higher in cross‐pollinated fruits maximizing embryonic fitness. Large hoverflies (Syrphidae) and Bombus patagiatus (gynes) were the only pollinarium vectors, but they often failed to disperse pollinaria. We interpret the temporary retention of the anther cap over the pollinarium as an adaptation lowering self‐pollination. Insect‐mediated rates of pollinarium removal were always higher than rates of pollinia deposition on stigmas. Over 3 years, natural rates of pollinarium removal differed significantly, whereas natural rates of fruit set were not significantly different (< 22%). Climate, herbivory and anthropogenic collections also inhibited some fruit set and maturation. Both biotic and abiotic factors appear to lower the fecundity of this endangered population. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 421–433.     

The effect of foliar nutrition on yield of greenhouse tomatoes and quality of the crop

Tomatoes grown in traditional mediums such as peat moss are usually supplied with essential nutrients by preplant fertilization and in the later growth stages by top dressing application to the root zone. According to the data from literature the efficient method of nutrient supply during the intensive stage of growth may be estimated as by foliar spraying. In the greenhouse experiment conducted in 1998–1999 a preplant fertilization by multicomponential fertilizer MIS-4 was applied to peat moss growing medium in full (4 kg per m³) and half (2 kg per m³) of recommended rate. Supplemental fertilization during the growing period was provided to the root zone or by using liquid multicomponential fertilizers Ekolist S and Mikrosol U in 5 sprays conducted at two week intervals. Results of the study proved that advantageous effect of foliar tomato nutrion grown in eat substrate was observed only in treatments with restricted supply of fertilizers to the growing medium. The maximum fruit yield was received from plots provided by the reduced preplant MIS-4 dose to 50 % of recommended rate combined with foliar sprays by Ekolist S. Such system of fertilization enhanced the marketable yield of fruit by 9.8 % and early yield by 11.3 % as compared to that obtained with preplant and top dressing soil application. Foliar nutrion did not change dry matter and vitamin C content and increased total and reducing sugars accumulation in tomato fruits.     

The Contribution of Ant-Plant Protection Studies to Our Understanding of Mutualism1

One common class of ant-plant mutualism involves ants that defend plants from natural enemies in return for food and sometimes shelter. Studies of these interactions have played a major role in shaping our broad understanding of mutualism. Their central contribution has come via their development of approaches to measuring the benefits, costs, and net outcomes of mutualism, and their explicit consideration of variability in all of these phenomena. Current research on these interactions is suggesting ecological and evolutionary hypotheses that may be applicable to many other forms of mutualism. It is also generating comparative data for testing the few general theories about mutualism that currently exist.     

Root disturbance of common ash, Fraxinus excelsior (Oleaceae), leads to reduced foliar toughness and increased feeding by a folivorous weevil, Stereonychus fraxini (Coleoptera, Curculionidae)

Abstract.

• 1 Bioassays were carried out to examine differences in the feeding of a folivorous weevil, Stereonychus fraxini De Geer, on leaves from ash saplings with undamaged roots, and those with damaged roots. Beetles ate significantly more of the leaves of root-damaged saplings in a choice experiment.
• 2 A separate study of the effect of root damage on leaf toughness was carried out on a second group of ash saplings. Saplings with damaged roots had less tough leaves than control saplings. Decreased leaf toughness in hypothesized as a mechanism to explain the preference of weevils for leaves from damaged trees.
• 3 Both chemical and physical changes may occur in the tissues of ash trees in response to environmental stress such as drought and root damage.
• 4 Root damage caused by agricultural disturbance is hypothesized as a mechanism making mature ash trees in hedgerow ecosystems more susceptible to insect herbivores.