Pollination of Euphorbia dendroides by lizards and insects: Spatio-temporal variation in patterns of flower visitation

The patterns of flower visitation by lizards (Podarcis lilfordi, Lacertidae) and insects (mainly flies, bees and wasps) on the shrub Euphorbia dendroides, were studied in the island of Cabrera (Balearic Islands) during the flowering seasons of 1995 and 1996. Lizards act as true pollinators of the plant, moving large quantities of pollen within and among shrubs. To our knowledge, this is the first time that pollination by lizards has been empirically demonstrated. Variation in the quantitative component of pollination (frequency of visits × flower visitation rate) by the two groups of pollinators (lizards and insects) is documented at both spatial (within a plant population) and temporal scales (throughout the flowering season and between seasons). Variation in lizard density on a small spatial scale (within c. 200 m), presumably due to differences in vegetation cover, strongly affected their frequency of flower visitation. Insects were rather scarce, mainly because the plant flowers at a time (mid-March) when temperatures are still low. At the site where lizards were abundant, their frequency of flower visits was more than 3 times that of insects, they stayed on the shrubs about 3 times longer and visited about 8 times more cyathia per minute than did insects. Fruit and seed set were greater at this site, and this is attributed to the different frequency of flower visits by lizards, as shrubs are similar in size and produce similar amounts of cyathia in the two sites compared. Both, lizards and insects went more frequently to plants with large flower crops. However, flower crop was not associated with seed viability. We found no evidence for pollinator-mediated selection on plant traits related to fitness. Received: 28 August 1996 / Accepted: 26 February 1997     

Sexual selection versus alternative causes of sexual dimorphism in teiid lizards

Summary The presence and extent of sexual dimorphisms in body form (size and shape) of adult macroteiid lizards were investigated. Males were significantly larger than females in the temperate species, Cnemidophorus tigris, and in the tropical species, Ameiva ameiva and C. ocellifer. Young adult C. tigris males grew faster than young adult females within and between reproductive seasons. Adult males of all species had larger heads than adult females of the same body size; this difference increased with body size. Moreover, male C. tigris were heavier than females of the same snout-vent length. The causes and consequences of the sexual dimorphisms were also examined. The possible causes of body size are especially numerous, and distinguishing the relative influences of the various causal selection factors on body size is problematical. Nevertheless, observational field data were used to tentatively conclude that intrasexual selection was the cause of larger body size of C. tigris males relative to females because (1) larger males won in male aggressive interactions, (2) the winning males gained access to more females by repelling competitors and by female acceptance, (3) larger males consequently had higher reproductive success, and (4) other hypothetical causes of larger male size were unsupported.     

中国沙棘(Hippophae rhamnoides L.ssp. sinensis Rousi)的开花特性及风媒传粉距离的检测

连续两年对雌雄异株的中国沙棘(Hippophae rhamnoides L.ssp. sinensis Rousi)的花期物候、开花式样进行了观察,检测了柱头可授性、花粉活力和花粉-胚珠比,并进行了人工授粉、套袋实验,检测结实率.结果显示中国沙棘风媒传粉发生在4月下旬或5月上旬,单花花期约7d;传粉盛期在第3天到第5天,柱头的可授性从第2天到第4天或第5天.中国沙棘花先叶开放、花小、无花冠、花药成熟时萼片从两个侧面的纵缝中裂开,形成有利于花粉散布的对流风洞.花粉活力和花粉-胚珠比都很高,具有典型的适应风媒传粉的花部特征和性状.中国沙棘花粉的传播距离受外界环境影响较大,通过重力玻片法检测可以看出,在风速小于3m/s时,主要集中在15～25m之间,当风速大于3m/s时,顺风向可超过85m以外.传粉效率对结实率的影响较大.     

大花百子莲的结实和结籽格局及种子产量影响因素分析

在2007和2008年对大花百子莲(Agapanthus praecox subsp.orientalis‘Big Blue’)在群体、果序和单果水平上的结实和结籽格局进行了观测,并依据每花序单花数、单花胚珠数和单粒种子质量推算其单株潜在种子产量;此外,采用人工补充授粉方法研究了不同授粉方式对大花百子莲结实和结籽的影响,并对其种子产量的影响因素进行了分析。结果表明:从始花期、盛花期至末花期,随开花时间的延迟,大花百子莲植株的每花序单花数和座果率均逐渐降低,其中始花期开花的植株每花序单花数和座果率均最高。从果序基部、中部至顶端,座果率和结籽率均逐渐减小且差异显著。在果序基部和中部,果实内种子败育率沿果实基部至顶端依次降低,而单粒种子质量则依次增加;且果序基部的果实各部位的种子败育率均低于果序中部的果实,而单粒种子质量则差异不大。大花百子莲的单株潜在种子产量约为43.18 g,而其单株实际种子产量约为2.87 g,远低于其潜在种子产量。自然授粉的大花百子莲每柱头花粉数为27.5粒,而自花授粉、同株异花授粉和异株授粉的每柱头花粉数均超过100粒;与自然授粉、自花授粉和同株异花授粉植株相比,异株授粉植株的座果率和结籽率均显著增加。研究结果显示:大花百子莲的结实和结籽格局呈现非随机分布规律,在引种地存在有性繁殖障碍;养分和授粉状况是制约大花百子莲种子产量的重要因素。     

芍药的访花昆虫和传粉昆虫

20 0 0～ 2 0 0 2年对内蒙古赤峰市高格斯台罕乌拉自然保护区内野生芍药 (PaeonialactifloraPall.)和内蒙古农校芍药园内栽培品种芍药的访花昆虫进行调查 ,经整理鉴定有 2 9种 ,自然保护区内芍药的访花昆虫种类有 1 7种 ,芍药园内的访花昆虫有 1 7种。根据传粉行为和数量的比较确定了自然保护区内主要传粉昆虫为丽斑芫菁、黄胫宽花天牛、黑胫宽花天牛、短毛斑金龟、饥星花金龟、白星花金龟和大淡脉隧蜂 ;芍药园内的主要传粉昆虫为意大利蜜蜂、棕边管食蚜蝇、长尾管食蚜蝇、大淡脉隧蜂、灰带管食蚜蝇和小淡脉隧蜂。     

Consequences of adaptive foraging in diverse communities

1.  Selective pressures acting on foraging activities constrain the strength of interaction, hence the stability and energetic availability in food webs.
2.  Because such selective pressures are usually measured at the individual level and because most experimental and theoretical works focus on simple settings, linking adaptive foraging with community scale patterns is still a far stretch.
3.  Some recent models incorporate foraging adaptation in diverse communities. The models vary in the way they incorporate adaptation, via evolutionary or behavioural changes, and define individual fitness in various ways.
4.  In spite of these differences, some general results linking adaptation to community structure and functioning emerge. In the present article, I introduce these different models and highlight their common results.
5.  Adaptive foraging provides stability to large food web models and predicts successfully interaction patterns within food webs as well as other topological features such as food chain length.
6.  The relationships between adaptive foraging and other structuring factors particularly depend on how well connected the local community is with surrounding communities (metacommunity aspect).     

Can honey bees change foraging patterns?

Abstract. 1. Foraging patterns were studied using honey bees on artificial flower patches to determine if given individuals could change behaviours under differing conditions.
2. Two types of flower patches were used; those simulating a population of flowers, dimorphic for colour, and grids simulating a single colour-dimorphic inflorescence.
3. In the simulated population of flowers bees were individually constant to colour over a range of reward volumes and flower patch sizes.
4. Each bee remained individually constant to a flower morph when visiting a population-type grid but changed to random visitation on the simulated inflorescence.
5. On the simulated inflorescence, with morphs providing unequal qualities of reward, most bees foraged on the higher molarity morph.
6. Most, but not all bees, failed to minimize uncertainty on the simulated inflorescence.
7. On the simulated inflorescence, bees failed to optimize when one morph provided a greater reward volume than did the other.
8. In the population of flowers bees flew from flower to flower, whereas, they walked on the simulated inflorescence.     

Co-evolution of seed size and seed predation

Using the evolutionarily stable strategy (ESS) approach in a model for the co-evolution of seed size and seed predation, I show that seed size variation within individual plants is favoured if there is a trade-off in the predator's attack rate for different seed sizes. A single seed size is not evolutionarily stable because a predator that is optimally adapted to one particular seed size cannot prevent invasion by plants with a different seed size. The model generates the following predictions. The ESS consists of a continuous range of seed sizes. Small seeds tend to be attacked more frequently than big seeds. Plants with many resources and plants with low (frequency-independent) juvenile mortality have more variable seeds than plants with few resources and a high juvenile mortality. Seed size variation is higher in fluctuating populations regulated by seed predation alone than in stable populations (partially) regulated by seedling competition. Predator searching behaviour does not directly affect the ESS seed size range, but may have an indirect effect by affecting population stability or the significance of seedling competition as a population regulating mechanism. Moreover, seed size distributions are found to be more skewed in favour of small seeds if predation is spatially non-uniform than if predation is more even. Application of the model to systems of several co-evolving plant and predator species is discussed.     

干热河谷麻疯树访花昆虫及主要传粉昆虫

膏桐为一种重要的油料作物,其种子可以提炼生物柴油,生物柴油在我国将成长为有一定规模的产业。为了增加膏桐结籽率,提高其产量,给膏桐规模化栽培方面提供传粉生物学的科学依据,于2006年对云南元江坝区半栽培膏桐(Jatropha curcas L.)居群的访花昆虫及主要传粉昆虫种类进行调查。膏桐开花示样醒目,具花香与蜜腺,花形态没有特化,这些特征使得它提供的酬物适合于不同的昆虫采食,其访花昆虫种类较丰富,共有35种访花昆虫,分属5目20科。综合访花昆虫的传粉数量,及传粉质量包括访花行为、访花频率与日活动规律等确定主要传粉昆虫,确定大头金蝇Chrysomya(Compsomyia)megacephala Fabricius、中华蜜蜂Apiscerana Fabricius、迁粉蝶(淡色型)Catopsilia pomona f.Crocale为该居群的主要传粉昆虫。3种传粉昆虫具有不同的访花习性和日活动规律。雌雄迁粉蝶日活动规律相似。访花者的组成受气象因素、开花示样及生境条件的影响。最后,探讨膏桐与访花昆虫的关系,以及主要传粉者的组成随时空变异而改变的规律。     

Seed size,pollination costs and angiosperm success

Summary Seed plants capture pollen before seeds are dispersed and abort unpollinated ovules. As a result, each seed is associated with an accessory cost that represents the costs of pollen capture and the costs of aborted ovules. Accessory costs may explain the minimum seed size among species, because these costs are likely to comprise a greater proportion of total reproductive allocation in species with smaller seeds. For very small propagules, the costs of pollination may not be worth the benefits, perhaps explaining the persistence of pteridophytic reproduction at small propagule sizes. The smallest angiosperm seeds are much smaller than the smallest gymnosperm seeds, both in the fossil record and in the modern flora. This suggests that angiosperms can produce pollinated ovules more cheaply than gymnosperms. Pollination becomes less efficient as a species decreases in abundance, and this loss of efficiency is greater for species with a higher accessory cost per seed. We propose that the greater reproductive efficiency of angiosperms when rare can explain why angiosperm-dominated floras were more speciose than the gymnosperm-dominated floras they replaced.