聚果榕两种非传粉小蜂产卵与果实脱落的关系

下载PDF阅读器在聚果榕与其传粉榕小蜂Ceratosolen fusciceps组成的互利共生系统中,与传粉榕小蜂共存的还有榕树的寄生性小蜂Platyneura testacea和Platyneura mayri.这些寄生性小蜂由于不能给榕树带来任何收益而只是利用榕树的种子或与传粉小蜂竞争植物的雌花资源,因而可能导致榕树与榕小蜂之间合作系统的崩溃.植物果实的脱落机制普遍被认为是维持系统稳定的关键因素之一.然而,定量实验和野外观测发现P. mayri产卵并不会引起果实脱落,只有P. testacea产卵会使果实大量脱落.通过对3株样树进行比较发现:当产卵时的P. testacea数量越多时,它产生的瘿花数就越多,榕果发生脱落的比例越高.P. testacea的过度产卵是导致榕果选择性脱落的主要原因.结果表明:脱落机制并不能完全阻止非传粉小蜂的寄生,榕树只能选择性地脱落掉先于传粉小蜂产卵的榕果.这也同时表明维持榕树与榕小蜂互利共存的机制不仅仅只有榕果的脱落机制,可能还存在其它未被发现的机制.

榕小蜂食性分化与榕树-榕小蜂系统稳定性

在榕树与其传粉小蜂组成的互利阿共生系统中,理解传粉小蜂与各种非传粉小蜂如何共存是解决这一系统稳定性维持机制问题的关键之一.生态位分化被普遍认为是传粉小蜂与各种非传粉小蜂共存的最主要动力.而作为生态位分化中最基础的食性分化在这一系统中如何具体实现尚小清楚.2006年12月至2007年6月.我们以聚果榕(Ficus racemosa)为材料,通过对果内6种榕小蜂进行独立放蜂及两两组合定最放蜂,并对传粉小蜂分别进行不携带花粉和不能产卵的技术处理,研究了寄生在聚果榕果内的5种非传粉小蜂的食性及相互关系,分析了在不同季节下寄生蜂与寄主间的相关系数.研究结果表明:在5种非传粉小蜂中,Platyneura testacea和P mayri是造瘿者,能独立刺激子房发育成瘿花,并使果实发育成熟;而 Apocrypta sp、A.westwoodi和P.agraensis只能寄生于某些已发育的虫瘿,为拟寄生者,它们各自分别与P.testacea,P.mayri和传粉小蜂Ceratosolen fusciceps存在着一对一的寄生关系.拟寄生者与寄主间的相关性在不同季节下会显示出不同的结果,这表明过去文献中用物种间的相关系数推理而确定的食性关系可能是不可靠的.对自然采集榕果内的小蜂群落分析表明,传粉小蜂处于优势地位,这说明在自然情况下非传粉小蜂的种群维持在一个较低水平,对榕树-传粉小蜂系统稳定性影响较小,故能与之长期共存.

非传粉小蜂的食性及其对榕树- 传粉小蜂系统稳定性的影响

榕树与其传粉小蜂形成了高度专一的互惠共生系统。非传粉小蜂则是该系统的资源掠夺者, 但它与 该系统共存的机制仍不清楚。于2003 年12 月—2004 年4 月在西双版纳以聚果榕( Ficus racemosa L. ) 为材料, 研究了寄生在聚果榕榕果内的5 种非传粉小蜂的食性及相互关系, 以探讨非传粉小蜂与榕树- 传粉小蜂系统共 存的机制。结果表明: 寄生在聚果榕榕果内的5 种非传粉小蜂中, 仅Platyneura testacea Motschulsky 和Platyneu2 ra mayri Rasplus 能刺激子房发育成瘿花, 是造瘿者; Apocrypta sp . , Apocrypta westwoodi Grandi 和Platyneura a2 graensis Joseph 不能刺激子房发育成瘿花, 是拟寄生者。传粉小蜂的拟寄生者和造瘿者对传粉小蜂有负的影响, 但在蚂蚁和造瘿者的拟寄生蜂作用下, 这种负面影响并不显著, 而且它们对榕树繁殖没有显著影响。对小蜂自 然种群的分析表明, 传粉小蜂处于优势地位。说明在自然情况下传粉小蜂的拟寄生者和造瘿者的种群维持在一 个较低水平, 对榕树- 传粉小蜂系统稳定性影响较小, 故能与之长期共存。

Structure of a fig wasp community: Temporal segregation of oviposition and larval diets

Observations were made on six fig wasp species on Ficus racemosa growing in the Xishuangbanna Tropical Botanic Garden, Yunnan Province, China. The oviposition sequence was determined for Apocryptophagus testacea, Apocrypta sp2, Apocryptophagus mayri, Cera

Diffusive coevolution and mutualism maintenance mechanisms in a fig-fig wasp system

In reciprocal mutualism systems, the exploitation events by exploiters might disrupt the reciprocal mutualism, wherein one exploiter species might even exclude other coexisting exploiter species over an evolutionary time frame. What remains unclear is how such a community is maintained. Niche partitioning, or spatial heterogeneity among the mutualists and exploiters, is generally believed to enable stability within a mutualistic system. However, our examination of a reciprocal mutualism between a fig species (Ficus racemosa) and its pollinator wasp (Ceratosolen fusciceps) shows that spatial niche partitioning does not sufficiently prevent exploiters from overexploiting the common resource (i.e., the female flowers), because of the considerable niche overlap between the mutualists and exploiters. In response to an exploiter, our experiment shows that the fig can (1) abort syconia-containing flowers that have been galled by the exploiter, Apocryptophagus testacea, which oviposits before the pollinators do; and (2) retain syconia-containing flowers galled by Apocryptophagus mayri, which oviposit later than pollinators. However, as a result of (2), there is decreased development of adult non-pollinators or pollinator species in syconia that have not been sufficiently pollinated, but not aborted. Such discriminative abortion of figs or reduction in offspring development of exploiters while rewarding cooperative individuals with higher offspring development by the fig will increase the fitness of cooperative pollinating wasps, but decrease the fitness of exploiters. The fig fig wasp interactions are diffusively coevolved, a case in which fig wasps diversify their genotype, phenotype, or behavior as a result of competition between wasps, while figs diverge their strategies to facilitate the evolution of cooperative fig waps or lessen the detrimental behavior by associated fig wasps. In habitats or syconia that suffer overexploitation, discriminative abortion of figs or reduction in the offspring development of exploiters in syconia that are not or not sufficiently pollinated will decrease exploiter fitness and perhaps even drive the population of exploiters to local extinction, enabling the evolution and maintenance of cooperative pollinators through the movement between habitats or syconia (i.e., the metapopulations).

Geographical distribution of testate amoebae in Tibet and northwestern Yunnan and their relationships with climate

In Asia, especially in China, our knowledge of the distribution of testate amoebae is still limited. In this paper, the geographical distribution of testate amoebae in Tibetan Plateau and northwestern Yunnan Plateau, southwest China and their relationships with the climatic factors have been studied. We found testate amoebae shifted in the most dominant species and increased in species (or genus) richness from northwest to southeast. Further, the linear regression analyses revealed that both species richness and genus richness have higher positive correlations with the mean temperature of the warmest month and annual mean precipitation as contrasted with the mean altitude, which showed weak negative correlation. This indicates that the temperature and precipitation are more significant influences on the richness than the altitude. The cluster analysis based on the community structure, defined by Sorenson's coefficient matrix, suggested four groups from the 10 physiographical regions. This geographical distribution pattern was also closely related with the climatic regionalization. The present climatic regionalization pattern of the study area originated from the uplift of Tibetan Plateau and mainly occurred in or after the late Pleistocene. Therefore, the geographical distribution of testate amoebae in our study area may have experienced complicated and drastic changes corresponding to the variation of the climate caused by the geological events.

Morphology, biometry and distribution of Difflugia biwae Kawamura, 1918 (Protozoa : Rhizopoda)

The freshwater testate amoeba Difflugia biwae Kawamura, 1918, isolated from Mulan Lake, Hubei Province, China is investigated using light microscopy and scanning electron microscopy. The morphology, biometry and distribution of this little known species are supplied. After careful comparison with three other similar species, including D. delicatula Gauthier-Livre et Thomas, D. elegans Penard and D. oblonga caudata Stepanek, we believe that the characteristics of smooth fusiform shell, conspicuous great collar flare (always larger than body-width) around the aperture, constriction behind the aperture and a somewhat curved aboral horn set D. biwae apart from all other Difflugia species. This species shows a great diversity in total length, collar height and aboral horn length which have high variability (CV between 11.76 and 24.52). However, body width, collar diameter, neck width, body length and aperture diameter are fairly constant with low variability (CV between 5.34 and 8.79) which shows a remarkable uniformity of D. biwae. Also, the size frequency distributions of both body width and body length yield bell-shaped (normally distributed) curves and indicate that D. biwae is a size-monomorphic species, characterized by a main-size class and a small size range. D. biwae is probably endemic to East Asia (China and Japan) because it has such a large size (165-306 mu m) that it would have been easily found in Europe and North America, if it were there. Consequently, D. biwae must have a restricted geographical distribution, disproving the old hypothesis that microscopic organisms are cosmopolitan.

Redescription of Difflugia tuberspinifera Hu, Shen, Gu et Gong, 1997 (Protozoa : Rhizopoda : Arcellinida : Difflugiidae) from China

The freshwater testate amoeba Difflugia tuberspinifera Hu et al. 1997 collected from pond and lake in China, is investigated by light and scanning electron microscopy. This little known taxon is redescribed and its morphology, biometry and ecology are supplied. After carefully comparison with other six similar species including Difflugia bartosi Stepanek, D. corona Wallich, D. corona cashi Deflandre, D. corona tuberculata Vucetich, D. muriformis Gauthier-Lievre et Thomas and Netzelia tuberculata (Wallich) Netzal we believe that the sub-spherical to spherical shell, the mulberry-shaped appearance, the 7-10 apertural tooth-like structures, the short collar and the conical spines numbering from 4 to 8 at the upper equatorial region in D. tuberspinifera set it apart from other species. Besides, statistical analysis indicates that D. tuberspinifera is a size-monomorphic species characterized by a main-size class and a small size range and the shell height is significant correlated with other morphometric characters at p < 0.05 excepting the number of aperture tooth-like structures and the number of spines. Moreover, D. tuberspinifera inhabits not only lotic but also lentic environment.

Lichen flora of the Mount Donna Buang Scenic Reserve, Victoria

This report investigated the lichen flora of the Mt Donna Buang Scenic Reserve in Victoria, There were several aims: to describe the lichens of the region, to produce a pictorial key enabling field identification and to determine any distribution patterns. A floristic survey covering approximately 50 square km was undertaken to determine lichen diversity of the region generally. Lichens were sampled along roads, tracks, walking trails and in sections of bush, taking into account forest type and, particularly, areas that were lichen rich. Seventy-five lichen species in 43 genera and 27 families were identified and described from the region. An unknown, species H, also was described. Of the 76 lichen species, 22 were crastose and the remainder macrolichens. The best represented families were: Cladoniaceae (8 species), Hypogymniaceae (6), Lobariaceae (7), Lecideaceae (6), Pannariaceae (6) and Parmeliaccae (6). This study described 12 species (17%) which previously were not known for Victoria and which are a first record for the state. These include: Cladonia sarmentosa (J.D. Hook & Taylor) Dodge, Graphis librata Knight, Parmelinopsis neodamaziana (Elix & Johnston) Elix & Hale, Pertusaria novaezelandiae Szatala, Placopsis pardlina f. microphylla Lamb, Porina leptalea AX. Sm., Pseudocyphellaria ardesiaca Galloway, Trapeliopsis congregant (Zahlbr.) Brako, Menegazzia myriotrema (Mull. Arg.) P. James, Bunodophoron scrobiculatum (Church. Bab,) Wedin, Parmelia testacea Stirton and Menegazzia purpurascens S. Louwhoff sp. nov.. The last eight species are new to the mainland and, apart from Menegazzia purpurascens, previously were known only from Tasmania. Five main elements of distribution were identified for the lichen flora of the Mt Donna Buang Scenic Reserve: cosmopolitan, austral/australasian, paleotropical, pantropical and western pacific. The majority of species (68%) had austral/australasian distributions, eleven (16%) were endemic to Australia and nine (13%) occurred only in Tasmania , Victoria and New Zealand. A pictorial, dichotomous key was constructed for the lichen flora of the Mt Donna Buang Scenic Reserve. Previously, keys to the lichen flora of Tasmanian rainforests were suggested as appropriate to similar areas in Victoria, however, the Victorian forests include a significant sclerophyll element The key presented is specific for the study site but is appropriate to similar regions in Victoria and has been tested in a number of these areas. The key was designed to be ‘user-friendly’ so that the experienced and inexperienced alike are able to use it. A more detailed investigation of the lichen flora of the Mt Donna Buang Scenic Reserve was carried out in order to determine distribution. A total of 50 quadrats, each 20m x 20m in size, were sampled. Within each, the dominant vegetation type was determined and individuals were identified and location noted. The cover abundance of each lichen species on each individual tree was estimated using a modified Braun-Blanquet scale. A total of 710 trees, representing 13 different species, were examined. Nothofagus cunninghamii (Hook.) Oerst, Eucalyptus regnans R Mull., Acacia dealbata Link, A. melanoxylon R. Br., Hedycarya angustifolia A. Cunn. and Atherosperma moschatum Labill. were the six most common tree species encountered at the study site. Nothofagus cunninghamii supported the greatest lichen diversity (39 species), although most species occurred on less than 10% of the trees. The majority of lichens occurring on N. cunninghamii A. melanoxylon, A. dealbata and H. angustifolia were foliose or crustose, those on Ł. regnans fruticose and foliose and those on A moschatum crustose. Bunodophoron australe was the only lichen species at the study site to occur on one host, Nothofagus cunninghamiL Many occurred on a number of different hosts, but were most common on one particular tree species. The distribution of lichens at the study site was analysed with a rnultivariate statistical package (PATN) which dealt with ‘pattern analysis’. The program ‘SSH’ in PATN which uses the Bray-Curtis ordination technique, was used to create scatterplots displaying the degree of dissimilarity between quadrats in terms of presence/absence of lichen species. The program ‘TWAY’ in PATN was used to construct a two way table to display which lichen species occurred in each vegetation type. The pattern analysis revealed that the lichens of the Mt Donna Buang Scenic Reserve were not restricted to any particular forest type, but particular lichens, or groups of lichens, tended to predominate in certain vegetation communities. This concurs with work done by others in Tasmanian forests. Quadrats which were situated in cool temperate rainforest were grouped more closely with each other than with quadrats in other vegetation types. These also supported the greatest number of lichen species. This was not surprising since N. cunninghamii the dominant tree species in cool temperate rainforest, supported the greatest lichen diversity.

Determination of ages and fossil Coleoptera fauna from eight sites in the London region

These data sets report the fossil beetle assemblages identified from the Mesolithic to Late Bronze Age at eight sites in the London region. All but one of the study sites are within 2 km of the modern course of the Thames. The sites produced 128 faunal assemblages that yielded 218 identified species in 41 families of Coleoptera (beetles).  Beetle faunas of Mesolithic age indicate extensive wetlands near the Thames, bordered by rich deciduous woodlands. The proportion of woodland species declined in the Neolithic, apparently because of the expansion of wetlands, rather than because of human activities. The Early Bronze Age faunas contained a greater proportion of coniferous woodland and aquatic (standing water) species. An increase in the dung beetle fauna indicates the presence of sheep, cattle and horses, and various beetles associated with crop lands demonstrate the local rise of agriculture, albeit several centuries after the beginnings of farming in other regions of Britain. Late Bronze Age faunas show the continued development of agriculture and animal husbandry along the lower Thames. About 33% of the total identified beetle fauna from the London area sites have limited modern distributions or are extinct in the U.K. Some of these species are associated with the dead wood found in primeval forests; others are wetland species whose habitat has been severely reduced in recent centuries. The third group is stream-dwelling beetles that require clean, clear waters and river bottoms.

Plio-Pleistocene benthic foraminifera of the Tyrrhenian Sea

Benthic foraminifers from Site 652, Site 653 (Hole 653A), and Site 654 of Leg 107 (Tyrrhenian Sea, Western Mediterranean), which penetrated with more or less good recovery the Plio-Pleistocene stratigraphic interval, were studied in a total of 699 close-spaced samples. A total number of 269 species have been classified and their quantitative distribution in each sample is reported. The benthic foraminifers assemblage is more diversified in Site 654, less diversified in Site 652. Less than a half of the benthic foraminifers species listed from Plio-Pleistocene Italian land sections are present in the coeval deep-sea Tyrrhenian record, in which shallow water species are missing and Nodosarids are poorly represented. A very few species have comparable stratigraphic distribution in the three deep-sea sequences and in Italian land sections when compared against calcareous plankton biostratigraphy. In the same three sites, the first appearance levels of several species are younger and younger, and last appearance levels are earlier and earlier from Site 654 to Site 653 and Site 652. Five biostratigraphic events, biochronologically evaluated and occurring at the same level in the deepsea Tyrrhenian record and in several land sections, have been selected as zonal boundaries of the proposed benthic foraminifers biostratigraphic scheme. The Plio-Pleistocene interval has been subdivided into four biozones and one subzone, recognizable both in the deep-sea and land-based sequences. The Cibicidoides (?) italicus assemblage zone stretches from the base of the Pliocene to the extinction level of the zonal marker, biochronologically evaluated at 2.9 Ma. The Cibicidoides robertsonianus interval zone stretches from the Cibicidoides (?) italicus extinction level to the Pliocene Mediterranean FO of Gyroidinoides altiformis, evaluated at 2.4 Ma. The Gyroidinoides altiformis interval zone stretches from the Mediterranean Pliocene FO of the zonal marker to the appearance level of Articulina tubulosa, evaluated at 1.62 Ma. The Articulina tubulosa assemblage zone stretches from the appearance level of the zonal marker to the Recent. In the Articulina tubulosa biozone, the Hyalinea baltica subzone is proposed. The appearance level of Hyalinea baltica is evaluated at 1.35 Ma, well above the Plio-Pleistocene boundary as defined in the Vrica stratotype section.