Pollen competition in a natural population of Cucurbita foetidissima (Cucurbitaceae)

The pollen competition hypothesis predicts that when the number of pollen grains deposited onto stigmas exceeds the number of ovules, selection can operate in the time frame between deposition and fertilization. Moreover, because of the overlap in gene expression between the two phases of the life cycle, selection on microgametophytes may alter the resulting sporophytic generation. The extent to which pollen competition occurs in nature has been unclear, because tests of the predictions of the pollen competition hypothesis have used cultivars and/or artificial growth conditions and hand-pollination techniques. In this study we used a wild species, Cucurbita foetidissima, in its natural habitat (southern New Mexico) to determine the amount and timing of the arrival of pollen onto stigmas, the relationship between pollen deposition and seed number, and the effects of the intensity of pollen competition on progeny vigor. We found that ～900 pollen grains are necessary for full seed set and that a single visit by a pollinator results in the deposition of 653.0 ± 101.8 pollen grains. About 29% of the flowers receiving a single pollinator visit had 900 or more pollen grains on its stigma. Moreover, within 2 h of anthesis, >4000 pollen grains were deposited onto a typical stigma, indicating that multiple pollinator visits must have occurred. Fruits produced by multiple visits had greater seed numbers (206 vs. 147) than fruits produced by a single visit. Finally, the progeny produced by multiple pollinator visits were more vigorous than those produced by single visits with respect to five measures of vegetative growth (MANCOVA, Wilks' lambda = 0.96, F(6,370) = 2.54, P < 0.02. These data demonstrate that conditions for pollen competition exist in nature and support the prediction that pollen competition enhances offspring vigor.     

浅水草型湖泊──扁担塘中桡足类的群落结构（英文）

本文研究了一浅水草型湖泊──扁担塘中桡足类的群落结构,包括种类组成、种群动态及现存量。在一周年的研究中,共发现14种浮游桡足类（9种剑水蚤和5种哲水蚤）。根据年平均密度,剑水蚤的优势种为：Mesocyclops notius,Cyclops vincinuis vincinus和Thermocyclops brevifurcatus,而哲水蚤的优势种为Meodiaptomus yantsekiangensis和Sinocalanus dorrii。通过比较长江沿岸的5个湖泊的桡足类的种类组成发现,桡足类的种类数并不与湖泊面积大小成正比,这与Dodson通过研究欧洲及北美湖泊中的枝角类得出的结论并不一致。此外,虽然这5个湖泊中的桡足类的种类数多达35种,但每个湖泊中的优势种都非常相似地集中到少数几个属或种,而其它均为偶尔性种类。     

吉林通化地区杨树栽培的生态区划

选取通化地区与杨树生长有密切关系的、具典型代表和鲜明时空分布规律的气候因子和自然地理因子作为统计指标,运用聚类分析方法对全区林业生态环境进行分类区划,划分为4个气候小区;调查全区26个引种的杨树生长状况,重点针对其抗寒性进行分类分级;针对杨树新品种与该地区环境适应性关系,确定杨树栽培的生态区划结果,并对每一气候小区的特殊情况具体分析,提出杨树引种栽培的科学依据．     

食用菌与生物资源的综合利用

叙述了食用菌生物学特性及其在工农业副产品的综合利用和农业生态系统中的重要作用。     

A coral-microbialite patch reef from the late jurassic (florigemma-Bank, Oxfordian) of NW Germany (Süntel mountains)

Summary Anin situ Oxfordian patch reef from the Süntel hills (florigemma-Bank, Korallenoolith, NW-Germany) is described. It is composed of an autochthonous reef core overlain by a ‘parautochthonous’ biostrome. The exposed reefal area amounts to about 20 m in lateral and up to 4 m in vertical direction. Nearly all major marine reefal fossil associations from the Tethyal realm are present. In the reef core two facies can be distinguished: (1)Thamnasteria dendroidea thicket facies and (2) thrombolite facies. The first facies is composed of a thin branched autochthonous coral thicket mainly constructed ofTh. dendroidea colonies with only a minor portion ofStylosmilia. Frequently, theTh. dendroidea branches laterally coalesce bridge-like forming a delicate initial framework which was subsequently reinforced by thick microbial coatings, that make up approximately 80% of the rock volume. This facies is an excellent example for microbialite binding in reefal architecture. Additionally, several generations of micromorphic and partly cryptic encrusting organisms settled on theTh. dendroidea branches and microbialite crusts. They successively overgrow each other and fill the space between the coral branches in the thicket forming a characteristic community replacement sequence. Initial colonization of theThamnasteria dendroidea took place on an oncoidic/bioclastic hardground. During this early phase of reefal development, microbialites also played an important role in stabilizing and binding the reef body. The thrombolite facies (2) occupying nearly the same volume of the reef body as facies type (1) consists of a thrombolitic microbialitic limestone which fills the interstice between the coral colonies. It shows a considerably lower faunal diversity than theTh. dendroidea facies. Numerous cavities are interspersed in the thrombolithe and are almost completely filled with dolomitized allomicrite. In contrast, microbialite and allomicrite adjacent to the reef core rarely reveal any dolomitized areas. Above the reef core, mostly toppledSolenopora jurassica thalli occur together with a few massiveIsastrea colonies forming a parautochthnous biostrome. They are inhabited by a low diverse assemblage of encrusting organisms. Microbialites are only rarely present in this biostromal unit. The patch reef is developed within a lagoonal limemud facies both separated by a sharp interface. In contrast, continuous facies transition exists between theSolenopora biostrome and adjacent deposits which are characterized by micritic to pelmicritic limestone sometimes with lenses of oncoids. Debris derived from the patch reef is only sporadically intercalated in the reef surrounding lagoonal sediments. Gastropods, bivalves, and dasycladalean algae dominate the lagoonal biota. Up-section following theSolenopora biostrome nerinean gastropods become the most abundant species amounting to a ‘Nerinea-bed’. This horizon moderately elevates above the patch reef indicating, that is arose above the surrounding sea floor forming a relief. The patch reef established on a secondary hardground probably released by a minor transgression and a nondepositional regime. It grew up on a well-illuminated sea floor only a few meters below sea level. Only a low background sedimentation rate and modest water circulation are assumed during reefal growth. These features characterize an open marine lagoon. A subsequent shallowing upwards trend caused emergence of the early lithifiedflorigemma-Bank sediments. In the following erosional phase the reef core,Solenopora biostrome and ‘Nerinea-bed’ were sharply cut. Paleokarst phenomena (karst solution of the rocks, selective leaching of the aragonitic corals) truncate the surface of theflorigemma-Bank. Released by a transgressive sea level, the paleokarst surface is densely inhabited by marine boring and encrusting organisms (oysters, serpulids). Karst cavities are filled with an oncoid-bearing bioclastic limestone with a large portion of siliciclastics. Theflorigemma-Bank is overlain by the reddish bioclastic sandstone of the ‘Zwischenfl?zregion’.     

Assessing the ecological integrity of a grassland ecosystem: the applicability and rapidity of the SAGraSS method

The Grassland Biome is currently one of the most threatened biomes in South Africa and is in dire need of a biomonitoring protocol. The components of ecological integrity in these ecosystems are, however, too diverse and time-consuming to measure scrupulously. It is therefore necessary to develop a set of grassland indicators that are efficient and rapid in their assessment of grassland ecosystem integrity. The South African Grassland Scoring System (SAGraSS), based on the grassland insect community, is such a suggested indicator. The present study is the first to investigate the applicability and rapidity of this proposed method. Although SAGraSS scores correlated significantly with Ecological Index values (the most commonly used index by which veld condition is evaluated in central South Africa), the method proved to be tedious and the identification of insects taxing. We offer a number of changes to make the SAGraSS method a more rapid method of assessment.     

Evolutionary dynamics of ecological niche in three Rhinogobio fishes from the upper Yangtze River inferred from morphological traits

In the past decades, it has been debated whether ecological niche should be conserved among closely related species (phylogenetic niche conservatism, PNC) or largely divergent (traditional ecological niche theory and ecological speciation) and whether niche specialist and generalist might remain in equilibrium or niche generalist could not appear. In this study, we employed morphological traits to describe ecological niche and test whether different niche dimensions exhibit disparate evolutionary patterns. We conducted our analysis on three Rhinogobio fish species (R. typus, R. cylindricus, and R. ventralis) from the upper Yangtze River, China. Among the 32 measured morphological traits except body length, PCA extracted the first four principal components with their loading scores >1.000. To find the PNC among species, Mantel tests were conducted with the Euclidean distances calculated from the four principal components (representing different niche dimensions) against the pairwise distances calculated from mitochondrial cytochrome b sequence variations. The results showed that the second and the third niche dimension, both related to swimming ability and behavior, exhibited phylogenetic conservatism. Further comparison on niche breadth among these three species revealed that the fourth dimension of R. typus showed the greatest width, indicating that this dimension exhibited niche generalism. In conclusion, our results suggested that different niche dimensions could show different evolutionary dynamic patterns: they may exhibit PNC or not, and some dimensions may evolve generalism.     

The neglected tool in the Bayesian ecologist's shed: a case study testing informative priors' effect on model accuracy

Despite benefits for precision, ecologists rarely use informative priors. One reason that ecologists may prefer vague priors is the perception that informative priors reduce accuracy. To date, no ecological study has empirically evaluated data‐derived informative priors' effects on precision and accuracy. To determine the impacts of priors, we evaluated mortality models for tree species using data from a forest dynamics plot in Thailand. Half the models used vague priors, and the remaining half had informative priors. We found precision was greater when using informative priors, but effects on accuracy were more variable. In some cases, prior information improved accuracy, while in others, it was reduced. On average, models with informative priors were no more or less accurate than models without. Our analyses provide a detailed case study on the simultaneous effect of prior information on precision and accuracy and demonstrate that when priors are specified appropriately, they lead to greater precision without systematically reducing model accuracy.     

WIDESPREAD HOST‐DEPENDENT HYBRID UNFITNESS IN THE PEA APHID SPECIES COMPLEX

Linking adaptive divergence to hybrid unfitness is necessary to understand the ecological factors contributing to reproductive isolation and speciation. To date, this link has been demonstrated in few model systems, most of which encompass ecotypes that occupy relatively early stages in the speciation process. Here we extend these studies by assessing how host‐plant adaptation conditions hybrid fitness in the pea aphid, Acyrthosiphon pisum. We made crosses between and within five pea aphid biotypes adapted to different host plants and representing various stages of divergence within the complex. Performance of F1 hybrids and nonhybrids was assessed on a “universal” host that is favorable to all pea aphid biotypes in laboratory conditions. Although hybrids performed equally well as nonhybrids on the universal host, their performance was much lower than nonhybrids on the natural hosts of their parental populations. Hence, hybrids, rather than being intrinsically deficient, are maladapted to their parents’ hosts. Interestingly, the impact of this maladaptation was stronger in certain hybrids from crosses involving the most divergent biotype, suggesting that host‐dependent postzygotic isolation has continued to evolve late in divergence. Even though host‐independent deficiencies are not excluded, hybrid maladaptation to parental hosts supports the hypothesis of ecological speciation in this complex.