不同起始数量对赤潮异弯藻和东海原甲藻种间竞争的影响

通过共培养的方法,研究了不同起始数量对赤潮异弯藻和东海原甲藻之间种间竞争的影响.结果表明:不同的接种数量对赤潮异弯藻和东海原甲藻种群竞争关系有明显的影响.在3种不同的接种比例下,赤潮异弯藻在与东海原甲藻的生长竞争中始终占优势,对东海原甲藻的生长存在抑制作用,且随着起始数量的提高,其种群竞争生长的优势愈加明显,对东海原甲藻生长的抑制作用愈加显著.东海原甲藻仅在较高的起始数量(处理I,H:P=1:4)下,对赤潮异弯藻的生长才表现出一定的抑制作用,处理Ⅱ和处理Ⅲ(H:P=1:1和H:P=4:1)对赤潮异弯藻的生长均无影响.     

Influence of interspecific competition on the recruitment behavior and liquid food transport in the tramp ant species Pheidole megacephala

This study was conducted on the reactions of Pheidole megacephala scouts when finding liquid food sources situated on territories marked by competing dominant ant species or on unmarked, control areas to see if the number of recruited nestmates is affected and if soldiers behave in ways adapted to the situation. We show that scouts recruit more nestmates, particularly soldiers, on marked rather than on unmarked areas. This recruitment allows P. megacephala to organize the defence and rapid depletion of these food sources prior to any contact with competitors. Soldiers can carry liquid foods both (1) in their crops like other Myrmicinae and (2), in a new finding concerning myrmicine ants, under their heads and thoraxes like certain poneromorph genera because the droplets adhere through surface tension strengths. Later, the liquids stored in the crop are distributed to nestmates through regurgitations during trophallaxis and the external droplets are distributed through social buckets, or the mode of liquid food transfer common in poneromorphs. Their flexibility to use or not use the latter technique, based on the situation, corroborates other reports that Pheidole soldiers have a relatively large behavioral repertoire.     

氮磷比对蛋白核小球藻和塔玛亚历山大藻种间竞争的影响

通过单独培养和共同培养的方法,以Na NO3和KH2PO3为氮源和磷源,研究了氮磷比(4、6、9、10、13、16、22、36和91)对蛋白核小球藻(Chlorella pyrenoidosa)和塔玛亚历山大藻(Alexandrium tamarense)生长和种间竞争的影响,并对其作用机制进行了探讨.结果表明:在单独培养模式下,蛋白核小球藻在N/P为4~22时生长适宜,N/P22时生长受抑制,而塔玛亚历山大藻在N/P为4和6时生长适宜,N/P6时生长受抑制;在共同培养模式下,蛋白核小球藻具有竞争优势,而塔玛亚历山大藻的生长受抑制,且N/P为13和16时蛋白核小球藻种群竞争优势最明显;蛋白核小球藻和塔玛亚历山大藻的培养滤液对彼此生长均未产生抑制作用,由此推测,两种微藻的种间竞争主要以资源利用性竞争为主.结果可为开发利用饵料藻进行赤潮生物防控提供一些理论依据.     

Convergent life-history shifts: toxic environments result in big babies in two clades of poeciliids

The majority of studies on ecological speciation in animals have investigated the divergence caused by biotic factors like divergent food sources or predatory regimes. Here, we examined a system where ecological speciation can clearly be ascribed to abiotic environmental gradients of naturally occurring toxic hydrogen sulfide (H₂S). In southern Mexico, two genera of livebearing fishes (Poeciliidae: Poecilia and Gambusia) thrive in various watercourses with different concentrations of H₂S. Previous studies have revealed pronounced genetic differentiation between different locally adapted populations in one species (Poecilia mexicana), pointing towards incipient speciation. In the present study, we examined female reproductive life-history traits in two species pairs: Gambusia sexradiata (from a nonsulfidic and a sulfidic habitat) and Gambusia eurystoma (sulfide-endemic), as well as P. mexicana (nonsulfidic and sulfidic) and Poecilia sulphuraria (sulfide endemic). We found convergent divergence of life-history traits in response to sulfide; most prominently, extremophile poeciliids exhibit drastically increased offspring size coupled with reduced fecundity. Furthermore, within each genus, this trend increased with increasing sulfide concentrations and was most pronounced in the two endemic sulfur-adapted species. We discuss the adaptive significance of large offspring size in toxic environments and propose that divergent life-history evolution may promote further ecological divergence through isolation by adaptation.     

Resource competition between two fungal parasites in subterranean termites

Subterranean termites live in large groups in underground nests where the pathogenic pressure of the soil environment has led to the evolution of a complex interaction among individual and social immune mechanisms in the colonies. However, groups of termites under stress can show increased susceptibility to opportunistic parasites. In this study, an isolate of Aspergillus nomius Kurtzman, Horn & Hessltine was obtained from a collapsed termite laboratory colony. We determined that it was primarily a saprophyte and, secondarily, a facultative parasite if the termite immunity is undergoing a form of stress. This was determined by stressing individuals of the Formosan subterranean termite Coptotermes formosanus Shiraki via a co-exposure to the virulent fungal parasite Metarhizium anisopliae (Metch.) Sorokin. We also examined the dynamics of a mixed infection of A. nomius and M. anisopliae in a single termite host. The virulent parasite M. anisopliae debilitated the termite immune system, but the facultative, fast growing parasite A. nomius dominated the mixed infection process. The resource utilization strategy of A. nomius during the infection resulted in successful conidia production, while the chance for M. anisopliae to complete its life cycle was reduced. Our results also suggest that the occurrence of opportunistic parasites such as A. nomius in collapsing termite laboratory colonies is the consequence of a previous stress, not the cause of the stress.     

The role of tending ants in host plant selection and egg parasitism of two facultative myrmecophilous butterflies

Ovipositing adult females of myrmecophilous lycaenids are expected to select plants based on ant presence in order to maximize the survivorship of immature stages. Usually, larvae feed ants with honey-like solutions and, in turn, ants ward off parasitoids. Nonetheless, a rarely investigated approach is whether ant partners can also extend their protective behavior towards lycaenids eggs. Here, we investigated the ant-related oviposition pattern of Allosmaitia strophius and Rekoa marius; then, we compared egg parasitism according to the presence of ants. Lycaenid oviposition and egg parasitism (in percent) were experimentally compared in ant-present and ant-excluded treatments. The study plant, Heteropterys byrsonimifolia, is an extrafloral nectaried shrub which supports several ant species. We sampled 280 eggs, of which 39.65 % belonged to A. strophius and 60.35 % to R. marius. Both lycaenids eggs were significantly more abundant on branches with ants, especially those with Camponotus crassus and Camponotus blandus, two ant species known to attend to lycaenids. A. strophius and R. marius parasitism was 4.5- and 2.4-fold higher, respectively, in ant-present treatments, but the results were not statistically significant. Our study shows that ant-mediated host plant selection in lycaenids might be much more widespread than previously thought, and not restricted to obligate myrmecophilous species. Tending ants may be inefficient bodyguards of lycaenid eggs, because unlike larvae which release sugared liquids, eggs do not offer obvious rewards to ants. Ants can ward off parasitoids of larvae, as observed elsewhere, but our findings show that positive ant–lycaenid interactions are conditional and depend on immature ontogeny.     

No evidence for sperm priming responses under varying sperm competition risk or intensity in guppies

Sperm competition theory predicts that males should tailor their investment in ejaculates according to the number of rival males competing to fertilize a female’s eggs. Research spanning several taxa supports this prediction by showing that males are often sensitive to the level of sperm competition and adjust their investment in sperm numbers accordingly. More recent work has revealed that males may also tailor the quality of sperm according to the number of males competing for fertilization. Here I test for both effects in guppies (Poecilia reticulata) in an experiment that simultaneously evaluates the risk and intensity models of sperm competition. The experiment determined whether male guppies adjust the number (stripped ejaculate size) and quality (sperm velocity and viability) of sperm that are primed over a 3-day period according to experimental changes in the perceived level of sperm competition. A total of 136 focal males were initially stripped of all retrievable sperm and assayed for these sperm traits before being allocated at random to one of four treatments simulating different levels of sperm competition risk and intensity. During the 3-day treatment phase, focal males had visual and olfactory access to a sexually receptive (initially virgin) female maintained with different numbers of stimulus males to simulate variation in the risk and intensity of sperm competition. Following this, males were assayed again for the sperm traits. Contrary to predictions, there was no significant change in any of the measured variables among treatments, although qualitatively the patterns for sperm velocity and viability did conform to expectation. The lack of any trend for the number of sperm primed was unequivocal and future work examining the effects of sperm competition on sperm production should focus on whether males differentially allocate sperm numbers among matings that differ in the level of sperm competition.     

Behavioral evidence for host fidelity among populations of the parasitic wasp, Diachasma alloeum (Muesebeck)

The concept of host fidelity, where host-specific mating occurs in close proximity to the oviposition site and location of larval development, is thought to impart a pre-mating isolation mechanism for sympatric speciation (sensu members of the genus Rhagoletis). The apple maggot fly, Rhagoletis pomonella, and the blueberry maggot fly, R. mendax, are morphologically similar sibling species thought to have speciated in sympatry by divergence of host plant association. Both of these fly species are attacked by the specialist braconid parasitoid, Diachasma alloeum. The current study demonstrates that both male and female D. alloeum exhibit a behavioral preference for the odor of the fruit of their larval Rhagoletis host species. Specifically, those D. alloeum emerging from puparia of R. pomonella are preferentially attracted to hawthorn fruit and those emerging from puparia of R. mendax are preferentially attracted to blueberry fruit. However, male D. alloeum reared from either R. pomonella or R. mendax were equally attracted to females originating from both Rhagoletis species. We suggest that the data herein present evidence for host fidelity, where populations of D. alloeum exhibit a greater tendency to mate and reproduce among the host plants of their preferred Rhagoletis hosts. Furthermore, host fidelity may have resulted in the evolution of distinct host races of D. alloeum tracking the speciation of their larval Rhagoletis prey.     

Effects of elevated CO_2 on sensitivity of six species of algae and interspecific competition of three species of alga

Introduction The atm ospheric C O 2 concentration increases at a rate of 1.5 滋 m ol/(m ol·a) and w ill double com pared to pre-industrial levels around the year 2050 (W atson et al., 1990). Its effects and m echanism by elevated CO 2 on global clim ate,…     

藻类光竞争模型构建及水体紊动对竞争的影响

光是藻类进行光合作用的重要能量来源,决定藻类的初始生产力,当多种浮游藻类共同生存时,会一起竞争光强.光竞争能力强的浮游藻类浓度增加,光竞争能力较弱的则减少,从而完成水体中浮游藻类优势藻的替代.本文通过在以往建立的单藻模型的基础上,耦合入竞争模型,构建两种（多种）浮游藻类光竞争模型,尝试通过数值模拟,研究不同水体紊动中竞争藻属分别取得竞争优势的机理.模拟结果表明：稳态水体中,竞争藻属的自身垂向迁移决定藻浓度的垂向分布,具有浮力调节能力的微囊藻属占据上层水体优势地位,并取得竞争优势;动态水体中,竞争藻属垂向分布均较为均匀,生长速率决定藻的竞争优势,小球藻属生长速率快,最终易取得竞争优势.此外,考虑浮游藻属的动态自遮蔽,会加速稳态水体中微囊藻属取得竞争优势,并限制动态水体中小球藻属的无限制生长,使得模拟结果更加符合实际情况.     

Effects of elevated CO2 on sensitivity of six species of algae and interspecific competition of three species of algae

Effects of elevated CO, （5000 μl/L） on sensitivity comparison of six species of algae and interspecific competition of three species of algae were investigated. The results showed that, the cell densities of six species of algae grown in elevated CO2 significantly increased compared to those in ambient CO2 （360 μl/L）, and with the time prolonged, the increasing extent increased. Therefore, elevated CO2 can promote the growth of six species of algae. However, there were differences in sensitivity between six species of algae. Based on the effects of elevated CO2 on biomass, the sensitive order （from high to low） was Platymanas sp., Platymanas subcordiformis, Nitzschia closterium, Isochrysis golbana Parke 8701, Dunoliella salina, Chlorella sp., on the condition of solitary cultivation. Compared to ambient CO2, elevated CO2 promoted the growth of three species of algae, Platymanas subcordiformis, Nitzschia closterium and Isochrysis galbana Parke 8701 under the condition of mixed cultivation. The sensitivity of the three species to elevated CO2 in mixed cultivation changed a lot compared to the condition of solitary cultivation. When grown in elevated CO2 under the condition of mixed cultivation, the sensitive order from high to low were Nitzschia clostertium, Platymonas subcordiformis; and Isochrysis galbana Parke 8701. However, under the condition of solitary cultivation, the sensitive order in elevated CO2 was Isochrysis galbana Parke 8701, Nitzschia clostertium, Platymonas subcordiformis, from sensitive to less sensitive. On the day 21, the dominant algae, the sub-dominant algae and inferior algae grown in elevated CO2 did not change. However, the population increasing dynamic and composition proportion of three algal species have significantly changed.     

Linear features and butterflies: the importance of green lanes

Green lanes are unmetalled tracks between fields of variable width, which may be sunk below or raised above field level, and bounded on both sides by ‘grass’ banks, hedgerows or dry-stone walls. In the UK they have no unique planning status and have been overlooked as discrete landscape elements. Green lanes were surveyed for butterflies in 1997 on lowland arable farmland on the Trafford/north Cheshire border (Warburton) and on upland grassland in the Yorkshire Dales (Ribble Valley). At the lowland site the green lanes were bounded by vegetation and were compared with grass banks and single hedgerow field boundaries; at the upland farm, the green lanes were bounded by dry-stone walls and were compared with grass banks and single dry-stone walls. Data from earlier work on a largely arable farm (Manydown) in Hampshire in 1987 and 1988 were re-analysed to make comparisons between a green lane, the rides and glades of two coppiced woodlands, and the grass banks and single hedgerows surrounding arable fields. Green lanes, whether bounded by vegetation or stone were superior to other common farmland biotopes with the exception of woodland, in terms of both butterfly abundance and species richness.Multiple regression of the Warburton data indicated the importance of green lanes, adjacent habitat type, and nectar sources for species richness and butterfly abundance. The interior of green lanes had lower windspeeds, and more bramble nectar sources than hedgerows or grass banks. By their nature they occupy a larger area of uncropped land, and are subject to a reduced disturbance regime and reduced inputs of agrochemicals and fertilisers. Their value as biodiversity reservoirs in intensively managed land is likely to be high.     

Experimental evidence for species-specific habitat preferences in two flycatcher species in their hybrid zone

Hybrid zones are often found in areas where the environmental characteristics of native habitat of both parental species meet. One of the plausible mechanisms that maintain species distinctiveness, or limit hybridization, is the existence of local species-specific preferences for the natal habitat type. We evaluated this hypothesis for two passerine bird species, the pied Ficedula hypoleuca and collared flycatcher F. albicollis, in their narrow hybrid zone in Central Europe. Both species have quite distinct habitat distributions, and they have also been reported to differ in their foraging niches. In a series of aviary experiments, we demonstrated that both species show distinct preferences for trees from their native area. The pied flycatcher preferred coniferous vegetation, while the collared flycatcher favored deciduous vegetation. In addition, both species differed in foraging substrate preferences. The pied flycatcher preferred to forage in the lower strata on the ground than the canopy, whereas the collared flycatcher foraged more at the canopy level. Both males and females of each species were highly consistent in their preference patterns. Due to the widespread nature of hybrid zones as places with transitional habitat features and the well-known habitat tight associations of various animal taxa with particular habitat types, we propose that habitat preferences might be an important and common mechanism that enhances the formation of conspecific pairs.     

Waterproof and translucent wings at the same time: problems and solutions in butterflies

Although the colour of butterflies attracts the most attention, the waterproofing properties of their wings are also extremely interesting. Most butterfly wings are considered “super-hydrophobic” because the contact angle (CA) with a water drop exceeds 150°. Usually, butterfly wings are covered with strongly overlapping scales; however, in the case of transparent or translucent wings, scale cover is reduced; thus, the hydrophobicity could be affected. Here, we present a comparative analysis of wing hydrophobicity and its dependence on morphology for two species with translucent wings Parantica sita (Nymphalidae) and Parnassius glacialis (Papilionidae). These species have very different life histories: P. sita lives for up to 6 months as an adult and migrates over long distance, whereas P. glacialis lives for less than 1 month and does not migrate. We measured the water CA and analysed wing morphology with scanning electron microscopy and atomic force microscopy. P. sita has super-hydrophobic wing surfaces, with CA > 160°, whereas P. glacialis did not (CA = 100–135°). Specialised scales were found on the translucent portions of P. sita wings. These scales were ovoid and much thinner than common scales, erect at about 30°, and leaving up to 80% of the wing surface uncovered. The underlying bare wing surface had a remarkable pattern of ridges and knobs. P. glacialis also had over 80% of the wing surface uncovered, but the scales were either setae-like or spade-like. The bare surface of the wing had an irregular wavy smooth pattern. We suggest a mode of action that allows this super-hydrophobic effect with an incompletely covered wing surface. The scales bend, but do not collapse, under the pressure of a water droplet, and the elastic recovery of the structure at the borders of the droplet allows a high apparent CA. Thus, P. sita can be translucent without losing its waterproof properties. This characteristic is likely necessary for the long life and migration of this species. This is the first study of some of the effects on the hydrophobicity of translucency through scales’ cover reduction in butterfly wings and on the morphology associated with improved waterproofing. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Phenoloxidase activity in the infraorder Isoptera: unraveling life-history correlates of immune investment

A termite colony is usually founded by a pair of alates, the primary reproductives, which produce all the nestmates. In some species, secondary reproductives appear to either replace the primaries or supplement colony reproduction. In termites, secondary reproductives are generally ergatoids derived from workers or nymphoids derived from nymphs. Silvestritermes euamignathus is a termite species that forms multiple nymphoid reproductives, and to date it was hypothesized that these secondary reproductives were the progeny of the primary founding reproductives. We developed markers for 12 microsatellite loci and used COI mitochondrial DNA (mtDNA) to genotype 59 nymphoid neotenics found in a colony of S. euamignathus to test this hypothesis. Our results showed that nymphoids of S. euamignathus are not all siblings. The microsatellite analysis suggests that the secondary reproductives derived from a minimum of four different pairs of reproductives belonging to at least two different matrilines. This is the first record of non-sibling secondary reproductives occupying the same nest in a higher termite. These unrelated reproductives might be the result of either pleometrotic colony foundation or colony fusion.

     

Effects of management cessation on grassland butterflies in southern Poland

The effects of natural succession and invasions of indigenous reed Phragmites australis and alien goldenrods Solidago sp. on butterfly communities of wet grassland were investigated in Kraków (southern Poland) after management cessation.The total number of species and individuals, mean number of species per survey and a species diversity (Shannon-Wiener index) were highest in fallow lands, old fallow lands and young forests, and the lowest in fallow lands invaded by reed and goldenrod and in mature forests. These results (1) reveal the importance of extensively mown meadows and fallow land for butterflies, (2) indicate that meadow restoration is still possible even several decades after abandonment and (3) show that invasion of reed and non-native goldenrods should be prevented.A few very rare species included in the Habitat Directive (Lycaena dispar, Lycaena helle, Maculinea teleius and Maculinea nausithous) were common on the wet grasslands in Krakow, thus the area should be protected. Moreover, it was shown that the presence and relative abundance of Maculinea butterflies were good indicators of general butterfly species richness and abundance in the investigated wet grasslands.     

2,2’,4,4’—四溴联苯醚对2种赤潮微藻种间竞争的影响

基于Logistic种群增长模型,研究了2,2’,4,4’—四溴联苯醚(BDE-47)的亚急性毒性胁迫对不同初始接种生物量比的赤潮异弯藻(Heterosigmaakashiwo)和米氏凯伦藻(Kareniamikimotoi)种间作用的影响.结果发现:不同的初始接种生物量比影响微藻间的竞争.加入0.05、0.25 mg/LBDE-47后,对于K. mikimotoi而言,不同初始生物量比的处理组表现出高浓度组的最大环境容纳量、种群瞬时增长率均大于低浓度组(P<0.05),而H. akashiwo高浓度组的最大环境容纳量、种群瞬时增长率均小于低浓度组(P<0.05).微藻之间的竞争表现出向着对K. mikimotoi有益方向发展的规律,因此一定浓度下的BDE-47干扰了两种微藻之间的竞争.