Local predator composition and landscape affects biological control of aphids in alfalfa fields

The biological control service supplied to croplands is a result of the predator community present within a focal crop, which is likely influenced by surrounding landscape composition and configuration. In this study, using cage experiments in two regions near Santiago, we determined if predator communities supplied a significant biological control service in alfalfa fields, examined how the abundance of exotic and native coccinellids, as well as other key predator groups, influenced biological control of aphids and measured how landscape composition and heterogeneity at three spatial scales influenced this service. We found that predators significantly suppressed aphid populations in both regions, but the relative importance of predators versus landscape variables on biological control differed between regions. In the region where predators were abundant, biological control was higher and related to the abundance of native coccinellids and syrphids, highlighting the importance of native species as providers of crucial ecological services. In the region where predators were not abundant, biological control was lower, and it was related to landscape composition, being positively associated with the abundance of woodlots and urban habitats, and negatively associated with fruit crops in the landscape. Therefore, landscape effects on biological control service may be weaker than local factors, and only become important when local predator abundance is low.     

Recovery of photosynthesis and phtosystem II fluorescence in Chlamydomonas reinhardtii after exposure to three levels of high light

Recovery from 60 min of photoinhibitory treatment at photosynthetic photon flux densities of 500, 1400 and 2200 μMmol m^?2 s^? was followed in cells of the green alga Chlamydomonas reinhardtii grown at 125 μMmol m^?2 s^?1. These light treatments represent photoregulation, moderate photoinhibition and strong photoinhibition, respectively. Treatment in photoregulatory light resulted in an increased maximal rate of oxygen evolution (P_max) and an increased quantum yield (Φ), but a 15% decrease in F_v/F_M. Treatment at moderately photoinhibitory light resulted in a 30% decrease in F_v/F_M and an approximately equal decrease in Φ. Recovery in dim light restored F_v/F_M within 15 and 45 min after high light treatment at 500 and 1400 μMmol m^?2 s^?1, respectively. Convexity (Θ), a measure of the extent of co-limitation between PS II turnover and whole-chain electron transport, and Φ approached, but did not reach the control level during recovery after exposure to 1400 μMmol m^?2 s^?1, whereas P_max increased above the control. Treatment at 2200 μMmol m^?2 s^?1 resulted in a strong reduction of the modeled parameters Φ, Θ and P_max. Subsequent recovery was initially rapid but the rate decreased, and a complete recovery was not reached within 120 min. Based on the results, it is hypothesized that exposure to high light results in two phenomena. The first, expressed at all three light intensities, involves redistribution within the different aspects of PS II heterogeneity rather than a photoinhibitory destruction of PS II reaction centers. The second, most strongly expressed at 2200 μmol m^?2 s^?1, is a physical damage to PS II shown as an almost total loss of PS II_α and PS II Q_B-reducing centers. Thus recovery displayed two phase, the first was rapid and the only visible phase in algae exposed to 500 and 1400 μmol m^?2 s^?1. The second phase was slow and visible only in the later part of recovery in cells exposed to 2200 μmol m^?2 s^?1.     

Enhancement of habitat heterogeneity and species richness on rocky shores inundated by sand

Summary Many rocky shores are subject to periodic inundation by sand, which is often thought to reduce species richness by eliminating organisms intolerant of sand scour or sand smothering. However, regular disturbance (e.g. inundation) should promote richness by preventing the development of low diversity climax communities. A study of faunal richness on 10 regularly inundated shores showed that inundation does promote richness, but by increasing habitat heterogeneity. Some species are excluded from parts of the shore by sand, but because of the patchiness of sand deposits they are rarely excluded from the entire shore. Other species are found only on rocks associated with sand, while typically sandy shore animals occur in the sand deposits themselves. Total richness (281 species) was greater than for local noninundated shores and sandy beaches combined.     

The wing vestiture of the non-ditrysian Lepidoptera (Insecta). Comparative morphology and phylogenetic implications

The ultrastructure of the dorsal forewing vestiture in exemplars of all family group taxa of non‐ditrysian Lepidoptera is examined, and the evolutionary implications at family level and above are discussed. Wing‐scale terminology is reviewed. Three different types of bilayer wing‐scale covering are recognized; only a few groups have a single‐layer wing‐scale covering. The general scale arrangement is random, but a few taxa have clustered scale arrangements and scattered heteroneurans have scales arranged in transverse rows. Cross ribs are present in all taxa, but only as vestiges in eriocraniid cover scales. Ridge dimorphism is widespread in Neolepidoptera. Surprisingly, ridges and cross ribs on the adwing scale surface are of general occurrence in Neopseustidae and Hepialidae, and are even found on parts of the ground scales of many other Neolepidoptera. Morphological evidence strongly indicates that the fused wing‐scale types found in non‐Coelolepidan Lepidoptera and Neolepidoptera are independently evolved, as evidenced from the presence of vestigial perforations. Absence of perforations is not infallible evidence that a scale is solid. Microtrichia are independently reduced in a number of taxa and probably re‐evolved in at least higher nepticulids. Wing vestiture and scale characters indicate that Tischerioidea may be the sister group of Ditrysia.     

Trait plasticity alters the range of possible coexistence conditions in a competition–colonisation trade‐off

Most of the classical theory on species coexistence has been based on species‐level competitive trade‐offs. However, it is becoming apparent that plant species display high levels of trait plasticity. The implications of this plasticity are almost completely unknown for most coexistence theory. Here, we model a competition–colonisation trade‐off and incorporate trait plasticity to evaluate its effects on coexistence. Our simulations show that the classic competition–colonisation trade‐off is highly sensitive to environmental circumstances, and coexistence only occurs in narrow ranges of conditions. The inclusion of plasticity, which allows shifts in competitive hierarchies across the landscape, leads to coexistence across a much broader range of competitive and environmental conditions including disturbance levels, the magnitude of competitive differences between species, and landscape spatial patterning. Plasticity also increases the number of species that persist in simulations of multispecies assemblages. Plasticity may generally increase the robustness of coexistence mechanisms and be an important component of scaling coexistence theory to higher diversity communities.     

Spatio‐temporal scaling of biodiversity and the species–time relationship in a stream fish assemblage

1. The increase of species richness with the area of the habitat sampled, that is the species–area relationship, and its temporal analogue, the species–time relationship (STR), are among the few general laws in ecology with strong conservation implications. However, these two scale‐dependent phenomena have rarely been considered together in biodiversity assessment, especially in freshwater systems. 2. We examined how the spatial scale of sampling influences STRs for a Central‐European stream fish assemblage (second‐order Bernecei stream, Hungary) using field survey data in two simulation‐based experiments. 3. In experiment one, we examined how increasing the number of channel units, such as riffles and pools (13 altogether), and the number of field surveys involved in the analyses (12 sampling occasions during 3 years), influence species richness. Complete nested curves were constructed to quantify how many species one observes in the community on average for a given number of sampling occasions at a given spatial scale. 4. In experiment two, we examined STRs for the Bernecei fish assemblage from a landscape perspective. Here, we evaluated a 10‐year reach level data set (2000–09) for the Bernecei stream and its recipient watercourse (third‐order Kemence stream) to complement results on experiment one and to explore the mechanisms behind the observed patterns in more detail. 5. Experiment one indicated the strong influence of the spatial scale of sampling on the accumulation of species richness, although time clearly had an additional effect. The simulation methodology advocated here helped to estimate the number of species in a diverse combination of spatial and temporal scale and, therefore, to determine how different scale combinations influence sampling sufficiency. 6. Experiment two revealed differences in STRs between the upstream (Bernecei) and downstream (Kemence) sites, with steeper curves for the downstream site. Equations of STR curves were within the range observed in other studies, predominantly from terrestrial systems. Assemblage composition data suggested that extinction–colonisation dynamics of rare, non‐resident (i.e. satellite) species influenced patterns in STRs. 7. Our results highlight that the determination of species richness can benefit from the joint consideration of spatial and temporal scales in biodiversity inventory surveys. Additionally, we reveal how our randomisation‐based methodology may help to quantify the scale dependency of diversity components (α, β, γ) in both space and time, which have critical importance in the applied context.     

Old and new challenges in using species diversity for assessing biodiversity

Although the maintenance of diversity of living systems is critical for ecosystem functioning, the accelerating pace of global change is threatening its preservation. Standardized methods for biodiversity assessment and monitoring are needed. Species diversity is one of the most widely adopted metrics for assessing patterns and processes of biodiversity, at both ecological and biogeographic scales. However, those perspectives differ because of the types of data that can be feasibly collected, resulting in differences in the questions that can be addressed. Despite a theoretical consensus on diversity metrics, standardized methods for its measurement are lacking, especially at the scales needed to monitor biodiversity for conservation and management purposes. We review the conceptual framework for species diversity, examine common metrics, and explore their use for biodiversity conservation and management. Key differences in diversity measures at ecological and biogeographic scales are the completeness of species lists and the ability to include information on species abundances. We analyse the major pitfalls and problems with quantitative measurement of species diversity, look at the use of weighting measures by phylogenetic distance, discuss potential solutions and propose a research agenda to solve the major existing problems.     

鱼类生物群落对太子河流域土地利用、河岸带栖息地质量的响应

河流生态系统的退化是多空间尺度环境因子作用的结果。探讨不同尺度环境因子及水生生物之间的作用关系,识别影响水生生物群落完整性的尺度问题,是有效开展水生生物保护的基础。基于2009年对太子河流域15个样点的鱼类、河岸带栖息地质量评价,结合遥感影像解译的太子河流域土地利用情况(包括流域尺度和河段尺度),研究鱼类完整性指数(F-IBI)与两种尺度土地利用、栖息地质量参数之间的关系。结果表明太子河上游地区河岸栖息地质量较好,下游地区由于农业用地、城镇用地比例的增加河岸栖息地质量明显下降。F-IBI与自然用地比例呈正相关,与农业、城镇用地比例呈负相关。农业用地对F-IBI的影响体现在流域尺度,而城镇用地在两种尺度上都存在显著影响。相比于农业用地,城镇用地相同比例的增加会导致F-IBI更快的下降。底质、水质状况、人类活动强度是显著影响F-IBI的栖息地质量评价参数。3项参数均随农业和城镇用地比例增加而降低,农业用地主要在流域尺度上对3项参数产生影响,城镇用地主要影响底质和水质状况2项参数,而在两种尺度上的影响相差不大。     

城市边缘区生态承载力时空分异研究——以甘井子区为例

以大连市甘井子区为例,利用1998年的土地利用数据和2003年、2007年、2013年的SPOT5遥感数据等多元数据,运用状态空间表征生态承载力量值的计量方法,计算了城市边缘区的社区生态承载力,并研究了甘井子区1998—2013年生态承载力的时空分异特征。结果表明:(1)时间上,1998—2013年,甘井子区整体的生态承载力呈现先快后慢的下降趋势,生态状态呈现出从优秀向良好,再向一般过渡的阶段特征。(2)空间上,甘井子区整体的生态承载力等级东西部差异明显,呈现出相同承载力等级小范围聚集和相近承载力等级间穿插分布的特征。(3)甘井子区内部各社区生态承载力程度差异明显。靠近市区的社区生态承载力15年间变化显著,生态承载程度迅速下降,远离市区的部分社区生态承载力变化不大,生态环境保持良好以上的状态。