Impacts of Alternative Timber Harvest Practices on Leaf-Chewing Herbivores of Oak

Abstract:  Studies of the effects of logging on Lepidoptera rarely address landscape-level effects or effects on larval, leaf-feeding stages. We examined the impacts of uneven-aged and even-aged logging on the abundance, richness, and community structure of leaf-chewing insects of white ( Quercus alba L.) and black ( Q. velutina L.) oak trees remaining in unharvested areas by sampling 3 years before and 7 years after harvest. After harvest, white oaks in uneven-aged sites had 32% fewer species of leaf-chewing insects than control sites. This reduction in species richness may have resulted from changes in microclimate (reducing plant quality and/or changing leaf phenology) that affected a much larger total area of each site than did even-aged cuts. For black oak after harvest, species richness in uneven- and even-aged sites increased relative to levels before harvest. Harvesting did not alter total insect density or community structure in the unlogged habitat for either oak species with one exception: insect density on black oak increased in the oldest forest block. Community structure of herbivores of black and white oaks in clearcut gaps differed from that of oaks in intact areas of even-aged sites. Furthermore, both richness and total insect density of black oaks were reduced in clearcut gaps. We suggest that low-level harvests alter herbivore species richness at the landscape level. Treatment effects were subtle because we sampled untreated areas of logged landscapes, only one harvest had occurred, and large temporal and spatial variation in abundance and richness existed. Although the effects of logging were greater in uneven-aged sites, the effects of even-aged management are likely to increase as harvesting continues.     

Contribution of Urban Expansion and a Changing Climate to Decline of a Butterfly Fauna

Butterfly populations are naturally patchy and undergo extinctions and recolonizations. Analyses based on more than 2 decades of data on California's Central Valley butterfly fauna show a net loss in species richness through time. We analyzed 22 years of phenological and faunistic data for butterflies to investigate patterns of species richness over time. We then used 18–22 years of data on changes in regional land use and 37 years of seasonal climate data to develop an explanatory model. The model related the effects of changes in land‐use patterns, from working landscapes (farm and ranchland) to urban and suburban landscapes, and of a changing climate on butterfly species richness. Additionally, we investigated local trends in land use and climate. A decline in the area of farmland and ranchland, an increase in minimum temperatures during the summer and maximum temperatures in the fall negatively affected net species richness, whereas increased minimum temperatures in the spring and greater precipitation in the previous summer positively affected species richness. According to the model, there was a threshold between 30% and 40% working‐landscape area below which further loss of working‐landscape area had a proportionally greater effect on butterfly richness. Some of the isolated effects of a warming climate acted in opposition to affect butterfly richness. Three of the 4 climate variables that most affected richness showed systematic trends (spring and summer mean minimum and fall mean maximum temperatures). Higher spring minimum temperatures were associated with greater species richness, whereas higher summer temperatures in the previous year and lower rainfall were linked to lower richness. Patterns of land use contributed to declines in species richness (although the pattern was not linear), but the net effect of a changing climate on butterfly richness was more difficult to discern. Contribución de la Expansión Urbana y un Clima Cambiante a la Declinación de la Fauna de Mariposas     

Protein content of spermatophores in relation to monandry/polyandry in butterflies

The evolution of a mating system, and specifically mating frequency, is dependent on the costs and benefits to both sexes of mating once or several times. In butterflies, males transfer a spermatophore that contains both sperm and accessory gland products. Accessory gland substances contain nutrients which, in some species, females use to increase their reproductive output and longevity. Nutrients contained in these packaged ejaculates represent investment by males in reproduction. Consequently, the nutritional composition of spermatophores may vary depending on the mating system. There are two lines of arguments concerning the evolution of the nutrient content of ejaculates. One hypothesis argues that male nuptial gifts evolved in the context of certainty of paternity and ease of finding mates; thus spermatophores of polyandrous males (with lower certainty of paternity and greater ease of finding mates) should contain less protein than those of monandrous males, since more spermatophores are produced on average. The other hypothesis argues that polyandry evolved in the context of maximization of male transfer of nutrients to females, and hence spermatophores of polyandrous males should contain more protein than those of monandrous males. In an attempt to distinguish between these two hypotheses, we determined how protein content of ejaculates varied with the degree of polyandry in nine species of pierid and two species of satyrid butterflies. We found that both relative ejaculate mass and protein content increased with the degree of polyandry. Hence our results are consistent with the view that polyandry has evolved in the context of male transfer of nutrients to females, and provides another example of a male adaptation to multiple mating in butterflies.     

Ontogenetic changes in social behaviour in the forest tent caterpillar,<Emphasis Type="Italic"> Malacosoma disstria</Emphasis>

Many animals, including gregarious caterpillars, begin life in groups and become increasingly solitary as they grow larger. These ontogenetic changes in social behaviour suggest that the costs and benefits of grouping change with increasing individual size. Forest tent caterpillar (Malacosoma disstria) colonies exhibit complex social behaviour during the early larval instars, using pheromone trails to move together between temporary bivouacs and feeding sites, and break up as the caterpillars grow. We demonstrate changes in individual responses to cues from conspecifics that explain changes in aggregation during caterpillar development. We used Markov chain analysis to test the influence of pheromone trails and colony-mates on an individual caterpillars tendency to switch between quiescence, searching, walking and spinning. Pheromone-laden silk trails increased the tendency to begin locomotion, whereas colony-mates increased switching from activity to quiescence. Trails also influenced the form taken by locomotor behaviour, and promoted directed walking over searching. Social cues thus increase the efficiency of individual locomotion. Younger larvae were more quiescent and more reluctant to walk in the absence of trails than were older insects. An increase in independent locomotion as the larvae grow provides a mechanism to explain colony break-up and points to an ontogenetic shift in the internal processes driving behaviour. Scaling relationships suggest that many of the benefits associated with group-living in caterpillars decrease as individuals grow larger, providing an adaptive explanation for observed ontogenetic changes in social behaviour.Communicated by N. Wedell     

Modelling pheromone anemotaxis for biosecurity surveillance: Moth movement patterns reveal a downwind component of anemotaxis

Insect pheromone traps are becoming an increasingly important tool in biosecurity and pest surveillance, alerting managers to the presence of unwanted organisms. To expand the role of these traps beyond their present sentinel role, it is necessary to develop reliable operational models of local insect dispersal. Following the detection of an insect incursion using a pheromone trap, such models could simulate the dispersal of the insect from its emergence site to the point of detection, enabling biosecurity managers to estimate the most likely proximal source of the incursion. An individual-based moth movement model was developed to simulate observed patterns of moth movement in response to the presence or absence of a pheromone. Using parameters derived from a genetic algorithm, it was possible to fit a model based on the three behavioural components (upwind, upwind with zigzags and casting) described in insect anemotaxis theory to a subset of observed movement patterns (0-135° to the wind), but not to the whole spectrum of movement patterns. It appears that current insect anemotaxis theory is missing a downwind flight component. Whilst the frequency of downwind movements is small; their ground speed could lead to significant downwind displacement, having a disproportionately strong influence on a moth movement model, and hence projections of the likely source or target locations.     

Rare Species and Ecosystem Functioning

Abstract:  The role of diversity in the maintenance of ecosystems has been studied widely in the past decade. By correlating richness and diversity with basic ecosystem processes, these investigations lend support to the hypothesis that species diversity significantly influences ecosystem functioning and, in turn, provide support for the conservation of biodiversity. Nonetheless, the majority of these investigations demonstrate that conservation of a relatively small number of generally dominant species is sufficient to maintain most processes. Indeed, there is remarkably little evidence to support the contention that less common species, those likely of highest conservation concern, are important in the maintenance of ecosystem functioning. Here we summarize studies, most employing alternative methodological strategies, wherein less common and rare species are demonstrated to make significant contributions to ecosystem functioning. Evidence exists among studies of keystone species, aggregate effects of less common species, and species turnover. Our findings suggest that (1) less common species can make significant ecosystem contributions; (2) further investigation into the effects of rare and less common species on ecosystem maintenance is sorely needed; (3) further investigation should embrace a variety of approaches; and (4) until further research is conducted a prudent conservation approach is warranted wherein the contribution of less common species to ecosystem functioning is assumed.     

Inhibition of glycosidases by Lepidoptera; roles in the insects and leads to novel compounds?

Summary Glycosidase inhibitors are widespread in plants and can be sequestered by Lepidoptera, for which they can presumably serve as defences by making the insects indigestible to a range of potential predators. As a result of this study of eight British species of moth and butterfly it was found that glycosidase inhibitors in the insects could then be detected in the larval food plants which were not previously known to contain them; however, some were only detectable in the plants after concentration. In some cases the inhibition of specific glycosidases by Lepidoptera was detected even though the insects had not apparently acquired them from their food plants. Inhibition of-N-acetylglucosaminidase was observed in most of the adult Lepidoptera analysed but further work is required to identify the inhibitors, though they are likely to be nitrogen-containing compounds. Weak anti-HIV activity was also observed in the glycosidase-inhibiting fractions ofAcherontia atropos and the plantUrtica dioica.     

Male mating bias and its potential reproductive consequence in the butterfly <Emphasis Type="Italic">Colias eurytheme</Emphasis>

Male mating biases may be a widespread feature of animal mating systems but the phenotypic consequences of these biases are often unclear, especially in species for which the operational sex ratio is strongly male-biased. In Colias butterflies, male choice is thought to be one of the factors responsible for maintaining a female-limited genetic color polymorphism, in which female wings appear either yellowish-orange or white (the “alba” variant). Previous studies have indicated that alba females of two montane Colias species mate fewer times during their lifetime, possibly as a partial consequence of this bias. Here we report the results of a field study of male mating behavior and female mating biology in Colias eurytheme, conducted under conditions of high (summer) and low (spring) population densities. Our data show that despite a substantial male bias in approaching alba vs yellowish-orange phenotypes [ratios of 0.08:1 (spring) and 0.28:1 (summer)], alba females did not contain, on average, fewer or smaller spermatophores. Not one of the 308 sampled females was virgin, but females of both phenotypes accumulated spermatophores with age, and tended to carry fewer, larger spermatophores in spring. These data suggest that significantly fewer (or lighter) spermatophores need not be an obligatory or simple consequence of a strong male bias in butterflies. We discuss these findings in light of the known, thermally and density-dependent complexities of alba reproductive biology and of the Colias mating system.     

Male mating history and female fecundity in the Lepidoptera: do male virgins make better partners?

In insects, large ejaculate and associated materials, including spermatophores, appear to have evolved via sexual selection acting on males to either delay female remating or to increase the rate of egg-laying. It is also possible, however, that females use nutrients transferred during mating to increase their lifetime fecundity. If so, male ejaculate size may also have evolved under natural selection as a form of paternal investment. In Lepidoptera, males with a greater number of prior matings tend to produce smaller spermatophores. However, the reported effects of male mating history on female fecundity vary widely among species. We therefore performed a meta-analysis using data from 29 studies of 25 species. Overall, the reproductive output of females mated to virgin males was significantly higher than that of females mated to sexually experienced males (Hedges d=0.33, P<0.01). A sample size of around 145 females per male mating type is required to detect an effect of this size with 80% statistical power at =0.05 (two-tailed). There was no difference in mean effect size between butterflies/skippers and moths. After controlling for any effect of taxonomic group, however, the mean effect size for polyandrous species was significantly greater than that for monandrous species (Hedges d=0.45 vs 0.25, P=0.01). We then discuss possible reasons why male mating history, presumably acting through its effect on spermatophore size, might have a stronger effect in polyandrous than monandrous species.Communicated by A. Cockburn     

Potential direct fitness consequences of ornament-based mate choice in a butterfly

Female mate choice has been shown to provide direct mating benefits in several animal groups. In butterflies, for which there are increasing reports of fine-scale color-based mate choice, the evolutionary benefits that accrue from such mating biases, if any, are largely unknown. We addressed this issue in the butterfly Colias eurytheme, a species in which females choose mates on the basis of iridescent ultraviolet (UV) wing ornamentation and in which males donate reproductively beneficial nuptial gifts. In the first experiment, we assessed the mass of gifts donated to 77 virgin females by males sampled directly from a field encounter site. Despite large variance in the male adult phenotype and ejaculate, no single aspect of dorsal wing coloration, including UV brightness, chroma, or hue, was related to ejaculate mass. There was, however, an interesting interaction between the effects of male body size and copula duration upon ejaculate mass, with size scaling positively with ejaculate mass among males involved in shorter copulations (those lasting <70 min) but negatively among males in longer copulations. In the second experiment, we assessed the lifetime fecundity, fertility, and longevity of 85 females mated under similar circumstances to free-flying wild males. Although several wing color parameters proved subtly informative in more sophisticated multivariable models, no model predicted more than about 20% of the variation in any single female fitness parameter. The duration of copulation, which ranged from 35 min to over 16 h and which carries putative costs for females, was, again, only very weakly predicted by male wing color parameters (i.e., R ² = 0.089). Given the overall minor predictive power of male wing coloration in general and of UV brightness in particular, our results do not strongly support the hypothesis that female C. eurytheme prefer bright UV males to obtain direct benefits or to minimize the costs associated with lengthy copulations.     

Contest behaviour in the speckled wood butterfly (Pararge aegeria): seasonal phenotypic plasticity and the functional significance of flight performance

Although contemporary animal contest theory emphasises the importance of physical asymmetries in resolving disputes, such asymmetries do not obviously settle fights in all groups. Territorial male butterflies, for example, compete via elaborate non-contact aerial interactions in which success is determined by relative persistence. Prior research suggests that the resolution of these contests is not clearly related to physical variables such as body size or energy reserves. However, given that the contests involve elaborate aerial manoeuvres, one long-standing suggestion is that asymmetries in flight performance, and thus flight morphology, may be important. We addressed this hypothesis via a manipulative investigation into the biophysical correlates of contest success in the speckled wood butterfly, Pararge aegeria. This species possesses the ability for significant adaptive phenotypic plasticity in relevant flight morphological parameters. We took advantage of this plasticity to rear 90 individuals of markedly varying flight morphologies, which we then pitted against each other in a semi-controlled experimental fashion. Multiple logistic and lognormal analyses provided little evidence for the relevance of morphological parameters, including relative flight musculature, wing loading and wing aspect ratio (wing length relative to area), to the outcome and/or duration of experimental contests. Instead, we found a positive effect of age upon contest success. Given that ability for high acceleration is strongly linked to variation in these morphological parameters, our findings suggest that flight performance is not a strong determinant of resource-holding potential in this notably territorial butterfly.     

鼎湖山20公顷森林样地单个物种对群落的构建

大型固定监测森林样地已成为研究森林群落组织机制的一个重要平台。群落里个体之间的相互作用对群落的构建有相当重要的作用。以往的研究主要针对于物种之间的相互作用,而用群落里单个物种与其它所有个体之间相互关系来解释群落构建的研究还很少。采用单个物种-面积关系（ISAR）这一指标对鼎湖山20 hm2样地和BCI 50 hm2样地数据分析,来研究不同样地单个物种是如何对森林群落进行构建的。结果显示,与BCI样地和Sinharaja样地不同,鼎湖山样地大树对周围其它个体的作用几乎是中性的;而对于小树（胸径小于10 cm）来说,鼎湖山样地和BCI样地一样,随着尺度的增加＂吸引型＂物种减少,而＂中性＂物种增加。说明了不同的群落在不同的发育阶段,单个物种对群落结构的构建有重要的作用不同,将来的研究应该结合群落其它方面的因素来分析群落内个体之间相互作用,例如从时间尺度的谱系和空间因素去分析。     

Mating system evolution in response to search costs in the speckled wood butterfly, Pararge aegeria

A general and intuitive prediction from models of mate preference is that when the cost of searching for mates increases, individuals should become less choosy. Here, we test this prediction by comparing the mating propensity of females in two populations of the butterfly Pararge aegeria. The populations originated from southern Sweden and Madeira and due to different adult emergence patterns throughout the year, the average density of males per female is likely to be lower on Madeira. Therefore, we expected that the cost of searching should be greater on Madeira and, consequently, that the Madeiran females should be less choosy. In line with predictions, the Madeiran females mated significantly sooner after the first interaction with males than did females from southern Sweden. This difference may reflect a weaker preference for territorial males over non-territorial patrollers in the Madeiran population, because of the greater costs of searching. The Madeiran females also showed a shorter time lag between mating and the start of oviposition. We discuss this unexpected result and propose that the same mechanism could also explain this population difference, i.e. different costs of searching for suitable host plants. Both search processes are fundamental for female reproductive success and we find it plausible that they can be generalised into the same theory of optimal search behaviour. Received: 14 May 1998 / Accepted after revision: 13 December 1998     

铜对水生生物的毒性:类群特异性敏感度分析

铜的毒性因受多种环境因素(如温度、pH等)的影响,其水质基准和标准经历过多次修改。由于不同区系生物受生活环境等因素的影响,不同物种对铜的耐受性和敏感度上存在很大的差异。本文通过构建类群特异性敏感度分布,以及对10%安全浓度值(10%hazardous concentration,HC_(10))及其95%置信区间(95%confidence interval,95%CI)的比较,分析了铜对淡水和海水各类群的敏感度差异,以期为我国在制定相关水质基准的物种选择上提供参考。结果显示,淡水系统中藻类为对铜毒性最敏感类群,其次为甲壳类,软体动物类,鱼类,寡毛类,而昆虫类为对铜的最耐受类群。海水各类群对铜的敏感度顺序与淡水类似,只是在寡毛类和鱼类顺序上有所不同。相对于海洋物种,淡水水体生物总体上比海水中各相应类群生物对铜更为敏感。     

Interactions between Ecological Traits and Host Plant Type Explain Distribution Change in Noctuid Moths

Abstract:  The ecological traits of species determine how well a species can withstand threats to which it is exposed. If these predisposing traits can be identified, species that are most at risk of decline can be identified and an understanding of the processes behind the declines can be gained. We sought to determine how body size, specificity of larval host plant, overwintering stage, type of host plant, and the interactions of these traits are related to the distribution change in noctuid moths. We used data derived from the literature and analyzed the effects of traits both separately and simultaneously in the same model. When we analyzed the traits separately, it seemed the most important determinants of distribution change were overwintering stage and type of host plant. Nevertheless, ecological traits are often correlated and the independent effect of each trait may not be seen in analyses in which traits are analyzed separately. When we accounted for other correlated traits, the results were substantially different. Only one trait (body size), but 3 interactions, explained distribution change. This finding suggests that distribution change is not determined by 1 or 2 traits; rather, the effect of the traits depends on other interacting traits. Such complexity makes it difficult to understand the processes behind distribution changes and emphasizes the need for basic ecological knowledge of species. With such basic knowledge, a more accurate picture of the factors causing distribution changes and increasing risk of extinction might be attainable.     

鼎湖山20公顷森林样地单个物种对群落的构建

大型固定监测森林样地已成为研究森林群落组织机制的一个重要平台。群落里个体之间的相互作用对群落的构建有相当重要的作用。以往的研究主要针对于物种之间的相互作用,而用群落里单个物种与其它所有个体之间相互关系来解释群落构建的研究还很少。采用单个物种-面积关系(ISAR)这一指标对鼎湖山20 hm2样地和BCI 50 hm2样地数据分析,来研究不同样地单个物种是如何对森林群落进行构建的。结果显示,与BCI样地和Sinharaja样地不同,鼎湖山样地大树对周围其它个体的作用几乎是中性的;而对于小树(胸径小于10 cm)来说,鼎湖山样地和BCI样地一样,随着尺度的增加吸引型物种减少,而中性物种增加。说明了不同的群落在不同的发育阶段,单个物种对群落结构的构建有重要的作用不同,将来的研究应该结合群落其它方面的因素来分析群落内个体之间相互作用,例如从时间尺度的谱系和空间因素去分析。     

Assessing the Risk of Introducing Exotic Species via the Live Marine Species Trade

Abstract:  Although the shipping industry has received considerable attention as a dispersal mechanism for aquatic nuisance species, many invasions have been linked to other mechanisms of transfer. The threat posed to coastal ecosystems by these alternative mechanisms, however, remains largely unquantified. We assessed the potential risks of introducing marine and estuarine species associated with seven mechanisms of transfer: seafood companies, aquaculture operations, bait shops, stores that sell marine ornamental species, research and educational organizations, public aquariums, and coastal restoration projects. For each, we compiled a comprehensive database of organizations in coastal Massachusetts. We then designed and administered a survey to a subset of organizations that inquired about (1) their proximity to saltwater and methods of handling live imports; (2) the type and quantity of marine species being imported; and (3) the organization's familiarity with marine invasions. Respondents in five of the seven categories acknowledged importing nonlocal live marine species to the area. Seafood companies handled the majority of individuals but relatively few taxa. This mechanism of transfer also had the most complex trade patterns and the greatest number of operations located near saltwater. In contrast, the other transfer mechanisms each had simpler trade pathways and fewer operations but varied in the quantity and taxonomic diversity of their imports. Significantly, no single mechanism of transfer stood out as presenting a primary risk. Rather, each had characteristics or used handling practices at different points in the importation process that could facilitate introductions. To prevent future marine invasions, better reporting requirements for live species imports are needed, and best-management practices and outreach strategies specific to the transfer mechanism should be developed and implemented.     

Reliability of a Higher-Taxon Approach to Richness, Rarity, and Composition Assessments at the Local Scale

Abstract:  A promising shortcut for quantifying species patterns is to use genera and families as surrogates of species. At large spatial scales, concurrence between patterns of richness, rarity, and composition of species and higher taxa is generally high. Only a few researchers, however, have examined this relationship at the local scale, which is frequently the relevant scale in land-use conflicts. We investigated the reliability of the higher-taxon approach in assessing patterns of species richness, rarity, and composition at the local scale. We studied diversity patterns of three commonly used surrogate taxa: vascular plants, ground-dwelling beetles, and moths. We conducted year-round field surveys for these taxa in the Jerusalem Mountains and the Judean foothills, Israel. Richness and composition of species were highly correlated with richness and composition of genera for all taxa. At the family level, correlations with richness and composition of species were much lower. Excluding monotypic genera and families did not affect these relations. Rarity representation based on higher taxa varied considerably depending on the taxon, and rarity scale and was weaker compared with richness and composition representation. Cumulative richness curves of species and genera showed similar patterns, leveling off at equivalent sampling efforts. Genus-level assessments were a reliable surrogate for local patterns of species richness, rarity, and composition, but family-level assessments performed poorly. The advantage of using coarse taxonomic scales in local diversity surveys is that it may decrease identification time and the need for experts, but it will not reduce sampling effort.     

Conservation Status as a Biodiversity Trend Indicator: Recommendations from a Decade of Listing Species at Risk in British Columbia

Abstract:  Species conservation status is commonly used as a broad-scale indicator of the state of biological diversity. To learn about its value for tracking trends, we examined provincial lists of terrestrial vertebrate species and subspecies at risk in British Columbia, Canada, for 1992 and 2002 to see whether changes in these lists reflected changes in the status of the taxa they represent. Examination of the case histories of individual species and subspecies showed that 65% of additions and deletions to the British Columbia Red List were the result of improvement in knowledge of species status, changes in assessment procedures, and refinements in taxonomy rather than actual changes in a species' status. Comparison to an alternate set of rank scores provided by NatureServe for taxa that appeared on both 1992 and 2002 British Columbia Red Lists revealed changes in status that were not reflected by movement from the list. Estimates of historical conservation status for species on the 1992 British Columbia Red List demonstrated ambiguity around the natural baseline with regard to tracking changes in list composition over time. We discourage the continued use of indicators based solely on conservation status as a means of tracking biodiversity. Instead we recommend advancing strategic indicators around species at risk based on long-term monitoring data, deliberate and explicitly stated baselines, and consistent methods of conservation ranking.     

The Value of Biodiversity in Reserve Selection: Representation, Species Weighting, and Benefit Functions

Abstract:  The limited availability of resources for conservation has led to the development of many quantitative methods for selecting reserves that aim to maximize the biodiversity value of reserve networks. In published analyses, species are often considered equal, although some are in much greater need of protection than others. Furthermore, representation is usually treated as a threshold: a species is either represented or not, but varying levels of representation over or under a given target level are not valued differently. We propose that a higher representation level should also have higher value. We introduce a framework for reserve selection that includes species weights and benefit functions for under- and overrepresentation (number of locations for each species). We applied the method to conservation planning for herb-rich forests in southern Finland. Our use of benefit functions and weighting changed the identity of about 50% of the selected sites at different funding levels and improved the representation of rare and threatened species. We also identified a small area of additional land that would substantially enhance the existing reserve network. We suggest that benefit functions and species weighting should be considered as standard options in reserve-selection applications.