Communities of Endophytic Sebacinales Associated with Roots of Herbaceous Plants in Agricultural and Grassland Ecosystems Are Dominated by Serendipita herbamans sp. nov

Endophytic fungi are known to be commonly associated with herbaceous plants, however, there are few studies focusing on their occurrence and distribution in plant roots from ecosystems with different land uses. To explore the phylogenetic diversity and community structure of Sebacinales endophytes from agricultural and grassland habitats under different land uses, we analysed the roots of herbaceous plants using strain isolation, polymerase chain reaction (PCR), transmission electron microscopy (TEM) and co-cultivation experiments. A new sebacinoid strain named Serendipita herbamans belonging to Sebacinales group B was isolated from the roots of Bistorta vivipara, which is characterized by colourless monilioid cells (chlamydospores) that become yellow with age. This species was very common and widely distributed in association with a broad spectrum of herbaceous plant families in diverse habitats, independent of land use type. Ultrastructurally, the presence of S. herbamans was detected in the cortical cells of Plantago media, Potentilla anserina and Triticum aestivum. In addition, 13 few frequent molecular operational taxonomic units (MOTUs) or species were found across agricultural and grassland habitats, which did not exhibit a distinctive phylogenetic structure. Laboratory-based assays indicate that S. herbamans has the ability to colonize fine roots and stimulate plant growth. Although endophytic Sebacinales are widely distributed across agricultural and grassland habitats, TEM and nested PCR analyses reinforce the observation that these microorganisms are present in low quantity in plant roots, with no evidence of host specificity.     

Ants of Three Adjacent Habitats of a Transition Region Between the Cerrado and Caatinga Biomes: The Effects of Heterogeneity and Variation in Canopy Cover

Habitat heterogeneity and complexity associated with variations in climatic conditions are important factors determining the structure of ant communities in different terrestrial ecosystems. The objective of this study was to describe the horizontal and vertical distribution patterns of the ant community associated with three adjacent habitats in a transition area between the Cerrado and Caatinga biomes at the Pandeiros River, state of Minas Gerais, Brazil. We tested the following hypotheses: (1) the richness and composition of ant species and functional group structure changes between different habitats and strata; (2) habitats with higher tree species richness and density support higher ant species richness; and (3) habitats with lower variation in canopy cover support higher ant species richness. Sampling was conducted in three adjacent habitats and at three vertical strata. Ant species richness was significantly different among vertical strata. Ant species composition was different among both habitats and vertical strata and functional group structure was divergent among habitats. Partitioning of the diversity revealed that the diversity for the three components was statistically different from the one expected by the null model; α and β ₂ were higher and β ₁ was lower than the values expected by chance. Tree density and variation in canopy cover negatively affected ant species richness. The occurrence of different species and the changing of functional group structures in different habitats and strata suggest an ecological–evolutionary relationship between ants and their habitats and emphasize the need to implement local conservation strategies in the ecotones between biomes.     

Land use influences harvestman diversity in northern Spain: a case study involving secondary grasslands and forest plantations (Arachnida: Opiliones)

Harvestmen have a general distribution pattern with more species and higher abundance in forests than in open habitats, as previously verified in mountain Cantabrian areas of northern Spain, of the Orocantabrian Province. The study of harvestmen of the low Cantabrian areas of the adjacent biogeographic Cantabro-Atlantic Province is highly appropriate to determine the influence of biogeographic position on the main diversity parameters and the effect of different land uses on harvestman assemblages. The main types of managed habitats (forest plantations and secondary grasslands), together with natural forests, non-planted young forests, shrublands and habitat boundaries were continuously sampled with seven pitfall traps during 1 year at 28 sites. The harvestman assemblages were classified using six different analyses, and indicator species were identified. The spatial patterns of harvestman diversity in low areas differed from those of mountain areas, although they have 15 species in common. Remarkably, higher average harvestman species richness was measured in low Cantabrian areas than in mountain areas. Shrublands and boundaries were the most species-rich habitats. Forested areas were the poorest in abundance, and were not the habitats richest in harvestman species, though they had higher average richness than mountain Cantabrian forests. Grasslands had a unique harvestman composition with significant extraordinary abundances, in particular of Homalenotus quadridentatus (indicator species of this habitat) and H. laranderas. Interestingly, H. laranderas, Paroligolophus agrestis and Ischyropsalis hispanica, indicator species of some open habitats in low Cantabrian areas, have recently been shown to be indicators of shady forests in mountain Cantabrian territories.     

Current status of the Russian desman habitats in small rivers of the Don River Basin in Saratov oblast and the abundance of this species

The Don Basin rivers confined to Saratov oblast were searched for the Russian desman in 2009–2011. The suitability of habitats for this species was assessed. Potentially negative factors for the Russian desman (Desmana moschata) in various types of habitats were detected, and their intensities were assessed. The small tributaries of the Khopyor and Medveditsa rivers have turned out to be suitable for the Russian desman; however, neither animals nor any sign of their life activities have been found using different techniques. Nonetheless, we cannot state that this species is absent in the small rivers of the Saratov oblast; however, if this species is present in the examined area, its abundance is extremely low. A drastic decrease in the Russian desman population and even its disappearance are most likely associated with intraspecific processes, factors of a global scale, and immigration of new species previously not found in the river ecosystems in the examined areas.     

Effect of competition on habitat utilization in two temperate climate gecko species

Competition over spatial niche utilisation is one of most common competitive interactions between species in sympatry. Moreover, competitive interactions may involve age classes, and can fluctuate temporally. Consequently, evasive strategies that enable co-existence are likely to be important in the evolution of species assemblages. Here we investigate a system of two co-existing species of temperate geckos with similar ecologies (the house gecko, Hemidactylus turcicus and the wall gecko, Tarentola mauritanica), providing an opportunity to study the effect of species interactions. Juveniles and adults of both species were investigated throughout their daily and annual cycle to explore the effect of inter- and intra-specific interactions on microhabitat use. The two species showed differences in habitat use for both age classes in sympatry. In sympatry, T. mauritanica uses more open habitats and is more active. In contrast, H. turcicus is found in more closed habitats, closer to the ground and to vegetation cover. In allopatry, H. turcicus was observed in more open habitats, closer to the ground, and to vegetation cover, when compared to the population in sympatry with T. mauritanica. These differences in habitat usage were significant for both age classes. Moreover, there were differences, both in sympatry and in allopatry, between age classes that were dependent on season. In conclusion, the presence of a competitor induces a spatial shift in individuals of both age classes of H. turcicus. Observed plasticity in habitat utilisation in both age classes of H. turcicus is used to argue for the invasive potential of this species.     

Feeding behavior and differential absorption of biochemical components by the infaunal bivalve Mulinia edulis and the epibenthic Mytilus chilensis in response to changes in food regimes

We measured changes in the feeding rate and food absorption efficiency of two suspension feeding bivalves, cross-trasplanted between habitats with special emphasis on their capacity for differential absorption of biochemical components from their food supply. Mulinia edulis were moved from the intertidal zone to the subtidal zone, and Mytilus chilensis from the subtidal to the intertidal zone for a period of 7 days, and then compared with animal that had not been transplanted. Experimentally prepared diets similar to those available in the two different environments were offered to the bivalves, and their rates of feeding and differential uptake of biochemical components were determined and statistically compared. The two species did not achieve complete acclimation of their feeding behaviour during the transplant period since the highest ingestion rates for biochemical components occurred under dietary conditions that reflected their habitats of origin. Absorption efficiency showed greater acclimation than the other physiological parameters measured, indicating the capacity of these species to modulate their enzymatic-digestive activity depending on food composition. We conclude that both Mytilus and Mulinia have a certain degree of physiological plasticity in their feeding behaviour and assimilatory balance of biochemical components, being greater in Mytilus. When both species encounter ambient food conditions characteristic of their normal habitats, they show maximum values of food absorption, while under conditions where their typical diets are exchanged (Mytilus in intertidal and Mulinia in subtidal), the energy absorbed declines in each, but in ways very different between the two species. Thus, Mytilus exposed to high concentrations of low quality seston reduced the energy absorbed by 31.7% compared to its normal habitat, while Mulinia exposed to low concentrations of high-quality food reduced their energy absorption by 64%.     

Genetic and allelopathic differences between populations of daisy fleabane Erigeron annuus (L.) Pers. (Asteraceae) from disturbed and stable habitats

The interactions between invasive plants and their habitats may vary at different phases of the invasion process and depend on the phenotypic plasticity or local adaptations of each species. In this study, we investigated whether habitat changes during the invasion process are related to variations in the physiological traits (allelopathic properties) and genetic differentiation of daisy fleabane (Erigeron annuus (L.) Pers.). E. annuus is a winter annual invasive species that originated in North America and is now distributed throughout Europe. Genetic and genotypic diversity analyses were performed for 37 populations of E. annuus based on inter simple sequence repeat (ISSR) polymorphisms. In total, 684 plants were analyzed; 342 were from stable habitats and 342 were from disturbed habitats. The genetic differences among the populations from the different habitats were studied using a Bayesian cluster analysis and an analysis of molecular variance (AMOVA) and by calculating the genetic and genotypic diversity parameters. A germination test using the juglone index was employed to examine the potential allelopathic properties of the plants from the different habitats. Bayesian cluster analysis, AMOVA and allelopathic effects evaluation revealed differences in the allelopathic potential and genetic structure of the E. annuus populations from the disturbed and stable habitats. This differentiation of populations could be associated with founder effects or with different selection pressures among habitats.     

When species’ ranges meet: assessing differences in habitat selection between sympatric large carnivores

Differentiation in habitat selection among sympatric species may depend on niche partitioning, species interactions, selection mechanisms and scales considered. In a mountainous area in Sweden, we explored hierarchical habitat selection in Global Positioning System-collared individuals of two sympatric large carnivore species; an obligate predator, the Eurasian lynx (Lynx lynx), and a generalist predator and scavenger, the wolverine (Gulo gulo). Although the species’ fundamental niches differ widely, their ranges overlap in this area where they share a prey base and main cause of mortality. Both lynx and wolverines selected for steep and rugged terrain in mountainous birch forest and in heaths independent of scale and available habitats. However, the selection of lynx for their preferred habitats was stronger when they were forming home ranges and they selected the same habitats within their home ranges independent of home range composition. Wolverines displayed a greater variability when selecting home ranges and habitat selection also varied with home range composition. Both species selected for habitats that promote survival through limited encounters with humans, but which also are rich in prey, and selection for these habitats was accordingly stronger in winter when human activity was high and prey density was low. We suggest that the observed differences between the species result primarily from different foraging strategies, but may also depend on differences in ranging and resting behaviour, home range size, and relative density of each species. Our results support the prediction that sympatric carnivores with otherwise diverging niches can select for the same resources when sharing main sources of food and mortality.     

Host Plants Affect the Foraging Success of Two Parasitoids that Attack Light Brown Apple Moth Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae)

The light brown apple moth, Epiphyas postvittana is a key pest of wine grapes in Australia. Two parasitoids, Dolichogenidea tasmanica and Therophilus unimaculatus, attack the larval stage of this pest. D. tasmanica is dominant in vineyards, whereas T. unimaculatus is mainly active in native vegetation. We sought to understand why they differ in their use of habitats. Plants are a major component of habitats of parasitoids, and herbivore-infested plants influence parasitoid foraging efficiency by their architecture and emission of volatile chemicals. We investigated how different plant species infested by E. postvittana could affect the foraging success of the two parasitoid species in both laboratory and field experiments. Four common host-plant species were selected for this study. In paired-choice experiments to determine the innate foraging preferences for plants, both parasitoid species showed differences in innate search preferences among plant species. The plant preference of D. tasmanica was altered by oviposition experience with hosts that were feeding on other plant species. In a behavioral assay, the two parasitoid species allocated their times engaged in various types of behavior differently when foraging on different plant species. For both parasitoids, parasitism on Hardenbergia violacea was the highest of the four plant species. Significantly more larvae dropped from Myoporum insulare when attacked than from the other three host-plant species, which indicates that parasitism is also affected by interactions between plants and host insects. In vineyards, parasitism by D. tasmanica was significantly lower on M. insulare than on the other three host-plant species, but the parasitism rates were similar among the other three plant species. Our results indicate that plants play a role in the habitat preferences of these two parasitoid species by influencing their foraging behavior, and are likely to contribute to their distributions among habitats.     

Persisting in a windy habitat: population ecology and behavioral adaptations of two endemic grasshopper species in the Cape region (South Africa)

Global biodiversity hotspots are rich in endemic insect species, many of which are threatened by the ongoing anthropogenic pressures on their habitats. The Cape region (South Africa) is one of these biodiversity hotspots, maintaining a high number of endemics. However, the ecology of most insect species in this region remains poorly understood. The two Orthoptera species Betiscoides meridionalis and Betiscoides parva are endemic to the Cape region and specialized on restio vegetation. They are threatened by increasing wildfire frequencies and invasions of non-native plant species. However, this information has been inferred from habitat changes, whereas no ecological study on these species has been conducted since they have been described. In order to facilitate conservation management, information on the ecology of these species is urgently required. The aim of our study was (1) to obtain data on the population ecology (particularly population sizes and mobility), and (2) to study the behavior of both species in response to environmental factors. For this purpose a mark-recapture-study and an observational behavior study were conducted. Both species had small population sizes and a low mobility with males moving greater distances than females. Wind had a strong influence on the behavior of Betiscoides, particularly on the small males of B. parva. Future studies might thus focus on the question whether wind-exposure is a critical factor for habitat choice of this species. We strongly recommend enhancing the connectivity of restio habitats and restoring these habitats to prevent extinction of specialized insect species.     

Ecological niches of species of the genus Ischnura (Odonata, Coenagrionidae) in oases of the Pamir-Alai Mountains

With development of irrigation and oases, new habitats suitable for dragonflies appeared, and unique assemblages of dragonflies were formed in artificial reservoirs. In the oases zone of the Pamir-Alai Mts., species of the genus Ischnura predominate among Zygoptera. The co-occurrence of Ischnura fountainei, I, evansi, I. elegans, I. forcipata, and I. pumilio was investigated. Divergence of ecological niches of these species is due to their adaptation to different habitats. Co-dominating species demonstrate complementation, i.e., they use the same habitat in different time intervals. The hygrothermal preferences of species determine the differences in their daily rhythms and microspatial distribution of adults.     

Mass-flowering crops enhance wild bee abundance

Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 % when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 % higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats.     

Studying exotics in their native range: Can introduced fouling amphipods expand beyond artificial habitats?

Knowledge of the habitat use patterns of introduced species in their native or naturalized range can provide unique insights into processes of secondary dispersal and colonization of natural habitats. Caprellid amphipods are small mobile marine epibionts with limited natural dispersal. The global distribution of some caprellid species is mostly the result of anthropogenic transport; however, their subsequent spread beyond artificial habitats is poorly understood. A biogeographic approach, mainly focused on the native-range ecology of introduced and common fouling caprellid amphipods of southern Europe, was used to understand the implications of habitat use patterns for predicting their spread in the introduced regions. Specifically, abundance and composition of caprellid populations were compared among different primary habitats including artificial (floating pontoons), sheltered and wave-exposed rocky shores along the southern and southeastern coasts of Brazil. The findings indicated that artificial habitats act as reservoirs for globally distributed species in both their native and introduced ranges, while endemic species are more scarcely represented. Environmental conditions provided by primary habitats appear important in structuring caprellid assemblages on secondary substrata (basibiont species). Most wide-ranging caprellids were negatively correlated with the level of wave exposure, being more abundant in sheltered (artificial or natural) than in exposed habitats. In this context, Caprella scaura and Paracaprella pusilla, the two introduced caprellids recorded in the Mediterranean, where they are virtually restricted to artificial habitats, may become established in sheltered and even highly polluted natural habitats but hardly colonize wave-exposed rocky shores.     

Variability in the Contribution of Different Life Stages to Population Growth as a Key Factor in the Invasion Success of Pinus strobus

Background

Despite the increasing number of studies attempting to model population growth in various organisms, we still know relatively little about the population dynamics of long-lived species that reproduce only in the later stages of their life cycle, such as trees. Predictions of the dynamics of these species are, however, urgently needed for planning management actions when species are either endangered or invasive. In long-lived species, a single management intervention may have consequences for several decades, and detailed knowledge of long-term performance can therefore elucidate possible outcomes during the management planning phase.

Methodology and Principal Findings

We studied the population dynamics of an invasive tree species, Pinus strobus, in three habitat types represented by their position along the elevation gradient occupied by the species. In agreement with previous studies on the population dynamics of long-lived perennials, our results show that the survival of the largest trees exhibits the highest elasticity in all of the studied habitats. In contrast, life table response experiments (LTRE) analysis showed that different stages contribute the most to population growth rates in different habitats, with generative reproduction being more important in lower slopes and valley bottoms and survival being more important on rock tops and upper slopes.

Conclusions

The results indicate that P. strobus exhibits different growth strategies in different habitats that result in similar population growth rates. We propose that this plasticity in growth strategies is a key factor in the invasion success of the white pine. In all of the investigated habitats, the population growth rates are above 1, indicating that the population of the species is still increasing and has the ability to spread and occupy a wide range of habitats.     

Biology and host specificity ofChamaesphecia hungarica andCh. Astatiformis (Lep.: Sesiidae) two candidates for the biological control of leafy spurge,Euphorbia esula (Euphorbiaceae) in North America

Leafy spurge (Euphorbia esula (s.1.)) is an herbaceous perennial and serious weed of Eurasian origin that has been accidentally introduced into North America. The two European root-boring mothsChamaesphecia hungarica andCh. astatiformis are univoltine and overwinter as mature larvae. Both species have a lower survival rate on leafy spurge than on their field hosts, and thus are not optimal candidates for the biological control of leafy spurge. However, the rate of larval development and larval growth on the target weed and on the two field hosts is nearly the same. The experimental host range of both species is restricted to a few species in the subgenusEsula within the genusEuphorbia. The two species occupy different habitats in the steppe biome and are targeted for similar leafy spurge habitats in North America.     

马鞍列岛多种生境中鱼类群聚的昼夜变化

为了解岛礁水域鱼类群聚的昼夜变化特征,以便更全面地设计采样方法和掌握采样的时间尺度,于2009年9月对马鞍列岛7种生境进行了共计24网次的刺网昼夜采样,结合排序和聚类方法,从种类组成、相对生物量和丰度、种类丰富度、多样性和相似性等方面对研究海域鱼类群聚特征的昼夜变化作了探讨.在采获的55种鱼类中,昼夜出现的分别为41和46种,数量差别不大,但其昼夜组成却随栖息水层的变化而不同,底层鱼类更趋向于夜间在硬相生境集群活动;近底层鱼类的昼夜集群随生境变化而变化,在同一生境中既有偏向白天也有趋向夜间的;中上层鱼类更多地出现在白天的人工生境(AH).AH白天的丰度渔获率显著大于晚上,而天然生境(NH)昼夜差别不大;生物量渔获率无论NH还是AH皆无显著昼夜差异.具体到种类,仅有小黄鱼Larimichthys polyactis和赤鼻棱鳗Thryssa kammalensis等少数种类的数量在AH有显著的昼夜差别,其他多数种类虽然昼夜的出现率大多有别,但渔获率昼夜差异皆不明显.多样性差异更多的表现在不同生境之间,而同一生境的昼夜差异往往不甚显著.各个生境中鱼类的昼夜种类交替现象非常明显,形成了以褐菖(鲐)Sebastiscus marmoratus和鳗鲇Plotosus anguillaris为代表的夜间优势类群为主的硬相生境群聚格局、以丝背细鳞鲀Stephanolepis cirrhifer和细刺鱼Microcanthus strigatus为代表的白天优势类群为主的硬相生境群聚格局以及缺乏底层优势类群、以石首鱼科鱼类为代表的近底层鱼类为绝对优势类群的软相生境群聚格局.因此,采用被动性渔具在近岸典型生境进行鱼类等相关生物调查时,应使采样时间覆盖昼夜两个时段,且至少保证24h.     

Conservation potential of semi-natural habitats for birds in intensively-used agricultural landscapes

Agricultural intensification resulted in substantial loss of farmland biodiversity. Semi-natural habitats may be viewed as potential buffers of these adverse impacts, but a rigorous assessment of their capacity for supporting farmland biodiversity is lacking. In this study, we explored conservation potential of two different types of semi-natural habitats for birds in intensively-used agricultural landscapes – farmland hedges (i.e., linear strips of shrubby and tree vegetation) and open scrubland (i.e., scattered shrubs and abandoned orchards). Specifically, we tested whether the abundance and species richness of birds differ between these habitats considering various species traits, such as habitat affinity (i.e., forest, farmland and urban species), diet specialization (i.e., animal eaters, plant eaters, and omnivores) and conservation status (Species of European Conservation Concern). We found that open scrubland hosted on average 37.9 bird species and 122.6 individuals per 1 km² of the transect, whereas farmland hedges hosted only 19 species and 61.8 individuals per 1 km² of the transect. However, results have substantially changed if we considered the area of suitable habitat into account. More specifically, open scrubland hosted more bird species and individuals when we considered open habitat species and the area of open habitats, whereas farmland hedges had higher species diversity and individuals of woodland bird species when we considered the area of woodland habitats. Similarly, analyses of habitat affiliations of individual species corresponded to the whole-community patterns; and revealed that several woodland bird species were mainly associated with farmland hedges (e.g., Chaffinch Fringilla coelebs, Common Nightingale Luscinia megarhynchos and Blackcap Sylvia atricapilla), whereas the open scrubland was preferred by open habitat bird species (e.g., Corn Bunting Emberiza calandra, Quail Coturnix coturnix and Skylark Alauda arvensis). These results demonstrate that semi-natural habitats, both open scrubland and farmland hedges, have large potential for promotion and conservation of bird communities within intensively used agricultural landscapes, as both may have represented suitable habitats for species with different ecological requirements. Therefore, management measures focused on the enlargement of the area of these habitats, in combination with suitable management (e.g., regulating the progress of natural succession in open scrubland; increasing structural diversity of existing farmland hedges), may substantially contribute to bird conservation within agricultural landscapes.     

Camouflage and Individual Variation in Shore Crabs (Carcinus maenas) from Different Habitats

Camouflage is widespread throughout the natural world and conceals animals from predators in a vast range of habitats. Because successful camouflage usually involves matching aspects of the background environment, species and populations should evolve appearances tuned to their local habitat, termed phenotype-environment associations. However, although this has been studied in various species, little work has objectively quantified the appearances of camouflaged animals from different habitats, or related this to factors such as ontogeny and individual variation. Here, we tested for phenotype-environment associations in the common shore crab (Carcinus maenas), a species highly variable in appearance and found in a wide range of habitats. We used field surveys and digital image analysis of the colors and patterns of crabs found in four locations around Cornwall in the UK to quantify how individuals vary with habitat (predominantly rockpool, mussel bed, and mudflat). We find that individuals from sites comprising different backgrounds show substantial differences in several aspects of color and pattern, and that this is also dependent on life stage (adult or juvenile). Furthermore, the level of individual variation is dependent on site and life stage, with juvenile crabs often more variable than adults, and individuals from more homogenous habitats less diverse. Ours is the most comprehensive study to date exploring phenotype-environment associations for camouflage and individual variation in a species, and we discuss the implications of our results in terms of the mechanisms and selection pressures that may drive this.     

Effects of flow on lateral interactions of fish and shrimps with off-channel habitats in a large river-floodplain system

Off-channel habitats play a crucial role in the life-cycles of many riverine fish species, but lateral movements of fish into these habitats are poorly understood. We tested how flow dynamics affects the movement of fish and shrimps between the main river channel and different types of off-channel habitats: a riverine lake and a wetland. Our study site was the lower Waikato River, North Island, New Zealand, where there are numerous off-channel habitats. Fish were sampled using directional fyke nets. Shortfin eel (Anguilla australis) migrated mostly into the wetland at night, particularly during high river flows. Common bullies (Gobiomorphus cotidianus) were most abundant during the day and in low-discharge conditions, moving mostly into the riverine lake, whereas freshwater shrimp (Paratya curvirostris) moved mostly into the wetland. High numbers of non-native larval common carp (Cyprinus carpio) moved out of the wetland with retreating flood water. This study emphasises the importance of lateral connectivity and flooding in functioning of this river system where numerous native fish, but also exotic fish, used off-channel habitats. Floodplain management strategies should promote ‘controlled connectivity’ measures that provide access for native species at key times while limiting opportunities for introduced species to utilise their favoured off-channel habitats.     

The Effect of Wind Exposure on the Web Characteristics of a Tetragnathid Orb Spider

Studies on spiders in their natural habitats are necessary for determining the full range of plasticity in their web-building behaviour. Plasticity in web design is hypothesised to be important for spiders building in habitats where environmental conditions cause considerable web damage. Here we compared web characteristics of the orb spider Metellina mengei (Araneae, Tetragnathidae) in two different forest habitats differing in their wind exposure. We found a notable lack of differences in web geometry, orientation and inclination between webs built along an exposed forest edge and those built inside the forest, despite marked differences in wind speed. This suggests that M. mengei did not exhibit web-building plasticity in response to wind in the field, contrasting with the findings of laboratory studies on other species of orb spiders. Instead, differences in prey capture and wind damage trade-offs between habitats may provide an explanation for our results, indicating that different species employ different strategies to cope with environmental constraints.