Spatiotemporal allozyme variation in the damselfly, Lestes viridis (Odonata: Zygoptera): gene flow among permanent and temporary ponds

Several insect species seem to persist not only in permanent but also in temporary ponds where they face particularly harsh conditions and frequent extinctions. Under such conditions, gene flow may prevent local adaptation to temporary ponds and may promote phenotypic plasticity, or maintain apparent population persistence. The few empirical studies on insects suggest the latter mechanism, but no studies so far quantified gene flow including both pond types. We investigated the effects of pond type and temporal variation on population genetic differentiation and gene flow in the damselfly Lestes viridis in northern Belgium. We report a survey of two allozyme loci (Gpi, Pgm) with polyacrylamide gel electrophoresis in 14 populations from permanent and temporary ponds, and compared these results with similar data from the same permanent populations one year before. The data suggested that neither pond-drying regime, nor temporal variation have a substantial effect on population genetic structuring and did not provide evidence for stable population differentiation in L. viridis in northern Belgium. Gene flow estimates were high within permanent and temporary ponds, and between pond types. Our data are consistent with a source-sink metapopulation system where temporary ponds act as sinks in dry years, and are quickly recolonized after local population extinction. This may create a pattern of apparent population persistence of this species in permanent and temporary ponds without clear local adaptation.     

High aquatic niche overlap in the newts Triturus cristatus and T. marmoratus (Amphibia,Urodela)

We studied spatial niche metrics of large-bodied newts (Triturus cristatus and T. marmoratus) in three breeding ponds in western France. Adults and larvae were sampled with underwater funnel traps. Larvae were identified to the species with diagnostic microsatellite DNA markers. The distribution of adult T. cristatus and T. marmoratus across pond regions differed in one out of six cases, no differences were observed between larvae (two ponds studied). Niche overlap and niche breadth indices across resource states defined as pond regions or individual traps were high (Schoener's C: pond regions 0.60–0.98, traps 0.35–0.71; Levins' B: pond regions 0.71–0.98, traps 0.35–0.76). Adults of large-bodied newts significantly differed in resource use from small-bodied newts (T. helveticus). The results are discussed in view of the occurrence of interspecific breeding attempts, and the unpredictable ecological characteristics of newt breeding ponds.     

Habitat requirements and local persistence of three damselfly species (odonata: coenagrionidae)

Habitat requirements and population persistence were investigated in three damselfly species, all coastal plain pond specialists: Enallagma recurvatum, E. laterale, and E. pictum. Because of geographic restriction, two are of special concern to conservation, E. recurvatum and E. laterale. We surveyed more than 70 ponds on Cape Cod, Massachusetts, and collected adult presence-absence data during the summers of 1999 and 2000. We achieved a detection rate approaching 100% for each species by visiting each pond up to three times. We looked for relationships between the presence of each damselfly species and presence of specific aquatic vegetation, the presence of the other Enallagma species, and the number of ponds within various distances of the 72 surveyed ponds. Using stepwise logistic regression, we found the following significant associations: E. recurvatum with the rush Juncus militaris; E. laterale with water lilies (Nuphar variegatum and Brasenia schreberi) the damselfly E. pictum, and the number of ponds within 2 km; and E. pictum with the water lily Nymphaea odorata, the damselfly E. laterale, and the number of ponds within 1.5 km and 2.5 km. Presence-absence data were used to calculate turnover and local extinction rates for each species between the two years. E. recurvatum's turnover and local extinction rates (33.3% and 41% respectively) were much higher than either E. laterale (9.8%, 11.5%) or E. pictum (7.7%, 10%). These results suggest that E. recurvatum occurs in a metapopulation, and that patch colonization rates might be important to local population persistence.     

Water turbidity affects predator–prey interactions in a fish–damselfly system

Community structure may differ dramatically between clear-water and turbid lakes. These differences have been attributed to differences in the cascading effect of fish on prey populations, owing to the reduced efficiency of fish predation in the presence of macrophytes. However, recent theoretical ideas suggest that water turbidity may shape predator–prey interactions, and it is predicted that prey will relax its antipredation behaviour in turbid water (H1). As a result, the nature of predator–prey interactions is expected to shift from both direct and indirect in clear water to dominantly direct in turbid water (H2). We tested these ideas in a fish–damselfly predator–prey system. In a first behavioural experiment, we looked at antipredation behaviour of damselfly larvae isolated from habitats that differ in turbidity, in the presence of fish in clear and turbid water. As predicted in H1, the larvae were more active in turbid than in clear water. In a complementary enclosure experiment, we reared larvae in a clear-water pond and a turbid pond, respectively, and manipulated the origin of the larvae (clear-water, turbid pond), fish presence (absent, present), and vegetation density (sparse, abundant). In both ponds, fish had a direct negative effect on survival of the larvae, which was mitigated in the presence of vegetation. In the fish treatment, the change in average body mass tended to be higher in the turbid pond than in the clear-water pond, suggesting indirect effects of fish were mitigated in the turbid pond. This was supported by a negative effect of fish on the effective growth rate of larvae in the clear pond, but not in the turbid pond. These results are compatible with the idea that predator–prey relationships are mainly governed by direct effects in turbid water, and by direct and indirect effects in clear water.     

不同水深条件下刺参养殖池塘大型底栖动物群落结构季节性变化特征

于2012年7月至2013年4月调查了荣成靖海湾3个不同水深的刺参(Apostichopus japonicus)养殖池塘内大型底栖动物的构成,以了解不同水深对刺参养殖池塘环境条件的影响以及由此引起的大型底栖生物群落结构的改变。结果表明:3个不同水深梯度池塘(1#浅水位、2#正常水位和3#高水位)底部光照强度、叶绿素a(Chla)和总有机物(TOM)含量存在显著差异,各池塘水温差异不显著。光强、Chla和TOM含量在夏季、冬季和春季均表现为1#池塘显著高于3#池塘;秋季各池塘间光强和TOM含量差异不显著,Chla含量则表现为3#池塘显著高于1#池塘。各季节3个池塘间大型底栖动物在种类组成、丰度、生物量和多样性指数上均存在显著性差异。大型底栖动物丰度和生物量夏季均表现为1#池塘显著高于3#池塘,秋季和冬季则相反;春季1#池塘丰度显著高于3#池塘,生物量则差异不显著。这些差异主要与其各自优势种及其优势度指数大小有关。大型底栖动物多样性指数夏季和秋季均表现为1#池塘高于3#池塘,春季则相反,冬季各池塘间多样性指数差异不显著。单因子相似性分析(ANOSIM)表明,各季节3个池塘间大型底栖动物群落结构均存在显著差异,表明水深梯度对刺参养殖池塘大型底栖动物群落结构造成显著性影响。相似性百分比分析(SIMPER)显示,各季节对3个池塘间大型底栖动物群落差异起主要作用的物种为各个池塘的优势种。典范对应分析(CCA)表明,水深、Chla和TOM含量为影响大型底栖动物群落的主要环境因子。     

The feeding activity of Colossoma macropomum larvae (tambaqui) in fishponds with water hyacinth (Eichhornia crassipes) fertilizer.

Analysis of macrophyte water hyacinth (Eichhornia crassipes) as an organic fertilizer of Colossoma macropomum (tambaqui) larvae in ponds is provided. Water hyacinth produce an organic fertilizer at the ratio of 100 g x m(-2) in tambaqui ponds. Two groups of 5,000 larvae were transferred to two fishponds with and without water hyacinth fertilizer and reared until day 43. The fertilized pond evidenced more plankton abundance during the entire production period when compared with the control pond (P < 0.001). The phytoplankton community in the pond was not significantly different than in gut contents (P > 0.05) in both ponds (with and without organic fertilizer). Fish larvae failed to show any preference or selectivity in relation to the different algae (P > 0.01) in the pond, but exhibited high ingestion selectivity for zooplankton (P < 0.05). Application of fertilizer increased (P < 0.05) the abundance of phytoplankton and zooplankton in the treatment pond. Since water hyacinth fertilizer is quite cheap and easily available, it may be conveniently used to enhance fish yield in ponds.     

Density-dependent population dynamics in larvae of the dragonfly Pachydiplax longipennis: a field experiment

Summary Several features of dragonfly population biology suggest that population regulation occurs in the larval stage. This study was designed to determine if density-dependent interactions among larval odonates can affect survival, growth and emergence. First-instar larvae of the dragonfly Pachydiplax longipennis were raised in outdoor experimental ponds at initial densities of 38, 152, and 608 larvae · m^-2, under two levels of food availability. Food availability was supplemented in half the pools by volumetric addition of zooplankton every other day. Pools in the low food treatment did not receive the zooplankton supplement.There was a strong negative effect of density on the mean growth rate of survivors, which included both emerging tenerals and individuals overwintering in the larval stage. A higher proportion emerged from low density than high density pools. Metamorphs from high density populations were smaller and emerged slightly later than those from low density, but the absolute number of metamorphs did not differ significantly among density treatments. Food supplementation significantly increased the proportion of overwintering larvae. There were no significant food-by-density interactions, indicating that food and density acted independently on larval population dynamics. Density-dependent mechanisms can clearly contribute to odonate population regulation, especially by controlling the number of larvae which emerge and the average age at reproduction. Population-level responses to density may be a result of interference among larvae.     

Do nymphs of Parameletus chelifer and P. minor (Ephemeroptera) reduce mortality from predation by occupying temporary habitats?

Summary The possible effect of predation on the habitat selection of nymphs of the two mayfly species Parameletus chelifer Bengtsson and P. minor (Bengtsson) was investigated for different habitats of a North Swedish boreal river. In spring, these two species migrate to river margins and subsequently, in different proportions, to adjacent seasonal ponds. Feeding rates on mayfly nymphs and mosquito larvae by some dytiscid beetles and larvae, a corixid waterbug and a caddisfly larva were studied in the laboratory. In the seasonal pond, the consumption rate of invertebrate predators on Parameletus nymphs was below that expected from their relative abundance, and mosquito larvae were preferred. At the river margin, where mosquito larvae were absent, Parameletus nymphs were consumed in agreement with their relative abundance. The absolute abundance of macroinvertebrate predators was similar at the river margin and in the pond. Fish predators visited the seasonal pond only during a short time of flood, while at the river margin their presence was continuous. In the seasonal pond, minnow and roach consumed nymphs of both P. chelifer and P. minor in a lower proportion than expected. At the river margin, nymphs of P. chelifer were consumed by minnow and ten-spined stickleback in a higher proportion than expected. Nymphs of P. minor were consumed according to expectance. Imagines of P. minor emerged early, and nymphs were equally abundant in the river and in the seasonal pond. In contrast, almost all nymphs of P. chelifer migrated to the seasonal pond. The later emergence of P. chelifer would probably result in a very high mortality from predation if it remained at the river margin.     

Indirect Monitoring of Agonistic Encounters in Larvae of Lestes viridis (Odonata: Lestidae) Using Exuviae Lamellae Status

Differences in interference competition between larvae of the damselfly Lestes viridis (Vander Linden) were examined using caudal lamellae status of exuviae. Exuviae from a small temporary fishless pond near Antwerp (Belgium) where L.viridis was the only odonate present were studied. No lamellae loss during emergence was seen. Therefore, the lamellae status of the exuviae reflects the lamellae status of the final instar larvae. The deviations of the distribution of the number of missing lamellae per individual from a binomial distribution suggested that lamellae are not always lost separately or that some animals are more prone to agonistic encounters. I found no difference in agonistic encounters between sexes. In accordance with the hypothesis of Pierce et al. (1985) interference competition was higher in the lestid species inhabiting small, temporary fishless ponds than in the coenagrionid damselfly Ischnura posita inhabiting large permanent fish containing water bodies that was studied by Robinson et al. (1991).     

Some notes on the ecology of a GermanBranchipus schaefferi population (Crustacea: Anostraca)

Habitat preference, seasonal occurrence, starvation resistance, hatching eggs ofBranchipus schaefferi, and effects of predation onB. schaefferi were studied.Branchipus was only present in turbid, unvegetated ponds and absent in ponds which contain higher aquatic vegetation and theSpirogyra sp. The first individuals ofB. schaefferi appeared in April when water temperature was 10 °C and the last adults in November at a water temperature of 3.5 °C. Up to 6 reproducing generations were observed during this period. Abundance ofB. schaefferi was higher in temporary ponds than in permanent ponds. Sex ratio was close to unity for most of the year. Body size ofB. schaefferi males and females was significantly positively correlated with pond volume. Without foodB. schaefferi could survive for 1.5 to 2 days at 20 °C and 4 to 5 days at 10 °C. Hatching success of eggs decreased when eggs were dried for 7 months. Freezing of eggs had no effect on hatching success. From] the predators tested,Chaoborus sp. larvae clearly selected smallB. schaefferi; one consumed approximately 6Branchipus d–1 at a density of 6 to 12 prey 1–1. The other predators, dragonfly larvae, and larvae and adults ofTriturus alpestris selected alternative prey types, for exampleTubifex sp. and ostracods.     

Adaptive divergence vs. environmental plasticity: tracing local genetic adaptation of metamorphosis traits in salamanders

In order to assess the significance of local adaptation relative to environmental plasticity on the evolution of life history traits, we analysed the possible genetic basis of differences between pond- and stream-breeding fire salamanders (Salamandra salamandra) in Germany. These salamanders typically deposit their larvae in small streams, where they grow until they are sufficiently large to metamorphose. However, some populations in Western Germany use ponds as larval habitat. Because habitat quality of streams differs from that of ponds one expects life history differences in the pond animals, which may result either from a plastic response or through genetic differentiation (i.e. local adaptation). Using a phylogeographical analysis of mitochondrial D-loop sequences, we show that both stream and pond populations in Western Germany are derived from a single lineage that recolonized following the last glaciation. This finding suggests that pond breeding originated very recently. Our studies of habitat quality and metamorphic behaviour of larvae in natural ponds and streams disclosed that pond larvae experience a significantly reduced food supply and greater risk of drying than do stream larvae. Pond larvae metamorphose earlier at the cost of reduced mass. Common-environment experiments with pond and stream larvae show that metamorphic behaviour of pond larvae under limited-food conditions is determined genetically and is not simply a plastic response to the differing habitat conditions. These results show that phenotypic plasticity is less important than local adaptation in explaining differences in ecological diversification within this species and suggests the possibility of rapid evolution of genetic adaptations when new habitats are exploited.     

Effects of predator-induced thinning and activity changes on life history in a damselfly

We investigated how the lethal and non-lethal presence and absence of a fish predator, perch (Perca fluviatils), influenced behaviour, numbers emerging, size at emergence, and development rate of the damselfly Lestes sponsa. The experiment was carried out in outdoor artificial ponds and spanned from the egg stage to emergence of the damselflies. During the experiment food resources for the damselflies were continuously monitored. Damselflies exposed to a lethal predator showed a significantly lower activity level than those in the absence of predators or subjected to a non-lethal predator. Half-way through the larval stage the reduction in activity level was correlated with the presence of lethal predators, and at the end of the larval stage with higher zooplankton densities. Though larvae decreased activity level, size at emergence was larger and development time faster for individuals in the lethal predator treatment. Since fewer larvae emerged from that treatment we interpret the larger size at emergence to be an effect of a combination of thinning and higher zooplankton densities.     

The significance of littoral and shoreline habitat integrity to the conservation of lacustrine damselflies (Odonata)

Human development of pond and lake shorelines may significantly impact native lacustrine biota including a variety of aquatic macroinvertebrate groups. In an effort to better understand the habitat associations and sensitivities of lacustrine damselflies (Odonata: Zygoptera), we sampled adults in littoral macrophyte habitat during two flight periods at 35 randomly selected pond and lake sites in southern Maine during 2000 and 2001. Data were also collected to help characterize water body, shoreline disturbance, and aquatic vegetation at each study site. Nonmetric multidimensional scaling was used for ordination of damselfly assemblages, and coordinates from the most stable solution were related to site variables using forward stepwise multiple regression. Our results suggest that the diversity and composition of damselfly assemblages is related to the abundance and richness of littoral zone macrophytes, extent of riparian disturbance, benthic substrate granularity, and lake productivity; all variables subject to anthropogenic degradation on excessively developed waterbodies. Additionally, we developed a Habitat Tolerance Index useful for distinguishing between relative habitat specialists and generalists from among a diverse assemblage of 19 lacustrine species. Finally, species-specific damselfly associations with multiple genera of floating and emergent macrophytes were assessed using both nonparametric correlation and multiplicative regression yielding significant relationships for 17 species, including two damselflies of global conservation concern (Enallagma laterale and E. pictum). We conclude that the protection of littoral and shoreline habitat integrity, with special emphasis on emergent and floating macrophytes, is critical to the conservation of lacustrine biodiversity.     

Effects of heating on growth and condition of pikeperch (Lucioperca lucioperca) in lowland ponds created by sand extraction

The growth rates of pikeperch (Lucioperca lucioperca L.) originating from two lowlands ponds in the north of Belgium, one of which is heated by the effluents of power plants, were compared by means of scalimetry and operculometry. The overall condition of the fish in both ponds was also investigated. The pikeperch grew significantly faster in heated water, although overall condition was comparable. Seasonal variations resulted in the heated pond arriving at a temperature higher than the optimum.     

Influence of Predator Presence and Prey Density on Behavior and Growth of Damselfly Larvae (Ischnura elegans) (Odonata: Zygoptera)

Foraging behavior is often determined by the conflicting benefits of energy gain and the risk of mortality from predation or other causes. Theory predicts that animals should have lower activity levels when either the risk of predation or the availability of resources in the environment is high. We investigated the adjustment of the behavior of I. elegans larvae to predator presence (Anax imperator) and prey density (Daphnia sp.) and their interaction in a completely crossed factorial experiment in the lab and the effect of behavior on growth. The foraging activity of the I. elegans larvae was significantly reduced in the presence of a free-swimming predator but not a caged predator. Abdominal movements were significantly reduced at a low prey density. Growth was significantly reduced by the presence of a free swimming predator and low prey densities. These results provide evidence that these damselfly larvae adjust their behavior to the presence of predators to increase their survival at the expense of reduced growth and development.     

Characteristics of dispersing Ischnura elegans and Coenagrion puella (Odonata): age, sex, size, morph and ectoparasitism

In this study we assessed whether individuals of the damselfly species Ischnura elegans and Coenagrion puella that moved between ponds differed in their mean characteristics from individuals that did not move. Overall, the sex (female) and species ( C. puella ) that spent the most time away from the breeding site was more likely to move between ponds. Ischnura elegans males that dispersed had significantly longer forewings than males that did not, while male C. puella parasitised by water mites were more likely to disperse than unparasitised males. There was no evidence for differences in dispersal rates among the female colour forms of either I. elegans or C. puella . In general, the differences in dispersal characteristics between sexes and species could be explained by underlying variation in activity and mobility. The majority of dispersal between breeding sites by C. puella and I. elegans did not appear to be directed, but probably arose from chance movements occasionally taking individuals to a different pond from which they emerged.     

Growth and population structure of Salamandra salamandra (L.) larvae in different limnological conditions

Salamandra salamandra (L.) larvae were studied in three types of aquatic systems, a permanent spring, a rock pool and temporary ponds. Growth was followed throughout ontogenesis until completion of metamorphosis. Growth patterns changed according to the pond type. Temporary ponds were rich in organic matter and subsequently larvae matured more rapidly there than those in a permanent pool or a spring. In the latter, cannibalism appears to be of major ecological importance, enabling survival and metamorphosis of large size tadpoles. The pattern of growth and metamorphosis is compared with European salamanders and the differences are discussed considering adaptations for survival of this species under xeric conditions.     

Spatiotemporal allozyme variation in the damselfly, <Emphasis Type="BoldItalic">Lestes viridis</Emphasis> (Odonata: Zygoptera): gene flow among permanent and temporary ponds

Several insect species seem to persist not only in permanent but also in temporary ponds where they face particularly harsh conditions and frequent extinctions. Under such conditions, gene flow may prevent local adaptation to temporary ponds and may promote phenotypic plasticity, or maintain apparent population persistence. The few empirical studies on insects suggest the latter mechanism, but no studies so far quantified gene flow including both pond types. We investigated the effects of pond type and temporal variation on population genetic differentiation and gene flow in the damselfly Lestes viridis in northern Belgium. We report a survey of two allozyme loci (Gpi, Pgm) with polyacrylamide gel electrophoresis in 14 populations from permanent and temporary ponds, and compared these results with similar data from the same permanent populations one year before. The data suggested that neither pond-drying regime, nor temporal variation have a substantial effect on population genetic structuring and did not provide evidence for stable population differentiation in L. viridis in northern Belgium. Gene flow estimates were high within permanent and temporary ponds, and between pond types. Our data are consistent with a source-sink metapopulation system where temporary ponds act as sinks in dry years, and are quickly recolonized after local population extinction. This may create a pattern of apparent population persistence of this species in permanent and temporary ponds without clear local adaptation.     

Response of littoral vegetation on climate warming in the boreal zone; an experimental simulation

The impact of climate warming on the littoral zone of a boreal lake ecosystem was studied experimentally for three growing seasons in two artificial ponds (10×27 m) and in replicated chamber experiments. One pond was enclosed in a plastic greenhouse and another untreated pond served as a reference system. During the growing seasons temperature in the greenhouse was maintained at levels 2–3 °C higher than ambient with a computer-controlled ventilation system. One growing season prior to initiation of the experiment, a vegetated littoral zone with equal densities of water horsetail (Equisetum fluviatile) was established in both ponds. Although changes occurred in the species dominance (E. fluviatile - Alisma plantago-aquatica - Sparganium erectum spp. microcarpum - Elodea canadensis) within the three years of the study, the emergent macrophytes emerged earlier and grew better in the warmer conditions of the greenhouse pond compared with those in the reference pond. The difference in above-ground biomass throughout the growing seasons was >2 fold and after three experimental growing seasons the difference in below-ground biomass of macrophytes was 2.5-fold between the ponds. In replicated chamber experiments the biomass growth of E. fluviatile was also significantly higher in a 2–3 °C higher temperature than under ambient conditions. An ecosystem-scale induced change, characterized by a heavy growth of filamentous algae (mainly chlorophytes) was evident in the vegetated littoral zone of the greenhouse pond. A hypothesis that macrophyte rhizomes function as `phosphorus pumps' from the sediment and thus accelerate eutrophication in a warmer climate should be further studied.     

Spatial and temporal fluctuations in presence and use of chironomid prey by shorebirds in the Odiel saltpans, south-west Spain

We studied the seasonal variation in abundance and distribution of shorebirds and chironomid Chironomus salinarius larvae in both traditional and industrial salines in the Odiel marshes, south-west Spain, in 2001. We selected 12 ponds that were representative of the different phases of the salt production process. The benthic chironomids were sampled in each pond every 2 months, and the birds were counted weekly. Chironomid larvae were most abundant in spring and autumn, and in the ponds of lower salinity. The density of larvae averaged 7023 ± 392 m⁻² (±SE) over the six sampling events. Shorebirds were always more abundant at high tide than at low tide, and were especially abundant during the spring and autumn migration periods when up to 20,775 birds were counted. A total of 24 species were recorded, six of which were present in internationally important numbers. The salines were especially important as foraging and roosting habitat during migration. The percentage of birds that were feeding in the ponds was positively correlated with the abundance of chironomid larvae at accessible depths. The number of feeding birds was also higher in ponds with more chironomid larvae available. Despite more intensive management, industrial salines held higher densities of birds and a similar abundance of chironomids when compared with traditional salines.