Article

Ecological traps for dragonflies in a cemetery: The attraction of Sympetrum species (Odonata: Libellulidae) by horizontally polarizing black gravestones

Authors:
  • Eötvös Loránd University, Danube Research Institute, Centre for Ecological Research, Hungarian Academy of Sciences
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Abstract

Summary1. We observed that the dragonfly species Sympetrum flaveolum, S. striolatum, S. sanguineum, S. meridionale and S. danae were attracted by polished black gravestones in a Hungarian cemetery.2. The insects showed the same behaviour as at water: (i) they perched persistently in the immediate vicinity of the chosen gravestones and defended their perch against other dragonflies; (ii) flying individuals repeatedly touched the horizontal surface of the shiny black tombstones with the ventral side of their body; (iii) pairs in tandem position frequently circled above black gravestones.3. Tombstones preferred by the dragonflies were in the open and had an area of at least 0.5 m2 with an almost horizontal, polished, black surface and with at least one perch in their immediate vicinity.4. Using imaging polarimetry, we found that the black gravestones, like smooth water surfaces, reflect highly and horizontally polarized light.5. In double-choice field experiments with various test surfaces, we showed that the dragonflies attracted to shiny black tombstones display positive polarotaxis and, under natural conditions, detect water by means of the horizontally polarized reflected light. This, and the reflection-polarization characteristics of black gravestones, explain why these dragonflies are attracted to black tombstones.6. If females attracted to the black gravestones oviposit on them, the latter constitute ecological traps for dragonflies that are not close to water.

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... Weigelhofer et al. 1992) interacting factors resulting in well-defined seasonal and diel dispersal patterns of aquatic insects (Csabai et al. 2006(Csabai et al. , 2012Boda and Csabai 2013). The regular dispersal flight of aquatic insects can be seriously distracted by various man-made objects Horváth et al. 2007;Málnás et al. 2011). ...
... The females of many aquatic insect species (e.g. Ephemeroptera and Odonata) have been observed to lay eggs onto polarized light-polluting surfaces (Kriska et al. 1998;Horváth et al. 2007). These eggs inevitably perish due to dehydration. ...
... These eggs inevitably perish due to dehydration. Such artificial surfaces can also cozen the males: Male dragonflies were reported to exhibit territorial behaviour above shiny car bonnets or black gravestones, like at their natural reproductive sites (Wildermuth and Horváth 2005;Horváth et al. 2007). This type of ecological trap can substantially reduce the fitness and reproductive success of aquatic insects ). ...
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Based on an earlier observation in the field, we hypothesized that light intensity and horizontally polarized reflected light may strongly influence the flight behaviour of night-active aquatic insects. We assumed that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of these insects than they would have separately. We tested this hypothesis in a multiple-choice field experiment using horizontal test surfaces laid on the ground. We offered simultaneously the following visual stimuli for aerial aquatic insects: (1) lamplit matte black canvas inducing phototaxis alone, (2) unlit shiny black plastic sheet eliciting polarotaxis alone, (3) lamplit shiny black plastic sheet inducing simultaneously phototaxis and polarotaxis, and (4) unlit matte black canvas as a visually unattractive control. The unlit matte black canvas trapped only a negligible number (13) of water insects. The sum (16,432) of the total numbers of water beetles and bugs captured on the lamplit matte black canvas (7,922) and the unlit shiny black plastic sheet (8,510) was much smaller than the total catch (29,682) caught on the lamplit shiny black plastic sheet. This provides experimental evidence for the synergistic interaction of phototaxis (elicited by the unpolarized direct lamplight) and polarotaxis (induced by the strongly and horizontally polarized plastic-reflected light) in the investigated aquatic insects. Thus, horizontally polarizing artificial lamplit surfaces can function as an effective ecological trap due to this synergism of optical cues, especially in the urban environment.
... atmospheric humidity, dimension and shape of the waterbody, undulation of the water surface, water plants on the surface and the shore, temperature and odour) are still ineffective (Fig. 20.2a, and see Chaps. 5 and 16). Following Schwind's (1985aSchwind's ( , b, 1991Schwind's ( , 1995 finding that aquatic bugs and beetles are polarotactic, other studies (Kriska et al. 1998(Kriska et al. , 2006aWildermuth 1998;Horváth et al. 1998Horváth et al. , 2007Bernáth et al. 2001b;Wildermuth and Horváth 2005;Csabai et al. 2006;Lerner et al. 2008;Horváth et al. 2011) found that dragonflies, mayflies, tabanid flies, stoneflies, chironomids and caddisflies also exhibit positive polarotaxis when searching for water. To date, more than 300 polarotactic aquatic insect species are known that recognize their aquatic habitat by positive polarotaxis ; see also Chap. ...
... The mortality associated with PLP may threaten populations of endangered aquatic insect species. Aquatic insects attracted to strongly and horizontally polarizing dry artificial surfaces may perish due to dehydration or may oviposit onto these surfaces where eggs universally fail to survive (Wyniger 1955;Horváth et al. 1998Horváth et al. , 2007Horváth et al. , 2009Horváth et al. , 2010aKriska et al. 1998Kriska et al. , 2006aKriska et al. , 2007Kriska et al. , 2008Wildermuth 1998Wildermuth , 2007Stevani et al. 2000a,b;Bernáth et al. 2001b;Günther 2003;Horváth and Varjú 2004;Csabai et al. 2006;Málnás et al. 2011). Within ecological and evolutionary science, such cases in which rapid environmental changes lead organisms to prefer the worst available habitat are known as ecological traps (Dwernychuk and Boag 1972;Schlaepfer et al. 2002;Fletcher et al. 2012). ...
... Polarizing Black Gravestones Horváth et al. (2007) observed that both sexes (matures or juveniles) of the dragonfly species Sympetrum flaveolum, S. striolatum, S. sanguineum, S. meridionale and S. danae were attracted by polished black gravestones in a cemetery in Kiskunhalas (Hungary) without any waterbody (Fig. 20.34). Tombstones preferred by these dragonflies had an area of at least 0.5 m 2 with an almost horizontal, polished, black surface, the sky was open above them and there was at least one perch in their immediate vicinity. ...
Chapter
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In the last decade it has been recognized that the artificial polarization of light can have uniquely disruptive effects on animals capable of seeing it and has led to the identification of polarized light pollution (PLP) as a new kind of ecological photopollution. In this chapter we review some typical examples for PLP and the resulting polarized ecological traps. All such polarized-light-polluting artificial surfaces are characterized by strongly and horizontally polarized reflected light attracting positively polarotactic aquatic insects, the larvae of which develop in water or mud, such as aquatic beetles (Coleoptera), water bugs (Heteroptera), dragonflies (Odonata), mayflies (Ephemeroptera), caddisflies (Trichoptera), stoneflies (Plecoptera) and tabanid flies (Tabanidae), for example. We survey here the PLP of asphalt surfaces, solar panels, agricultural black plastic sheets, glass surfaces, black gravestones and the paintwork of black-, red- and dark-coloured cars. We show how the maladaptive attractiveness (PLP) of certain artificial surfaces to polarotactic insects can be reduced or eliminated. We consider how birds, spiders and bats exploit polarotactic insects trapped by different sources of PLP. We deal with the phenomenon that the vertically polarized mirror image of bridges seen at the river surface can deceive swarming polarotactic mayflies, which is an atypical kind of PLP. We explain why strongly polarizing black burnt-up stubble fields do not attract aquatic insects, which is an example for a horizontal, black polarizing surface that does not induce PLP and thus is an exception proving the rule. Finally, we show that phototaxis and polarotaxis together have a more harmful effect on the dispersal flight of night-active aquatic insects than they would have separately. This provides experimental evidence for the synergistic interaction of phototaxis and polarotaxis in these insects.
... In Kuweit wurden kleinere Erdöl-Tümpel (Überreste entstanden durch die Zerstörung von Öltanks und Ölpipelines während des Golfkrieges) durch Libellen als Eiablageorte aufgesucht (Horváth & Zeil 1996;Horváth et al. 1998). Ebenfalls Horváth et al. (2007) beobachteten in Ungarn an verschiedenen Vertretern der Gattung Sympetrum, dass diese durch die polierte Oberfläche von schwarzen, horizontal ausgerichteten Grabsteinen auf einem Friedhof zur Eiablage motiviert wurden und untersuchten daraufhin die möglichen Ursachen für derartiges Verhalten. Durch die Verwendung von bildgebender Polarimetrie fanden sie in Feldexperimenten heraus, dass diese polierten Steine ebenfalls wie glatte Wasseroberflächen horizontal polarisiertes Licht reflektieren, auf welche Libellen polarotaktisch reagieren. ...
... Habitatfalle. Die Libellen, die die Fähigkeit besitzen, Wasserflächen anhand von polarisiertem Licht zu erkennen, können nicht zwischen realen und fiktiven Wasseroberflächen differenzieren (Horváth & Varjú 1997;Horváth et al. 2007;Wildermuth 1998Wildermuth , 2007. Bei der hier nachfolgend beschriebenen Beobachtung handelt es sich ebenfalls um eine Beobachtung, die in die Kategorie fällt, bei der eine erfolgreiche Reproduktion von vornherein ausgeschlossen werden kann. ...
... Foto: M. Frank. Horváth & Zeil 1996;Horváth & Varjú 1997;Horváth et al. 1998;Horváth et al. 2007;Wildermuth & Horváth 2005;Wildermuth 2007). Nach eigenen Recherchen handelt es sich bei dieser Beobachtung um die erste derartige dokumentierte Feststellung einer durch Polarotaxis verursachten Eiablage von Anax imperator in unnatürliches Substrat. ...
... atmospheric humidity, dimension and shape of the waterbody, undulation of the water surface, water plants on the surface and the shore, temperature and odour) are still ineffective (Fig. 20.2a, and see Chaps. 5 and 16). Following Schwind's (1985aSchwind's ( , b, 1991Schwind's ( , 1995 finding that aquatic bugs and beetles are polarotactic, other studies (Kriska et al. 1998(Kriska et al. , 2006aWildermuth 1998;Horváth et al. 1998Horváth et al. , 2007Bernáth et al. 2001b;Wildermuth and Horváth 2005;Csabai et al. 2006;Lerner et al. 2008;Horváth et al. 2011) found that dragonflies, mayflies, tabanid flies, stoneflies, chironomids and caddisflies also exhibit positive polarotaxis when searching for water. To date, more than 300 polarotactic aquatic insect species are known that recognize their aquatic habitat by positive polarotaxis ; see also Chap. ...
... The mortality associated with PLP may threaten populations of endangered aquatic insect species. Aquatic insects attracted to strongly and horizontally polarizing dry artificial surfaces may perish due to dehydration or may oviposit onto these surfaces where eggs universally fail to survive (Wyniger 1955;Horváth et al. 1998Horváth et al. , 2007Horváth et al. , 2009Horváth et al. , 2010aKriska et al. 1998Kriska et al. , 2006aKriska et al. , 2007Kriska et al. , 2008Wildermuth 1998Wildermuth , 2007Stevani et al. 2000a,b;Bernáth et al. 2001b;Günther 2003;Horváth and Varjú 2004;Csabai et al. 2006;Málnás et al. 2011). Within ecological and evolutionary science, such cases in which rapid environmental changes lead organisms to prefer the worst available habitat are known as ecological traps (Dwernychuk and Boag 1972;Schlaepfer et al. 2002;Fletcher et al. 2012). ...
... Polarizing Black Gravestones Horváth et al. (2007) observed that both sexes (matures or juveniles) of the dragonfly species Sympetrum flaveolum, S. striolatum, S. sanguineum, S. meridionale and S. danae were attracted by polished black gravestones in a cemetery in Kiskunhalas (Hungary) without any waterbody (Fig. 20.34). Tombstones preferred by these dragonflies had an area of at least 0.5 m 2 with an almost horizontal, polished, black surface, the sky was open above them and there was at least one perch in their immediate vicinity. ...
... Recently, Horváth et al. (2007) observed that the dragonfl y species Sympetrum fl aveolum, S. striolatum, S. sanguineum, S. meridionale and S. danae were attracted by polished black gravestones in a Hungarian cemetery without any water body. These dragonfl ies showed the same behaviour to that which they display in the presence of water: (i) they perched persistently in the immediate vicinity of the chosen gravestones and defended their perch against other dragonfl ies; (ii) fl ying individuals repeatedly touched the horizontal surface of the shiny black tombstones with the ventral side of their body; and (iii) pairs in tandem position frequently circled above black gravestones. ...
... Gravestones with matt, bright or non-horizontal surfaces refl ect light with low degrees of linear polarization or with non-horizontal direction of polarization, and thus are unattractive to polarotactic dragonfl ies. In doublechoice fi eld experiments, Horváth et al. (2007) showed that the dragonfl ies attracted to shiny black tombstones possess positive polarotaxis and therefore, under natural conditions, detect water by means of the horizontally polarized refl ected light. The positive polarotaxis and the refl ection-polarization characteristics of black gravestones explain why the observed Sympetrum dragonfl ies were attracted to black tombstones. ...
Article
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We review the polarization vision of aquatic insects, which detect water from a distance by the horizontally polarized light reflected from the water surface. Reflection-polarization characteristics of different water bodies, as functions of sky conditions and solar elevation, are examined in relation to how they influence the detection of water bodies by polarotactic aquatic insects. Examples are given showing how aquatic insects can be deceived by, attracted to and trapped by highly and horizontally polarizing artificial reflectors, such as oil surfaces, horizontal black plastic sheets, asphalt roads, red or black car-bodies and black gravestones. We explain why mirages and polarizing black burnt stubble-fields do not attract polarotactic aquatic insects. The existence of a polarization sun-dial, which dictates the optimal time of day for dispersal by flying aquatic insects, is demonstrated. We finish by examining some unexpected aspects of polarization vision in insects: a polarotactic mayfly that never leaves the water surface and thus does not need polarotaxis, and polarotactic vision of several tabanid flies.
... Ovitraps are typically baited with an attractant to increase female oviposition and treated with an insecticide. This intentional manipulation of mosquito oviposition habitat selection behavior and early survivorship creates an ecological trap (Schlaepfer et al. 2002, Horváth et al. 2007. Local reproductive effort is funneled into aquatic habitat patches from which few adult mosquitoes will recruit (e.g., attract and kill strategy, Barbosa et al. 2010), potentially enhancing the population level impact over application of an insecticide alone. ...
... The goal of this study was to disentangle the independent and interactive effects of both leaf litter as an oviposition attractant and Bti as larvicide on oviposition and larval survival in order to better understand the contributions of each to adult recruitment. Specifically, we were interested in whether the combined manipulation of mosquito oviposition habitat selection and early survivorship would result in an ecological trap (Schlaepfer et al. 2002, Horváth et al. 2007 in which local reproductive effort is funneled into aquatic habitat patches from which few adult mosquitoes will recruit, enhancing the population level impact over application of an insecticide alone. We found that Bti and leaf litter are highly effective in combination, attracting as much as nine times more Culex spp. ...
Article
Mosquito egg traps, aquatic habitats baited with oviposition attractant and insecticide, are important tools for surveillance and control efforts in integrated vector management programs. The bioinsecticide Bacillus thuringiensis subsp. israelensis (Bti) is increasingly used as an environmentally friendly alternative to chemical insecticides and the combination of Bti with a simple oviposition attractant like leaf litter to create an effective egg trap seems appealing. However, previous research suggests that Bti may itself alter oviposition, and that leaf litter may dramatically reduce Bti toxicity. Here we present results from field experiment designed to link the effects of litter and Bti on mosquito oviposition habitat selection and post-colonization survival to production of adult mosquitoes. Tripling litter increased Culex spp. oviposition nearly nine-fold, while Bti had no effect on oviposition. Neither factor altered egg survival, thus larval abundance reflected the effects of litter on oviposition. Both Bti and litter reduced larval survival by ∼60%. We found no evidence that increased litter reduced Bti toxicity. Adult production was dependent upon both litter and Bti. In the absence of Bti, effects of litter on oviposition translated into three-fold more adults. However, in the presence of Bti, initial increases in oviposition were erased by the combined negative effects of Bti and litter on post-colonization survival. Thus, our study provides field evidence that combined litter and Bti application creates an effective ovitrap. This combined treatment had the highest oviposition and the lowest survival, and thus removed the greatest number of mosquitoes from the landscape.
... Parks in South Africa have shown high odonate diversity, whereas alien plantation forests where Eucalyptus sp. was the most abundant had the lowest odonate richness (Samways & Steytler, 1996). From a social perspective, increased biodiversity of odonates in urban green areas such as botanical gardens and parks is also important because they help attract tourists and increase awareness of the role of wetlands (Lemelin, 2007). Additionally, urban ecosystems offer a vast diversity of pond types, ranging from ornamental ponds to drainage systems, each of these being subjected to different management plans (Hassall, 2014). ...
... This is particularly important in cities because by meeting the conditions required for odonates to survive, other species' requirements will be met as well (Bried et al., 2007), thus saving time and effort in developing biodiverse, sustainable cities. They also work as " fl agship species " for wetlands due to their attractiveness (Lemelin, 2007), which may help attract visitors to urban green areas. ...
Article
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The expansion of urban areas is one of the most significant anthropogenic impacts on the natural landscape. Due to their sensitivity to stressors in both aquatic and terrestrial habitats, dragonflies and damselflies (the Odonata) may provide insights into the effects of urbanisation on biodiversity. However, while knowledge about the impacts of urbanisation on odonates is growing, there has not been a comprehensive review of this body of literature until now. This is the first systematic literature review conducted to evaluate both the quantity and topics of research conducted on odonates in urban ecosystems. From this research, 79 peer-reviewed papers were identified, the vast majority (89.87%) of which related to studies of changing patterns of biodiversity in urban odonate communities. From the papers regarding biodiversity changes, 31 were performed in an urban-rural gradient and 21 of these reported lower diversity towards built up city cores. Twelve of the cases of biodiversity loss were directly related to the concentrations of pollutants in the water. Other studies found higher concentrations of pollutants in odonates from built-up catchments and suggested that odonates such as Aeshna juncea and Platycnemis pennipes may be candidate indicators for particular contaminants. We conclude by identifying current research needs, which include the need for more studies regarding behavioural ecology and life-history traits in response to urbanisation, and a need to investigate the mechanisms behind diversity trends beyond pollution. © Institute of Entomology, Biology Centre, Czech Academy of Sciences, Ceské Budejovice.
... This is the situation when an organism-usually an animal-attempts to reproduce in sites where reproduction is in fact not possible, even though such sites are plentiful (Kokko and Sutherland 2001;Gilroy and Sutherland 2007;Robertson et al. 2010). It is usually the effect of a broken link between the real quality of a site and the aspect that persuades an organism to select it (Oaks et al. 2004), or of perceptual errors as in the mechanism of sensory exploitation (Horváth et al. 2007;. Ecological traps are usually fairly easily distinguishable, often anthropogenic, objects in space (Robertson and Hutto 2006;Horváth et al. 2007;Harabiš and Dolný 2012), so analysing the extent and range of their impact is perfectly feasible. ...
... It is usually the effect of a broken link between the real quality of a site and the aspect that persuades an organism to select it (Oaks et al. 2004), or of perceptual errors as in the mechanism of sensory exploitation (Horváth et al. 2007;. Ecological traps are usually fairly easily distinguishable, often anthropogenic, objects in space (Robertson and Hutto 2006;Horváth et al. 2007;Harabiš and Dolný 2012), so analysing the extent and range of their impact is perfectly feasible. A well-known example of this approach is analysing the spatial impact of light pollution: there are convincing descriptions of how artificial light sources act as ecological traps (Longcore and Rich 2004;Robertson et al. 2013). ...
Article
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Although the negative impact of timber stacks on populations of saproxylic beetles is a well-known phenomenon, there is relatively little data concerning the scale of this impact and its spatial aspect. Beech timber stored in the vicinity of the forest can act as an ecological trap for the Rosalia longicorn (Rosalia alpina), so in this study we have attempted to determine the spatial range of the impact of a network of timber stacks. Timber stacks in the species’ range in the study area were listed and monitored during the adult emergence period in 2014–2016. Based on published data relating to the species’ dispersal capabilities, buffers of four radii (500, 1000, 1600, 3000 m) were delineated around the stacks and the calculated ranges of potential impact. The results show that the percentage of currently known localities of the Rosalia longicorn impacted by stacks varies from 19.7 to 81.6%, depending on the assumed impact radius. The percentage of forest influenced by timber stacks was 77% for the largest-radius buffer. The overall impact of the ecological trap network is accelerated by fragmentation of the impact-free area. It was also found that forests situated close to the timber stacks where the Rosalia longicorn was recorded were older and more homogeneous in age and species composition than those around stacks where the species was absent. Such results suggest that timber stacks act as an ecological trap in the source area of the local population.
... In temperate regions, tree cover near aquatic habitats can also restrict visitation and colonization rates at ponds by amphibians (Skelly et al., 2014), adult dragonflies (Remsburg et al., 2008), and beetles (Binckley & Resetarits, 2009). Canopy cover may decrease the amount of polarized light reflected from aquatic surfaces, a visual cue commonly used by dragonflies to detect oviposition habitats (Wildermuth, 1998), as well as the amount of sunlight available for adult thermoregulation (Horváth et al., 2007;Remsburg et al., 2008;De Marco et al., 2015). Low light availability at these habitats may affect the composition of a dragonfly assemblage by constraining adults' detection of habitat or limiting their persistence in the area, thus reducing colonization success (e.g. ...
... Many taxa use polarized light as a visual cue to orient themselves towards potential habitats, as is the case for many insects with aquatic larval stages (Kriska et al., 2009), and possibly some amphibian and reptile species (Vitt & Caldwell, 2014). Different dragonfly species may also be attracted to aquatic habitats with varying levels of polarized light (Bernáth et al., 2002;Horváth et al., 2007). For our study, we generated rough estimates of reflected polarized light intensity off the mesocosms, which were collinear with canopy cover and thus not included in our analysis but which provided similar results (French & McCauley, unpublished data). ...
Article
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The mechanisms structuring aquatic communities across environmental gradients are often difficult to distinguish from one another and can produce similar patterns of species distributions. In freshwater systems, the amount of canopy cover from surrounding trees is often associated with transitions in local community structure. These community changes could be driven by habitat selection prior to colonization of the aquatic habitat and/or species-sorting post-colonization. To assess the contributions of pre- versus post-colonization processes in structuring larval dragonfly assemblages, we tested the impact of artificial and natural canopy cover on the selection of experimental aquatic mesocosms by adult dragonflies, and monitored the performance (i.e. growth and survival) of larval dragonflies that were placed in mesocosms under a gradient of natural canopy cover. We found that greater levels of canopy cover resulted in fewer adult visits to mesocosms, and more natural canopy cover decreased the species richness of visitors. There were no effects of canopy cover on the growth and survival of larvae added to the mesocosms. Our results suggest that adult habitat selection plays a dominant role in structuring larval dragonfly assemblages across a canopy cover gradient, and that canopy cover can be an important environmental filter on species distributions.
... Dragonflies can increase reproductive success by choosing the best available habitat for egg and larval survival (Michiels and Dhondt 1990). They locate water bodies by detecting horizontally polarized light reflected from the water surface (Bernáth et al. 2001(Bernáth et al. , 2002Horváth et al. 1998Horváth et al. , 2007. Visual habitat recognition in dragonflies is also based on vegetation structure (Corbet 1999;Wildermuth 1994) and polarotaxis is probably an essential part of this process Wildermuth 1998). ...
... For each pond, the average value for the particular variables is given. For subsequent analysis of the cues affecting habitat choice, we used only the following attributes: trophic state (which may influence polarization patterns ;Schwind 1995), dominant plant species (which serve as perches for adults ;Corbet 1999;Horváth et al. 2007), and dominant littoral vegetation (used by dragonflies for oviposition ;Corbet 1999;Wildermuth 1994). For analysis of factors that may determine the survival of the eggs/larvae of particular species, we chose a set of attributes from habitat preferences of the species (Sternberg and Buchwald 2000): date of flooding, date of draining, winterizing, amount of reared fish, and fish predation pressure. ...
Article
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The concept of ecological traps, in which animals settle in low-quality habitats, is well-established. Dragonflies are a good model for investigating the effects of ecological traps because their habitat selection process can be directly observed. Unfortunately, most such studies focus on oviposition on artificial materials, such as car surfaces, gravestones, and plastic foils, which results in complete mortality of the clutch. It remains unclear to what extent intensive fish ponds, ubiquitous in the European agricultural landscape, act as ecological traps for some dragonfly species and how they influence their vulnerability. We investigated the effects of putative ecological traps on the threatened dragonfly Sympetrum depressiusculum and the common closely related species S. sanguineum in a Central European agricultural landscape. Observations of adult behavior were used to parameterize GLMs examining the attractiveness of five fish ponds (three fish breeding and two intensive) to each species. We also counted exuviae at each pond as a measure of each species’ survival. We used GLMMs to determine which factors affected selection of oviposition sites and the environmental factors resulting in ecological traps for each species. All five ponds were attractive to ovipositing pairs of both species, although they were largely unsuitable for subsequent development (four for S. depressiusculum and two for S. sanguineum). Our results provide evidence that intensive fish ponds act as ecological traps for both species. We believe that cutting of the vegetation surrounding trap habitats could be an effective way to decrease their attractiveness to a wide range of dragonfly species.
... Some authors consider that the breakdown in communication between habitat quality and the signals an organism receives to assess this can only be key to the existence of an ecological trap if such a habitat assessment is of an indirect character (Schlaepfer et al. 2002;Robertson and Hutto 2006;Robertson et al. 2013). The classic example in this respect relates to insects that develop in water, which make use of light polarization when ovipositing, as a result of which they will frequently lay their eggs on dry glass or polished granite surfaces (Horváth et al. 2007;Robertson et al. 2010). In the case of timber stacks and the Rosalia longicorn, the assessment of attractiveness is indirect: the stored timber could provide appropriate conditions for larval development, were it not transported out of the forest and processed. ...
Article
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Ecological traps are serious, anthropogenic threats to animal populations. However, in certain cases it is difficult to determine whether they really act in the expected manner. This applies to the harmful effects of beech timber stacked in forests on the endangered saproxylic beetle Rosalia longicorn Rosalia alpina, which have been mentioned in numerous scientific articles, conservation action plans and similar publications. The aim of this paper is to determine whether beech timber stacks meet the criteria of an ecological trap for the Rosalia longicorn. Two basic criteria of such a trap are analysed: the attractiveness of timber stacks and the impossibility of complete larval development. The results show that beech timber stacks are highly attractive to Rosalia longicorn imagines. Moreover, the time during which the timber is stacked is shown to be significantly shorter than the species’ larval development period. These results suggest that timber stacks can be treated as operative ecological traps for the Rosalia longicorn, even though the extent of their influence on the demographic parameters of this beetle’s population has not been estimated. Forest management practices, i.e. increasing amounts and shifts in timing of wood storage, could intensify this threat.
... Many aquatic insects, for example, use polarized light reflected off horizontal surfaces to identify ponds suitable for laying their eggs. As a result, misguided insects are also being enticed to oviposit on artificial structures that have the same reflective properties as water bodies, such as dry asphalt roads, cars, and gravestones (Kriska et al. 1998(Kriska et al. , 2006Horváth et al. 2007). ...
Article
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Humans have brought about unprecedented changes to environments worldwide. For many species, behavioral adjustments represent the first response to altered conditions. In this review, we consider the pivotal role that behavior plays in determining the fate of species under human-induced environmental change and highlight key research priorities. In particular, we discuss the importance of behavioral plasticity and whether adaptive plastic responses are sufficient in keeping pace with changing conditions. We then examine the interplay between individual behavioral responses and population processes and consider the many ways in which changes in behavior can affect ecosystem function and stability. Lastly, we turn to the evolutionary consequences of anthropogenic change and consider the impact of altered behaviors on the evolutionary process and whether behavior can facilitate or hinder adaptation to environmental change.
... This effect is not unique to roads, as these species are also attracted to dark plastic surfaces used in agriculture (Kriska et al. 1998;Kriska et al. 2009), concrete floors, bright car bodies (especially dark) or windshields, solar panels, wet city streets (Kennedy 1938;Neville 1960;Wildermuth 1998;Horváth and Zeil 1996;Horváth et al. 1998;Bernáth et al. 2001;Wildermuth and Horváth 2005;Kriska et al. 2009), and even black gravestones in cemeteries (Horváth et al. 2007). ...
Article
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In the last few decades, mounting evidence points to a negative impact of roads on several groups of animals. Most studies on the effects of roads on animal populations concentrate on vertebrates, and only a few on insects. It is difficult to determine the real effects of roads on insects due to the variety of methods used. We review recent literature examining the ecological impact of roads on insects. The objectives of our synthesis are to gain insight into the effects of the construction and operation of a road on insect groups, and to determine the gaps of knowledge. We found that roads negatively affect the abundance and diversity of insects due to two main factors: (1) the high mortality of some groups when crossing the road, with more impact at higher traffic volumes. (2) The unwillingness of many species to cross a road or live close to it. Roads are major barriers for small or flightless species, although the response varied for flying species. Finally, both experimental and observational evidence support the idea that air pollutants and de-icing salt used for the road maintenance negatively affect insects.
... This study quantified (in means of egg counting) the use of polarization for choosing oviposition site by chironomids, a phenomenon that was previously qualitatively described (as pre-oviposition behaviour) in other dipteran families (e.g. Horváth et al. 2007;Kriska et al. 2007). Following the study of Lerner et al. (2008), eight more European chironomid species were found to show pre-oviposition behaviour towards highly and horizontally polarizing surfaces (Horváth et al. 2011). ...
Chapter
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Recently, a new utilization for light polarization has been demonstrated: the use of reflection polarizations from water surface to assess habitat quality and choose oviposition sites for water-living insects. While contradicting results were shown in the laboratory and at the natural habitat of long-living mosquitoes, their short-living, non-biting relatives, the chironomids (Chironomidae, midges, which serve as the host of the Cholera pathogen among many other species of bacteria), have shown clear response both under confined and unconfined conditions. The understanding of the advantage of following reflection polarizations to detect suitable reservoirs for oviposition opens a new research field of controlling pest insects using reflection-polarization traps, which has not been addressed to date.
... The Anisoptera are generally large bodied and are good flyers, with the roads possibly acting as open areas for these generalist hunters. An alternative, suggested by Horvath et al. (2007), is that Anisoptera mistake roads for rivers in search of food and oviposition sites. This seems unlikely here, as the roads were dirt and do not have a reflective surface. ...
Article
Ecological networks (ENs) are able to mitigate the negative effects of commercial forestry on terrestrial biodiversity, yet this remains untested for the aquatic fauna. Understanding the anthropogenic and natural variables that drive dragonfly diversity at the landscape and habitat scales, allows the design and implementation of ENs that minimise biodiversity loss across production landscapes.Here, we determine the relative contribution of anthropogenic disturbances and natural environmental variables to dragonfly assemblages within ENs. Sixty sites, of various freshwater body types, were sampled for adult dragonflies across ENs in a commercial forestry landscape.Overall, species richness was significantly influenced by river width, water turbidity, water depth and the presence of invasive plants. Nevertheless, overall species composition was influenced by water body type, flow rate and substrate type. Further differences were found when analyses were conducted separately for Anisoptera and Zygoptera.Counter-intuitively, anthropogenic disturbances had less effect on dragonfly species richness and composition than did natural environmental variables, emphasising the importance of conserving natural heterogeneity. Overall, dragonfly diversity can be successfully conserved in ENs provided that conservation planning incorporates appropriate local scale variables. These results also suggest that impacts on water quality and dragonfly diversity are minimised by well-designed ENs within this production landscape.
... In multiple-choice field experiments, Kriska et al. (2009) measured the threshold d* of ventral polarization sensitivity in mayflies, dragonflies and tabanid flies, the positive polarotaxis of which has been shown earlier (mayflies: Kriska et al. 1998Kriska et al. , 2007dragonflies: Wildermuth 1998;Horváth et al. 1998Horváth et al. , 2007Bernáth et al. 2002;tabanids: Horváth et al. 2008). Kriska et al. (2009) captured dragonflies, mayflies and tabanids with white, light grey, medium grey, dark grey and black salad oil-filled trays reflecting horizontally polarized light with different degrees of linear polarization d (Fig. 5.13). ...
Chapter
In this chapter we show that primary aquatic insects fly predominantly in mid-morning, and/or around noon and/or at nightfall. We describe the different types of their diurnal flight activity rhythm characterised by peaks at low and/or high solar elevations. We present here experimental evidence that the polarization visibility Q(θ) of water surfaces is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation θ for dark waters, while Q(θ) is maximal at dawn and dusk (low solar elevations) for bright waters both under clear and partly cloudy skies. The θ-dependent reflection-polarization patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. This phenomenon is called the “polarization sundial” of dispersing aquatic insects. We also show that non-biting midges (Chironomidae, Diptera) are positively polarotactic and like many other aquatic insects, their females are attracted to horizontally polarized light. We present here measured thresholds (i.e., the minimum degrees of linear polarization of reflected light that can elicit positive polarotaxis) of the ventral polarization sensitivity in mayflies, dragonflies and tabanid flies. The mayflies Palingenia longicauda swarm exclusively over the river surface; thus, they need not search for water. It could be assumed that this species is not polarotactic. We show here that also P. longicauda has positive polarotaxis, which, however, can be observed only when the animals are displaced from the water and then released above artificial test surfaces. P. longicauda is the first species in which polarotactic water detection was demonstrated albeit it never leaves the water surface, and thus, a polarotactic water detection seems unnecessary for it. The yellow fever mosquito, Aedes aegypti, has been thought to locate its breeding habitats exclusively by chemical cues. We demonstrate here that horizontally polarized light can also attract ovipositing Ae. aegypti females when they are deprived of chemical cues. Aedes aegypti is the first known water-associated species in which polarotaxis exists, but does not play a dominant role in locating water bodies and can be constrained in the presence of chemical cues. Finally, we deal with the negative polarotaxis in the desert locust, Schistocerca gregaria, the ventral eye region of which detects the horizontally polarized water-reflected light, and thus can navigate towards or away from large water surfaces.
... Most known examples of ecological traps come from avian studies (reviewed by Battin 2004;Robertson and Hutto 2006;Schlaepfer et al. 2002;Robertson et al. 2013), but arthropods, which often have more specialized sensory capabilities than birds, may be even more prone to making habitat selection errors in the context of human-induced rapid environmental change (e.g,. Hedin et al. 2008;Horváth et al. 2009;Horváth et al. 2007;Kriska et al. 2006;Ries and Fagan 2003) and can serve as valuable indicators of disturbance (Uehara-Prado et al. 2009). Harvestmen are among the most abundant arthropods in tropical forests (Wade et al. 2011) and are strongly affected by habitat fragmentation and other anthropogenic disturbances (Bragagnolo et al. 2007). ...
Article
Situations in which animals preferentially settle in low-quality habitat are referred to as ecological traps, and species that aggregate in response to conspecific cues, such as scent marks, that persist after the animals leave the area may be especially vulnerable. We tested this hypothesis on harvestmen (Prionostemma sp.) that roost communally in the rainforest understory. Based on evidence that these animals preferentially settle in sites marked with conspecific scent, we predicted that established aggregation sites would continue to attract new recruits even if the animals roosting there perished. To test this prediction, we simulated intense predation by repeatedly removing all individuals from 10 established roosts, and indeed, these sites continued to attract new harvestmen. A more likely reason for an established roost to become unsuitable is a loss of overstory canopy cover caused by treefalls. To investigate this scenario, without felling trees, we established 16 new communal roosts by translocating harvestmen into previously unused sites. Half the release sites were located in intact forest, and half were located in treefall gaps, but canopy cover had no significant effect on the recruitment rate. These results support the inference that communal roost sites are potential ecological traps for species that aggregate in response to conspecific scent.
... Each photo was converted into a 100 Â 100 pixel image using 250 shades of gray in MATLAB. While it is known that odonates are able to detect movement at long distances (Horváth et al., 2007;Bernáth et al., 2002), little is known of long-distance odonate vision. This method of image analysis results in a high resolution image which is a reasonable representation of M. caerulatus's view of the landscape based on the number of ommitidia and forwardfacing acute zones in zygopteran eyes (Corbet, 1999). ...
... A number of insects living underwater or living on moist substrates use linearly polarized-light reflected from flat water surfaces as a clue to find water bodies, such as the backswimmer Notonecta glauca (Schwind, 1985), mayflies (Kriska et al., 1998(Kriska et al., , 2009M aln as et al., 2011), dragonflies (Wildermuth, 1998;Horv ath et al., 1998Horv ath et al., , 2007Bern ath et al., 2002), and many other aquatic insects (Schwind, 1991;Csabai et al., 2006;Kriska et al., 2006Kriska et al., , 2008. A. japonicus also have to find water bodies; larvae usually form a cell in the soil of the shore and return to water as adults. Adults occasionally fly to a new habitat when the former one becomes uninhabitable or dries up (Larson et al., 2000;Saijo, 2001). ...
Article
The fine structure of the compound eyes of the adult diving beetle Agabus japonicus is described with light, scanning, and transmission electron microscopy. The eye of A. japonicus is mango-shaped and consists of about 985 ommatidia. Each ommatidium is composed of a corneal facet lens, an eucone type of crystalline cone, a fused layered rhabdom with a basal rhabdomere, seven retinula cells (including six distal cells and one basal cell), two primary pigment cells and an undetermined number of secondary pigment cells that are restricted to the distalmost region of the eye. A clear-zone, separating dioptric apparatus from photoreceptive structures, is not developed and the eye thus resembles an apposition eye. The cross-sectional areas of the rhabdoms are relatively large indicative of enhanced light-sensitivity. The distal and central region of the rhabdom is layered with interdigitating microvilli suggesting polarization sensitivity. According to the features mentioned above, we suggest that 1) the eye, seemingly of the apposition type, occurs in a taxon for which the clear-zone (superposition) eye is characteristic; 2) the eye possesses adaptations to function in a dim-light environment; 3) the eye may be sensitive to underwater polarized light or linearly water-reflected polarized light. J. Morphol., 2014. © 2014 Wiley Periodicals, Inc.
... Similarly, the data on its detailed habitat requirements from any post-mining landscapes are limited, as the only existing studies included whole odonate communities, with not enough effort dedicated to individual species (Tichanek and Tropek 2015), or only very limited numbers of post-mining ditches, as the study focused on more landscapes types (Harabiš and Dolný 2015). Moreover, although odonates were repeatedly documented to breed at sites which are unsuitable for larvae (Horváth et al. 2007;Šigutová et al. 2015), all the published information on C. ornatum in post-mining sites were based on its adults or with a suspected effect on odonates in post-mining sites (Harabiš et al. 2013;Tichanek and Tropek 2015;Harabiš 2016). The variables were recorded in June and early July 2012. ...
Article
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The damselfly Coenagrion ornatum represents a threatened species of lowland headwater streams. Although the species is threatened in Western and Central Europe, it is known at a system of post-mining drainage ditches in the Radovesicka spoil heap (northwestern Bohemia, Czech Republic). This study aimed to estimate its population size in this post-mining stream system, and to explore habitat preferences of both its larvae and adults with respect to various environmental factors. The adults were captured-recaptured along 5.2 km of the ditches in June 2012; larvae were sampled in 64 study sites (i.e., 27-meter-long sections of the same ditches) in April 2012. The adult population size was estimated via log-linear models with the robust design on 4544 individuals (1560 ± 391 females and 2983 ± 298 males). Larvae were present in a third of the sections. GLMs revealed that both larvae and adults required emergent vegetation with a high proportion of Eleocharis spp. plants. The adults preferred the slow-flowing and shallow streams with 2-meter-high banksides covered by intermediately tall vegetation (~40 cm), whereas the larval abundance was supported by a high in-stream vegetation heterogeneity and a patchy cover of rocks on the streambeds. These results indicate that the post-mining streams could represent a valuable secondary habitat for the complete life cycle of this relatively large population of the endangered headwater specialist. Therefore, we recommend consideration of the conservation potential of such ditches during post-mining sites restoration and their subsequent management.
... However, these habitats may also attract individuals of species that cannot efficiently cope with heavy metals, for example females of flying insects looking for oviposition sites. This could turn the fly ash lagoons into population sinks or even ecological traps for some species [83]. This study cannot resolve these issues as it focuses on the net concentrations and not on the biological availability of the individual heavy metals at the studied sites. ...
Article
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Deposits of coal combustion wastes, especially fly ash, are sources of environmental and health risks in industrial regions. Recently, fly ash deposits have been reported as habitat surrogates for some threatened arthropods in Central Europe. However, the potential environmental risks of fly ash have not yet been assessed in the region. We analysed concentrations of 19 minor and trace elements in 19 lignite combustion waste deposits in the Czech Republic. We assessed their environmental risks by comparison with the national and EU legislation limits, and with several commonly used indices. Over 50% of the samples exceeded the Czech national limits for As, Cu, V, or Zn, whilst only V exceeded the EU limits. For some studied elements, the high-risk indices were detected in several localities. Nevertheless, the measured water characteristics, the long-term presence of fly ash, previous leaching by acid rains, and the low amount of organic matter altogether can infer low biological availability of these elements. We presume the revealed high concentrations of some heavy metals at some studied sites can be harmful for some colonising species. Nevertheless, more ecotoxicological research on particular species is needed for final decision on their conservation potential for terrestrial and freshwater biota.
... However, as the adults' home ranges also include areas not suitable for larvae (Dolný et al. 2014), there are general concerns about the accuracy of local assessments based solely on adults (Raebel et al. 2010;Patten et al. 2015). Although the risk of misleading results could be substantially reduced via recording of breeding behaviour (Bried et al. 2012aPatten et al. 2015), even this has been repeatedly observed in habitats unsuitable for larval development (Horváth et al. 2007;Šigutová et al. 2015). On the other hand, because larvae monitoring often requires a substantial amount of time, efort and experience, its involvement in the common monitoring and assessment schemes can be problematic and inefective. ...
Article
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The damselfly Coenagrion ornatum is a threatened species, specialized for lowland headwater streams. As the species is declining and protected across Europe, it represents a species of particular conservation interest. This work aims to provide the first evaluation of fine-scale spatial ecology in this species, especially to assess its general mobility and distribution of adults in relation to larval habitats, and to suggest implications for conservation and efficient monitoring of this species. Adults were captured-recaptured along four distinct streams (5.2 km together) in the Radovesická spoil heap, Czech Republic. Immature adults and breeding individuals were recorded simultaneously. Larvae were sampled in 64 sections of 27 m, evenly distributed across the studied streams. In total, 1152 adult individuals were marked; from these, 240 individuals were recaptured at least once. Larvae were detected in 21 sites with a total number of 61 individuals. The adults were highly sedentary, with a median lifetime dispersal of 11 m. Only one male was reported to move between two distinct streams. Model comparisons revealed that female and breeding pair abundances are a significantly more reliable indicator of larval abundance than male and total adult abundances, especially when used along with records of the immature adults. Moreover, the weighted least square models showed that the female abundances are spatially more specific (i.e., less autocorrelated) than male abundances. These results imply that surveying the adult females, along with the breeding and immature adults, offers the best method for local habitat quality assessment for this Natura 2000 species.
... Evidence for the presence of ecological traps has grown considerably since the term was first coined in the 1970s (Dwernychuk & Boag, 1972;Hale & Swearer, 2016). Although much of the initial work focused on birds, the increasing interest in, and importance of, ecological traps has led to evidence of their impact on insects (Horvath et al., 2007), amphibians (Ward-Fear et al., 2009), mammals (Balme, Slotow & Hunter, 2010;van der Meer et al., 2014) and reptiles (Hawlena et al., 2010;Rotem et al., 2013). Multiple anthropogenic activities have now been implicated in the formation of ecological traps, such as agriculture (Gilroy et al., 2011), ecological restoration ) pollution (Boda et al., 2014, harvesting and climate change (Sherley et al., 2017). ...
Thesis
The speed and scale at which humans are altering natural systems creates novel challenges for many species. Some species can cope with human-induced rapid environmental change by exhibiting adaptive behavioural or phenotypic plasticity. Many others, however, respond maladaptively in ways that can impact individual fitness. When rapid environmental change triggers mismatches between perceived and actual habitat quality, animals can prefer inferior habitats, that are known as ecological traps. Using a meta-analysis, I show that ecological traps are an unexplored but potentially important conservation risk to animals within wetland habitats (Chapter 2). Focusing on urbanisation and stormwater wetlands as a case study, I assess how anthropogenic environmental change affects frogs, in terms of the environmental variables influencing species occurrence (Chapter 3), the capacity of individuals to make adaptive habitat selection decisions (Chapter 4), and the fitness and behavioural consequences of these decisions (Chapter 4 and 5). I show that frogs occupied wetlands across a broad spectrum of pollution levels, including even the most contaminated, and that pollution exposure reduced survival and impaired predator avoidance behaviours. Breeding frogs did not avoid wetlands where these fitness reductions occurred, demonstrating that stormwater wetlands can function as ecological traps. Collectively, my results highlight that we need to a greater focus on individual-level metrics (e.g. fitness and habitat preferences) in addition to the more commonly measured populationand community-level metrics (e.g. richness and abundance). Based on my research, I propose three key recommendations to maximise biodiversity at wetlands within urban landscapes. Firstly, appreciate that poor water quality at stormwater wetlands may impact resident wildlife, and attempt to reduce the causal factors. Second, despite this, do not ignore the potential value of stormwater wetlands in providing habitat and enhancing connectivity amongst aquatic habitats, particularly when they are appropriately designed and managed. Finally, it is important to design and construct wetlands for wildlife that are not connected to stormwater networks, with their placement within the landscape carefully considered.
... However, the high availability of specific resources on roads could be act as an ecological trap -defined as a lowquality habitat that organisms prefer over superior habitats (Dwernychuk and Boag 1972) -affecting the abundance. In fact, several authors (Ries and Fagan 2003;Horváth et al. 2007;Hedin et al. 2008) have probed that other specific resources as forest fuel piles after clearcutting or habitat edges, and polarized black tombstones in graveyards can be ecological traps for generalist insect species. ...
Article
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Forestry companies have replaced and fragmented the native landscapes, generating a large number of unpaved roads, which can have a negative effect on non-flying invertebrates. Polynoncus bullatus is a common necrophagous beetle species depend on fox scats present on unpaved roads in fragmented landscapes in central Chile. Here, the effect of different habitat types (native forest, clear-cuts and unpaved roads) on the abundance of Lycalopex culpaeus scats as well as abundance and survival of P. bullatus in the fragmented landscape was evaluated. Scats and beetles were counted in seven independent fragments during 6 months and through sampling transects. Both responses and factors were associated with GLM, whereas survival was evaluated with a Kaplan-Meier test. Higher scats abundance was found on unpaved roads than other habitat types. Higher P. bullatus abundance was also significantly associated with unpaved roads than clear-cuts and native forest fragments. An additive model between habitat type and scat abundance was correlated with beetle abundance. Survival was significantly lower in unpaved roads, generating up to 42 % of beetles road-killed. Lycalopex culpaeus response positively to fragmentation defecating more on unpaved roads because foxes use it to move through the landscape. This fact attracts more P. bullatus individuals, being run-over by cars and trucks, representing an ecological trap for beetles. This interaction can be predictable and modeled for any period, length or road type avoiding potential massive road-kill events. Implications for insect conservation. Common and threatened invertebrate species are run-over when minor roads cross valuable natural or protected areas, evidencing the need of advance in road designs compatible with their conservation and mitigating negative impacts of forestry.
... Hence, these surfaces are typically lighter coloured equivalents of the same material (e.g. Schwind 1983Schwind , 1989Schwind , 1991Kriska et al. 1998;Kriska et al. 2006;Csabai et al. 2006;Horváth et al. 2007;Kriska et al. 2009;Boda et al. 2014). While reflections from these surfaces are lower in DoP, measurements are required to ensure that other cues are not introduced by the change in intensity and reflectance spectrum. ...
Preprint
In recent years, the study of polarization vision in animals has seen numerous breakthroughs, not just in terms of what is known about the function of this sensory ability, but also in the experimental methods by which polarization can be controlled, presented and measured. Once thought to be limited to only a few animal species, polarization sensitivity is now known to be widespread across many taxonomic groups, and advances in experimental techniques are, in part, responsible for these discoveries. Nevertheless, its study remains challenging, perhaps because of our own poor sensitivity to the polarization of light, but equally as a result of the slow spread of new practices and methodological innovations within the field. In this review, we introduce the most important steps in designing and calibrating polarized stimuli, within the broader context of areas of current research and the applications of new techniques to key questions. Our aim is to provide a constructive guide to help researchers, particularly those with no background in the physics of polarization, to design robust experiments that are free from confounding factors.
... It has been proposed that different dragonfly species known to show a preference for dark versus bright ponds might use the degree of polarization to distinguish between these habitats, yet it remains to be shown how insects would be able to perform this computationally difficult task (Bernath, Szedenics, Wildermuth, & Horvath, 2002). Numerous accounts exist where female insects erroneously oviposit onto shiny surfaces they mistakenly take for water, like parked cars or black gravestones (Horvath, Bernath, & Molnar, 1998;Horvath, Malik, Kriska, & Wildermuth, 2007Kriska, Horvath, & Andrikovics, 1998, while other insects are attracted by glass buildings (Kriska, . Many of the extremely short-lived mayflies (Ephemeropta) show strong attraction to water (Kriska, Bernath, & Horvath, 2007). ...
Chapter
Evolution has produced vast morphological and behavioral diversity amongst insects, including very successful adaptations to a diverse range of ecological niches spanning the invasion of the sky by flying insects, the crawling lifestyle on (or below) the earth, and the (semi-)aquatic life on (or below) the water surface. Developing the ability to extract a maximal amount of useful information from their environment was crucial for ensuring the survival of many insect species. Navigating insects rely heavily on a combination of different visual and non-visual cues to reliably orient under a wide spectrum of environmental conditions while avoiding predators. The pattern of linearly polarized skylight that results from scattering of sunlight in the atmosphere is one important navigational cue that many insects can detect. Here we summarize progress made toward understanding how different insect species sense polarized light. First, we present behavioral studies with “true” insect navigators (central-place foragers, like honeybees or desert ants), as well as insects that rely on polarized light to improve more “basic” orientation skills (like dung beetles). Second, we provide an overview over the anatomical basis of the polarized light detection system that these insects use, as well as the underlying neural circuitry. Third, we emphasize the importance of physiological studies (electrophysiology, as well as genetically encoded activity indicators, in Drosophila) for understanding both the structure and function of polarized light circuitry in the insect brain. We also discuss the importance of an alternative source of polarized light that can be detected by many insects: linearly polarized light reflected off shiny surfaces like water represents an important environmental factor, yet the anatomy and physiology of underlying circuits remain incompletely understood.
... If adult odonates are choosing stormwater ponds based on plant communities but the habitat is too poor for aquatic life stages (nymphs), these ponds may be ecological traps (Battin 2004;Harabiš and Dolný 2012). Odonata may be quite vulnerable to ecological traps as adults have been observed ovipositing in environments completely unsuitable for egg and nymphal development such as gravestones with reflective surfaces (Horváth et al. 2007). To determine if stormwater ponds are in fact acting as ecological traps for odonates it would be necessary to demonstrate that: (1) stormwater ponds are being selected over other available habitats of higher overall quality, and (2) adult odonates are reproducing in stormwater ponds but egg and/or nymph development is impaired, hindering odonate emergence rates (nymph to adult). ...
Article
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Urbanization significantly alters hydrological regimes in cities by reducing infiltration rates and increasing runoff. Stormwater ponds have been constructed in North American cities to mitigate the effects of increased urban runoff by dampening floods and filtering out contaminants. However, these ponds may also provide habitat for wetland species in cities. This study aimed at determining the significance of stormwater ponds as attractive habitats for the adult stages of Odonata (dragonflies and damselflies), widely considered bioindicators of aquatic and wetland ecosystem health. A total of 41 urban stormwater ponds and ten rural natural ponds were sampled across the National Capital Region of Canada. On average, stormwater ponds had fewer species and lower abundance of dragonflies but, in contrast, more species of damselflies. Stormwater ponds had a higher total plant species richness because of a higher number of non-native species. However, some stormwater ponds had similar odonate and plant species assemblages to natural ponds. The variation in odonate abundance and species composition was largely explained by plant community composition and significantly linked to the presence of specific obligate wetland plant species. Overall, this study highlights the importance of wetland features in cities and points to design elements of stormwater ponds that could be implemented to enhance biodiversity and ecosystem services.
... However, these structures may also function as an ecological trap (i.e. when animals prefer habitats where their fitness is lower than in other available options; Schlaepfer et al., 2002). Examples of ecological traps in freshwater ecosystems include some amphibian species that may be attracted by stormwater ponds in urban areas where embryos and larvae are exposed to higher concentrations of pollutants or are stranded during fluctuations in water level (Brand and Snodgrass, 2010) and aquatic insects that are attracted by polarized light of polished black gravestones (similar as water surface) laying their eggs in these artificial structures and resulting in high mortalities (Horváth et al., 2007). Ecological traps can lead to reductions in population size, and in some extreme cases can increase the risk of species extinction. ...
Article
Anthropogenic habitats may serve as a refuge for aquatic species, including freshwater mussels (Bivalvia, Unionida). Evaluating the role of anthropogenic habitats is a fundamental, but still ignored, conservation issue given the pace that humans have been converting natural ecosystems. In this study, possible differences in abundance, size and condition index of the freshwater pearl mussel Margaritifera margaritifera colonizing an-thropogenic (water mill canals) and natural (Tuela River) habitats were assessed. No differences were found in the abundance of freshwater pearl mussels colonizing both habitats, but individuals present in the water mill canals have a significantly higher condition index and size. Water mill canals seem to provide stable conditions for the settlement, growth and survival of freshwater pearl mussels. However, the occurrence of an exceptional drought during the late summer of 2017 was responsible for an almost 100% mortality in one of the two water mill canals surveyed in this study. Therefore, and during extreme climatic events, these anthropogenic structures may function as an ecological trap for freshwater pearl mussels. This study can be used by managers to promote future actions that enhance freshwater pearl mussel protection and guarantee their survival, including on an-thropogenic habitats.
... At least part of the answer for aquatic species is by detection of polarized light reflected from water surfaces, a phenomenon demonstrated by Horváth and his associates (Bernath, et al. 2001;Horváth 1995a, b;Horváth and Kriska 2008). Several researchers have taken advantage of this phenomenon by using other polarizing surfaces, such as black plastic, as a means of attracting and collecting insects for study (e.g., Boda and Csabai 2009); this also explains the strange propensity for dragonflies to attempt oviposition on black gravestones and on the surface of cars (Horváth et al. 2007;Wildermuth and Horváth 2005). More than likely some insects use other visual, tactile, or chemical cues to locate appropriate habitat, but few of these have been identified. ...
Chapter
All habitats change over time, so most organisms must resist unfavorable conditions or disperse to more favorable localities. Typically, aquatic habitats are relatively short lived because of drying or infilling. Aquatic insects, then, often have adaptations for effective dispersal, sometimes over long distances and most often by flight. This chapter examines some of the environmental drivers and organismal responses that affect the nature of dispersal. These include consideration of how different habitats affect dispersal, especially some differences between lentic and lotic habitats. Dispersal characteristics may also have major effects on genetic structure of populations. Both selective forces and proximate cues affect when insects disperse and when and where they colonize new habitats; availability of space, presence of predators, and availability of food may all play a role, depending on species and circumstances. Adaptations for dispersal include, in addition to active flight, behaviors that promote passive movement by wind, dispersal polymorphism (i.e., changes in body structure, such as wing development, that enhance dispersal, usually hormonally controlled and incurring some cost in fecundity), increased body size, and timing of diapause and reproduction. In a few species dispersal extends to migrations of hundreds of kilometers and may have important seasonal effects on habitats of origin and of destination. Dispersal is also integral to the concept of metapopulations and in fact may be a major driver of community composition and dynamics. Simultaneous dispersal of very large insect populations can have an important effect on nutrient and energy flow to and from communities. Finally, dispersal may be a critical determinant of whether and how aquatic insects respond to climate warming.
... In order to moderate the emission of special chemicals used in cemeteries, for instance, it was suggested to use peat for horticulture in cemeteries instead of artificial fertilisers and to implement 'green' funerals (burials free of chemicals and other modern funeral supplies), which would result in a much lower ecological footprint. Holden and McDonald-Madden (2017) also vote on green funerals with a low ecological footprint after reviewing the available literature on the natural values of cemeteries. ...
Article
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During the past centuries human-induced land use changes resulted in a considerable loss of natural habitats worldwide. In transformed landscapes historical burial places such as cemeteries and churchyards can have the potential for biodiversity conservation. In our review we aimed at evaluating the conservation role of these sites and at revealing factors that can threaten their biota. Altogether we evaluated the results of 97 relevant studies from five continents. We found that cemeteries and churchyards have a considerable conservation role, as even in heavily transformed landscapes they often act as refuges for the populations of rare and endangered species; altogether 140 protected taxa were listed in the reviewed studies. We revealed that the high biodiversity of burial places is supported by their long-term existence and their undisturbed status. However, in parallel with changes in the social attitude the management of these natural refuges has also been altered worldwide. We identified the major threats for the flora and fauna to be altered burial habits decreasing the area of grasslands, intensified management of the cemeteries by frequent mowing and logging, the spontaneous and human-induced introduction of invasive species and the overexploitation of natural resources present in cemeteries. As conservation and spirituality is tightly interwoven in cemeteries, the preservation of these refuges can be achieved by the reconstruction of their sacred spirituality, by raising the attention of local populations for the natural values of these areas and also by specific, focused management providing proper habitats for the natural flora and fauna.
... Some authors consider that the breakdown in communication between habitat quality and the signals an organism receives to assess this can only be key to the existence of an ecological trap if such a habitat assessment is of an indirect character (Schlaepfer et al. 2002;Robertson and Hutto 2006;Robertson et al. 2013). The classic example in this respect relates to insects that develop in water, which make use of light polarization when ovipositing, as a result of which they will frequently lay their eggs on dry glass or polished granite surfaces (Horváth et al. 2007;Robertson et al. 2010). In the case of timber stacks and the Rosalia longicorn, the assessment of attractiveness is indirect: the stored timber could provide appropriate conditions for larval development, were it not transported out of the forest and processed. ...
... Ecological traps affect a variety of taxa (Hale & Swearer, 2016;Robertson, Rehage, & Sih, 2013). Perhaps the most compelling examples are aquatic insects that are attracted to artificial surfaces (e.g., roads, buildings) reflecting polarized light more strongly than streams (e.g., Horvath, Malik, Kriska, & Wildermuth, 2007), where they lay their eggs which subsequently die. ...
Article
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Theory predicts that animals should prefer habitats where their fitness is maximized but some mistakenly select habitats where their fitness is compromised, that is, ecological traps. Understanding why this happens requires knowledge of the habitat selection cues animals use, the habitats they prefer and why, and the fitness costs of habitat selection decisions. We conducted experiments with a freshwater insect, the non‐biting midge Chironomus tepperi to ask: (a) whether females respond to potential oviposition cues, (b) to explore whether oviposition is adaptive in relation to metal pollution and conductivity, and (c) whether individuals raised in poor quality sites are more likely to breed in similarly poor locations. We found the following: (a) females responded to some cues, especially conductivity and conspecifics, (b) females preferred sites with higher concentrations of bioavailable metals but suffered no consequences to egg/larval survival, (c) females showed some avoidance of high conductivities, but they still laid eggs resulting in reduced egg hatching, larval survival, and adult emergence, and (d) preferences were independent of natal environment. Our results show that C. tepperi is susceptible to ecological traps, depending on life stage and the relative differences in conductivities among potential oviposition sites. Our results highlight that (a) the fitness outcomes of habitat selection need to be assessed across the life cycle and (b) the relative differences in preference/suitability of habitats need to be considered in ecological trap research. This information can help determine why habitat preferences and their fitness consequences differ among species, which is critical for determining which species are susceptible to ecological traps.
... Odonates rely on physical cues (e.g. macrophytes, standing water) over the habitat selection continuum and can fail to distinguish suboptimal conditions or ecological traps (McPeek, 1989;Corbet, 1999;Horv ath et al., 2007;Sigutov a, Sigut & Doln y, 2015). Thus, immigrant species may lack preadaptation for local hydroperiod, shading, predators and other withinsite influences that cause resident community structure to diverge (Crumrine et al., 2008). ...
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... Hence, these surfaces are typically lighter coloured equivalents of the same material (e.g. Schwind 1983Schwind , 1989Schwind , 1991Kriska et al. 1998;Kriska et al. 2006;Csabai et al. 2006;Horváth et al. 2007;Kriska et al. 2009;Boda et al. 2014). While reflections from these surfaces are lower in DoP, measurements are required to ensure that other cues are not introduced by the change in intensity and reflectance spectrum. ...
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In recent years, the study of polarisation vision in animals has seen numerous breakthroughs, not just in terms of what is known about the function of this sensory ability, but also in the experimental methods by which polarisation can be controlled, presented and measured. Once thought to be limited to only a few animal species, polarisation sensitivity is now known to be widespread across many taxonomic groups, and advances in experimental techniques are, in part, responsible for these discoveries. Nevertheless, its study remains challenging, perhaps because of our own poor sensitivity to the polarisation of light, but equally as a result of the slow spread of new practices and methodological innovations within the field. In this review, we introduce the most important steps in designing and calibrating polarised stimuli, within the broader context of areas of current research and the applications of new techniques to key questions. Our aim is to provide a constructive guide to help researchers, particularly those with no background in the physics of polarisation, to design robust experiments that are free from confounding factors. Electronic supplementary material The online version of this article (10.1007/s00114-018-1551-3) contains supplementary material, which is available to authorized users.
... Urban activities cause point-source and diffuse pollution (Faulkner et al. 2000) and result in the direct mortality of biota (Kriska et al. 1998). Urban landscapes also present major obstacles to dispersal, such as light pollution (Bilton et al. 2001;Horváth et al. 2007) and road infrastructure (e.g. amphibians, Parris 2006;caddisflies, Blakely and Harding 2005). ...
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Urbanisation represents a growing threat to natural communities across the globe. Small aquatic habitats such as ponds are especially vulnerable and are often poorly protected by legislation. Many ponds are threatened by development and pollution from the surrounding landscape, yet their biodiversity and conservation value remain poorly described. Here we report the results of a survey of 30 ponds along an urban land-use gradient in the West Midlands, UK. We outline the environmental conditions of these urban ponds to identify which local and landscape scale environmental variables determine the biodiversity and conservation value of the macroinvertebrate assemblages in the ponds. Cluster analysis identified four groups of ponds with contrasting macroinvertebrate assemblages reflecting differences in macrophyte cover, nutrient status, riparian shading, the nature of the pond edge, surrounding land-use and the availability of other wetland habitats. Pond conservation status varied markedly across the sites. The richest macroinvertebrate assemblages with high conservation value were found in ponds with complex macrophyte stands and floating vegetation with low nutrient concentrations and little surrounding urban land. The most impoverished assemblages were found in highly urban ponds with hard-engineered edges, heavy shading and nutrient rich waters. A random forest classification model revealed that local factors usually had primacy over landscape scale factors in determining pond conservation value, and constitute a priority focus for management.
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The capability to detect the polarization state of light is crucial in many day‐life applications and scientific disciplines. Novel anisotropic 2D materials such as TiS3 combine polarization sensitivity, given by the in‐plane optical anisotropy, with excellent electrical properties. Here, the fabrication of a monolithic polarization‐sensitive broadband photodetector based on a mixed‐dimensionality TiS3/Si p–n junction is demonstrated. The fabricated devices show broadband responsivity up to 1050 nm, a strong sensitivity to linearly polarized illumination with difference between the two orthogonal polarization states up to 350%, and a good detectivity and fast response time. The discussed devices can be used as building blocks to fabricate more complex polarization‐sensitive systems such as polarimeters. A mixed‐dimensionality TiS3/Si p–n junction with polarization‐sensitive and broadband photodetection is designed and fabricated. The heterostructure device shows a broadband responsivity from 405 to 1050 nm and a high sensitivity to polarized infrared illumination photodetection. The polarized contrast between b‐ and a‐axis directions of the TiS3 lattice is up to 350%.
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Polarization sensitivity (PS) is a common feature of invertebrate visual systems. In insects, PS is well known for its use in several different visually guided behaviours, particularly navigation and habitat search. Adult dragonflies use the polarization of light to find water but a role for PS in aquatic dragonfly larvae, a stage that inhabits a very different photic environment to the adults, has not been investigated. The optomotor response of the larvae of the Emperor dragonfly, Anax imperator, was used to determine whether these larvae use PS to enhance visual contrast underwater. Two different light scattering conditions were used to surround the larval animals: a naturalistic horizontally polarized light field and non-naturalistic weakly polarized light field. In both cases these scattering light fields obscured moving intensity stimuli that provoke an optokinetic response in the larvae. Animals were shown to track the movement of a square-wave grating more closely when it was viewed through the horizontally polarized light field, equivalent to a similar increase in tracking ability observed in response to an 8% increase in the intensity contrast of the stimuli. Our results suggest that larval PS enhances the intensity contrast of a visual scene under partially polarized lighting conditions that occur naturally in freshwater environments.
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Perception is a product of evolution. Our perceptual systems, like our limbs and livers, have been shaped by natural selection. The effects of selection on perception can be studied using evolutionary games and genetic algorithms. To this end, we define and classify perceptual strategies and allow them to compete in evolutionary games in a variety of worlds with a variety of fitness functions. We find that veridical perceptions-strategies tuned to the true structure of the world-are routinely dominated by nonveridical strategies tuned to fitness. Veridical perceptions escape extinction only if fitness varies monotonically with truth. Thus, a perceptual strategy favored by selection is best thought of not as a window on truth but as akin to a windows interface of a PC. Just as the color and shape of an icon for a text file do not entail that the text file itself has a color or shape, so also our perceptions of space-time and objects do not entail (by the Invention of Space-Time Theorem) that objective reality has the structure of space-time and objects. An interface serves to guide useful actions, not to resemble truth. Indeed, an interface hides the truth; for someone editing a paper or photo, seeing transistors and firmware is an irrelevant hindrance. For the perceptions of H. sapiens, space-time is the desktop and physical objects are the icons. Our perceptions of space-time and objects have been shaped by natural selection to hide the truth and guide adaptive behaviors. Perception is an adaptive interface.
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Most organisms exhibit phenotypic plasticity as an evolved response to environmental variation; hence there is widespread hope that adaptive plasticity might lessen the detrimental impacts of environmental change on individuals and populations. Here, I discuss the special role that plasticity in behaviour can play under rapid environmental change. This role arises because behavioural modes of plasticity are common and permit relatively rapid and reversible responses to changing conditions. Key issues are the degree to which behavioural plasticity improves individual fitness, and the impact that plasticity has on population persistence. Behavioural plasticity is quite often beneficial for individuals, and in some cases accounts for most of the observed phenotypic response to environmental change. However, there are several reasons for expecting that maladaptive behavioural plasticity may be especially important in the context of anthropogenic impacts, and the many reports of ecological traps suggest that maladaptive responses to environmental changes caused by humans are widespread. The population-level consequences of plasticity are not well studied, but limited evidence suggests that behavioural responses have enabled persistence or reduced population declines. I conclude by highlighting several topics on which further research is needed.
Chapter
Humans are fascinated by the colour vision, colour signals and ‘dress codes’ of other animals as we can see colour. This property of light may be useful for increasing the contrast of objects during foraging, defence, camouflage and sexual communication. New research, largely from the last decade, now suggests that polarisation is a quality of light also used in signalling and may contain information at least as rich as colour. As many of the chapters in this book detail, polarisation in animals is often associated with navigation, habitat choice and other tasks that require large-field processing. That is, a wide area of the light field, such as the celestial hemisphere, is sampled from. Polarisation vision that recognises and extracts information from objects is most likely confined to processing through small numbers of receptors. This chapter examines the latest evidence on polarised signals from animals and their environments, including both linear and circular polarisations. Both aquatic and terrestrial examples are detailed, but with emphasis on life underwater as it is here that many recent discoveries have been made. Behaviour relative to signals is described where known, and suggestions are given as to how these signals are received and processed by the visual system. Camouflage as well as signalling in this light domain is also considered, with the inevitable conclusion for this new field that we need to know more before solid conclusions can be drawn.
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The e-vector orientation of linearly polarized light represents an important visual stimulus for many insects. Especially the detection of polarized skylight by many navigating insect species is known to improve their orientation skills. While great progress has been made towards describing both the anatomy and function of neural circuit elements mediating behaviors related to navigation, relatively little is known about how insects perceive non-celestial polarized light stimuli, like reflections off water, leaves, or shiny body surfaces. Work on different species suggests that these behaviors are not mediated by the “Dorsal Rim Area” (DRA), a specialized region in the dorsal periphery of the adult compound eye, where ommatidia contain highly polarization-sensitive photoreceptor cells whose receptive fields point towards the sky. So far, only few cases of polarization-sensitive photoreceptors have been described in the ventral periphery of the insect retina. Furthermore, both the structure and function of those neural circuits connecting to these photoreceptor inputs remain largely uncharacterized. Here we review the known data on non-celestial polarization vision from different insect species (dragonflies, butterflies, beetles, bugs and flies) and present three well-characterized examples for functionally specialized non-DRA detectors from different insects that seem perfectly suited for mediating such behaviors. Finally, using recent advances from circuit dissection in Drosophila melanogaster, we discuss what types of potential candidate neurons could be involved in forming the underlying neural circuitry mediating non-celestial polarization vision.
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Our perceptual systems are products of evolution and have been shaped, in part, by natural selection. It is widely assumed that natural selection favors veridical perceptions—that is, perceptions that accurately describe aspects of the objective world relevant to fitness. This assumption has been tested using the mathematics of evolutionary game theory. It is false. Monte Carlo simulations reveal that veridical perceptions are never more fit, and generically are less fit, than nonveridical perceptions of equal complexity that are tuned to fitness. Veridical perceptions go extinct, and their extinction rate increases as complexity increases. These results motivate a new theory of perceptual systems—as species-specific interfaces shaped by natural selection to hide objective reality and guide adaptive behavior. For Homo sapiens, space-time is the desktop of the interface and physical objects are icons on the desktop. The shapes and colors of physical objects no more resemble objective reality than the shapes and colors of desktop icons resemble files in a computer.
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Artificial objects can polarize ultraviolet light sources to a higher degree than natural objects like water bodies. This can induce a strong attraction response by insects that use such cues as proxies of habitat suitable for reproduction. Visible range polarized light (VRPL) can create evolutionary traps for aquatic insects, but it remains unclear whether insects can use ultraviolet polarized light (UVPL) as a habitat selection cue or if UVPL pollution can create evolutionary traps for aquatic insects like VRPL can. Odonate (dragonflies and damselflies) insects require an aquatic habitat to perform their mating and egg-laying behaviours yet they also perform such behaviours on artificial surfaces (i.e. metal pieces). We measured the preference for UVPL versus VRPL via exposing three species of odonates (Enallagma praevarum, Ischnura denticollis and Sympetrum illotum) to experimental test surfaces differing in these visual cues and assessing behavioural preference via differences in mating behaviour, body condition (i.e. lipid and protein content and body size) and visual acuity (based on eye width size). Ischnura denticollis performed more diverse mating behaviours in association with the VRPL treatment, while S. illotum preferentially exhibited these behaviours in association with the UVPL. Ischnura denticollis individuals associated with the preferred habitat had lower lipid reserves, smaller body size and larger eyes, while habitat preference was unrelated to individual condition and morphology in E. praevarum and S. illotum. These results suggest intra-and interspecific variation in trap preferences, which are related to individual condition. They also show that UVPL is a cue that odonates use in habitat selection that has the potential to create evolutionary traps, suggesting conservation problems for aquatic insects that rely upon it to locate water bodies.
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Ecological traps occur when a species makes maladaptive habitat-selection decisions. Human-modified environments including deforested riparian habitats can change how organisms respond to environmental cues. Stream amphibians alter their habitat selection in response to abiotic cues associated with riparian clearing, but little research exists to determine if behavioral shifts to abiotic cues may make them more susceptible to predation. To evaluate if deforested habitats create ecological traps, we studied habitat-selection behavior of larval Black-bellied Salamander (Desmognathus quadramaculatus (Holbrook, 1840)) when given conflicting environmental cues. We also evaluated the potential for learning or adaptation to cues in deforested reaches by evaluating individuals from forested and deforested reaches. We anticipated that individuals from deforested reaches would make adaptive antipredator choices when presented with well-lit habitat, whereas individuals from forested reaches would select shaded habitat closer to a predator. We found that habitat origin, light, and predator presence all interacted to influence habitat selection. Although individuals from forested habitats selected shaded environments, all observed individuals adaptively avoided a predator. Individuals from deforested reaches were more willing to enter well-lit habitat to avoid the predator. Despite documented declines of salamanders associated with forest removal, it appears that individuals are capable of making adaptive antipredator decisions in degraded habitats.
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During the field session of the 10th National Odonatological Symposium of the Polish Entomological Society the Biosphere Reserve “Kampinoski Forest” was faunistically investigated. The biosphere reserve lies in Central Poland encompassing the Kampinoski National Park and its buffering zone. At 16 sites 34 dragonfly species were discovered, the most valuable habitats were peat bogs and fish ponds. Erythromma viridulum and Gomphus flavipes have been recorded for the first time within the boundaries of the Kampinoski National Park. Other rare species in the studied area were: Calopteryx virgo, Lestes virens, Erythromma najas, Aeshna affinis, A. juncea, Anax parthenope, Ophiogomphus cecilia, Libellula fulva, Orthetrum albistylum and Leucorrhinia pectoralis. Territorial males of E. najas were found among others in untypical habitat: the zone of the riverbank of Vistula. This can be explained as a mistake in choice of the habitat: males were fighting fiercely for patches of foam and plant debris floating on the water surface after the rising of the river which looked like the stems of Ceratophyllum sp. approaching the water surface. The initial inventory of the population of Nehalennia speciosa was taken specifying its numbers from a few to about 10000 specimens. It inhabits the raised bog “Długie Bagno”, regenerated after complete removal of peat about 90 years ago, with untypical of the habitats N. speciosa plant composition: without sedges, with dominating Eriophorum vaginatum and numerous Betula pubescens which died mostly after 2009 (according to the analysis of aerial photographs). This indicates the recent colonization of the raised peat bog or the fresh explosion of previously small population which inhabited not numerous, the wettest depressions. The numbers of N. speciosa were the highest in Eriophorum vaginatum-Sphagnum fallax: the number of imagines in two areas with this plant community was estimated at 1800-1900 individuals. Together with Erythromma viridulum and Gomphus flavipes in the Kampinoski National Park 51 dragonfly species have been recorded, nevertheless, at least a few next species are expected very likely to be found in the future. This is one of the richest in this respect Polish national parks. It is an important “hot spot” of the species richness of dragonflies, especially for Central Poland, including relatively faunistically poor Mazowsze region. This is all the more interesting that the Kampinoski National Park is poor in surface waters (0.4% of the area) – however, they are habitually diversified, situated in compact forest complex, and the lack of some natural habitats is compensated by anthropogenic waters. However, the role of the discussed park in protection of rare and endangered species is small.
Chapter
Anthropogenic changes to inland waters have significantly affected an estimated >83% of land surface surrounding aquatic systems.
Chapter
In this chapter we show that tabanid flies are attracted to horizontally polarized light stimulating their ventral eye region. Female and male tabanids use this polarotaxis governed by the horizontal E-vector to find water, while another type of polarotaxis based on the degree of polarization serves host finding by female tabanids. We show that female tabanids are less attracted to bright than dark hosts, the reason for which is partly that dark hosts reflect light with higher degrees of polarization than bright hosts. We also demonstrate that the use of a striped fur pattern has the advantage that such coat patterns attract far fewer tabanids than either homogeneous black, brown, grey or white equivalents. The attractiveness of striped patterns to tabanids is also reduced if only polarization modulations (parallel stripes with alternating orthogonal directions of polarization) occur in homogeneous grey surfaces. The attractiveness to tabanids decreases with decreasing stripe width, and stripes below a certain width threshold are unattractive at all to tabanids. Further, the stripe widths of zebra coats fall in a range where the striped pattern is most unattractive to tabanids. Tabanids are strongly attracted by CO2 and ammonia emitted by their hosts. We show here that the poor visual attractivity of stripes to tabanids is not overcome by olfactory attractiveness. Finally, we show that dark spots on a bright coat surface also disrupt the visual attractiveness to tabanids. The smaller and the more numerous the spots, the less attractive the host is to tabanids. The attractiveness of spotty patterns to tabanids is also reduced if the target exhibits spottiness only in the angle of polarization pattern, while being homogeneous grey with a constant high degree of polarization. This could be one of the possible evolutionary benefits that explains why spotty coat patterns are so widespread in mammals, especially in ungulates, many species of which are tabanid hosts.
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Animals must anticipate future conditions according to current environmental clues. When habitats are rapidly modified, these signs may not reflect the actual environmental quality, leading to a decreased fitness of an individual and its population. During an activity of faunal rescue and scaring away in the coast of Rio Grande do Norte, Brazil, evidence of an ecological trap for the lizard Cnemidophorus ocellifer was observed. We suggest some actions which can minimize the impact of vegetation removal activities on lizards, such as: i) better planning before proceeding with deforestation; and ii) capture and release of lizards in appropriate locations.
Article
The flying individuals of tabanids, similarly to other water-related and aquatic insects, detect water by the horizontally polarized light reflected from the water surface. The positive polarotaxis (i.e. the attraction to horizontally polarized light) of tabanids, discovered in 2008, made it possible to develop new tabanid traps based on reflected light polarization. The recent results on the polarotactic behaviour of tabanids, such as evidences for polarotactic host detection, contributed to the design of polarization tabanid traps. Furthermore, they made it possible to answer the old questions: What benefits the striped or spotted patterns of mammal coats do have? In this work we give a short summary about the most recent results in this topic.
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The waste oil lake in Budapest (Hungary) deceived, attracted and killed insects in large numbers and acted as a huge insect trap for 50 years from 1951. From August, 1997 to September, 1998 we observed and collected certain typical insects trapped by the oil. An estimate was made of numbers of insects associated with water of different groups identified in the 3000 m3 of the waste oil lake. Many insects associated with water (e.g., aquatic insects, insects living on moist substrata, dragonflies and mayflies) find their aquatic habitat by means of polarotaxis, that is, on the basis of the horizontally polarized light reflected from the water surface. We measured the reflection-polarization characteristics of the surface of the waste oil lake through time. In warm weather the surface of the oil was flat, shiny and acted as an efficient reflector and polarizer, like a water surface. Then the shiny oil surface occurred as an exaggerated, attractive water surface offering a supernormal optical stimulus to flying, polarotactic water-seeking insects. In cool or cold weather, however, the surface became dull, matt, or even wrinkled and lost its polarization and attractiveness to polarotactic insects. To investigate how dragonflies behave at the waste oil lake, and how they are entrapped by the oil, and what is their behaviour like prior to the moment of entrapping, we observed the typical water-specific behaviour of dragonflies at the oil surface. To study the visual ecological impact of the huge shiny black or white plastic sheets used in agriculture, we performed dual-choice field experiments with certain insects associated with water. We laid a shiny black and a shiny white plastic sheet onto the ground and observed the attracted insects and their behaviour. The measured and calculated reflection-polarization characteristics of these plastic sheets are also presented. Finally, some environmental protective and animal welfare arrangements are suggested that should be taken urgently in the vicinity of the habitats and biotopes of insects associated with water in order to eliminate the dangerous visual attractiveness of any open-air oil reservoirs and tar, asphalt or plastic surfaces to these insects.
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Dragonflies of the genus Sympetrum have compound eyes conspicuously divided into dorsal and ventral regions. Using anatomical, optical, electrophysiological, in-vivo photochemical and microspectrophotometrical methods, we have investigated the design and physiology of the dorsal part which is characterized by a pale yellow-orange screening pigment and extremely large facets. The upper part of the yellow dorsal region is a pronounced fovea with interommatidial angles approaching 0.3, contrasting to the much larger values of 1.5–2 in the rest of the eye. The dorsal eye part is exclusively sensitive to short wavelengths (below 520 nm). It contains predominantly blue-receptors with a sensitivity maximum at 420 nm, and a smaller amount of UV-receptors. The metarhodopsin of the blue-receptors absorbs maximally at 535 nm. The yellow screening pigment transmits longwavelength light (cut-on 580 nm), which increases the conversion rate from metarhodopsin to rhodopsin (see Fig. 11a). We demonstrate that because of the yellow pigment screen nearly all of the photopigment is in the rhodopsin state under natural conditions, thus maximizing sensitivity. Theoretical considerations show that the extremely long rhabdoms (1.1 mm) in the dorsal fovea are motivated for absorption reasons alone. A surprising consequence of the long rhabdoms is that the sensitivity gain, caused by pumping photopigment into the rhodopsin state, is small. To explain this puzzling fact we present arguments for a mechanism producing a gradient of rhodopsin concentration along the rhabdom, which would minimize saturation of transduction units, and hence improve the signal-to-noise ratio at high intensities. The latter is of special importance for the short integration time and high contrast sensitivity these animals need for spotting small prey at long distances.
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We reveal here the visual ecological reasons for the phenomenon that aquatic insects often land on red, black and dark-coloured cars. Monitoring the numbers of aquatic beetles and bugs attracted to shiny black, white, red and yellow horizontal plastic sheets, we found that red and black reflectors are equally highly attractive to water insects, while yellow and white reflectors are unattractive. The reflection-polarization patterns of black, white, red and yellow cars were measured in the red, green and blue parts of the spectrum. In the blue and green, the degree of linear polarization p of light reflected from red and black cars is high and the direction of polarization of light reflected from red and black car roofs, bonnets and boots is nearly horizontal. Thus, the horizontal surfaces of red and black cars are highly attractive to red-blind polarotactic water insects. The p of light reflected from the horizontal surfaces of yellow and white cars is low and its direction of polarization is usually not horizontal. Consequently, yellow and white cars are unattractive to polarotactic water insects. The visual deception of aquatic insects by cars can be explained solely by the reflection-polarizational characteristics of the car paintwork.
Article
The reflection-polarization patterns of small freshwater habitats under clear skies can be recorded by video polarimetry in the red, green and blue ranges of the spectrum. In this paper, the simple technique of rotating-analyzer video polarimetry is described and its advantages and disadvantages are discussed. It is shown that the polarization patterns of small water bodies are very variable in the different spectral ranges depending on the illumination conditions. Under clear skies and in the visible range of the spectrum, fiat water surfaces reflecting light from the sky are most strongly polarized in the blue range. Under an overcast sky radiating diffuse white light, small freshwater habitats are characterized by a high level of horizontal polarization at or near the Brewster angle in all spectral ranges except that in which the contribution of subsurface reflection is large. In a given spectral range and at a given angle of view, the direction of polarization is horizontal if the light mirrored from the surface dominates and vertical if the light returning from the subsurface regions dominates. The greater the degree of dominance, the higher the net degree of polarization, the theoretical maximum value being 100% at the Brewster angle for the horizontal E-vector component and approximately 30% at fiat viewing angles for the vertical E-vector component. We have made video polarimetric measurements of differently coloured fruits and vegetables to demonstrate that polarized light in nature follows this general rule. The consequences of the reflection-polarization patterns of small bodies of water for water detection by polarization-sensitive aquatic insects are discussed.
Article
By Gabor Horvath and Dezso Varju Springer-Verlag (2004) pp. 447. ISBN 3-540-40457-0 £ 138.50 (hbk) ![Figure][1] Polarisation is widely regarded as difficult, obscure and, in any case, unimportant, yet nearly all of the natural light we see is partially
Article
1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood. 2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid-morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid-morning; (ii) in the evening; (iii) both in mid-morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic. 3. We found experimental evidence that the proportion (%) P(θ) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (θ) for dark reflectors while P(θ) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies. 4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(θ) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations θ. The θ-dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid-morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun-dial’ of dispersing aquatic insects.
Article
SUMMARY 1. Based on the findings that some dragonflies prefer either ‘dark’ or ‘bright’ water (as perceived by the human eye viewing downwards perpendicularly to the water surface), while others choose both types of water bodies in which to lay their eggs, the question arises: How can dragonflies distinguish a bright from a dark pond from far away, before they get sufficiently close to see it is bright or dark? 2. Our hypothesis is that certain dragonfly species may select their preferred breeding sites from a distance on the basis of the polarisation of reflected light. Is it that waters viewed from a distance can be classified on the basis of the polarisation of reflected light? 3. Therefore we measured, at an angle of view of 20° from the horizontal, the reflection-polarisation characteristics of several ponds differing in brightness and in their dragonfly fauna. 4. We show that from a distance, at which the angle of view is 20° from the horizontal, dark water bodies cannot be distinguished from bright ones on the basis of the intensity or the angle of polarisation of reflected light. At a similar angle of view, however, dark waters reflect light with a significantly higher degree of linear polarisation than bright waters in any range of the spectrum and in any direction of view with respect to the sun. 5. Thus, the degree of polarisation of reflected light may be a visual cue for the polarisation-sensitive dragonflies to distinguish dark and bright water bodies from far away. Future experimental studies should prove if dragonflies do indeed use this cue for habitat selection.
Article
Light polarized by reflection was tested in the field for its attractiveness to flying insects. Attracted insects include bugs: some living in water (Corixidae, Notonectidae, Pleidae), others living on its surface (Gerridae) or near it (Saldidae). Beetles were also attracted: some are aquatic (Hydrophilinae, Dytiscidae, Haliplidae, Hydraenidae), others inhabit moist substrates (Sphaeridiinae). Also included are Chironomidae among other nematocerans. Non-polarized reflected light failed to attract any of these insects even at intensities far higher.Three response groups emerge. One is attracted whenever the degree of polarization is high in the UV-range, irrespectively of the degree of polarization in other wavelength ranges, and irrespectively of colour or brightness of the background beneath the polarizing, reflecting surface. The polarization vision of these insects operates in the UV-range. Another group was attracted only by the reflecting surface over a dark background, where the reflected light was highly polarized at all wave-lengths visible to insects. The third group ranges in between.Some Helophorus species behave in spring like members of the first group; in fall, like members of the second group.The distribution of the above response groups within various taxa is provided. Sensory mechanisms and eco-physiological implications are discussed.
Article
Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become ‘trapped’ by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid ‘trapping’ them.
Article
The reflection-polarization patterns of small freshwater habitats under clear skies can be recorded by video polarimetry in the red, green and blue ranges of the spectrum. In this paper, the simple technique of rotating-analyzer video polarimetry is described and its advantages and disadvantages are discussed. It is shown that the polarization patterns of small water bodies are very variable in the different spectral ranges depending on the illumination conditions. Under clear skies and in the visible range of the spectrum, flat water surfaces reflecting light from the sky are most strongly polarized in the blue range. Under an overcast sky radiating diffuse white light, small freshwater habitats are characterized by a high level of horizontal polarization at or near the Brewster angle in all spectral ranges except that in which the contribution of subsurface reflection is large. In a given spectral range and at a given angle of view, the direction of polarization is horizontal if the light mirrored from the surface dominates and vertical if the light returning from the subsurface regions dominates. The greater the degree of dominance, the higher the net degree of polarization, the theoretical maximum value being 100 % at the Brewster angle for the horizontal E-vector component and approximately 30 % at flat viewing angles for the vertical E-vector component. We have made video polarimetric measurements of differently coloured fruits and vegetables to demonstrate that polarized light in nature follows this general rule. The consequences of the reflection-polarization patterns of small bodies of water for water detection by polarization-sensitive aquatic insects are discussed.
Polarized Light in Animal Vision – Polarization Patterns in Nature Kuwait oil lakes as insect traps
  • G Horvá
  • D Varjú
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Notes and observations
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Paine A. (1992) Notes and observations. Journal of the British Dragonfly Society, 8, 14–18.
Libellenbeobachtungen in der umgebung von Karlsruhe (Baden) Beiträ zur naturkundlichen Forschung in Sü dwest-Deutschland
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Jagderfolg und Jagdtaktik bei Sympetrum striolatum (Charpentier) (Ansiptera: Libellulidae)
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Male Sympetrum striolatum 'defends' a basking spot rather than a particular locality (Anisoptera: Libellulidae) Notulae odonatologicae
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Visual cues in oviposition site selection of Somatochlora arctica (Zetterstedt ) (Anisoptera: Corduliidae)
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