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Abstract
This chapter introduces the insect order Odonata. It provides the most recent phylogeny and up-to-date systematics as well as genera and species numbers of the various families in the biogeographic regions. We also present an overview about the general biology, ecology and behavior of Odonata. This includes details on morphology and ultrastructures. We also attempt an updated categorization of odonate life cycle types. The subchapters on ecology and behavior focus on various aspects of habitat selection and microhabitat occupancy, including effects of biotic interactions and antipredation behavior. Finally, we summarize collection and sampling methods for adult and larval Odonata.
... These semivoltine taxa reside in cold to cool environments (see Table 1) where larvae may reach the final (F-0) instar stage by the end of summer but do not emerge as adults until the following year (Suhling, Sahlén, et al., 2015). For these taxa, larval diapause provides a mechanism to ensure overwinter survival, followed by spring metamorphosis and emergence. ...
... The strongest negative associations between PHOTO and DOY were exhibited by genera with semivoltine life cycles and cool to cold thermal preferences (Calopteryx sp., Hetaerina sp.), while positive associations were exhibited by univoltine genera with warm to hot preferences (Argia sp., Sympetrum sp., Plathemis sp.; see Table 1; Figure 4). This functional distinction is intuitive because photoperiod is a key predictor of diapause and as mentioned above, diapause is common to many odonate life cycles (Suhling, Sahlén, et al., 2015). For odonates with Type 1 life cycles, longer days (increasing photoperiod) may allow larvae to reach a mid to late instar stage prior to winter diapause, with rapid development and emergence the following spring (Corbett, 2003). ...
... We propose that aquatic habitat stability may provide a useful lens for understanding phenological responses to precipitation. Because odonates at temperate latitudes are rarely multivoltine (Suhling, Sahlén, et al., 2015), they will be vulnerable to any hydrologic disturbance that disrupts egg or larval development. Relevant disturbances would include intermittent drying in low precipitation regions or flooding in high precipitation regions. ...
Global change may cause widespread phenological shifts. But knowledge of the extent and generality of these shifts is limited by the availability of phenological records with sufficiently large spatiotemporal extents. Using North American odonates (damselflies and dragonflies) as a model system, we show how a combination of natural history museum and community science collections, beginning in 1901 and extending through 2020, can be leveraged to better understand phenology.
We begin with an analysis of odonate functional traits. Principal coordinate analysis is used to place odonate genera within a three‐dimensional trait ordination. From this, we identify seven distinct functional groups and select a single odonate genus to represent each group. Next, we pair the odonate records with a list of environmental covariates, including air temperature and degree days, photoperiod, precipitation, latitude and elevation. An iterative subsampling process is then used to mitigate spatiotemporal sampling bias within the odonate dataset. Finally, we use path analysis to quantify the direct effects of degree days, photoperiod and precipitation on odonate emergence timing, while accounting for indirect effects of latitude, elevation and year.
Path models showed that degree days, photoperiod and precipitation each have a significant influence on odonate emergence timing, but degree days have the largest overall effect. Notably, the effect that each covariate has on emergence timing varied among functional groups, with positive relationships observed for some group representatives and negative relationships observed for others. For instance, Calopteryx sp. emerged earlier as degree days increased, while Sympetrum sp. emerged later.
Previous studies have linked odonate emergence timing to temperature, photoperiod or precipitation. By using natural history museum and community science data to simultaneously examine all three influences, we show that systems‐level understanding of odonate phenology may now be possible.
... Worldwide there exist about 6000 species (Stork 2018: 5899; another 1000 to 1500 species are expected to exist per Pessaq et al. 2018) of Odonata which comprise the three suborders Zygoptera (damselflies), Anisoptera (dragonflies), and Anisozygoptera (damsel dragons) (Suhling et al. 2015;Morse 2017;St. Quentin and Beier 1968). ...
... In addition predators of Odonata larvae, their prey, and their various defense mechanisms against opponents are well known in spite of the fact that there was not realized any chemical defense mechanism in larvae or adults of this insect order (Corbet 1999;Suhling et al. 2015). The risk of fish predation is reduced by various behavioral and morphological features of the odonate larvae. ...
... As was shown by Crespo (2011), larvae of Odonata can sense infochemicals from various predators and even learn to associate them with predator presence. Invertebrate predators include other Odonata larvae including conspecifics (cannibalism), dytiscid beetles (larvae and adults), crayfish, belostomatid bugs, and several water birds (see Suhling et al. 2015). Other larvae exhibit nocturnal circadian rhythms in order to reduce predation pressure (Pierce 1988). ...
This chapter compiles active and passive defensive mechanisms of aquatic and semiaquatic developmental stages of all insect orders against various predators. Mainly escape reactions, mechanical defense, defensive stridulation, and especially chemical defenses are described, illustrated, and tabulated. Apart from the large aquatic groups of ephemeropteran, Odonata or Trichoptera larvae especially aquatic bugs and water beetles are considered by even including small groups from Collembola up to Mecoptera. Differences between defensive mechanisms and strategies in aquatic and terrestrial insects are described. Aquatic insects especially rely on escape, mechanical defenses, defensive stridulation, and chemical defenses. Exocrine glands are mainly restricted to large taxa with both terrestrial and aquatic representatives (adephagan beetles, Heteroptera) and not invented in aquatic groups. Chemically aquatic insects especially evolved biosynthesis of aromatic and few aliphatic compounds against microorganisms. In contrast mainly steroids are targeted against cold-blooded vertebrates such as fishes and amphibians. As compared with terrestrial insects, aquatic representatives lack many mechanisms of defense such as reflex bleeding, incorporation of toxic compounds from plants, freshwater animals, or microorganisms. Exocrine secretions of water insects are usually externalized by secretion grooming in order to receive a clean body surface, to achieve an optimal breathing, and to modify the wettability of the body surface. Generally there exists a considerable lack of knowledge concerning bionomy and especially defenses of aquatic insects.
... However, in some cases, their identification may be complicated (e.g. females of Coenagrionidae), and their presence close to water is only temporary as they disperse to terrestrial surroundings until sexually mature (Wildermuth, 2010;Suhling et al., 2015). Nevertheless, based on our data, we may conclude that the primary question is not what to sample but the purpose of that sampling. ...
... Although odonate exuviae and juveniles are evidence for species indigeneity, drawing conclusions based on their sampling may lead to considerable bias. In most cases, the mature adult life span exceeds the emergence period as well as the length of the juvenile period (Suhling et al., 2015). Therefore, in a long-term study with visits realised only several times per season, the probability of species' detection would be highest when focusing on adults. ...
• Most ecological studies involving insects are based on medium‐ and short‐term observations; however, the extent to which such data captures reality remains unclear.
• We investigated the long‐term dynamics of two Odonata communities (disturbed and undisturbed sites) over 18 years and analysed the differences in the short‐ and long‐term results. We also focused on the sampling methodology to enhance the efficacy and objectivity of long‐term monitoring involving Odonata.
• During one year, we captured only 53% of the overall species richness; during three consecutive sampling years, it was 65%. To capture 95%, we needed 16 years. Changes in quantitative similarity (Renkonen index, P) were more pronounced within sites over time than between sites. Species constancy significantly increased with the maximum abundance class but decreased with increasing fluctuation ratio and specialisation (Dragonfly Biotic Index). Based on exuviae, we detected half of the species compared to adults, but the species accumulation curves peaked after a few sampling years.
• Long‐ and short‐term monitoring yield different results, both qualitatively (species richness, specialisation) and quantitatively (abundance, dominance). Ideal sampling should be sequential, lasting at least 10 years (capturing >80% of species). Intermittent sampling (one‐year interspersed with pauses), allowing the inclusion of multiple sites in monitoring programme, may also provide satisfactory results when performed over a longer period.
• Over the long term, sampling adults semi‐quantitatively and exuviae qualitatively provided sufficient information, while being feasible in terms of both personnel and costs, thereby overcoming the main pitfalls of long‐term monitoring programmes.
... Odonates occur in streams in their immature stages, and they are important representatives of the trophic structure in these ecosystems due to their predatory feeding mode (Corbet, 2004). Immature stages of odonates have a diverse range of life habits and ecological requirements, thus the assemblage structure of immature odonates is influenced by several habitat characteristics, such as water current, water abiotic conditions and microhabitat type (Hofmann & Mason, 2005;Suhling et al., 2015). The sensitiveness of the immature stages of Odonata foi testada através de diagramas de ordenação e análise de redundância. ...
... The differential occupation of stream habitats by odonates is generally associated with their relationships with the aquatic vegetation and water flow regime (Corbet, 2004). The immature stages of odonate species that usually prefer either stronger or depositional areas in streams show large differences in the morphology and life habits associated with the adaptation to water current variation (Corbet, 2004;Suhling et al., 2015). In this study, Argia, Heteragrion and Calopterygidae showed preference by riffles. ...
Aim
Describe the diversity of immature stages of Odonata (Insecta) in streams from a subtropical island in southern Brazil and investigate the influence of environmental variables on the composition of their assemblages.
Methods
Eleven low-order streams (1st to 3rd order) were sampled in two conservation units located in the island of Santa Catarina (southern Brazil) between 2010 and 2012. Immature specimens of Odonata were collected using a Surber sampler. The influence of water abiotic parameters and habitat structure (mesohabitats: riffle vs. pool areas, microhabitats: litter vs. stone substrates) on the composition of Odonata was tested through the seasons using ordination diagrams and redundancy analysis.
Results
Nine odonate genera from seven families were recorded in the study region. The genera Desmogomphus, Epigomphus (Gomphidae), Heteragrion (Heteragrionidae) and Perilestes (Perilestidae) have their first records described for the state of Santa Catarina. Additionally, biological notes are provided for other odonate genera concerning substrate use. The composition of Odonata communities changed over the seasons and they were influenced by water temperature and velocity. Additionally, odonate composition differed significantly between microhabitats (substrate type) and mesohabitats (riffle vs. pool areas) in the streams studied.
Conclusions
The lower genera richness of Odonata recorded in the island of Santa Catarina in relation to other Brazilian subtropical streams is probably associated with the insular condition of the study region. This study also demonstrated that substrate (organic and inorganic) and mesohabitat (riffle and pool) types were important drivers of the composition of the fauna of immature odonates, evidencing the role of climate and habitat structure in influencing subtropical stream insect communities.
... The order Odonata is regarded as a monophyletic group; it comprises three suborders: Zygoptera or damselflies, Anisoptera or true dragonflies and a small suborder Anisozygoptera with four species (Suhling et al. 2015). Odonata has a tropical origin (Corbet 1999), and today the highest diversity is found near the equatorial areas (Paulson 2006 and a larger pterothorax where the wings are inserted. ...
... Water extraction is a primary threat to desert springs, but invasions by non-native species also pose serious threats . These threats are the main factors of the decline of odonate populations (Suhling et al. 2015) and therefore the main threats to the species that occur in the CCB. ...
In this chapter we review some of the main characteristics of the Cuatro Ciénegas Basin, touching upon the physical setting, its geologic history, and animal diversity. We go through all the chapters of the volume summarizing the different interpretations of the authors regarding the origin and structuring of the particular communities. We present a list of animal taxa that have been recorded from the area, noting the number of species and supraspecific taxa that are endemic to the CCB: a total of 885 species are reported for the CCB in this volume, of which 38 (4.3%) are endemic. A brief discussion on the future challenges that the CCB faces is presented.
... The order Odonata is regarded as a monophyletic group; it comprises three suborders: Zygoptera or damselflies, Anisoptera or true dragonflies and a small suborder Anisozygoptera with four species (Suhling et al. 2015). Odonata has a tropical origin (Corbet 1999), and today the highest diversity is found near the equatorial areas (Paulson 2006). ...
... Water extraction is a primary threat to desert springs, but invasions by non-native species also pose serious threats (Hendrickson et al. 2008). These threats are the main factors of the decline of odonate populations (Suhling et al. 2015) and therefore the main threats to the species that occur in the CCB. ...
A summary of the present knowledge on the diversity of Odonata occurring in the Cuatro Ciénegas Basin (CCB) is presented. The work is based on published records, and the results from samplings are carried out between the years 2009 and 2013 in 23 sites. A list of the 67 Odonata species from the CCB is provided including 19 new state records. Finally, the biogeographic affinities, conservation status, and major threats are discussed.
... The order Odonata is regarded as a monophyletic group; it comprises three suborders: Zygoptera or damselflies, Anisoptera or true dragonflies and a small suborder Anisozygoptera with four species (Suhling et al. 2015). Odonata has a tropical origin (Corbet 1999), and today the highest diversity is found near the equatorial areas (Paulson 2006 and a larger pterothorax where the wings are inserted. ...
... Water extraction is a primary threat to desert springs, but invasions by non-native species also pose serious threats . These threats are the main factors of the decline of odonate populations (Suhling et al. 2015) and therefore the main threats to the species that occur in the CCB. ...
Soil is one of the less studied resources of terrestrial ecosystems, both in terms of its biodiversity and internal processes. In particular, microarthropods of desert ecosystems have been poorly studied worldwide, and probably less than 10% of the total soil species have been described. Nevertheless, microarthropods are responsible for one of the most important environmental functions: the decomposition of organic matter. In this chapter, we present the results of the first survey of soil microarthropod communities from the CCB. The study was conducted in 2015–2016 to identify the microarthropods’ diversity in its components of richness and abundance. We collected 6721 organisms of 6 classes, 26 orders, and 60 families. Acari was the most abundant and diverse group and is dominated by Prostigmata (20 families) and Oribatida (16 families). Hexapoda is represented by Collembola, Coleoptera, Hemiptera, Hymenoptera, and Psocoptera. Differences in mite assemblages are attributable to the type of vegetation in the different sites of the CCB. The site’s taxonomic diversity is associated with habitat heterogeneity. The high productivity micro-habitats could produce high levels of biomass and not necessarily more diverse communities. We observed broad similarities in microarthropod composition at familial level among arid-semiarid ecosystems elsewhere in the world. Knowledge of soil microarthropod community will be helpful to understand the network of interactions and the flow of nutrients and energy within this desert ecosystem; all these are crucial elements to assess the health of the soil and to establish appropriate strategies for it use, management, and conservation.
... Therefore, the simple ratio of Zygoptera/Anisoptera may be too robust to detect more subtle differences within individual taxa. Specifically, the two largest families Coenagrionidae (Zygoptera) and Libellulidae (Anisoptera) include species with the greatest migratory capacity which dominate in open, unshaded habitats Suhling et al., 2015), suggesting their affinity with highly disturbed sites. ...
... Although the proportion of forest specialists may correlate with the proportion of Zygoptera (Dolný et al., 2012), the largest cosmopolitan family of Zygoptera, Coenagrionidae, is known to contain most of the most widespread or ubiquitous odonate species. The same applies to Libellulidae Suhling et al., 2015). Considering that these two groups comprised a large portion of our dataset (41% and 79%, respectively), it is clear that the family-level approach is more accurate and thus, may serve a fast assessment of forest degradation level better. ...
Odonata have proven to be good indicators of freshwater as well as terrestrial habitat conditions. Several studies have shown changes in odonate species richness and/or community composition in response to deforestation, suggesting their potential as bioassessment tools in the tropics. However, former approaches using Odonata as an indicator group required comparative samples from differently disturbed sites and/or knowledge of the focal species environmental specificity. Here, we tested a robust, adult-based bioassessment method assuming that the level of tropical forest degradation reflects the proportional representation of the taxa above species. Based on Web of Science, ScienceDirect, and Scopus databases, we used data from previously published studies linking odonate assemblages to human-mediated disturbances in tropical forests. We hypothesized that along a disturbance gradient (from primary forest to non-forest), (i)the proportion of the suborder Zygoptera (mostly habitat specialists sensitive to deforestation)will decrease in favor of the suborder Anisoptera (high proportion of generalists); and (ii)the proportions of largely generalist families Coenagrionidae and Libellulidae will increase at the expense of other Zygoptera and Anisoptera, respectively. Our results revealed that a ratio of Zygoptera/Anisoptera is a poor indicator of tropical forest conditions, probably because of ecological diversity within these groups. However, the proportions of Coenagrionidae/other Zygoptera and Libellulidae/other Anisoptera significantly increased along a disturbance gradient, suggesting their potential to be a good indicator of well-preserved, altered, and heavily degraded forest habitats. Therefore, our results are in line with studies presenting the usefulness of adult Odonata as versatile indicators for assessing human-mediated changes in tropical forest environments, supporting the practical use of this group in biological monitoring.
... These are more prolific due to their requirements in terms of temperature, oxygen concentration in water, etc., that are less restrictive. Many of these taxa, particularly Odonata that inhabit seasonal streams, use to show a preference for slow flowing waters typical of many Mediterranean seasonal streams of mid to low order, or at least of some microhabitats found in them, such as pools in the shores (Suhling et al. 2015). Perlodidae are also frequent in permanent streams, where they can coexist with Perlidae which, under these conditions, probably act as top predator relegating Perlodidae to a lower trophic level. ...
... When considering both prey and non-animal matter, the five studied taxa show a relatively high niche breadth, supporting their previously mentioned generalist habits (Stewart & Stark 2002, Askew 2004. Broadly, Odonata nymphs feed on all kinds of prey they can overcome (even from their same species under certain conditions, van Buskirk 1989), and the type of prey depends more on the habitat of the nymph (Suhling et al. 2015). In our study, this generalist behaviour is also found when including non-animal matter. ...
– In the present article, we show the results of a study carried out in a seasonal stream where several taxa of Plecoptera and Odonata coexist. We analyzed the diet of selected top predators within these macroinvertebrate groups during a whole hydrological year and we studied the possible variations of diet with size. Moreover, we quantified their niche breadth and diet overlap. The results show that only in two taxa, one stonefly and one dragonfly, ontogenetic shifts in diet occur. The stonefly (isoperla morenica) reduces its intake of animal matter with size and the dragonfly (onychogomphus forcipatus) increases it. From a trophic niche point of view, all the studied taxa show a relatively narrow niche considering only prey (discarding non-animal resources), and a high niche overlap. This could lead to competition among them, but the fact that they are coexisting in this relatively adverse environment suggests that this is not the case and that prey are not limiting. © 2018 Universite de Paris VI (Pierre et Marie Curie). All rights reserved.
... Two Odonata families, Coenagrionidae and Libellulidae have the largest number of damselfly and dragonfly generalists respectively (Kalkman et al., 2008;Suhling et al., 2015). It is therefore worth assessing the proportion of odonates of these families in relation to those of other families such as the Gomphidae and Aeshnidae which comprise species that prefer cleaner and less disturbed habitats and are sensitive to changes in habitats (Dijkstra & Clausnitzer, 2014;Siregar, 2006). ...
Urbanisation continues to increase at an alarming rate and its effects on the natural environment are very profound now more than ever. Moreover, studies on terrestrial urban landscapes seems to be more than that on urban freshwater habitats. Furthermore, studies have shown that the Odonata are effective indicators of the effects of urbanisation on freshwater habitats. However, not much is known about their responses to urbanisation in sub‐Saharan Africa, especially given the unique set of conditions that characterise the area. Therefore, this study was conducted to investigate differences in Odonata responses, measured as the proportion of habitat generalists, to three levels of habitat disturbance in the Cape Coast Metropolis of Ghana. Results showed that Phaon camerunensis was a potential indicator of habitat disturbance. Also, differences in habitat disturbance significantly affected Odonata composition. The most important variables that influenced Odonata responses were the individual and interaction effects of altitude and preservation of riparian vegetation. Therefore, conservation strategies that are targeted at reducing the impacts of urbanisation on Odonata must focus on these variables.
... The order Odonata (dragonflies and damselflies) contains more than 6300 described species (Schorr & Paulson, 2021). The estimated number of extant species varies from 7000 to 7500, suggesting that about 10%-20% of species diversity is still unknown (Suhling et al., 2015). Odonates can be good bioindicators of environmental quality disturbance. ...
The use of mitochondrial markers for taxonomic identification and biodiversity monitoring is not without risks or limitations. Most importantly, the natural transfer of DNA from the mitochondria to the nucleus generates nonfunctional nuclear copies of mitochondrial DNA (NUMTs). Their abundance and size vary significantly among taxa, and NUMTs have been reported to complicate molecular studies based on mitochondrial markers in several insect orders, most prominently in Orthoptera. The significance of this phenomenon in Odonata has not yet been properly addressed. Here, we present a complete mitochondrial genome and a draft nuclear genome of Leucorrhinia albifrons (Odonata: Libellulidae), as well as NUMT and cox1 sequences from the related species Leucorrhinia dubia. We document the presence of NUMTs in the L. albifrons nuclear genome and in nuclear genomes of two other Odonata species available in public databases. Our results show that NUMTs can have a serious impact on barcoding, phylogenetic, population and phylogeographic studies of Odonata, especially when the barcode is located in the cox1 gene, the most frequently used molecular marker for Odonata. We suggest that nad1 should be used alone or in combination with cox1 to minimize unintended confusion with NUMTs. Finally, we present a mitophylogenomic analysis of Odonata and document several cases of misidentified mitochondrial genomes belonging to species different from those indicated in public databases. In conclusion, our findings represent an important step for future metabarcoding studies of Odonata based on mitochondrial DNA markers.
... Odonates are insects with aquatic nymphal development and terrestrial (aerial) adults [36]. While some rare dispersal events have been reported at the nymphal stage, the vast majority of the movements are performed by flying adults [37]. ...
Anthropogenic activities cause loss and fragmentation of natural habitats and have strong effects on population maintenance by increasing their isolation. Pond ecosystems are scattered waterbodies that can interact as a network connected by dispersal events of freshwater organisms. Identifying local genetic differentiations and understanding how gene flow occurs across these networks is essential to prevent risks associated with environmental perturbations. This study aimed to investigate genetic diversity and structure of Anax imperator Leach, 1815 populations at both regional and European scales using seven microsatellites markers. Seven populations of A. imperator were sampled in northwestern France and four populations were sampled in Italy (Sicily), Czech Republic, Switzerland and United Kingdom (U.K.). French populations presented a low genetic differentiation indicating a high gene flow and confirming dispersal events of this species between ponds at regional scale. No pattern of isolation by distance was found at the European scale. The populations presented a low genetic differentiation and no pattern of isolation by distance, suggesting historical or current movements of individuals. Only the U.K. population presented a significant genetic differentiation from other European populations, suggesting that the English Channel might act as a barrier to gene flow for A. imperator. However, Bayesian analysis showed that some dispersal events could occur between the U.K. and France (Normandy), probably facilitated by prevailing winds.
... The Dinaric Western Balkans area is characterized by an extremely complex hydrological network [41] and extraordinary diversity of biota [42], yet it is still greatly understudied. Although Odonata are considered to be among the well-studied aquatic insect orders [43], their ecological requirements in karst rivers and streams are very poorly known [22,44], especially in intermittent habitats. Therefore, the main objectives of this study were (i) to compare Odonata assemblages (species richness, diversity, and abundance) in two focal habitat types: macrophyte rich and macrophyte poor, in the Mediterranean intermittent karst rivers; (ii) to examine the functional diversity of Odonata assemblages and detect changes in functional traits; and (iii) to determine the main environmental drivers that shape these assemblages. ...
Assemblages of adult Odonata were studied in four intermittent karst rivers encompassing macrophyte-rich (MRH) and macrophyte-poor habitats (MPH) in southern Europe, where temporary lotic habitats are the predominant freshwater type but are still understudied. With a total of 25 recorded species, the studied habitats support species-rich Odonata assemblages, as already shown for intermittent rivers in the Mediterranean. Aquatic macrophyte abundance, conductivity, and water velocity are the most significant determinants of Odonata assemblages in the studied IRES. MRH promote higher Odonata abundance and the taxonomic and functional diversity of their assemblages compared to the MPH. Odonata assemblages in MRH are characterized by higher values of body size and a higher share of species preferring lentic and temporary hydrological conditions. Moreover, their assemblages are characterized by various patterns of nymphal development and drought resilience strategies. In contrast, MPH are preferred by lotic species, with nymphal development all year round and with no specific drought-resisting strategies. Our results contribute to the knowledge of diversity and ecological requirements of dragonflies and damselflies in IRES habitats, which could provide scientific background for future conservation activities and bioassessment protocols of such habitats and their biota.
... The differences in life habit and behavior usually lead to specific association and preference by substrate types among larval odonate taxa (Corbet, 2004). In view of the low mobility of the larval stage, most odonate taxa tend to avoid microhabitats with stronger flow in lotic environments (Corbet, 2004;Suhling et al., 2015). Stream flow is generally higher in microhabitats characterized by coarser particles such as stone and gravel, while litter substrates are characterized by areas accumulation and deposition of organic material, with reduced water flow (Lampert & Sommer, 2007;McCabe, 2011). ...
Aim
We assessed the influence of substrate type and categories of riparian vegetation widths on the community structure of Odonata (Insecta) in southern Brazilian streams.
Methods
Sampling took place in twelve stream reaches differing in their riparian vegetation widths (from more than 40 m up to less than 5 m). Larval odonates were collected in inorganic (stone and gravel) and organic (leaf litter) substrates at each stream reach. Differences in Odonata composition among substrates and categories of riparian vegetation width were tested using PERMANOVA and visualized with ordination diagrams. In addition, we assessed the influence of riparian vegetation width taking into account two levels of resolutions: fine (four categories: > 40 m, 30-15 m, 15-5 m and < 5 m) and coarse (narrower and broader than 15 m).
Results
Odonata composition differed more strongly according to substrate type regardless of the level of resolution. Organic substrate (litter) had different composition and higher richness than inorganic ones. Odonata composition significantly differed between riparian vegetation widths at the coarser level of resolution (narrower and broader than 15 m); at the coarser level, the interaction between substrate and riparian widths was significant, with the composition from litter substrate in broader widths differing from stone and gravel in narrower widths.
Conclusions
The composition of odonate larvae responded to the major reductions in riparian widths (above > 15 m), indicating that reductions above this level are enough to affect the community structure of Odonata. Additionally, the different composition of Odonata in organic substrates in broader riparian vegetation widths compared to inorganic substrates in narrower widths indicate a complex relationship between riparian vegetation and substrate in the assembly of insect communities in southern Brazilian forest streams. The interaction between riparian vegetation widths and substrate suggests that the effects of reductions in riparian widths on Odonata composition are not similar across substrate types.
... The choice of which group to use would depend on the specific question asked, and other considerations such as the amount of resources and personnel available, the time of year, time constraints, and level of taxonomic experience. Adult male Odonata are colourful, conspicuous and easy to locate at their riverside territories (Suhling et al., 2015;Moore and Martin, 2018). They are quick to sample, requiring only a net, and are easy to identify to species level with the use a field guide . ...
Biological surrogates in conservation biology are valuable for rapid biodiversity and environmental surveys, and as an early warning of potential threats. However, these surrogates need to be simple and inexpensive to apply. The umbrella index was applied here to quantify the selection of surrogate species for biodiversity assessments, but requires interrogation for application in areas rich in threatened endemic species. Aquatic larvae of Ephemeroptera, Plecoptera and Trichoptera (EPT), as well as the adult Odonata, are all highly responsive to changes in freshwater condition. Using the umbrella index, we evaluated the performance of the surrogate species approach for aquatic insect conservation in a region (Greater Cape Floristic Region) with an exceptional level of rare and endemic species, across multiple rivers with different disturbance levels. Due to a lack of species level information, EPT taxa were calculated using morphospecies within families, and Odonata were identified to species level. The umbrella index identified eight EPT species and seven Odonata species as potential sur-rogates. Both these groups co-occurred with high percentages of their own overall groups (EPT surrogates for overall EPT, and Odonata surrogates for overall Odonata), as well as for the other group (EPT surrogates for overall Odonata, and Odonata surrogates for overall EPT). The index was surprisingly flexible, and performed well in an area with so many species of conservation concern, as well as across spatial scales greater than a single river, with varying degrees of disturbance. Both EPT and Odonata showed promise as potential biodiversity surrogates, and for future conservation planning. Ideally, conservationists should aim to use taxa that are easy to identify to species level, with known sensitivities to human disturbance. However, when this is not a possibility, the umbrella index is still applicable and accurate for morphospecies (family level sensitivities).
... Damselflies and dragonflies (Order Odonata, hereafter dragonflies or odonates) are considered one of the oldest insect groups and occur in most regions of the world, especially in the tropics (Corbet & Brooks 2008). Almost all odonate larvae live in freshwater habitats, wheras the adults are terrestrial, often spending much time on the wing (Suhling et al. 2015). In both life stages they require specific physical and chemical conditions to survive and tend to react quickly to any alteration of their natural environment . ...
Compared to other archipelagos of the Pacific, the New Caledonian Odonata fauna is rich and diverse with 56 valid species or subspecies (23 endemics, 41%) from eight families (four Zygoptera: Argiolestidae, Coenagrionidae, Isostictidae, Lestidae, and four Anisoptera: Aeshnidae, Corduliidae, Synthemistidae, Libellulidae) and 31 genera (including four endemics, 13%). In Zygoptera, we record 19 species including 12 endemics (63%), and among Anisoptera, we record 37 species or subspecies, including 11 endemics (30%). We removed five species from the list that had been erroneously recorded as occurring in New Caledonia: Tramea carolina (Linnaeus, 1763), Austroargiolestes icteromelas (Selys-Longchamps, 1862), Ischnura torresiana Tillyard, 1913, Xiphiagrion cyanomelas Selys-Longchamps, 1876 and Hemicordulia oceanica Selys-Longchamps, 1871. The occurrence of Tramea limbata (Desjardins, 1835) appears also doubtful, but we were unable to clarify to which taxon this record referred hence we excluded it from our update. From a biogeographic perspective, the New Caledonian fauna has mostly Australian affinities with some connections with southeast Asia and the Pacific region. We provide for each species, whenever information was available, a distribution map with a brief review of its known ecology, behaviour and phenology. We also evaluated each species’ conservation status, in light of known threats (range restriction, scarcity and human activity including altered water flow). We consider seventeen species (30%) endangered. The most immediate threats concern water pollution including alteration to the flow of water courses caused by mining, deforestation and fires. Invasive species, such as alien fish, may be predators of concern for odonata larva, although this has not yet been proven in New Caledonia.
... Damselflies and dragonflies (Order Odonata, hereafter dragonflies or odonates) are considered one of the oldest insect groups and occur in most regions of the world, especially in the tropics (Corbet & Brooks 2008). Almost all odonate larvae live in freshwater habitats, wheras the adults are terrestrial, often spending much time on the wing (Suhling et al. 2015). In both life stages they require specific physical and chemical conditions to survive and tend to react quickly to any alteration of their natural environment . ...
Compared to other archipelagos of the Pacific, the New Caledonian Odonata fauna is rich and diverse with 56 valid species or subspecies (23 endemics, 41%) from eight families (four Zygoptera: Argiolestidae, Coenagrionidae, Isostictidae, Lestidae, and four Anisoptera: Aeshnidae, Corduliidae, Synthemistidae, Libellulidae) and 31 genera (including four endemics, 13%). In Zygoptera, we record 19 species including 12 endemics (63%), and among Anisoptera, we record 37 species or subspecies, including 11 endemics (30%). We removed five species from the list that had been erroneously recorded as occurring in New Caledonia: Tramea carolina (Linnaeus, 1763), Austroargiolestes icteromelas (Selys-Longchamps, 1862), Ischnura torresiana Tillyard, 1913, Xiphiagrion cyanomelas Selys-Longchamps, 1876 and Hemicordulia oceanica Selys-Longchamps, 1871. The occurrence of Tramea limbata (Desjardins, 1835) appears also doubtful, but we were unable to clarify to which taxon this record referred hence we excluded it from our update. From a biogeographic perspective, the New Caledonian fauna has mostly Australian affinities with some connections with southeast Asia and the Pacific region.
We provide for each species, whenever information was available, a distribution map with a brief review of its known ecology, behaviour and phenology. We also evaluated each species’ conservation status, in light of known threats (range restriction, scarcity and human activity including altered water flow). We consider seventeen species (30%) endangered.
The most immediate threats concern water pollution including alteration to the flow of water courses caused by mining, deforestation and fires. Invasive species, such as alien fish, may be predators of concern for odonata larva, although this has not yet been proven in New Caledonia.
... Extant dragonflies are widely used to study insect ecology, behaviour and biogeography (van Tol and Müller, 2003; van Tol et al., 2009;S anchez-Herrera and Ware, 2012;Suhling et al., 2015). The larvae (nymphs) mostly live in an aquatic environment, helping to reconstruct the past ecology (Zhang, 1999;Huang and Lin, 2001) and ancient behaviour can be recovered deduced from body structures (Zheng et al., 2017a). ...
Climate change is expected to exert a large impact on the spatial distribution of insects, yet limited analyses are available for assessing the influences of climate change on the distribution of Libellula angelina (Odonata: Libellulidae), which hindered the development of conservation strategies for this critically threatened dragonfly species. Here, a consensus model (BIOCLIM, GAM, MaxEnt and Random Forest) and niche analysis approach were applied to predict the dynamic change of potential distribution areas and ecological niche for L. angelina under future climate change. Meanwhile, the important environmental variables affecting the potential distribution of L. angelina were identified. The results demonstrated that the potential distribution pattern and ecological niche of L. angelina will not shift significantly in face of future climate change, but its highly suitable area in southern Beijing (China), the western and southern South Korea, and the southern Honshu Island (Japan) will decrease constantly. Further analyses indicated that the human influence index (23.8% of variation) is the highest factor in predicting the potential distribution of L. angelina, followed by the precipitation of warmest quarter (18.4% of variation). Based on the obtained results, we suggest that extensive cooperation among the countries (China, South Korea and Japan) be advocated to formulate the international conservation strategies, especially more attention and conservation efforts should be paid in those high-suitability areas of L. angelina to gain better protection efficiency, and proper artificial ecological restoration measures (e.g., creating suitable habitats, establishing additional natural wetlands, and raising citizens’ awareness) should also be exerted.
Implication for insect conservation: Our results indicate that there is no significant change in the location of the suitable habitat for L. angelina confronted with climate change, but the total area would constantly decrease due to human activities. Therefore, we should make more conservation efforts in those highly suitable areas, including Aosen and Hanshiqiao parks in China, Gangwon do and Doowoong parks in South Korea, and Chichibu Tama Kai and Ise-Shima parks in Japan, especially we should pay much attention to the anthropogenic impact such as human population and land use there.
Heterospecific interactions are an important phenomenon of animal epigamic behaviour; however, they remain understudied within important groups, such as insects. Dragonflies are an ideal group for research on interspecific mating and possible hybridisation as they are easily identifiable, large insects, with a conspicuous mating process, often striking territorial behaviour and several mating systems.
Using the genus Sympetrum as the model group, we examined heterospecific mating at three different levels. In the field, we identified whether species identity, time and weather affected heterospecific mating frequency. One important part of heterospecific mating is whether the process is completed. For dragonflies, this means that flying in tandem is followed by successful copulation, gamete fusion and oviposition (which comprise mating completeness). In a mesocosm experiment, we determined mating completeness (tandems, copulation, oviposition) of hetero‐ and homospecific pairs and the possible role of species density in heterospecific mating. In the laboratory, we compared the viability of the offspring from heterospecific pairs with different epigamous behaviour.
We found heterospecific mating to be a relatively common phenomenon unaffected by environmental variables, that was primarily influenced by species identity, temporal distribution and abundance of dragonfly species. Consequently, the presence of counterparts of other species is the main predictor of the frequency of heterospecific mating.
The probability of completed epigamic behaviour (copulation and subsequent oviposition) connected with gamete fusion is lower in heterospecific mating. Generally, based on our results we can assume that successful heterospecific mating (leading to gamete fusion) occurs in closely related species (e.g., Sympetrum striolatum and Sympetrum vulgatum ). However, as pre‐copulatory barriers are not strongly developed in some dragonfly groups, less closely related species (e.g., Sympetrum sanguineum and S. striolatum ) also may mate. This phenomenon requires further study as it may present a threat to the survival of some species in the context of changing environmental conditions, including climate change.
Run-of-river (ROR) power plants impound limited terrestrial areas compared to traditional hydropower plants with large reservoirs and are assumed to have reduced impacts on mercury cycling. We conducted a study on periphyton and benthic communities from different habitats of the St. Maurice River (Québec, Canada) affected by two ROR power plants and their effect on the bioaccumulation and biomagnification of monomethylmercury (MMHg). Proportion of total mercury as MMHg reached maximum values about 2.9 times higher in flooded sites compared to unflooded sites. Impoundment by ROR would therefore provide favorable environments for the growth of periphyton, which can produce and accumulate MMHg. Periphyton MMHg concentrations significantly explained concentrations in some benthic macroinvertebrates, reflecting a local transfer. Through the analysis of δ¹³C and δ¹⁵N signatures, we found that flooding, creating scattered lenthic habitats, led to modifications in trophic structures by the introduction of new organic matter sources. The computed trophic magnification slopes did not show significant differences in the transfer efficiency of MMHg between sectors, while intercepts of flooded sectors were higher. Increases in MMHg concentrations in flooded areas are likely due to the impoundment, combined with watershed disturbances, and the creation of small habitats favorable to periphyton should be included in future predictive models.
Sympetrum striolatum (Charpentier, 1840) and S. vulgatum (Linnaeus, 1758) are two closely related Libellulidae that are widespread and common in Central Europe. The idea for this research originates from normally using saltwater shrimps for rearing young larvae, the observations of Sympetrum species laying eggs in seawater and the suggested ability of S. striolatum to colonize brackish water habitats. This topic will also be of rising relevance for dragonfly populations as in the future due to climatic changes or anthropo-genic activity the salinization of freshwaters will likely increase. The experiments presented in this study served to find out whether eggs and larvae of both species can develop in brackish water. For this purpose, eggs of both species were kept at four different salinities from 0.5-1.5% and the development duration, hatching curves and growth rates as well as mortality were recorded and compared to respective data from an earlier experiment conducted in tap water. It was possible to investigate whether embryonic development, the hatching behaviour and larval growth are disturbed by different salinity levels compared to rearing in freshwater. We found for both species that the eggs can develop at different salt concentrations up to 1.5% and the larvae survive and grow in the brackish water. Especially for S. striolatum a slightly increased salinity even seems to be advantageous compared to rearing in tap water shown by high hatching and survival rates. The results of this study add some knowledge about the influencing effects of salt on both species. It seems that low salt concentrations seem to be well tolerated by both species or become even beneficial for S. striolatum. Furthermore, the results provide methodological aspects about the rearing of young dragonfly larvae.
Some structural characters, such as wing venation, have been used in odonates to differentiate taxa. In Cordulegaster boltonii, a species widely distributed throughout the western Palaearctic, the main characteristics of its wing venation have not been quantified until now. A six-variable analysis of wing venation (number of antenodal and postnodal cross-veins, number of cells in the anal triangle and in the anal loop) in specimens from several European countries was carried out. The results showed that: (a) females had a greater number of transversal veins and cells in the anal loop than males; (b) the values of these four variables were significantly lower in males from the Iberian Peninsula than in those from elsewhere; (c) within the Iberian Peninsula two groups of populations can be distinguished: one covers the north and the other the rest of the peninsula, the latter with two subgroups, one in the centre and one in the south and east. The number of cells in the anal loop is a valid variable for analyzing geographic differences in this species.
Oviposition behaviour of three Indian Elattoneura spp. is described and discussed. Endophytic oviposition in dry rigid substrates away from water by the endemic E. nigerrima and E. tetrica is recorded; this differs from the typical recorded use of submerged vegetation substrates in the genus. Contrasting behavioural observation of oviposition in E. campioni is also discussed.
Discussion regarding the gaps of knowledge on Odonata is common in the literature. Such gaps are even greater when dealing with basic biological data for biodiverse environments like the Amazon Rainforest. Therefore, studies that address, classify, and standardize functional traits allow the elaboration of a wide range of ecological and evolutionary hypotheses. Moreover, such endeavors aid conservation and management planning by providing a better understanding of which functional traits are filtered or favored under environmental changes. Here, our main goal was to produce a database with 68 functional traits of 218 Odonata species that occur in the Brazilian Amazon. We extracted data on behavior, habit/habitat (larvae and adults), thermoregulation, and geographic distribution from 419 literature sources classified into different research areas. Moreover, we measured 22 morphological traits of approximately 2500 adults and categorized species distributions based on approximately 40,000 geographic records for the Americas. As a result, we provided a functional matrix and identified different functional patterns for the Odonata suborders, as well as a strong relationship between the different trait categories. For this reason, we recommend the selection of key traits that represent a set of functional variables, reducing the sampling effort. In conclusion, we detect and discuss gaps in the literature and suggest research to be developed with the present Amazonian Odonata Trait Bank (AMO-TB).
Aim
To project the impact of climate change on dragonfly and damselfly diversity in West and Central Asia.
Location
West and Central Asia.
Time period
1900–2020 data used to predict distributions in 2070 and 2100.
Taxon studied
Odonata.
Methods
Based on 149,001 records, distribution models were created for 159 species using MaxEnt. Environmental variables consisted of climate variables taken from BIOCLIM, river data and soil data. The future climate data were obtained from CHELSA from CMIP6 climate models. The same variables were collected for three scenarios (SSP1‐2.6, SSP3‐7.0 and SSP5‐8.5) of shared socioeconomic pathways for the years 2050–2070 and 2080–2100. For each scenario and period, diversity maps were prepared for six species groups: all species, Lentic, Lotic, Oriental, Afrotropical and Palaearctic species.
Results
Strong declines in diversity are expected in western Turkey, the Levant and Azerbaijan, and to a lesser extent in parts of Iran and southern Central Asia. An increase is expected in eastern Turkey and at higher elevations in Central Asia with a limited increase throughout the Arabian Peninsula. In contrast to expectations, a decrease in areas with <15 species was found. Faunal composition is predicted to show strong shifts, with Palaearctic species declining and Oriental and Afrotropical species increasing. No clear difference between the trend of lentic and lotic species is found, although there are clear spatial differences in trend between these groups.
Main Conclusions
Climate change will result in strong changes in diversity and distribution of dragonflies and damselflies in West and Central Asia with regional declines and increases. None of the species are predicted to go extinct based on the impact of climate change only, however, the combined impact of climate change and anthropogenic forces is likely to push some of the species to near extinction by 2100.
1. Climate change has the potential to modify habitat characteristics and, consequently, induce species responses to ongoing environmental changes. Functional traits determine both if a species can persist and maintain stable population sizes in particular ecological conditions, and its capacity to disperse to more favourable habitats.
2. Given that functional traits evolve over time, one could expect closely related species to show similar responses to climate change, which should identify vulnerable lineages. Alternatively, species-specific functional traits may anticipate species responses to climate change, and therefore, trait composition should be a strong predictor.
3. We compiled a comprehensive dataset of functional traits of 84 Iberian and Moroccan odonate species and built a phylogenetic tree to determine if dissimilarity of traits and phylogenetic relatedness are relevant to better discriminate species range-shift responses to climate change.
4. Modelling results for 66 species showed clear impacts of the increase in temperature and drought events on their potential distribution. The traits that best discriminated species that expanded their ranges were multivoltinism, short-life cycles and preference for temporary habitats, whereas species with a reduced and displaced potential distribution were mostly semivoltine, with a short flying season, oviposition on gravel and restricted to permanent streams, small rivers or oligotrophic lakes. Trait conservatism was rejected and phylogenetic relatedness
was a poor predictor of range shifts.
5. Considering odonates as model organisms, traits such as voltinism, beginning and prolongation of flight period and preference of temporal habitats should be examined to anticipate range-shift responses of freshwater insects to climate change.
The present study aimed to determine the wing asymmetry and sexual asymmetry of Pantala flavescens (Fabricius 1798) collected from a paddy field. P. flavescens is known as the longest migratory insect species and the morphological architecture of their hindwing aids in long-distance gliding. In our study, we collected F1 generation of male and female P. flavescens and used for geometric morphometric study to investigate wing asymmetry. We observed no difference in wing size between sexes from the study, but there are significant (p < 0.05) shape differences. The female population was more asymmetric than male population, with a high shape-related fluctuation asymmetry (FA). Discriminant function analysis was used to validate wing asymmetry (right-left) and sexual asymmetry of P. flavescens. Canonical variant analysis discriminated the forewings and hindwings of P. flavescens both sexes in a distinct morphospace. The PC’s warp shape analysis proved that, when compared to forewings, the highest amount of shape variations was observed in hindwings, especially in anal lobe regions. Based on the results, pesticide and fertilizer used in the paddy fields are the primary reason for the high level of FA, and the morphological variations observed in the hindwings may influence the migratory behaviour of P. flavescens.
Members of the insect order Odonata are known as good ecological indicators. Many are sensitive to habitat modifications and are easily monitored for use in environmental assessment studies. Rapid assessments rely on efficient sampling techniques. However, there is limited information available on sampling techniques for adult odonates, and protocols require evaluation. To do this, we standardized counting methods during sampling of odonates from August to November 2016 at the Mula River, Pune, India. We used four counting techniques; full-width belt transect (FWBT), full-circle point count (FCPC), half-width belt transect (HWBT), and half-circle point count (HCPC). For HWBT and HCPC areas facing the river were sampled, and for each technique we took multiple temporal replicates. We compared species detected per unit time, species detected per unit area, new species detected per unit time, and new species detected per unit area. Additionally, we compared species estimates. With HCPC we detected the maximum number of species and new species per unit area, whereas FWBT returned maximum coverage of recorded species. We recommend our proposed techniques be considered in the future across various habitats to decide the most suitable sampling strategy for the different habitats or situations.
This research-level text documents the latest advances in odonate biology and relates these to a broader ecological and evolutionary research agenda. Despite being one of the smallest insect orders, dragonflies offer a number of advantages for both laboratory and field studies. In fact, they continue to make a crucial contribution to the advancement of our broader understanding of insect ecology and evolution. This new edition provides a critical summary of the major advances in these fields. Contributions from many of the leading researchers in dragonfly biology offer new perspectives and paradigms as well as additional unpublished data. The editors have carefully assembled a mix of theoretical and applied chapters (including those addressing conservation and monitoring) as well as a balance of emerging (e.g. molecular evolution) and established research topics, providing suggestions for future study in each case. This accessible text is not about dragonflies per se, but rather an essential source of knowledge that describes how different sets of evolutionary and ecological principles/ideas have been tested on a particular taxon. This second edition of Dragonflies and Damselflies is suitable for graduate students and researchers in entomology, evolutionary biology, population and behavioral ecology, community ecology, and conservation biology. It will be of particular interest and use to those working on insects and an indispensable reference text for odonate biologists.
Background
The spatial and temporal changes of assemblages of aquatic insect can be used to detect the anthropic impacts that influence the biological communities.
Goals
We compared the assemblages of aquatic insect in 1997 and 2014 in two subtropical river drainages, the association with water characteristics, and we discuss their implications for ecosystems conservation.
Methods
True diversity of the aquatic insect fauna at family level and their community structure for 27 study sites in 1997 and 2014 were assessed. Multivariate analyzes were used to compare aquatic insect assemblages and the abundance of functional feeding groups.
Results
There were significant differences in the dissolved oxygen (DO) of the water between 1997 and 2014, decreasing its values. Other variables correlated to DO were also modified, with a decrease in pH and an increase in temperature. We found a correlation between reduction of DO and water pH with a decline in the overall abundance of aquatic insects; also, with shifts in the community structure, from the decrease of groups such as some Ephemeroptera and scrapers, to the increase in opportunistic families such as Chironomidae, Culicidae, and other predator families such as Coenagrionidae, Corixidae and Veliidae, and more abundance of collectors. Families such as Heptageniidae and Caenidae decreased in abundance, as well as other benthic groups.
Conclusions
The assemblages of aquatic insect are useful to indicate a generalized degradation of environmental conditions across localities and time in two subtropical river drainages, related to water quality degradation symptoms such as reduction of pH levels and dissolved oxygen, usually associated with anthropogenic stressors.
This research numerically investigates the flapping motion effect on the flow around two subsonic airfoils near a ground wall. Thus far, the aerodynamic efficiency of the dragonfly-inspired flapping airfoil has not been challenged by an asymmetric cambered airfoil considering the ground effect phenomenon, especially in the MAV flight range. The analysis is carried out on the basis of an unsteady Reynolds-averaged Navier-stokes (URANS) simulation, whereby the Transition SST turbulence model simulates the flow characteristics. Dragonfly-inspired and NACA4412 airfoils are selected in this research to assess the geometry effect on aerodynamic efficiency. Moreover, the impacts of Reynolds number (Re), Strouhal number (St), and average ground clearance of the flapping airfoil are investigated. The results indicate a direct relationship between the airfoil’s aerodynamic performance (Cl/Cd) and the ground effect. The Cl/Cd increases by reducing the airfoil and ground distance, especially at h0=c. At Re=5×104, by increasing the St from 0.2 to 0.6, the values of Cl/Cd decrease from 10.34 to 2.1 and 3.22 to 1.8 for NACA4412 and dragonfly airfoils, respectively. As a result, the Cl/Cd of the NACA4412 airfoil is better than that of the dragonfly airfoil, especially at low oscillation frequency. The efficiency difference between the two airfoils at St=0.6 is approximately 14%, indicating that the Cl/Cd difference decreases substantially with increasing frequency. For Re=5×103, the results show the dragonfly airfoil to have better Cl/Cd in all frequencies than the NACA4412 airfoil.
Human activities affect the structure, dynamics, and energy flow of aquatic ecosystems. River damming, a common anthropic impact in Brazil, changes solar incidence, water flow, and temperature of waterbodies, thereby affecting their fauna. Due to their high sensitivity to environmental changes, the Odonata may be indicators of these impacts. We sampled two ecologically distinct sites, (1) a quasi‐pristine forested area; and (2) a nearby human‐impacted reservoir landscape, to evaluate the effects of damming on odonate community structure. The species composition of quasi‐pristine communities was more heterogeneous and differed almost completely (indicating high turnover) from that of the reservoir‐area communities. The capacity of the reservoir to maintain local fauna was almost nil. The communities in the changed landscape had the highest local diversity, which is related to the high occurrence of widespread generalist South American species. We also tested two recently proposed bioindication ratio tools based on the richness or abundance of high‐level taxonomic categories; both effectively reflected the extent of the impacts of damming. The best performing ratios were Coenagrionidae/other Zygoptera richness ratio, Zygoptera/Anisoptera abundance ratio, and Libellulidae/other Anisoptera richness ratio. The reservoir landscape promotes biotic homogenization. However, the water supply system entails the preservation of part of the native habitat in its surrounding areas, consequently maintaining forest‐dependent biodiversity in quasi‐pristine environments.
The global population structure and dispersal patterns of Pantala flavescens (Fabricius, 1798) are evaluated using a geographically extensive mitochondrial DNA dataset, a more limited samples of nuclear markers, wing isotopic (δ²H) data and a literature review. No spatial or temporal haplotype structure was recovered between the samples. Isotope data suggest that most samples were immigrants at the collection locations. A literature review of migration events for the species confirms regular inter-and intra-continental migrations occur (the majority reported from Asia, Africa and Australasia), with individuals and swarms dispersing thousands of kilometers over land and oceans. Migrations coincide with prevailing winds and seasonal rains, which points to a mechanism we name the “pantropical Pantala conveyor belt”, suggesting widespread gene flow is possible for an aquatic insect with excellent flying ability linked to rapid larval development.
Macroinvertebrates and small fishes can both be important predators of zooplankton in littoral zones of shallow lakes. The aim of this study is to analyze how these predators may interact to affect zooplankton, algal biomass, and water turbidity. We performed a 15-day mesocosms experiment in 12 tanks (1300 l) simulating a littoral zone. A 2 × 2 factorial experiment was designed as follows: (1) Control without predators, (2) 7 nymphs of Anisoptera, (3) 2 visual zooplanktivorous fish and (4) 7 Anisoptera and 2 fishes. Results showed significant effects of fish on the abundance of Cladocera and its concentration among the macrophyte zone. On the other hand, we found no effects of Anisoptera on zooplankton abundance or distribution. No significant interaction between the predator effects was found on most response variables. Water turbidity increased only in the treatments with fish. Macrophytes offer a refuge for zooplankton to fish predation, but antagonist interactions appear when both predators were present, and the shelter effect of vegetated patches to the main herbivores against fish predation was less important when Anisoptera was present. The macroinvertebrate fauna of the littoral zone should be carefully considered in the restoration plans of shallow eutrophic lakes.
Ponds are lentic waterbodies with a high conservation value for biodiversity that have long been overlooked by management policies. Recent initiatives aimed to promote the conservation of these ecosystems by restoring or creating new ponds throughout Europe. Therefore, studying responses of aquatic invertebrates to local pond characteristics and connectivity between them is determinant to understand community dynamics and colonization processes of these scattered ecosystems. We studied larval communities of odonates in 20 created or restored ponds to assess their colonization during the first 2 or 3 years. Community dynamics in relation to pond vegetation, landscape context and connectivity with other ponds were also investigated. No difference in species richness was found between restored and created ponds. Most species colonized the ponds during the first year, but a different pattern in colonization was observed between Anisoptera and Zygoptera. Community composition was related to the landscape context of ponds and the time since pond creation or restoration. Abundances were positively related to pond connectivity, especially in the suborder Zygoptera. No relationship was found between vegetation and Anisopteran larvae, while Zygoptera seem more sensible to the vegetation structure due to their endophytic oviposition. This work confirms the high colonization capacity of odonates and shows that creation of new ponds could be as efficient as pond restoration to enhance the conservation of freshwater species. It also highlights that landscape characteristics and connectivity between ponds are determinant to support higher abundances and a posteriori increase population viability at the landscape scale.
Farming expansion has negative impacts on freshwater biodiversity. However, the effects of agricultural land use are not similar across taxa and depend on local context. For instance, the impacts of agricultural expansion are understudied in the Neotropics (one of the leading regions in cropland expansion). Knowledge of the effects of agricultural land use on aquatic insects from South American subtropical grasslands (Pampa) is even more incipient. We tested whether landscape modification related to increased agricultural land use was associated with taxonomic homogenization in odonate communities in waterbodies in the Brazilian Pampa. Odonates were collected in waterbodies differing in the main land-use class in their surroundings (cropland or grassland). Cropland and grassland sites differed with respect to their abiotic conditions (water chemistry) and species composition of Odonata. Additionally, we found higher variation in the composition of Odonata (and suborders Anisoptera and Zygoptera separately) in grassland than cropland sites. We found an interplay between agricultural and grassland land uses and the variation in the composition of odonate communities in the Brazilian Pampa. Specifically, landscape modification by agriculture modified the abiotic conditions in the waterbodies, which may have favored species able to establish as larvae under harsher environmental conditions.
Implications for insect conservation
We suggest that the maintenance of mixed-grassland and cropland land uses in the fields adjacent to waterbodies can limit the negative effects of agricultural encroachment on Odonata communities with respect to biotic homogenization in the Brazilian Pampa.
Interspecific interactions, such as competition, are among the key factors that determine the distribution, abundance and diversity of organisms in natural communities of aquatic ecosystems. However, a marked reduction in the environmental integrity of streams may lead to modifications of the natural dynamics of these communities, including co-occurrence patterns and body size. In the Amazon, the replacement of forests by production systems is one of the leading causes of alterations to riverine ecosystem. The insects of the order Odonata (dragonflies and damselflies) are predators known to compete for environmental resources but are also sensitive to environmental changes such as those caused by shifts in land use. In this scenario, the present study evaluated species co-occurrence and body size patterns in adult odonates found at preserved and altered Amazonian streams, to determine whether there are morphological differences among the species that enable their coexistence. During the study, 98 streams in the eastern Amazon region were sampled, and a habitat integrity index (HII) was used to evaluate the integrity of each stream (based on variables such as the condition of the riparian vegetation and channel, and land use). Ten male individuals were selected from each species, and nine morphometric measurements were taken from each individual. A total of 3588 specimens were collected and distributed in nine families, 49 genera and 134 species. We found a non-random pattern of co-occurrence in the species of the odonate suborder Zygoptera and a random pattern in the suborder Anisoptera, in both preserved and altered streams. We found morphological divergence between pairs of zygopteran species, in the whole sample and both categories of stream integrity separately. No such morphological divergence was found in the pairs of anisopteran species. The distribution patterns of odonate species are limited by specific environmental processes, especially in preserved environments and in specialists, such as most zygopterans. Zygopteran species have more specific microhabitat requirements, which could explain this pattern, whereas anisopterans prefer open environments, which usually have a greater supply of resources, although there tends to be less microhabitat heterogeneity, which leads to reduced competition. Given this, future studies should use limiting similarity (e.g. morphological attributes) in addition to environmental and spatial factors to better understand the factors structuring these communities. Among these mechanisms, the effects of common ancestry (phylogenetic inertia) and biogeography are important factors that should also be considered in future studies.
Understanding species responses to urbanization is important to realize their specific conservation needs. Odonates (dragonflies and damselflies) are freshwater insects perceived as good ecological indicators. To investigate responses of tropical odonates to an urbanization gradient, we sampled adult odonates along an urbanization gradient at six sites along the Mula River across Pune City, Maharashtra, India. For species–habitat analysis, we first performed a variable reduction using principal component analysis. we analyzed species–habitat data using redundancy analysis and canonical correspondence analysis. We documented 15 odonates across 6 sites. Our statistical analyses on patterns of odonate assemblages across sites and environmental variables did not return significant results. However, we detected site-exclusivity in a few species based on occurrence data and identified urban sensitive, urban tolerant and generalist species. We found that the odonate diversity was highest at a moderately urbanized site. We believe that increase in diversity due to moderate amounts of disturbance can be explained by the intermediate disturbance hypothesis. Based on our data, we suggest that for the conservation of odonates in the urban context, anthropogenic disturbance needs to be regulated. Here, we demonstrate that understanding species–habitat associations is the first step towards understanding their ecological and conservation requirements. To conserve odonates and rivers in metropolitan cities like Pune, restoring original river-side habitat and reducing the disturbance at highly urbanized sites to at least intermediate levels needs to be done on an urgent basis.
Three media (sediment, surface water, and dragonfly larvae tissue) were collected from wetlands surrounding an industrial effluent treatment facility prior to closure. Samples were analyzed for metals, total mercury, and polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/PCDF) concentrations. Sediment and surface water concentrations were compared to provincial and federal guidelines, as well as reference wetland concentrations. Exceedances of arsenic, cadmium, chromium, copper, zinc, and PCDD/PCDF guidelines were found in deeper areas of wetlands historically contaminated from effluent, as well as wetlands exposed to current effluent inputs. Composite Libellulidae samples were collected from wetlands, and comparisons were made to reference tissue concentrations +20%. Elevated As, Cu and Pb tissue concentrations were measured at two site wetlands, but total mercury (THg) and PCDD/PCDF reference tissue concentrations were higher than wetlands near the effluent treatment facility. Spearman rho tests identified a significant correlation between sediment and tissue Pb concentrations and between surface water and sediment THg concentrations. Results suggest relatively low ecological risk to macroinvertebrates within wetlands near the effluent treatment facility from current effluent inputs.
All natural populations show fluctuations in space or time. This is fundamental for the maintenance of biodiversity, as it allows species to coexist. Long-term ecological studies are rare, mainly due to logistics, but studies like the one presented below recognize the dimensionality of temporal change and the ecological processes that lead to shifts in community composition over time. Here, we used three sampling occasions from a dataset spanning 20 years where dragonflies in central Sweden were monitored. Our aim was to investigate how the prevalence of ecological and biological species traits varied over time measured as Community-level Weighted Means of trait values (CWM). Most CWM values varied significantly between years. Most of the traits changed between the second and the last sampling occasion, but not between the two first ones. These changes could be linked to major changes in species abundance. Our work indicates that fundamental shifts in community structure can occur over a short time, providing environmental drivers act on species turnover. In our case, Climate change and pH levels in lakes are most likely the most important factors.
The department of Ñeembucú, in southwestern Paraguay, is home to the virtually unexplored Ñeem-bucú Wetlands, the second largest wetland system in the country, representing a major gap in biodiversity knowledge. As organisms ubiquitous with wetlands, the Odonata, or dragonflies (Anisoptera) and dam-selflies (Zygoptera), have the potential to be effective indicators of wetland habitats in the face of increasing anthropogenic impacts in the region. We therefore comprehensively surveyed the Odonata in central Ñeembucú over a period of two years using a listing method. Here, we present an annotated checklist and identification key to the species present in central Ñeembucú with details on their habitat preferences, phenology and behaviour. We found 60 species but estimate a total of between 62 and 90 species. Eleven (18%) are new records for Paraguay. Species composition is similar to the Argentine Humid Chaco, with four bioregional endemics, whilst representatives from the Andean-Patagonian subre-gion are present in open areas. Such partitioning of species from different bioregions into different habitats is typical of ecotonal regions. Two further species are endemic to the Paraná-Paraguay basin and three are highly localised, indicating the high conservation value of the Ñeembucú Wetlands. Eleven species have the potential to be effective indicators of the Paraguay River, large permanent wetlands, grassy temporary wetlands and wooded temporary wetlands, providing an effective tool to identify critical wetland ecosystems in the face of the growing threats from human activities. We also provide recommendations for the protection and management of wetlands in the region.
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Odonatans are rare as amber inclusions, but quite diverse in Cretaceous Burmese amber. In the past two years, over 20 new species have been found by the present authors after studying over 250 odonatans from 300,000 amber inclusions. Most of them have now been published, and here we provide a brief review. Three suborders of crown Odonata have been recorded, including the damselfly families or superfamilies Platycnemididae, Platystictidae, Perilestidae, Hemiphlebiidae, Coenagrionoidea, Pseudostigmatoidea, Mesomegaloprepidae and Dysagrionidae, plus the dragonfly families Lindeniidae, Gomphaeschnidae and Burmaeshnidae, and the damsel-dragonfly family Burmaphlebiidae.
We investigated the effects of the presence of bladderwort plants on survival of early instar larvae of one coenagrionid and two libellulids in laboratory experiments. In all three species survival was reduced compared to treatments with a non-carnivorous submerged plant, with effective mortality that could be related to bladderwort being 19–45% dependent on the prey species. Individuals of all species were found in capture bladders. We also recorded the microhabitat use of the early instar larvae and found that the species with highest use of vegetation had highest mortality due to bladderwort. We conclude that bladderwort may have effects on odonate larvae that translate into natural conditions and we discuss factors that may affect predation by bladderwort on odonates in the field.
Central Iran has been faced with deterioration of water quality and quantity, but yet the biodiversity of freshwater-associated insects in this area remains uncertain and without this information the development of conservation strategies is not possible. Here we explore Odonata diversity patterns and species assemblages in three terrestrial ecoregions of Central Iran. We used the first three Hill numbers and phylogenetic generalizations of these indices to compare the species diversity between the ecoregions. To compare Odonata species composition a PERMANOVA analysis was performed. Alpha-diversity of each water body was estimated by Hill numbers, taxonomic diversity, taxonomic distinctness and average taxonomic distinctness. The effects of habitat and environmental factors on Odonata diversity indices were modelled using a linear mixed model. About 42% of all Odonata that have been reported in Iran were found during this study. Species richness in the Desert and Steppe ecoregions were almost equal, the same pattern was observed for phylogenetic diversity indices. The Steppe ecoregion also had significantly different Odonata assemblage. Results of the linear mixed model showed that environmental factors have different effects on different diversity indices. Additionally different diversity indices resulted in different outcomes when comparing ecoregions, demonstrating that single measure cannot precisely assess the properties of an assemblage’s diversity. The high diversity of Odonata observed in such an arid environment shows the importance of man-made water bodies, as well as the necessity of preparing a conservation plan for these ecosystems.
Insect extraordinary evolutionary success is due to different reasons among which their ability to receive and respond to a great variety of sensory cues thanks to their developed sense organs encompassing a high number of diversified sensilla, mainly located on their antennae. The successful invasion of lotic and lentic freshwaters by terrestrial insect required physiological constraints also regarding sensory systems. This chapter reviews the present knowledge about antennal sensory equipment in adult and aquatic stages of Ephemeroptera, Odonata, Plecoptera and Trichoptera. These insect orders have aquatic larval stages well adapted to this environment, while they move to the terrestrial habitat as adults. To be able to receive sensory cues in two very different biotopes during the young and the adult stage is a fundamental prerequisite for these insects. The data reported are mainly based on morphological investigations under scanning and transmission electron microscope (SEM, TEM), and behavioural and electrophysiological investigations (the latter available only for Odonata and Plecoptera). The chapter considers separately the main sensory capacities located on the antennae in the above-reported aquatic insect orders, in particular mechanoreception, chemoreception, thermo-hygroreception and their modifications from the aquatic to the adult stage.
Habitat loss and fragmentation induce a decline and endangerment of freshwater organisms such as Aeshna viridis, an endangered dragonfly species characterised by a specific insect–plant association to the macrophyte Stratiotes aloides. In order to implement conservation measures, a good level of knowledge about the occurrence, habitat requirements and quality, as well as patch size of the species is important. We analysed the influence of several habitat parameters on the presence/absence and abundance of A. viridis exuviae using habitat models (generalised linear mixed-effect models). The ditches populated by A. viridis were classified as moderately polluted and meso- to eutrophic with a high cover of emerged S. aloides stands. The main factor contributing to the presence of A. viridis was the coverage of emerged S. aloides combined with the ditch width. The 90% probability of the presence of A. viridis was achieved at a cover of 14% (8.4 m²) and/or 77% (46.2 m²) of emerged S. aloides. The number of A. viridis exuviae was positively affected by the cover of emerged S. aloides and negatively affected by the sediment thickness, water maintenance and water temperature in March and August. The habitat parameters – water temperature and sediment thickness – are associated with S. aloides in the beginning of siltation of ditch succession. If ditch cleaning takes place during larvae development, eggs and larvae are removed by these procedures. In an optimal situation, the S. aloides populations occur in a mosaic of different states of siltation, which is managed by adapted water maintenance.
Aim
Land use change, such as urbanization and intensification of agricultural practices, poses major threats for biodiversity. We examined whether the composition of freshwater species differs between landscapes dominated by urban, agricultural or more natural structures in a region with a long history of landscape transformation. We determined the differences and characteristics of the dragonfly fauna in relation to major land use categories. We particularly focused on urban land use, as it generally induces a high level of landscape transformation.
Location
Germany.
Methods
We used distribution data of dragonflies derived from a citizen science database, which was compiled for the German distribution atlas. To analyse whether different land use categories are associated with distinct species compositions, we performed the classification method random forest.
Results
Based on dragonfly abundance per grid cell, we identified distinct land use‐related assemblages that were separated by two gradients, that is, the level of transformation and a gradient from open land to forest. In particular, urban landscapes possessed a distinct species composition with specific species, all of which were opportunistic and supported by warm climate. They also comprised significantly higher α‐diversity than intensive agricultural landscapes. Similar values of γ‐diversity over all land use categories implied a countrywide homogenized dragonfly fauna, which is probably caused by historic land use.
Main conclusions
Our results indicate that land use is a relevant driver for the composition of freshwater species at the landscape scale. Urban landscapes maintain species diversity better than agricultural landscapes, but they modify the species composition. Additional research on the effects of land use change is required to understand species responses and predict future distributions in a changing world in order to plan sustainable conservation strategies.
Based on a distribution database brought together for the recently published Atlas of the European dragonflies and damselflies, we describe the patterns of diversity and endemism of these insect groups. Highest species richness, as well as richness of predominantly lentic species, occurs in central and western-central Europe. Strictly lotic species have their centre of diversity in southwest France and parts of the Iberian Peninsula. The highest number of endemic species is found in southwest France, the Iberian Peninsula and the Balkan Peninsula. A comparison of the diversity patterns of Odonata species listed in the EU Habitats Directive with those listed in the European Red List highlights a strong mismatch between species threatened in Europe, which are mainly found in the Mediterranean, and species legally protected by the European Union, which are concentrated in central and western Europe. This mismatch has a historical origin, as the species listed in the Habitats Directive were mostly selected in the 1970s and 1980s when water quality in western and central Europe was poor. Since the 1990s, water and habitat quality has improved in these parts of Europe while in the same period the pressure on aquatic habitats in the Mediterranean has increased greatly.
Reflex immobilization in dragonfly larvae (Odonata)-Larv ae of 18 European Anisoptera species, mainly final instar, were studied with respect to reflex immobilization (RI). In Brachytron pratense, Somatochlora flavomaculata. S. meridionalis and S. metallica RI revealed an obligatory reaction to disturbance in the water. An additional 4 species exhibited facultative RI. All the other species reacted by rapid escape or became immobile for some time but only when they were brought on land. RI was released exclusively by tactile stimulation, especially by a firm grip on the thorax or abdomen, but not on the legs or antennae. In 3 Somatochlora spp. RI lasted 83, 87 and 154 s (median values) and varied between 5 and 679 s. The posture during RI, depicted in 10 line drawings, differed according to the species. In Somatochlora up to 3 postures were recorded: larvae either extended their legs laterally or folded them closely against the body or held them obliquely upwards. In individuals that were successively stimulated, the duration of RI tended to decrease, but not in all cases. Larvae of 2 Somatochlora alpestris. S. arctica and S. flavomaculata exhibited RI already in the first free-living larval instar. The adaptive value of RI which is assumed to be an antipredation strategy, is discussed with respect to the species, microhabitats and potential predators.
Filed guide and introduction to ecology and distribution of all Odonata recorded in Namibia up to 2007.
Understanding the ecology and evolution of morphological defences in animals and plants may help us to understand and protect biodiversity. Several species of dragonfly larvae express lateral and dorsal abdominal spines. In some species these spines seem to be fixed, and in others they are induced by the presence of predatory fish. Larger spines are adaptations to reduce predation risk by fish, but incur a cost because large spines are associated with a higher predation risk by invertebrate predators. The difference in vulnerability to different predators has the potential to affect temporal and spatial variation in the morphology of dragonfly larvae, and may ultimately result in speciation. Future focus on the joint evolution of correlated defensive traits such as morphology and behaviour and their plasticity might be fruitful for a better understanding of the development of animal diversity.
In this paper the trends of dragonfly expansions during the last decades in Germany and Europe are summarized. It is shown, that there is a general expansion of many species to the north: Mediterranean species expanded to Central and Northern Europe, whereas some African species expanded to Southern Europe, some are even new to the continent. In general this means an increase of biodiversity, but looking at the ecological effects, in the medium term a decrease can be expected for mooreland and alpine species. Dragonflies can be regarded as a good indicator group for climatic change. Already now in some areas or regions negative effects on waters bodies and their dragonfly communities can be observed and more will occur if e.g. temperature rises or precipitation decreases. The consequences for nature conservation strategies – such as the NATURA 2000 network – are outlined and the general need for monitoring programmes is emphasised.
For nine dragonfly species (five aeshnids and four libellulids) all previous and verifiable data are related to the vertical climate zones and nature regions of the western Peruvian Andes and the Peruvian Pacific coast. Climate changes due to the El Niño and La Niña phenomena, as well as the global climate change have an influence on the different natural regions and also restrict aquatic biotopes. These changes influence the dispersal and behavior of some dragonflies and concern also loss of habitats as well as alterations of biotic and abiotic factors at and in water.
However new waters and habitats also are formed in most nature regions. Specialists like Rhionaeschna peralta, a species of high mountain regions and the Puna, are not able to react to habitat losses by adaptation, while other species such as R. maita and R. marchali do colonize new habitats also in higher altitudes. While the here represented aeshnids change their distribution ranges within the vertical nature regions of the west Andes, this is suspected for three of the four libellulids (Orthemis ferruginea, O. discolor and Pantala flavescens) as latitudinally respectively longitudinally immigrations and expansions of their areals.
For all species discussed, a seasonally earlier flight beginning is detectable, but for no species an extension of their flight time.
Altogether, the above named three libellulid do react more flexibly and faster to the alterations by climate changes than the majority of the five aeshnid species.
The influence of increased UV-B and UV-A radiation possibly affects also the site occurrence of some species in high altitudes of the Andes.
Several of Anisoptera maintain their body temperature more constant than ambient temperature. Species that spend most of their active period on perches (perchers) and make only short flights thermoregulate heliothermically, primarily by means of postural adjustments. Some of the species that fly continuously (fliers) are endothermic regulators during flight. They control body temperature by: (1) controlling metabolic heat production by alternately using gliding or powered flight; (2) controlling heat loss by altering circulation between thorax and abdomen. Small fliers are unable to regulate well because they are subject to high rates of convective heat loss. Cooling constants, as defined by Newton's law of cooling, are related to thoracic weight by a negative power function over a wide size range. Cooling constants are higher in live dragonflies than in dead ones, a difference that is accentuated at high ambient temperatures. High cooling constants at high temperatures probably result from increased rates of circulation. Most fliers, and some large perchers, are able to elevate their body temperature by @'wing-whirring.@' In some species the rate of heat production apparently varies in response to ambient temperature. The body temperature at which flight begins after warm-up is positively correlated with body weight, probably because wing loading increases with increasing body size. The maximum voluntarily tolerated temperature and the threshold of heat torpor of several species were determined. Both parameters are correlated with habitat. The minimum temperature at which flight is possible is positively correlated with body weight and is slightly higher in tropical dragonflies than in temperate zone species. Body temperature is probably more variable relative to air temperature in tropical than in temperate zone species. The ability of dragonflies to maintain a relatively constant body temperature is determined primarily by climate, body size, and behavior.
Many populations are heterogeneous collections of different sizes or stages of conspecifics. Existing overlap indices do not account for the size-/stage-structured nature of these populations. In this paper I present new overlap indices that use information about the sizes of individuals that co-occur in time and space to predict the potential for interactions in size-structured guilds. An index of the opportunity for competition (IOC) calculates the frequency with which similar size classes of two species encounter each other, whereas an index of the opportunity for intraguild predation (IOP) calculates the frequency of encounters among disparate size classes of the same two species. To illustrate that these indices are more appropriate for size-structured populations than conventional indices, I calculated overlap, IOP, and IOC for all species pairs in a diverse assemblage of dragonfly larvae. The new indices revealed size-specific patterns of overlap that were not detected by the conventional index, including that (1) some species with high overlap values should interact mainly as competitors, others mainly as intraguild predators, and many as both competitors and predators, (2) subtle differences in phenology and/or size-specific shifts in habitat distribution can lead to the potential for asymmetric interspecific interactions, (3) some species with low pairwise IOP and IOC values are nonetheless vulnerable to the effects of diffuse competition or intraguild predation, (4) seasonal segregation reduces competitive overlap but at the same time increases the opportunity for intraguild predation. The indices are general in form and should be useful for analyzing distributional data for any size-structured assemblage in which the type and intensity of interaction varies as a function of relative size.
A phylogeny including 26 families of Odonata is presented based on data from large and small subunit nuclear and mitochondrial ribosomal RNAs and part of the nuclear EF-1α. Data were analyzed using Bayesian methods. Extant Zygoptera and Anisoptera are monophyletic. The topology of Anisoptera is ((Austropetaliidae, Aeshnidae) (Gomphidae (Petaluridae ((Cordulegastridae (Neopetaliidae, Chlorogomphidae)) ((Synthemistidae, Gomphomacromiidae) (Macromiidae (Corduliidae s.s., Libellulidae))))))). Each of the major groups among anisopterans is well supported except the grouping of Neopeta lia with Chloropetalia. Lestidae and Synlestidae form a group sister to other Zygoptera, and Coenagrionoidea are also monophyletic, with the caveat that Isostictidae, although well supported as a family, was unstable but not placed among other coenagrionoids. Calopterygoidea are paraphyletic and partly polytomous, except for the recovery of (Calopterygidae, Hetaerinidae) and also (Chlorocyphidae (Epallagidae (Diphlebiinae, Lestoidinae))). Support for Epallagidae as the sister group of a clade (Diphlebiinae, Lestoideinae) is strong. Within Coenagrionoidea, several novel relationships appear to be well supported. First, the Old World disparoneurine protoneurids are nested within Platycnemididae and well separated from the protoneurine, Neoneura. The remaining coenagrionids are divided into two well-supported subdivisions. The first includes Pseudostigmatinae, stat. nov., Protoneurinae, a group of coenagrionids mostly characterized by having an angulate frons, and Argiinae (Argia). The second division includes typical Coenagrionidae.
Pericnemis triangularis Laidlaw (Coenagrionidae), Indaeschna grubaueri (Foerster) (Aeshnidae) and Lyriothemis cleis Brauer (Libellulidae) are reported breeding in phytotelmata in the understorey of lowland mixed dipterocarp rainforest in Borneo. The pattern of utilization by the 3 spp. of phytotelmata of varying sizes is surveyed and observations are made in field and laboratory on larval behaviour, especially territoriality and intra- and interspecific predation, and developmental rates. Possible adaptations to special conditions found in phytotlmata, including low oxygen tensions, limited food and close proximity to other larvae are discussed. Descriptions are provided for the larvae of P. triangularis and I. grubaueri.
An updated classification and numbers of described genera and species (until 2010) are provided up to family level. We argue for conserving the family-group names Chlorocyphidae, Euphaeidae and Dicteriadidae, as well as retaining Epiophlebiidae in the suborder Anisozygoptera. Pseudostigmatidae and New World Protoneuridae are sunk in Coenagrionidae and Old World Protoneuridae in Platycnemididae. The families Amphipterygidae and Megapodagrionidae as traditionally recognized are not monophyletic, as may be the superfamily Calopterygoidea. The proposal to separate Chlorogomphidae, Cordulegastridae and Neopetaliidae from Libelluloidea in their own superfamily Cordulegastroidea is adopted. Macromiidae, Libellulidae and Synthemistidae and a restricted Corduliidae are accepted as families, but many genera of Libelluloidea are retained as incertae sedis at present. 5952 extant species in 652 genera have been described up to 2010. These are placed here in 30 families; recent proposals to separate additional families from Amphipterygidae and Megapodagrionidae have not yet been incorporated.
An extensive molecular phylogenetic reconstruction of the suborder Zygoptera of the Odonata is presented, based on mitochondrial (16S, COI) and nuclear (28S) data of 59% of the 310 genera recognized and all (suspected) families except the monotypic Hemiphlebiidae. A partial reclassification is proposed, incorporating morphological characters. Many traditional families are recovered as monophyletic, but reorganization of the superfamily Coenagrionoidea into three families is proposed: Isostictidae, Platycnemididae and Coenagrionidae. Archboldargia Lieftinck, Hylaeargia Lieftinck, Palaiargia Förster, Papuargia Lieftinck and Onychargia Selys are transferred from Coenagrionidae to Platycnemididae, and Leptocnemis Selys, Oreocnemis Pinhey and Thaumatagrion Lieftinck from Platycnemididae to Coenagrionidae. Each geographically well-defined clade of Platycnemididae is recognized as a subfamily, and thus Disparoneurinae (i.e. Old World ‘Protoneuridae’) is incorporated, Calicnemiinae is restricted, and Allocnemidinae (type genus: Allocnemis Selys) subfam.n., Idiocnemidinae (type genus: Idiocnemis Selys) subfam.n. and Onychargiinae (type genus: Onychargia Selys) subfam.n. and Coperini trib.n. (type genus: Copera Kirby) are described. Half of Coenagrionidae belongs to a well-supported clade incorporating Coenagrion Kirby and the potential subfamilies Agriocnemidinae, Ischnurinae and Pseudagrioninae. The remainder is less well defined, but includes the Pseudostigmatidae and New World Protoneuridae that, with Argiinae and Teinobasinae, may prove valid subfamilies with further evidence. Ninety-two per cent of the genera formerly included in the polyphyletic Amphipterygidae and Megapodagrionidae were studied. Pentaphlebiidae, Rimanellidae and Devadattidae fam.n. (type genus: Devadatta Kirby) are separated from Amphipterygidae, and Argiolestidae, Heteragrionidae, Hypolestidae, Philogeniidae, Philosinidae and Thaumatoneuridae from Megapodagrionidae. Eight further groups formerly placed in the latter are identified, but are retained as incertae sedis; the validity of Lestoideidae, Philogangidae and Pseudolestidae is confirmed. For some families (e.g. Calopterygidae, Chlorocyphidae) a further subdivision is possible; Protostictinae subfam.n. (type genus: Protosticta Selys) is introduced in Platystictidae. Numerous new combinations are proposed in the Supporting Information. Many long-established families lack strong morphological apomorphies. In particular, venation is incongruent with molecular results, stressing the need to review fossil Odonata taxonomy: once defined by the reduction of the anal vein, Protoneuridae dissolves completely into six clades from five families.
Although Europe is the cradle of dragonfly systematics and despite great progress in the last 2 decades, many issues in naming its species and understanding their evolutionary history remain unresolved. Given the public interest, conservation importance and scientific relevance of Odonata, it is time that remaining questions on the species’ status, names and affinities are settled. We review the extensive but fragmentary literature on the phylogeny, classification and taxonomy of European Odonata, providing summary phylogenies for well-studied groups and an ecological, biogeographic and evolutionary context where possible. Priorities for further taxonomic, phylogenetic and biogeographic research are listed and discussed. We predict that within a decade the phylogeny of all European species will be known.
Currently, many rare and endangered species occur in fragmented habitats. Habitat patch size is often used as an easily measured surrogate of habitat quality and local population size. We investigated whether habitat patch size affects the presence and density of larvae of the endangered dragonfly Aeshna viridis, which for a large part of their life history depend on the macrophyte Stratiotes aloides rosette. The study was performed in four populations, two from Finland and two from Latvia. Our main result was that density of A. viridis and patch occupation increased with area of S. aloides patch. The results may be due to larvae actively avoiding enemies (higher survival) and/or to the possibility that females laid higher number of eggs in the large S. aloides patches. Our results indicate that local abundance and persistence of A. viridis population may depend on the few, large S. aloides patches rather than several small patches of equal total area.
Recent studies show a remarkable scarcity of faunal exchange events between Australia and New Guinea in the Pleistocene despite the presence of a broad land connection for long periods. This is attributed to unfavourable conditions in the connecting area associated with the long established northern Australian Monsoon Climate. This would be expected to have impacted strongly on freshwater faunas with the following results: (1) limited overlap in species, (2) most higher taxonomic groups present in both areas sharing no species or even genera and (3) shared species dominated by lentic species with high dispersal capacity. Testing these predictions for dragonflies showed the turnover in the family, genus and species composition between Australia and New Guinea to be higher than anywhere in the world with only 50% of families and subfamilies, 33% of the genera and 8% of the species being shared. Only one of the 53 shared species favors lotic waters compared with 64% of the 652 combined Australian–New Guinean species. These results agree with our predictions and indicate that the dragonfly fauna of Australia and New Guinea have effectively been separated during the Pleistocene probably due to the prolonged unfavourable climatic conditions in the intervening areas.
Compared to other insect groups, libellulids have a rather high mean number of ovarioles. In addition, the mean ovariole diameter differs greatly between and within species. In general, 2 different types of ovariole arrangement exist: (1) all developing oocytes mature and equal in size; in some species without, and in others with, surrounding connective tissue and (2) oocytes displaying gradual maturation, with only the outermost ovarioles mature. These differences have ecological consequences: the first arrangement occurs in spp. that have stepwise egg production. These spp. will lay one or more clutches, after which an interclutch interval of ovariole regrowth follows. Spp. with the second arrangement have continuous egg production and are able to lay at least some eggs all the time, reducing the length of interclutch intervals. However, no direct connection between mate-guarding strategies and ovariole arrangements can be seen. Nevertheless, it is believed that the process of ovariole maturation differs between these groups. It is concluded that ovary morphology in libellulids may exhibit evolutionary fixed traits, although the whole picture still remains complex. The ovariole arrangement may have a crucial impact on the reproductive ecology of the species.
1. Larvae of Macromia illinoiensis Walsh are often colonised by the zebra mussel, Dreissena polymorpha Pallas, a recent invader to North America. To determine how mussel attachment affects an individual's foraging behaviour, we quantified capture of Hexagenia limbata Hexes mayfly prey and the distance moved by newly-molted final instars before and after an individual's colonisation with zebra mussels.
2. In night trials, larvae sprawled above the sand, and caught more mayflies than individuals in daytime trials, but the estimated distance travelled did not differ. When resting under a layer of sand with only its eyes exposed during the day, an individual could capture a mayfly prey using a sit-and-wait ambush strategy. When sprawled above the sand, some larvae caught prey that rested on their legs.
3. When mussel-free, individuals captured more prey than they did when carrying zebra mussels, although mussel attachment per se did not affect the estimated distance that a larva moved.
4. During day trials, but not night ones, the increasing mussel load of colonised individuals decreased prey capture and the distance moved in an apparent step-wise function. Although the number of mussels carried did not differ, night foragers carried a heavier load. Independent of time of the day, the distance an individual travelled when mussel-free was predictive of the number of prey it caught when colonised, suggesting that the greater general activity of some individuals helped mitigate negative effects that mussel attachment had on prey capture.
5. Our results add to a growing number of negative effects of zebra mussel colonisation on sprawling and hiding dragonfly larvae. Although the impact of these costs on dragonfly populations remains to be determined, a decrease in this guild of predators whose life cycle spans aquatic and terrestrial habitats might have cascading effects across ecosystems.
The oxygen tolerance of aquatic insect larvae with tracheal gills or comparable respiratory mechanisms can be used for bioindication of limiting minimal contents of dissolved oxygen. An analysis of the community permits the retrospective evaluation of critical values. Specific lethal oxygen concentrations and their temperature dependence are given for 22 species. Above a critical temperature, Tc, and specific LC sub(50) increases exponentially. Tc is considerably lower with cold-adapted than with warm-adapted species. The values of oxygen tolerance determined demonstrate that restriction of a species to running water is not determined by oxygen level, temperature and water flow only.
Literature and personal information on the distribution of I. hastata and other odon. spp. in the Azores is reported. I. hastata and I. pumilio are recorded for the first time from the islands of Corvo and Sao Jorge, respectively. I. hastata appears the most common and abundant sp. and its population is formed by only ♀♀ (no ♂♂ were ever recorded). The asexual reproduction of these populations was demonstrated by means of laboratory rearing during several generations. The dispersal ability of this sp. and the possible origin of parthenogenesis after its colonisation of the Azores are briefly discussed. The possible causes of threat are identified and the need for conservation measures is outlined.
Mortality during emergence in two species of dragonfly, Onychogomphus uncatus and Orthetrum coerulescens, was studied at a Mediterranean irrigation canal in France. Overall mortality was 5.2% (n =1901) and 5.7% (n =611), respectively. Predation was low in both species. The prime cause of mortality was incomplete ecdysis resulting from different factors among which heavy wind was the most important in O. coerulescens and lack of suitable emergence supports in O. uncatus. Besides data on mortality the emergence curves of both species are provided.
In order to describe the assemblages of adult Odonata of running waters in the Upper Guinean forest, 36 sites in Liberia and Ghana were analysed using Non-metric Multidimensional Scaling. Five groups were identified, which correspond with different assemblages in the sequence of habitats from small streams to large rivers. Taxonomically related species demonstrate distinct ecological segregation within this gradient, occupying different sections of running waters, or different microhabitats therein. The balance of sun and shade, resulting from a varying degree of habitat openness, is thought to be an important factor in habitat selection, but it is difficult to distinguish from other factors associated with stream size. Anthropogenic opening of stream habitat (e.g. by deforestation or damming) can downscale the present fauna, i.e. result in the invasion of species of downstream habitats (more open) and the disappearance of upstream (dense forest) species.
A brief account is presented of mass dragonfly migrations observed previously in Russia and West Siberia in particular. A mass migration in Libellula quadrimaculata is described in detail. It occurred on 1 July 1981 in the south-western part of the West Siberian Plain in the valley of the Ishym River. From 1968 to 2008 we studied population dynamics, spatial distribution and displacement in dragonflies in the West Siberian forest-steppe. Detailed research was conducted at the biological station of the Russian Academy of Sciences near the Chany Lake. Mass migrations in L. quadrimaculata and some Leucorrhinia spp. followed situations with an extremely high population density and local mass aggregations and occurred with a period of c.10 years, correlated with fluctuation of water level in the region, mainly in the south. It is suggested that dragonfly migration not only optimizes their population size but increases the rate of transport of chemical elements and organic matter to dry land from eutrophic water bodies, which increases the importance of dragonflies to ecosystems at large.
Lestes macrostigma is a stenotopic dragonfly species of Western Palaearctic distribution that has high conservation status almost throughout its range. It inhabits mainly brackish water with a typical plant species, sea club-rush Bolboschoenus maritimus. Due to the absence of special investigations, the nature of this insect–plant association is not clearly understood, but it was supposed that L. macrostigma prefers egg laying in B. maritimus. In this paper we describe the ovipositor morphology and the egg laying behaviour of L. macrostigma in detail. The cutting ovipositor reveals several morphological peculiarities recorded previously in other lestids. The internal surface of the valves reveals rich microsculpture. Numerous single and clustered sensilla of different shape are found on the valves and styli and are probably involved in oviposition–plant recognition by females and/or in production of an egg clutch. Oviposition is carried out in stems of B. maritimus and Juncus maritimus. An egg clutch consists of a row of single eggs deposited in line along the long axis of a plant. Results are discussed in the light of possible morphological and behavioural adaptation to oviposition into specific plant substrates.
In the tropical Indian Ocean, the Maldive Islands lack surface freshwater, so are unsuitable for dragonfly reproduction. Nevertheless, millions of dragonflies (Insecta, Odonata; mostly globe skimmer, Pantala flavescens) appear suddenly every year starting in October. Arrival dates in the Maldives and India demonstrate that the dragonflies travel from southern India, a distance of some 5001000 km. Dates of arrival and occurrence coincide with the southward passage of the Inter-tropical Convergence Zone (ITCZ). Circumstantial evidence suggests that the dragonflies fly with north-easterly tail winds, within and behind the ITCZ, at altitudes over 1000 m. It is proposed that this massive movement of dragonflies is part of an annual migration across the western Indian Ocean from India to East Africa. Arrival dates in the Seychelles support this hypothesis. Dragonflies also appear (in smaller numbers) in the Maldives in May, with the onset of the southwest monsoon, suggesting a possible return migration from Africa. These proposed migrations of dragonflies, regularly crossing 3500 km or more of open ocean, were previously unknown. It is known that these dragonflies exploit ephemeral rain pools for reproduction; the monsoons and ITCZ bring not only alternating, seasonal rains to India and Africa, but also appropriate winds for dragonflies to follow those rains. Several bird species migrate from India across the western Indian Ocean to wintering grounds in Africa. They do so at the same time as the dragonflies, presumably taking advantage of the same seasonal tail winds. Many of these birds also eat dragonflies; the possible significance of this was not previously appreciated.
This is the first continent-wide overview of insect diversity and status sufficiently fine-scaled to be used in conservation planning. We analyze patterns of richness and the conservation status of African dragonflies and damselflies (Insecta: Odonata), commonly referred to as dragonflies, to determine threats to species and freshwater habitats, location of diversity hotspots, necessary conservation actions, and research gaps. Major centers of dragonfly diversity in Africa are tropical forest areas that include highlands. Most threatened species – as classified by the International Union for Conservation of Nature global Red List – are concentrated in highlands from Kenya to South Africa (together with the Cape Floristic Region), western Africa (including mountains on the Cameroon–Nigeria border), and Ethiopia. Currently available knowledge can be applied throughout Africa's freshwater systems to help minimize or mitigate the impact of future development actions, allowing dragonflies to act as “guardians of the watershed”. The private sector can be advised to safeguard sensitive habitats and species when selecting sites for development. Key sites and species for monitoring can be identified by checking the distribution of threatened species at www.iucnredlist.org.
Nymphs of the dragonfly, Erythrodiplax berenice, are common on rocky mangrove flats in the lower Florida Keys at salinities of 36-48 ppt. Erythrodiplax berenice appears to be the only truly marine odonate, and the nymphs are able to tolerate wide variations in salinity. Hemolymph osmotic pressures for nymphs freshly captured in seawater or held in artificial seawater were 358-412 mOsm. There was little further variation at salinities between freshwater and 260% seawater (2,612 mOsm). In 300% seawater, hemolymph osmotic pressure rapidly increases to about 1,000 mOsm, and death ensues. The transition point between hyper- and hypoosmotic regulation occurred at approximately 350 mOsm seawater. Freshwater- and seawater-acclimated nymphs differ little in body water content (about 80%), but Na content is elevated from 50 to 89 Mmol/g wet wt, respectively. In 35 ppt seawater, Na influx and efflux were approximately balanced near 400 μmol/100g·h. In freshwater (1 mM Na), these fluxes decline to about 10 μmol/100g·h. The time for complete turnover of body Na increases from 0.9 day in seawater to 21 days in freshwater. On rapid transfer from water of 470 mM Na to water of 1 mM Na, the Na efflux in 1 mM was only slightly higher than expected for freshwater-acclimated nymphs. At a water Na level of 0.25 mM, Na efflux increases greatly, and there is a large net loss of Na. Water influxes of nymphs in distilled water or 35 ppt seawater were similar (33 and 40 μ1/g·h, respectively); complete turnover of body water occurs in about 0.8 day. Nymphs of E. berenice rival the better-known dipterans in osmoregulatory abilities and should be studied further to compare mechanisms of hypoosmotic regulation that have presumably evolved independently in these two orders.
Water mites are ubiquitous parasites in freshwater ecosystems. The interaction between water mites and aquatic insects has been scarcely studied from an evolutionary ecology viewpoint. Host finding is an important feature of the water mite's life cycle. The host finding success is suggested to depend upon host behaviour and quality. Water mite parasitism lowers host fitness via different routes: by draining nutrients hosts can suffer from decreased fecundity, increased mortality etc. Host sexes and closely related species are affected differently. Recent studies on host fitness, whilst taking the parasite behaviour into account, revealed results contrasting older studies where knowledge of the parasites' life cycle was absent. The potential for coevolution is discussed. For exploring evolutionary trends a water mite phylogeny is needed. Water mite-aquatic insect interactions can be assumed to provide excellent conditions to conduct experimental studies on direct and indirect effects of multiple natural enemies in freshwater ecosystems.
In the absence of weeds, Notonecta exhibited a Type 2 functional response, but this changed to a Type 3 response as weed density increased. -from Author
Enallagma hageni, Lestes disjunctus, Sympetrum costiferum, Sympetrum danae, Sympetrum internum, and Sympetrum obtrusum were observed emerging from brackish pools with an overall salinity range of 6.0-17.3 ppt in three saltmarshes in Gaspé, Quebec. Lestes congener, Libellula quadrimaculata, and species of Sympetrum were prominent among the larvae in these pools.
By analysis of slow-motion films of dragonflies and damselflies in free flight, released in front of a backdrop or startled during flight, the following flight parameters have been quantified for symmetrical manoeuvres: wingbeat frequency, relative durations of up-and downstroke, phase relationships of the beats of fore-and hindwings, stroke amplitude, mean stroke velocity, flight velocity, nondimensional flight velocity, advance ratio, acceleration, angle of attack and stroke plane.
The wingbeat frequencies are higher in the smaller species and in those with relatively large wing loading. As a rule, Zygoptera have a wingbeat frequency only half that of Anisoptera. The stroke amplitude is almost always much larger in Zygoptera than in Anisoptera, which have a greater range of variation in this respect. Stroke velocity is higher in Anisoptera than in Zygoptera; it is also higher in the more elaborate flight manoeuvres than in others. The calculated stroke velocities resemble those actually measured.
Anisoptera fly more rapidly than Zygoptera. With respect to the nondimensional flight velocities, it is notable that although the values for Anisoptera are higher than those for Zygoptera, they are exceeded by the Calopterygidae; the latter can fold their wings back during rapid forward flight and shoot away, as in the ‘ballistic’ flight of small songbirds. However, the advance ratio is higher in Anisoptera than in Calopterygidae.
Anisoptera also perform better than Zygoptera with respect to acceleration. Three categories of phase relationships between the beats of the fore-and hindwings are established: counterstroking, phase-shifted stroking and parallel stroking. Counterstroking produces uniform flight, whereas the flight produced by phase-shifted and, in particular, parallel stroking is irregular. The angles of attack of the wings are shown to be associated with particular flight manoeuvres, as are the stroke planes. Flight manoeuvres are discussed without drawing detailed aerodynamic conclusions. The flight of Anisoptera is compared with that of Zygoptera.
Cannibalism is a likely mechanism of population regulation in dragonflies that inhabit fish-free temporary ponds. I tested for density-dependent effects of cannibalism on survival and size structure of larvae of the dragonfly Tramea carolina in two short-term experiments in replicated artificial ponds. I was able to distinguish mortality due to cannabalism from other sources of mortality by preventing some populations from engaging in cannibalism. The first experiment included two density levels and the presence or absence of cannabilism in a factorial design. The no-cannibalism treatment was achieved by removing the labial palps from all individuals to prevent them from grasping large prey. T. carolina survived significantly better in the no-cannibalism populations at both densities, and this difference was greater at high density than low density, indicating that the proportion cannibalized was density dependent. A second experiment explored the form of the density-dependent cannibalism curve over a broad range of density. The results were adequately fitby a predator-prey model incorporating size structure, so that not all members of the population were vulnerable to cannibalism. In both experiments the survival of only the smaller instars was reduced, suggesting that cannibalism may reduce variation in the size distributions of dragonfly populations and contribute to emergence synchrony. The results demonstrated that cannibalism was strongly density dependent and may contribute to population regulation of dragonflies in temporary ponds.
The foraging behaviours and vulnerabilities to predation of larvae of four odonate species were studied in the laboratory. Predation by large Aeshna juncea larvae was compared in the presence and absence of zooplankton, and with odonate species presented individually and together. The large larvae of A. juncea showed high foraging activity irrespective of odonate prey treatment. Predation by A. juncea was lowest on Coenagrion hastulatum larvae, which had a "sit and wait" foraging mode, and highest on actively foraging Leucorrhinia dubia larvae. However, both activity and predation on L. dubia were lower in the presence of zooplankton and large A. juncea, perhaps reflecting avoidance of predation risk when foraging. Small larvae of A. juncea showed about the same foraging activity and vulnerability to predation as did L. dubia. Cordulia aenea larvae had intermediate foraging activity levels which were lower in the presence of zooplankton, but suffered high predation, indicating a low odonate predator escape ability. When all four odonate prey larvae were presented together, C. hastulatum and C. aenea experienced the lowest and highest predation, respectively, whereas predation on A. juncea and L. dubia was intermediate. About 25% of the large A. juncea larvae from field populations had preyed on L. dubia and C. hastulatum. The low abundances of A. juncea and C. aenea in the study ponds may explain why these species were not found in the fecal pellets of large A. juncea larvae. The results show that large A. juncea larvae frequently prey on odonate larvae. The intensity of this predation depends on the foraging behaviour of prey odonate larvae. However, the presence of alternative prey (zooplankton) and escape ability of the odonate larvae may also be important.
(1) Larval dragonfly populations were manipulated in large littoral zone enclosures to determine the importance of inter-odonate interactions and the effects of dragonflies on their prey. (2) Initial densities of early emerging odonate cohorts were about six times greater in one group of pens than in others. When initial densities were low, survivorship was higher and growth appeared to be faster than when initial densities were high. Highly significant differences of early species densities were maintained between treatment pens during the 6-month experimental period. (3) Early emerging odonates had a highly significant influence on the abundance of the smaller, late emerging odonates, indicating a strong interaction between odonate species. The interaction appeared to be due to predation by large odonates on small odonates. This is interpreted as an extreme form of interference competition which plays an important role in odonate population regulation. (4) Although there was a large treatment bias in prey species abundance, the results indicate that abundance of early emerging odonates plays some role in prey (especially Tanypodinae) abundance. (5) It is suggested that the primary determinant of community structure and production is an interaction between refuge level and predation rate. It is necessary for prey to be turning over at an unusually high rate and it is possible that odonates function in stimulating the rate of prey production.
We undertook a comprehensive morphological and molecular phylogenetic analysis of dragonfly phylogeny, examining both extant and fossil lineages in simultaneous analyses. The legitimacy of higher-level family groups and the phylogenetic relationship between families were tested. Thirteen families were supported as monophyletic (Aeshnidae, Calopterygidae, Chlorocyphidae, Euphaeidae, Gomphidae, Isostictidae, Lestidae, Libellulidae, Petaluridae, Platystictidae, Polythoridae, Pseudostigmatidae and Synthemistidae) and eight as non-monophyletic (Amphipterygidae, Coenagrionidae, Corduliidae, Megapodagrionidae, Protoneuridae and Synlestidae), although Perilestidae and Platycnemididae were recovered as monophyletic under Bayesian analyses. Nine families were represented by one species, thus monophyly was not tested (Epiophlebiidae, Austropetaliidae, Chlorogomphidae, Cordulegastridae, Macromiidae, Chorismagrionidae, Diphlebiidae, Lestoideidae and Pseudolestidae). Epiprocta and Zygoptera were recovered as monophyletic. Ditaxinerua is supported as the sister lineage to Odonata, Epiophlebiidae and the lestid-like damselflies are sister to the Epiprocta and Zygoptera, respectively. Austropetaliidae + Aeshnidae is the sister lineage to the remaining Anisoptera. Tarsophlebia's placement as sister to Epiprocta or as sister to Epiprocta + Zygoptera was not resolved. Refinements are made to the current classification. Fossil taxa did not seem to provide signals crucial to recovering a robust phylogeny, but were critical to understanding the evolution of key morphological features associated with flight. Characters associated with wing structure were optimized revealing two wing character complexes: the pterostigma–nodal brace complex and the costal wing base & costal–ScP junction complex. In turn, these two complexes appear to be associated; the pterostigma–nodal brace complex allowing for further modification of the wing characters comprised within the costal wing base & costal–ScP junction complex leading the modern odonate wing.
© The Willi Hennig Society 2008.
Females of Forcipomyia paludis were studied microscopically during their feeding action on Odonata wings where they were mostly attached to main veins in the basal half of the wings. In some individuals rhythmic nodding of the head was noted. Conspicuously many midges lifted the abdominal tip every one or two minutes and from the anus fast growing gas bubbles appeared that burst after about half a second. We suppose that the insects, having punctured the host's veins with their stout proboscis, sucked much air (as well as haemolymph) from the tracheae which they had to get rid of afterwards. From these observations, combined with further indications, it is inferred that F. paludis acts as a true parasite of Odonata and that the association is not only phoretic as previously assumed.
Survey data from New England showed that assemblages of Lestes damselflies are organized along the entire gradient of pond permanence and predator presence. One assemblage occupies vernal ponds lacking large dragonfly predators and fish; four are largely confined to temporary ponds that typically contain dragonfly predators; one dominates fishless permanent ponds and lakes where dragonflies are the top predators; and one dominates permanent ponds and lakes where fish are the top predators. We determined the role of life history and predation in maintaining this striking pattern by conducting a series of transplant experiments in the field and a laboratory experiment manipulating presence and absence of local predators. Life history (1) shaped the ability of species to cope with drying regime, thereby excluding temporary-pond Lestes from vernal ponds and permanent-water Lestes from temporary ponds, and (2) generated size differences among species due to differences in the timing of hatching. This mediated the exclusion of temporary-pond Lestes from permanent water bodies through asymmetric intraguild predation by permanent-water Lestes. Dragonfly predation on permanent-water Lestes had an indirect positive effect on the survival of temporary-pond Lestes; however, this effect apparently is too small to allow coexistence of both Lestes groups. Predation by large dragonfly larvae excluded the Lestes species of vernal ponds from temporary ponds, and differential vulnerability to large dragonfly larvae and fish shaped the reciprocal dominance of L. eurinus and L. vigilax in fishless and fish-containing permanent water bodies, respectively. Taken together, these results show that life history constraints and predation both shape the distributions of Lestes species along the pond permanence gradient in New England. We discuss the importance of this freshwater habitat gradient in shaping local and regional species diversity.
Interommatidial angles and numbers of ommatidia that viewed each segment of the visual field were mapped for a variety of dragonfly larvae from four families, selected for different behaviors and phylogenetic divergence, by measuring the directions of view of ommatidia contributing to the pseudopupil.
The size of the visual field and the amount of interommatidial angle specialization are greater than reported from histological sections, primarily because the optical axes are not perpendicular to the cornea.
Each species has interommatidial angle specializations that match its behavior. Larvae which are visual predators (family Aeshnidae) have interommatidial angles which vary from 4.9° in some parts of the eye to as little as 0.13° in the developing ommatidia at the anterior border. A foveal area can be defined with interommatidial angles of 0.2° which is the theoretical limit for ommatidia of their diameter, and is narrower than the interommatidial angles reported for adult insects. Foveal interommatidial angles measured along a vertical plane are considerably smaller than along a horizontal plane, resulting in an extremely elongate pseudopupil.
Larvae which are less dependent on vision for prey capture have correspondingly less structural specialization in the eye, but the same pattern of regional variation is still recognizable.
In contrast to the great range of interommatidial angles, ommatidial diameters are relatively uniform; the inverse relationship expected for highest visual acuity is not found.
Larval growth of Lestes disjunctus was completed in 70 d in the field, whereas in Coenagrion resolutum it took 10–22 months. This was not simply the result of occupying warmer microhabitats, because L. disjunctus larvae grew faster than C. resolutum at all constant temperatures between 10 and 25 °C in the laboratory. Multiple regression analysis showed that growth rates of both species were positively related to temperature and negatively related to larval size and to the square of temperature. The latter term is necessary to describe the decrease in growth rate at high temperatures. The equation predicted that the growth rate of L. disjunctus reached a maximum at 28.8 °C, whereas that of C. resolutum decreased above 22.4 °C. Small and medium-sized larvae of L. disjunctus ate more prey (Daphnia magna) in 15 min than C. resolutum at all prey densities. In 15-min experiments the attack coefficient for small L. disjunctus larvae was significantly larger than for small C. resolutum larvae and handling time for medium larvae was shorter. Other comparisons had large associated sampling errors, but the trends were the same. These differences may be associated with the relatively longer labia of L. disjunctus and its ability to change hunting methods from ambush to active search.
Dragonfly larvae catch prey by rapid protraction of a curiously modified labium. There are two main types of predatory behavior; 'climbers' move amongst aquatic vegetation and use their large compound eyes to detect prey at a distance and subsequently to orient towards it, while 'sprawlers' live at the bottom and detect most of their prey by tactile stimulation. Five species of dragonfly larvae were successful in 60 to 70% of their attacks on mosquito larvae, but in only 25 to 28% on gammarids. Size and movement of prey are important in its recognition, while shape, color, and odor are not. The forward thrust of the labium takes only 15 to 20 milliseconds, and at the time of the strike the anal siphon is closed so that the blood pressure, which provides the force for labial extension, is all directed forwards and is not used to expel water from the colon.
The Nyirkai-Hany wetland reconstruction area in northwestern Hungary is now designated as a Ramsar and a Natura 2000 site. It was created in 2001–2002 by the Fertő-Hanság National Park Directorate to restore a part of the formerly drained large wetland called Hanság and to offer waterbirds a suitable habitat for feeding and breeding. We focused on this aim of the restoration project and studied the temporal and spatial variation in abundance of birds and their invertebrate prey in this newly created wetland. From April 2007 until May 2008, we sampled plankton, nekton and benthos of different habitats monthly and monitored waterbirds weekly on the three different areas of the Nyirkai-Hany. During our investigations, 135 invertebrate and 53 waterbird species were recorded. Benthos and macrophyte decomposition accelerating guilds were the most abundant waterbird guilds—besides the dominant grazing importer material transporter guild, represented primarily by geese—in the Nyirkai-Hany. Zooplankton assemblages primarily consisted of small species not easily used as a food by planktivorous waterbirds. The low density of zoobenthic biomass and the small extent of shallow water mudflats probably accounted for the scarcity of the bioturbing guild group of birds. Nektonic biomass varied greatly among locations having different vegetation types, was greatest in the shallow water areas dominated by Typha, Carex and Phragmites species and lowest at offshore vegetation-free sites. Chironomids, mayflies and odonates were especially abundant and their biomass significantly correlated with several waterbird species, mainly belonging to the macrophyte decomposition accelerating guild (e.g. Anas platyrynchos, Fulica atra). This guild itself, which has increased in abundance in recent years, showed an exceptionally strong correlation with odonate abundance. These results indicate the growing importance of the Nyirkai-Hany wetland area as a foraging site for waterbirds.
A terminology is presented for structures and events in larval development of Odonata with the aim of bringing terms into conformity with those used for other insect orders in the light of accepted views of homology. The terms ‘exuvia’, ‘larva’, ‘prolarva’ and ‘stadium’ receive special mention. Records of the number of stadia required to complete larval development for 118 species are listed and analysed, showing that the range for Odonata is 8 through 18 stadia (8 through 18 for 8 species of Anisoptera; 8 through 17 for 38 species of Zygoptera) averaging 12.4 stadia for the order (Anisoptera 12.5 and Zygoptera 12.2), in which >90% of records range from 10 through 16 stadia (both Anisoptera and Zygoptera >90%). The number of stadia varies between and within species, sometimes within members arising from a single egg batch. No unifying hypothesis exists to rationalize variation in the number of stadia. Duration of successive stadia within a species can be a smooth, increasing progression but can also show wide departures from such a pattern. Duration of a single stadium can range from 1 day (or >1 day in the prolarva) through >1 year. Uniformity of size of the final-stadium larva can be achieved by the growth ratio (between successive ecdyses) compensating for the number of stadia. Aeshnidae typically have more stadia than do Libellulidae and also have a smaller average growth ratio. Ontogenetic profiles of growth ratios for different dimensions tend to have a characteristic form for each dimension, regardless of the eventual number of stadia. For some dimensions (e.g. headwidth) and some species the profile forms a smooth declining progression but for others (e.g. length of caudal appendage) it fluctuates irregularly. Headwidth therefore represents the dimension of choice for specifying stages of larval development. Rewarding avenues for research include the documentation of prospective links between larval life style on the one hand and stadial numbers and growth-ratio profiles on the other, and discovery of morphological characters that make it possible to determine to species larvae of early stadia.
In two bog-dwelling dragonflies, Somatochlora alpestris and S. arctica, the influence of oviposition date and temperature upon duration of embryonic development was studied. Egg diapause was facultative. With advancing season, the proportion of diapause eggs increases from 0 to 37% in S. alpestris and from 0 to 18% in S. arctica. Eggs needed at least 17 to 38 days for development. Hatching curves were temperature-independent in nearly all experiments but developmental rate increased at higher ambient temperature. In S. arctica, responses of developmental rate to temperature differed in eggs laid on different dates. In S. alpestris, duration of egg development decreased as season progressed. The duration of egg development of non-diapause eggs and proportion of diapause eggs in S. alpestris and possibly in S. arctica may also both be a function of female age at the time of oviposition. The ecological significance of the different development patterns is discussed.
1. Intra-guild predation between early larval instars of two co-existing dragonflies, Sympetrum fonscolombii and Trithemis kirbyi, was investigated with respect to temporal advantage and growth. Three situations were simulated experimentally: (1) Sympetrum fonscolombii began development 11 days before T. kirbyi. (2) Trithemis kirbyi began development 11 days before S. fonscolombii. (3) Both species began on the same day.
2. With a temporal advantage of 11 days to the second species, the resulting larval density of the respective first species was significantly higher than that of the second species.
3. Without a temporal advantage, the survival of S. fonscolombii was higher than that of T. kirbyi, and S. fonscolombii had a larger size due to faster growth than T. kirbyi. Hence, it is assumed that survival depended on early oviposition as well as on larval growth.
4. To test the relevance of the laboratory results, observations at artificial ponds in the Namibian semi-desert were conducted. Trithemis kirbyi was the first species colonising these ponds while S. fonscolombii arrived 15 days later. In field samples, many more Trithemis larvae than Sympetrum larvae were found, a pattern similar to the laboratory experiments in which T. kirbyi enjoyed a temporal advantage.