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Distance crawled by the larvae of G. flavipes and G. vulgatissimus from the waterfront to the emergence substrate at the reach of the river Tisza in Szeged. 

Distance crawled by the larvae of G. flavipes and G. vulgatissimus from the waterfront to the emergence substrate at the reach of the river Tisza in Szeged. 

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Abundance, phenology, sex ratio, emergence pattern, mortality and larval emergence behaviour of riverine dragonflies (Odonata: Gomphidae) were studied at the Lower-Tisza reach at Szeged (168–173 rkm) during the emergence period in 2011. Three 20 meter long sampling sites were chosen and searched systematically for exuviae, dead specimens and dragon...

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... mortality of G. flavipes during the emergence period was 5,58%. According to the literature (Farkas et al. 2011, 2012b) this is a normal value by this abundance of the species. Larvae consumed by predators (4,9%) make up the largest proportion of the total value, and within predation birds are liable for the most consumed larvae (4,48%). These specimens can be easily distinguished from those that were consumed by other, unknown predators (0,42%) in most cases. When birds eat the emerging dragonflies they leave the uneatable wings of the insects behind, so if the wings are found nearby the exuviae that refers to bird predators. Linear regression shows that there is a significant and positive correlation between the amount of emerged dragonflies and mortality caused by birds (β=0,52; F=15,4; df=1 and 12; p=0,002, n=12). The remaining proportion of mortality was caused by abnormal moulting (0,34%) and the abnormal decompression of the wings (0,34%). I used data of 763 specimen of G. flavipes exuviae to the examination of substrate preference, because the original support could be identified without doubts by that many exuviae (in the other 420 case the exuviae were found lying on their back, or due other reasons I could not identify the original support). According to one-way ANOVA there is a significant difference between the support choice (F=7,832; df=7,16; p<0,0003), the majority of the larvae chose soil as an emergence support (Table 1.). Tukey’s pairwise comparison shows (Table A.1.) that soil is significantly differ from any other supports and between other support types there are no significant difference in terms of preference. According to the distance data crawled by larvae, there is a significant difference between G. vulgatissimus and G. flavipes populations (Kruskal- Wallis-test: H=13,35; Hc=13,35; p<0,0005). G. vulgatissimus crawl greater distance (horizontal+vertical) from the waterfront than the other species, although there was no vertical movement observed of G. vulgatissimus specimens. (Figure 4. and Table 2.). Water level, water temperature and air temperature (investigated their effects individually) have no significant effect on the distance crawled by G. flavipes larvae (Linear regression: β= -0,24; F=0,35; df=7,3; p=0,79; n=12), and they have no significant effect if we assume interaction between them either (Linear regression: β= 0,07; F=1,11; df= 7,3; p=0,51; n=12). None of the models were supported by the AIC. Nevertheless, marginally significant positive connection was found between water temperature and the number of exuviae (Linear regression: β=0,52; F=14,1; df= 1,11; p=0,003; n=13). At the investigated reach of the river Tisza G. vulgatissimus and G. flavipes seem to form stable populations. Although there is a huge difference between the abundance of the two species this phenomenon seems to be normal along the river Tisza and every other places where the two species occur to gether. (Jakab and Dévai 2008). In 2011 at Szeged the abundance of G. flavipes was 36 times bigger than G. vulgatissimus , many authors inform about a similar result, nevertheless, the differences in abundance quoted by these papers are greatly variable. According to Jakab (2006) at the reach between Tiszafüred and Tiszacsege in 2001 the abundance of G. flavipes was 8 times greater, during the following years the abundance of G. flavipes was much more greater than the abundance of G. vulgatissimus : 11 times greater in 2002; 23 times greater in 2003 and 26 times greater in 2012 (Farkas et al. 2012a). At Vásárosnamény in 2008 the abundance of G. flavipes was 2 times greater than the abundance of G. vulgatissimus (Farkas et al. 2008). As we can also see the differences increase toward the south greatly, it could be possible that the southern regions of the river Tisza can provide better conditions for the populations of G. flavipes , as this species, in his paper Berzi-Nagy (2011) made the same conclusions. In the case of O. cecilia it is quite sure that the species has no stable population at the investigated reach of Tisza. This species, as well as the Small Pincertail ( Onychogomphus forcipatus ), the fourth occurring Gomphid in Hungary, prefers small rivers and streams with high oxygen level and moderate flow (Raab et al. 2006). The two specimens might have drifted from the river Maros, where they form populations (Jakab and Dévai 2008). The result of the investigation shows that in 2011 at Szeged there was no significant difference between the ratio of sexes either in case of G. vulgatissimus or G. flavipes . In the case of G. flavipes the number of individuals in both sexes are almost the same. Although, for the subgenus Anisoptera it is general that the number of females is higher than the number of males (Berzi-Nagy 2011; Farkas et al. 2009; Jakab 2006) similar result may occur (Jakab 2006). It is also an example that the sex ratio of a certain species differ at the same reach of a river between years (Corbet 1999 – cit. Farkas et al. 2009), so it is possible that next years the sex ratio of the G. flavipes also will change. In 2011 at Szeged the G. vulgatissimus acted as a ’spring species’ (the species emerged strongly synchronized within a short time) the G. flavipes as a ’summer species’. (the emergence was less synchronized and stretched in time) This phenomenon can be observed at other regions of the river Tisza during the last decade as well. According to Berzi-Nagy (2011) the emergence pattern of G. flavipes showed the trait of a ’spring species’ at the Middle-Tisza region near Szolnok. Jakab (2006) reported the same phenomenon from that region, but during his three year long investigation the pattern of the emergence of G. flavipes varied between years, too, and the differences were significant. Similarly to sex ratio, the pattern of emergence can vary between years, and also between different reaches of one certain river. Variability could be caused by water temperature: lower water temperature in winter and higher one during summer caused more synchronized emergence (Suhling 1995 – cit. Jakab 2006). The emergence pattern of G. flavipes shows two peaks, but this cannot be explained with weather conditions, because these peaks do not coincide with the highest air temperatures. So in this case, cohort splitting seems to be the best explanation to the emergence pattern as cohort splitting and unsuitable weather conditions can cause a long-drawn emergence period too. The reason of cohort splitting is that females lay eggs during the entire emergence period and some larvae winter in the final (F0) larval, while some in the penultimate (F-1) larval stage. Those that winter in F-1 stage will emerge a few days or weeks later and they cause the second peak in the emergence pattern. The fact that more than 90% of the larvae chose soil as emergence support does not necessarily mean that there is a specific attachment to the soil as substrate. 92% of the 763 G. flavipes larvae emerged within 2 meters from the waterfront and 78% of them within 1,5 metres. There is a possibility that the over-representation of the soil has caused this phenomenon, as during most of the emergence period there were no – or was in very low proportion of – other substrates in the first 1,5-2 meter zone from the waterfront. Former studies (Farkas et al. 2009, 2011) claim that in the case of G. flavipes larvae there is no substrate-specific attachment, but they choose supports that are available within a certain distance from the waterfront. This idea is supported by the observation that larvae that chose 13 green leaves (second most frequently chosen emergence support) did not crawl further than the mean distance but most of them emerged in late June and July, when the vegetation had grown in this zone too (68% of them emerged within 2 metres; 68 % emerged in July and 54% of them emerged within 2 metres in July). During the emergence period in 2011 there were 66 G. flavipes exuviae, larvae or young imagines found consumed by predators or wounded mortally at the investigated reach of the river. This proportion at this density is quite normal (Farkas et al. 2011, 2012a,b). Due to the emergence strategy of the species [larvae emerge close to the waterfront and the entire process takes 15-59 minutes, which is very short compared to other Anisoptera taxa (Farkas et al 2012b)] the major factor for mortality is predators, especially birds as common blackbird ( Turdus merula ) and white wagtail ( Motacilla alba ) (personal observation and Farkas et al. 2012a,b). Results of the present study shows that G. vulgatissimus larvae crawl greater distances from the waterfront than G. flavipes larvae, as there is a strong significant difference between the crawled distance (from the waterfront to the emergence support) of the two species. This seems to be general along the river Tisza (Farkas et al. 2009, 2011, 2012a,b), and the explanation is that G. vulgatissimus starts emerging in late April or early May when greater fluctuations of the water-level is possible, while in late May or early June, when the G. flavipes starts the emergence, there is a less chance of the fluctuation of the water level (Farkas et al. 2012b). The background variables could have a strong effect to the emergence of the Gomphidae species: Berzi-Nagy (2011) claims that the level and temperature of water could influence the rate of synchronization and the timing of emergence. Moreover, according to former studies (Farkas et al. 2009) water level has a positive and water temperature has a negative effect on the crawled distance. In the case of this present study, the fact that none of the background factors showed to effect the distance, might be due to the low sample size. My sincere thanks go to Judit Márton and Róbert Gallé for the English language corrections and ...

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... Until now, studies on the selection of emergence sites have been conducted on single species [23][24][25], while most studies on the ecological niches of coexisting species have focused more on temporal rather than spatial segregation. Considering larvae, in most cases a spatial segregation was observed [26,27], while a temporal separation in the emergence patterns occurs when several congeneric species coexist in the same habitat [28][29][30]. For instance, two congeneric species, Anax imperator Leach 1815 and A. parthenope Sélys 1839, share similar environmental requirements but avoid competition through a temporal shift of their emergence peak [31]. ...
... Based on our results, the preservation of the aquatic vegetation, and especially of aquatic plants, is therefore crucial not only to guarantee the complex habitat structure that favors the emergence of A. grandis but also to permit the coexistence of the two congeneric species of Aeshnidae in the investigated sites. Although the coexistence of multiple dragonfly species is often mediated by a temporal segregation in the emergence peaks [28][29][30], the structure of the vegetation could enhance species coexistence through spatial segregation. ...
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... The inter-year variations at the same site might have been attributed to the differences in annual fluctuations in the water temperature, indicating that rising temperatures may influence not only the onset of emergence but the synchrony as well. Abundance, phenology, sex ratio, emergence pattern, mortality and larval emergence behaviour of riverine dragonflies (Odonata: Gomphidae) at the Lower-Tisza reach at Szeged (168-173 rkm) was studied during the emergence period in 2011 [8]. Horváth (2012) [8] found 1,217 exuviae during the emergence period in 2011. ...
... Abundance, phenology, sex ratio, emergence pattern, mortality and larval emergence behaviour of riverine dragonflies (Odonata: Gomphidae) at the Lower-Tisza reach at Szeged (168-173 rkm) was studied during the emergence period in 2011 [8]. Horváth (2012) [8] found 1,217 exuviae during the emergence period in 2011. Differences in abundance increased towards the south greatly, it could be possible that the southern regions of the Tisza River can provide better conditions for the population of G. flavipes [2]. ...
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Till now, altogether 50 species of dragonflies have been found in the Danube and its arms in Slovakia. One of the most important indicator species is Gomphus (Stylurus) flavipes, listed as strictly protected by Appendix II of the Bern Convention. Large population of Gomphus flavipes was found in the Malý Dunaj (Small Danube), in the area called Danube’s “Inland Delta”, in 2000–2001. Watching of dragonflies in the Danube Delta (Romania) demonstrated another large population in 2007–2008. In contrast with these observations are our results, from long–term monitoring of dragonflies in the Danube, in the area influenced by the Gabčíkovo power plant (operational since 1992). Changes in hydromorphology in this section started in 19th century and at present dam represents a significant impact on the functioning of the Danube ecosystem. During 20 years monitoring we found only one larva of Gomphus flavipes in the Danube at the site downstream of the dam. Another critically endangered species, mayfly Palingenia longicauda was found in the Danube Delta in 2009. We observed emergence of giant mayfly in the Danube´s arm in Romania. Palingenia longicauda disappeared totally in the 1930s from many European rivers. At present it occurs in Tisza and Rába rivers (Hungary) and has been reintroduced in Lippe and Odra rivers (Germany). New findings of large populations of Palingenia longicauda in the Romanian Delta has been unknown till now. Findings of large population of Gomphus flavipes in deltas confirm that river deltas are of high importance for aquatic biodiversity conservation.
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Understanding the consequences of past and future climatic changes on biodiversity has become one of the most important challenges of current ecological research. Due to the funda-mental importance of climate for determining the distribution and abundance of species, climatic changes have led to strong shifts of species’ ranges to higher altitudes and latitudes as well as to local changes in the phenology and abundance of species during the last decades. Nevertheless, most organisms are incapable of rapid responses to such changes as they are constrained by, for instance, phylogenetic conservatism in thermal adaptations and dispersal limitations. Therefore, a mechanistic understanding of the variation in functional traits of species is crucial for predicting biological responses to climate change. 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From a physiological perspective, strong arguments exist that biophysical principles link variation in species’ colour lightness and body size to heat gain and loss in endothermic animals. Larger species retain body heat more efficiently than smaller species owing to their lower surface-area-to-volume ratio, and darker coloured species heat up faster than lighter coloured species because they absorb more solar radiation. Other functions include enhanced immunocompetence of larger species and enhanced pathogen re-sistance (Gloger’s rule) as well as UV protection of darker species. Mechanistic links between these two morphological traits, species’ physiolo-gy and climate are hence probably important determinants of variation in the distribution and abundance of ectotherm organisms, but the limited availability of distributional and morphologi-cal data has so far hampered a large-scale perspective on the physiological processes that shape biogeographical patterns in insects. Constraints to the evolution of species’ morphological traits and dispersal abilities can limit the colonization of regions characterized by new climates or habitats and thereby influence geographical patterns in the phylogenetic diversity or geographical rarity of taxa. On the one hand, spatial concentrations of rare species are important conservation targets, because they indi-cate the distribution of species that are both particularly vulnerable to extinction in the future and unique elements of biodiversity. On the other hand, overall patterns of these facets of diversity provide information about past dispersal events and the ecological processes that shaped contemporary patterns of biodiversity. In six chapters of my thesis I investigate whether biogeographical patterns of insect assemblages are driven by variation in the colour lightness and the body size. I show that melanin-based thermoregulation, pathogen resistance and UV protection are important mechanisms that influence the distribution of dragonflies, butter-flies and moths at both local and continental scales. In all studies, species assemblages in cooler climates are on average darker coloured than assemblages in warmer climates. Furthermore, in line with the prediction that darker colouration is advantageous in regions with high humidity and in regions with high solar radiation due to the protective functions of melanin, colour lightness generally decreases with increasing precipitation and insolation. Body size clines are less strong and differ considerably among the considered taxa. In addition, I demonstrate that contrasting effects of the benefits and the energetic costs of an investment into body size and melanization on the range size and abundance of butterfly species can offset each other when their interactions with components of the energy budget are not taken into account. Thus, larger and darker butterfly species only have wider distributions and are more abundant if they compensate the costs of an investment into body size and melanization by reducing mobility costs or increasing energy uptake. In three additional chapters, I investigate whether evolutionary constraints on species’ thermal adaptations and dispersal ability influence the composition of insect assemblages and I assess the extent to which diversity patterns of insects are shaped by the contemporary climate and historical climatic changes. Using European dragonflies, I show that both phylogenetic conservatism of thermal adaptations and dispersal limitations constrain the recolonization of previously glaciated areas of Europe, resulting in a decrease of the endemism and phylogenetic di-versity of assemblages with decreasing tempera-ture and the increasing proportion of species with a high dispersal ability. In addition, I demonstrate that the climatic changes since the Last Glacial Maximum are consistently major drivers of the endemism and species richness of mammals, birds, amphibians and dragonflies across Africa. However, the results of this study also indicate that the signatures of species’ responses to historical climatic changes differ considerably between the considered taxa and are currently less effectively protected. Finally, using a group of flightless orthopterans endemic to Africa, I exemplify that the diversity of this group, and probability most of the insect diversity today found in the Eastern Arc Mountain biodiversity hotspot, has been generated by the interplay of humid periods that allowed the spread of forest-bound lineages across Africa with aridity-driven fragmentations of forests and their associated faunas. In conclusion, I demonstrate that both body size and colour lightness are major determinants of distribution and abundance of insects, across taxa, regions and scales. Despite the significant contributions of other functions of colour lightness, such as pathogen resistance and UV protection, as well as of the thermoregulatory function of body size, melanin-based thermoregulation is the most important and a strikingly general mechanism that shapes biogeographical patterns of insect. To understand and predict the effects of body size and colour lightness on ecological dynamics of insect species it is, however, crucial to account for their interactions with components of the energy budget, because the contrasting effects of an investment into body size, wing size and melanization on the range size and abundance of species can partly offset each other. Purely correlative approaches that predict spatio-temporal variation in the distribution and abundance of insect species based on easily measured morphological traits are therefore prone to false mechanistic conclusions and likely underestimate the functional importance of morphological traits. Furthermore, phylogenetic conservatism of thermal adaptations and dispersal limitations affect trait-environment relationships and species’ responses to historical climatic changes. Together these results highlight the potential of models that integrate morphological, climatic and phylogenetic data for improving predictions of species’ responses to climate change as well as our understanding of the processes that generated and maintain the remarkable diversity of insects on Earth.
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1. Previous macrophysiological studies suggested that temperature-driven color lightness and body size variations strongly influence biogeographical patterns in ectotherms. However, these trait-environment relationships scale to local assemblages and the extent to which they can be modified by dispersal remains largely unexplored. We test whether the predictions of the thermal melanism hypothesis and the Bergmann's rule hold for local assemblages. We also assess whether these trait-environment relationships are more important for species adapted to less stable (lentic) habitats, due to their greater dispersal propensity compared to those adapted to stable (lotic) habitats. 2. We quantified the color lightness and body volume of 99 European dragon-and damselflies (Odonata) and combined these trait information with survey data for 518 local assemblages across Europe. Based on this continent-wide yet spatially explicit dataset, we tested for effects temperature and precipitation on the color lightness and body volume of local assemblages and assessed differences in their relative importance and strength between lentic and lotic assemblages, while accounting for spatial and phylogenetic autocorrelation. 3. The color lightness of assemblages of odonates increased, and body size decreased with increasing temperature. Trait-environment relationships in the average and phylogenetic predicted component were equally important for assemblages of both habitat types but were stronger in lentic assemblages when accounting for phylogenetic autocorrelation. 4. Our results show that the mechanism underlying color lightness and body size variations scale to local assemblages, indicating their general importance. These mechanisms were of equal evolutionary significance for lentic and lotic species, but higher dispersal ability seems to enable lentic species to cope better with historical climatic changes. The documented differences between lentic and lotic assemblages also highlight the importance of integrating interactions of thermal adaptations with proxies of the dispersal ability of species into trait-based models, for improving our understanding of climate-driven biological responses.
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Monitoring of conservation status is an obligation arising from Article 11 of the Habitats Directive for all species of community interest. However, the development of monitoring methods for invertebrate species has received relatively little attention. Gomphus flavipes (Charpentier, 1825) and Ophiogomphus cecilia (Fourcroy, 1785) are two dragonfly species, listed in the annexes of the Habitats Directive, which suffered severe declines in the last century and have since recovered. Methods for the monitoring of these two gomphids have been proposed, but these have not been extensively tested and no abundance classes have been proposed for the evaluation of the conservation status of these species. A time-based standard sampling method is proposed for both species and results from numerous sites in Lombardy, northern Italy, are presented. Applying the standard method revealed that it is common for rivers that high water levels preclude sampling of exuviae through the summer and it is better to allow for two seasons when planning the monitoring. A further result is the fact that it was not always possible to sample the same stretches as the dynamic nature of the rivers and fluctuations in water level lead to some river banks becoming unsuitable for sampling during some visits. In these cases the time-based approach was advantageous, as the method did not need to be modified in response to the original bank section becoming unsuitable.