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Instances of heat waves and cold snaps are becoming more frequent and of increasing duration worldwide. It is well established that short exposure to high or low-temperatures, such as during extreme weather events, often results in adaptive (acclimation/hardening) or maladaptive plastic changes in tolerance of organisms to subsequent thermal stressors. However, little information is available about how the duration of a prior stressful thermal event mediates future organismal thermal responses. Understanding durational effects of thermal conditioning can help predict ectothermic survival in response to novel extreme weather patterns. We assessed the effect of stressful temperature duration on tolerance to subsequent cold exposure in a widespread freshwater invertebrate species in Britain. Following a week-long acclimation period at 15°C, wild-caught blue-tailed damselfly Ischnura elegans larvae were held at stressful thermal extreme (2°C or 30°C) temperatures for varying durations designed to mimic a range of extreme to plausible durations of heat waves or cold snaps in the wild (30 min, 2 h, or 24 h). After a period of re-equilibration to ambient temperatures (15°C), we then experimentally assessed CTmin, the temperature which renders an individual unresponsive, as an index of cold tolerance. Prior exposure to 2°C, simulating a cold snap, improved future cold tolerance, but only when individuals experienced very brief prior exposures to these conditions (30 min up to 2 h), and this benefit was lost following 24 h prior exposure. Prior exposure to 30°C, simulating a heat wave, consistently worsened the subsequent cold tolerance of individuals, with the detrimental effect of prior heat exposure increasing linearly as a function of duration. The research indicates that cold snaps can provide beneficial hardening effects against future cold exposures, but only when these (priming) extreme weather events are of very short duration (here, 30 min or 2 h). Longer durations of exposure to either extreme heat or cold weather events can reduce the ability of individuals to beneficially react to subsequent cold stresses, and may have deleterious effects on future thermal tolerance. The results suggest that increasing durations of extreme temperature events will reduce cold hardening ability of freshwater invertebrates, and that the duration of extreme weather events, or durational changes in freshwater thermal regimes resulting from changes in snowmelt dynamics, is an important parameter to consider when studying organismal responses to climate change. [ABSTRACT FROM AUTHOR]

Coenagrion mercuriale is rare in the UK and is threatened across Europe. Ischnura pumilio is also threatened in the UK. Both species have suffered population declines in recent years and are vulnerable to habitat fragmentation and loss. Yet, reliable population size and survival estimates are scarce in odonate species. This study provides mark-release-recapture estimates of these parameters for UK stronghold populations of both species., Surveys were performed at four locations in southern England between 2001 and 2006. A total of 12 071 adult individuals were marked across nine populations. Mark-release-recapture modelling techniques were used to provide survival and recapture probabilities and population size estimates., This study presents the first Horvitz-Thompson estimates of population size in odonates, which are among the highest reported for damselflies. Maximum estimates for a single site were 63 662 ± 4997 for C. mercuriale and 7453 ± 382 for I. pumilio. More males than females were captured at all sites, but calculated estimates indicated a female-biased sex ratio in adult I. pumilio at one location., Daily survival probability is among the highest published for damselflies. Male and female survival was equal or very similar in all populations. Further effects of maturity, age, site, and time on survival were identified., Estimated population sizes are much greater than previously thought, suggesting that where habitat is maintained, populations of threatened odonates can be very large. Furthermore, greater proportions of females have been estimated where wider searching techniques were employed. This has implications for future study design if estimates are to be reliably used for conservation management. [ABSTRACT FROM AUTHOR]

Many species, particularly insects, pass through a series of distinct phases during their life history, with the developmental timing directed towards appropriate resources. Any factor that creates variation in developmental timing may partition a population into discrete populations-or 'cohorts'. Where there is continued failure to recruit outside the natal cohort then alternate cohorts will have their own internal dynamics, eventually leading to independent demographic and evolutionary trajectories. By contrast, continued variation in development rates within a cohort-cohort splitting-may homogenise otherwise independent demographic units. Using a panel of 14 microsatellite loci, we quantify the genetic signature of apparent demographic isolation between coexisting, but alternate, semivoltine cohorts of the damselfly Coenagrion mercuriale at locations that span its distribution in the UK. We find consistently low levels of genetic divergence between sympatric cohorts of C. mercuriale, indicative of developmental plasticity during the larval stage (unregulated development) whereby some individuals complete their development outside the predominant 2-year (semivoltine) period. Thus, individuals that alter their developmental rate successfully recruit to a different cohort. Despite maintaining contrasting population sizes, gene flow between alternate cohorts broadly is sufficient to place them on a similar evolutionary trajectory and also buffers against loss of genetic diversity. Such flexible larval development permits a response to local conditions and may facilitate response to environmental change. [ABSTRACT FROM AUTHOR]

Geographic range expansion is one of the best documented macroecological consequences of climate change. A concomitant change in morphology has been demonstrated in some species. The relationship between latitudinal variation in morphology (e.g. Bergmann's rule) and the morphological consequences of microevolutionary pressures at expanding range margins have received little attention in the literature. Here we compare morphology of males of two Palaearctic damselfly (Odonata: Zygoptera) species, Coenagrion puella (Linnaeus, 1758) and Pyrrhosoma nymphula (Sulzer, 1776). C. puella has recently expanded its range from the north of England into Scotland. P. nymphula does not exhibit a range margin in the United Kingdom and has established populations in northern Scotland. We demonstrate evidence for spatially correlated variation in body size across the sampling sites between the two species but a deviation in patterns of dispersal-related morphology. P. nymphula exhibited very weak relationships between dispersal-related morphology (wing loading and thorax : abdomen mass ratio) and latitude. However, the more southerly-distributed C. puella exhibited strong relationships between mass investment in dispersal-related morphology and latitude. These trends appear to indicate compensatory growth patterns in cooler environments like those demonstrated for other species. The limits of this compensation for conditions that are close to the limits of a species' tolerance may contribute to the determination of the range margin. Greater variation in morphology towards the range margin has been observed in previous studies in Odonata. As such, the location of the sampling sites relative to the range margin of each species (closer in C. puella than P. nymphula) is highlighted as a potential contributing factor to the variation observed. [ABSTRACT FROM AUTHOR]

Coenagrionid damselflies are in general decline in the British Isles. Numerous factors have been implicated in the loss of these species including recent speculation that hybridisation between congeners may result in species decline. Here we use a panel of 12 microsatellite loci to examine levels of genetic divergence and the likely occurrence of hybridisation in five populations of Coenagrion puella and C. pulchellum using samples from four sites in south-east England. Coenagrion puella and C. pulchellum were highly genetically divergent, and there was no evidence of hybridisation between any of the populations examined, even where C. puella and C. pulchellum were sympatric. There was some suggestion that C. pulchellum was less genetically diverse than C. puella, though this may have been a result of ascertainment bias associated with cross-species application of microsatellite markers. We conclude that there is no evidence that hybridisation between C. puella/pulchellum could be responsible for the on-going demographic decline in C. pulchellum. Nevertheless, further genetic studies such as this one are likely to provide estimates of diversity, population structure and dispersal capacity that will be invaluable in future conservation management strategies for coenagrionid damselflies. [ABSTRACT FROM AUTHOR]

Coenagrion mercuriale (Charpentier) (Odonata: Zygoptera) is one of Europe's most threatened damselflies and is listed in the European Habitats directive. We combined an intensive mark-release-recapture (MRR) study with a microsatellite-based genetic analysis for C. mercuriale from the Itchen Valley, UK, as part of an effort to understand the dispersal characteristics of this protected species. MRR data indicate that adult damselflies are highly sedentary, with only a low frequency of interpatch movement that is predominantly to neighbouring sites. This restricted dispersal leads to significant genetic differentiation throughout most of the ltchen Valley, except between areas of continuous habitat, and isolation by distance (IBD), even though the core populations are separated by less than 10 km. An urban area separating some sites had a strong effect on the spatial genetic structure. Average pairwise relatedness between individual damselflies is positive at short distances, reflecting fine-scale genetic clustering and IBD both within- and between-habitat patches. Damselflies from a fragmented habitat have higher average kinship than those from a large continuous population, probably because of poorer dispersal and localized breeding in the former. Although indirect estimates of gene flow must be interpreted with caution, it is encouraging that our results indicate that the spatial pattern of genetic variation matches closely with that expected from direct observations of movement. These data are further discussed with respect to possible barriers to dispersal within the study site and the ecology and conservation of C. mercuriale. To our knowledge, this is the first report of fine-scale genetic structuring in any zygopteran species. [ABSTRACT FROM AUTHOR]

Focuses on species of the damselfly genus Coenagrion regularly bred in Great Britain. Which species of Coenagrion have become extinct, or have highly restricted distributions; Distributions of the azure damselfly (C. puella) and the variable damselfly (C. pulchellum); Data suggesting that variable damselfly is experiencing a national decline in Great Britain; Aim of this study with regard to the genetic relationships among populations of C. puella and C. pulchellum; Mitochondrial sequence data from several C. puella and C. pulchellum individuals; How this data revealed three haplotypes with high overall similarity; Suggested methods of hybridisation between C. puella and C. pulchellum including the sharing of a haplotype between C. puella and C. pulchellum, and the fact that morphological characters of sympatric C. puella and C. pulchellum populations are not always species-specific; View that more research is required before we can determine whether or not hybridisation is playing a role in the decline of Coenagrion species in the U.K.