Habitat use and movements of a large dragonfly (Odonata: Anax imperator) in a pond network

Abstract

Local movements of aquatic insects within the surroundings of waterbodies aim essentially to find food, mates, resting sites, or avoid predation. Distances moved are very variable among species and may also differ depending on sex or age at the intraspecific scale. Despite a large panel of studies on odonate activities near waterbodies, little is known about their movements and behaviour in the surrounding landscape matrix. This knowledge is, however, crucial to support management schemes of pond networks and allow improvement of connectivity between them. In this study, 87 individuals of the large dragonfly Anax imperator were identified with a unique code on the wings and monitored visually on five ponds during summers 2017 and 2018. Simultaneously, 54 individuals were equipped with radio transmitters and tracked for up to 15 days. We built Cormack Jolly Seber models to test which factors are important for movement and survival of individuals, and calculated home ranges. Additionally, we performed a step selection analysis on the telemetry data to identify the terrestrial habitats selected by A. imperator at the interface between a rural area and a suburban area in north‐western France. A reduction of the survival rate was observed on the day immediately following capture regardless of the marking method. Individuals equipped with radio transmitters had a lower estimated daily survival (0.78; 95% confidence interval = 0.70–0.85) compared to wing‐marked individuals (0.89; 95% confidence interval = 0.85–0.92). Wing loading and age were the main variables influencing dragonfly survival for both methods. The probability of movement between ponds was similar for both sexes, but radio‐tracking data showed that females moved significantly further away in the landscape matrix than males, with one female detected up to 1,902 m away from the release pond. Females also had a larger home range (mean 95% kernel: 50 ha) than males (mean 95% kernel: 5 ha). Reproductive behaviour of males and flying behaviour of females were positively related to air temperature. Individuals of both sexes were present on ponds more often than in all other habitats whatever their activity. High trees were the preferred place to rest when air temperatures were low, especially for females. Overall, this study highlights the importance of integrating neighbouring trees in management schemes of ponds. It also confirms that preservation of pond networks must include on several hectares of land around ponds to meet the aquatic and terrestrial needs of amphibious organisms such as odonates. Our radio‐tracking data provide a basis for further studies on the persistence of odonate meta‐populations in fragmented landscapes.

Genetic Diversity and Structure of Anax imperator Leach, 1815 Populations (Odonata: Aeshnidae) in Ponds at Regional and European Scales

“…Anax imperator populations sampled in the Normandy region in France had a low level of genetic differentiation (i.e., F ST -values all below 0.03) compared to previous studies on European odonates at a local or regional scale (i.e., F ST up to 0.08, 0.10, 0.24 and 0.28 for Leucorrhinia dubia Vander Linden 1825, Coenagrion scitulum Rambur 1842, C. mercuriale, respectively) [45,[82][83][84]. Such results confirm the high mobility of A. imperator [85] and its efficient dispersal between ponds at the regional scale [54]. However, at the European scale, a moderate level of genetic differentiation was found between populations.…”

“…Mature adults present a territorial behaviour but are also very mobile around their mating sites. Movements of individuals have been recorded over few kilometers only, whereas this species is expected to undertake flights on much longer distances [54]. However, lack of information on longdistance dispersal events of Anax imperator can be explained by the difficulty to track insects during long periods with available capture-mark-recapture techniques.…”

Integrating high‐speed videos in capture‐mark‐recapture studies of insects

“…Data on survival probability are crucial for demographic modeling (Carey, 1993). The estimated survival probability in A. junius was similar to that reported for the congeneric A. imperator surveyed with conventional capture-mark-recapture in Northwestern France (Minot et al, 2020). Our results show that HSV improved the estimates of survival probability in both species.…”

“…The model accounts for imperfect detection, gives estimates of the survival and resighting probabilities, and tests how the latter are determined by intrinsic factors such as age, body size, and extrinsic factors such as the weather (Kéry & Schaub, 2012). In odonates, many studies have used CJS to estimate rates of recapture and survival (Cordero-Rivera et al, 2019;Khelifa et al, 2019;Macagno et al, 2008;Minot et al, 2020;Outomuro et al, 2016: Stoks, 2001b).…”

Fall of giants: European diversity resistance to waterscape degradation and its potential continental drivers

“…The distance at which the probability of dispersal was 0.5 was used as an indicator of the dispersal ability of the species under analysis (Borthagaray, Cunillera-Montcusí, Bou, Tornero, et al, 2023); Supplementary material 2). We defined 7 different dispersal abilities ranging from 0.001km, which would represent organisms with very limited movement capacity (e.g., Incagnone et al 2015), to 10km, which would represent organisms able to cover large distances across the waterscape (e.g., Figuerola & Green, 2002;Minot et al, 2020) including intermediate dispersal ranges (i.e. 0.1, 0.5, 1, 2, 5km).…”