Higher investment in flight morphology does not trade off with fecundity estimates in a poleward range‐expanding damselfly

1. Evolutionary increases in dispersal‐related traits are frequently documented during range expansions. Investment in flight‐related traits is energetically costly and a trade‐off with fecundity may be expected during range expansion. 2. However, in contrast to wing‐dimorphic species, this trade‐off is not general in wing‐monomorphic species. In the absence of a dispersal‐‐fecundity trade‐off, an increased investment in clutch size at the expansion front is expected possibly at a cost of reduced offspring size. 3. The study evaluated investment in female flight morphology and fecundity‐related traits (clutch size, hatchling size) and potential trade‐offs among these traits in replicated populations of the poleward range‐expanding damselfly Coenagrion scitulum. 4. Females at the expansion front had a higher relative thorax length, indicating an increased investment in flight; this can be explained by spatial sorting of dispersal ability or in situ natural selection at the expansion front. Edge females produced larger hatchlings, however, this pattern was totally driven by the population‐specific thermal larval regimes and could not be attributed to the range expansion per se. By contrast, clutch sizes did not differ between core and edge populations. There was no signal of a dispersal–fecundity trade‐off either for a trade‐off between clutch size and hatchling size. 5. These results indicate that evolution of a higher dispersal ability at the expansion front of C. scitulum does not trade off with investment in fecundity, hence a dispersal–fecundity trade‐off is unlikely to slow down range expansion of this species.     

Microhabitat selection as an antipredator strategy in the aquatic insect Pachydiplax longipennis Burmeister (Odonata: Libellulidae)

Summary An investigation of the larval dragonfly fauna associated with the plant, Sagittaria platyphylla, was conducted in a small pond. Despite the presence of several larval anisopteran species in the pond, only Pachydiplax longipennis larvae were found on Sagittaria plants. A study of the microspatial distribution of P. longipennis larvae on S. platyphylla indicated that larvae use the various regions of a plant in a highly non-random fashion. Larvae show a strong preference for the leaf axil area. A generalized predator, the bluegill sunfish (Lepomis macrochirus), was allowed to selectively eat either of two larvae placed in various plant regions. This experiment indicated that larvae in a leaf axil area were significantly less susceptible to bluegill predation than larvae positioned in other plant regions. The microspatial distribution of starved larvae revealed that larvae with high hunger levels occupied the leaf axil area significantly less than well fed larvae, suggesting 1) larvae do not use these regions as feeding sites, and 2) high hunger levels may induce a behavioral shift in habitat use, with starved larvae forced into areas of high predation risk by the need to fulfill nutritional requirements.     

Temporal dynamics of mating and predation in mosquito swarms

We determined the numbers of copulations and predatory attacks in swarms ofAnopheles freeborni (Diptera: Culicidae), and the distribution of these events throughout the duration of the swarming period each day. On 19 evenings of observation, we recorded 2724 copulating pairs leaving swarms and 1351 dragonfly (Pantala hymenaea andErythemis collocata) attacks. Mating activity partially coincided with predator activity. Most copulations occurred between 10 and 20 min after the swarms formed, while predation events were most frequent during the initial 15 min of the swarm. We calculated the ratio of copulations to predatory attacks during the swarming period. This ratio was significantly higher in an area sheltered by trees than it was in the open. We suggest that physiological and ecological constraints other than predation operate on the mating system of this anopheline to affect the timing of swarm initiation and swarm site selection.     

SEXUAL SELECTION AND SURVIVAL SELECTION ON WING COLORATION AND BODY SIZE IN THE RUBYSPOT DAMSELFLY HETAERINA AMERICANA

I review methodological problems that can lead to false evidence for selection on secondary sexual characters and present a study of selection in rubyspot damselflies (Hetaerina americana) that avoids these pitfalls. Male rubyspots have a large red spot on each wing that grows to a terminal size after sexual maturity. Selection gradient analyses revealed evidence for positive sexual and survival selection on both terminal wing spot size and body size. Phenotype manipulations confirmed that wing spot size was subject to direct sexual selection, but showed that the positive slope of survival on wing spot size was an indirect effect of selection on unmeasured traits. This study provides the strongest evidence yet for sexual selection on coloration in Odonata, but also provides clear examples of why phenotypic selection statistics must be calculated and interpreted cautiously.     

中国隼[虫忽]科二新种（蜻蜓目：隼[虫忽]科）

记述采自海南省太阳隼[虫忽]属1新种：华氏太阳隼[虫忽]Heliocypha huai．sp．nov．和采自贵州省印度隼[虫忽]属1新种：赤水印度隼[虫忽]Indocypha chishuiensis,sp．nov．。模式标本保存于浙江自然博物馆昆虫标本室。     

Investigating damselfly populations at springs in Banff National Park, Canada, with special focus on Argia vivida, Amphiagrion abbreviatum, and Ischnura cervula (Odonata: Coenagrionidae)

The objective of this study was to estimate Argia vivida (Odonata: Coenagrionidae) populations, identify breeding habitat, and investigate movement of adults within Banff National Park, Alberta, Canada, during the summer of 2003. Mark-recapture techniques and standardized dip-net surveys were used to monitor Argia vivida at various life stages. A reproductive index identified which sites Argia vivida recognized as suitable breeding habitat, and exuvia surveys confirmed breeding sites. The basic structure of emergent and surrounding vegetation was measured to investigate the importance of available ovipositing or roosting sites and the condition of the matrix habitat. Data was recorded for Amphiagrion abbreviatum and Ischnura cervula (both Odonata: Coenagrionidae) to determine if these spring-associated damselflies were successfully breeding within Banff National Park. Comparisons were made between the highly protected Middle Springs and the heavily altered Cave & Basin Springs. Additional surveys at the Vermilion Lake cool spring and Middle Springs Bog investigated their use as breeding habitat for Amphiagrion abbreviatum and Argia vivida, respectively. Results suggest the ecological value of thermal springs extends beyond their origin to outflows and downstream pools. Conservation of Argia vivida must recognize the value of unobstructed thermal outflows, and consider the condition of the forested habitat surrounding springs with regard to its potential use as nocturnal roosts and dispersal corridors. Amphiagrion abbreviatum was confirmed breeding within Banff National Park, while no sign of breeding activity was recorded for Ischnura cervula.     

Are all Mexican odonate species documented? An assessment of species richness

With the aim of protecting Mexican diversity, one current governmental task is to complete national biological inventories. In the case of odonate insects, several researchers have hypothesized that species richness is complete (205 dragonflies and 151 damselflies), but there has not been any formal exercise to test this. Thus, we have investigated whether odonate species richness (for Mexican endemics, dragonflies (suborder Anisoptera), damselflies (suborder Zygoptera) and total species) is complete using sample-based and coverage-based rarefaction curves. Along with this, we also showed how good distribution data are in the country. The rarefaction curves have indicated 100% completeness for all groups suggesting that the inventory is complete. However, species' distribution data is highly patchy regarding areas either well (e.g. central Mexico) or badly (e.g. coast of Guerrero and Oaxaca) collected. We encourage researchers to continue odonate sampling in order to support at least three conservation actions: (i) conservation assessment of endangered species; (ii) knowledge of range shifts given rising global temperatures; and (iii) increase public interest and awareness in protected, touristic areas.