The roles of temperature and diapause in the life history of a temperate-zone dragonfly: Argia vivida (Odonata: Coenagrionidae)

Abstract. 1. The life cycle of Argia vivida Hagen generally took longer to complete in the field than was predicted on the basis of the thermal sum accumulated in laboratory rearing.
2. The prediction of a bivoltine life-cycle from geothermal sites with either a constant annual temperature of 26°C or thermal range of 11–31°C was not borne out because the intervention of short-day induced developmental delays in later larval instars extended the life cycle to 1 year.
3. This diapause, which synchronizes adult emergence with favourable summer temperatures, was also present in larvae from sites with annual temperature ranges of 0–33°C and 5–20°C.
4. At these colder sites completion of the life cycle takes 2 and 3 years respectively and dragonflies must be in cold-resistant stages during the winter. A long-day diapause, principally affecting late-instar larvae below a certain size during the summer, achieves this.
5. Large diurnal temperature fluctuations at the 0–33°C site markedly increase the useful thermal energy available to larvae for growth over that predicted by the thermal sum equation.
6. The interaction between the effects of temperatures favourable for growth and day-length-governed diapause, synchronize the emergence of the low-temperature sensitive adult stage of this tropical dragonfly with northern-latitude summers at a variety of habitats.     

Thermal preference and activity thresholds in populations of Argia vivida (Odonata: Coenagrionidae) from habitats with different thermal regimes

The hypothesis was tested that isolated populations of Argia vivida Hagen living in habitats with different thermal regimes would show similar larval temperature preferenda, similar distributions in a temperature gradient, similar larval upper temperature acitivity thresholds, and similar adult minimum temperature flight thresholds. The hypothesis was supported in all cases, except for distribution within the gradient, where there were significantly fewer observations below 22°C in a population from a habitat with a fluctuating diel and annual temperature regime than in a population from a more thermally stable habitat. Larval modal temperature preferendum was 28°C; escape temperature (EST) was 35.4–36.4°C, critical thermal maximum (CTM) was 39.1–41.0°C, and upper lethal temperature (ULT) was 44.4–46.0°C. While technical difficulties affected the estimates of flight thresholds, there was no difference between the field estimates from different sites. Minimum body temperature for flight appears to be about 25°C, apparently higher than for several other zygopterans, while larval activity thresholds and 96 hr LD50 of 36.8°C are similar to those recorded for other odonates.     

Sex in a cyclical parthenogen: mating behaviour of Chydorus sphaericus (Crustacea; Branchiopoda; Anomopoda)

1. We describe the interactions during mating in Chydorus sphaericus, a cyclical parthenogenetic anomopod. Mating behaviour is more complex than previously assumed, with evidence for a diffusible chemical to which males react at the onset of mating, for reproductive isolation, and for postcopulatory mate guarding. 2. During mating, the male and female form a ‘mating cross’ that may be maintained for several hours, while copulation itself typically lasts less than a minute. Furthermore, males invariably attach to the right valve of females. Copulation involves intromission of the postabdomen between the valves, so that the gonopores approach the left ovarium. 3. This behaviour is reflected in the morphology of both sexes: males have a specialised anterior valve margin, postabdomen, first limb and rostrum, under selective pressure for successful mate guarding and copulation, while gamogenetic females have asymmetric ovaries, and a species‐specific setulation of the valves. Males of the structurally related Chydorus ovalis react to the presence of C. sphaericus, but fail to dock to females, suggesting a lock‐antilock element in the reproductive isolation of both species. 4. The morphological and ethological adaptations in C. sphaericus suggest that there is a strong selective pressure on mating behaviour in this cyclical parthenogen and specifically towards the formation of the ‘mating cross’.     

Fluctuating asymmetry and lifetime mating success are correlated in males of the damselfly Coenagrion puella (Odonata: Coenagrionidae)

Abstract.

• 1 The influence of fluctuating asymmetry on lifetime mating success of males of the damselfly Coenagrion puella (Odonata: Coenagrionidae) was investigated. Fluctuating asymmetry was measured as the difference in length of left and right fore and hind wings.
• 2 Males with more symmetrical wings enjoyed higher lifetime mating success.
• 3 Larger males, in contrast to a previous study of this species, also had higher mating success. This may be attributed to differences in the weather conditions prevailing at the time of the studies.

     

Flexible Mate Guarding Tactics in the Dragonfly Sympelrum Internum (Odonata: Libellulidae)

Mate guarding–a behaviour prevalent in odonates–is a post copulatory association during which males prevent females from re-mating. Some species use two forms of guarding: contact mate guarding, which is energetically costly but highly effective and non-contact mate guarding, which is less costly but less effective. This study aimed to determine if male Sympetrum internum (Odonata:Libellulidae) adjust the duration of contact mate guarding according to environmental, temporal and physiological factors. There was a significant interaction between male density and season on duration of contact mate guarding. Early in the season males increased the duration of contact guarding as the density of rivals increased. Later in the season males guarded mates longer irrespective of male density. Wind and temperature did not detectabiy alter the duration of contact mate guarding, suggesting that the trade-off between current and future reproductive success was more important than were physiological costs.     

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.     

Size-related mating and mate guarding in the orb-web spiderNephila clavata (Araneae,Araneidae)

The orb-web spiderNephila clavata satisfies three conditions for assortative mating proposed by Ridley (The Explanation of Organic Diversity. The Comparative Method and Adaptations for Mating, Clarendon, Oxford, 1983); (1) a large male advantage in male-male competition, (2) a correlation between female size and fecundity, and (3) a long pairing duration. To test Ridley's hypothesis, size assortative mating and guarding were examined in the field. When data were pooled over time, assortative mating was found but this was due to temporal covariation of body sizes of males and receptive females. After controlling for the effect of time, size assortative guarding was not detected, although females guarded by males were larger than those not guarded in the early breeding season. Possible reasons for the absence of size assortative guarding were discussed.     

Explicit experimental evidence for the effectiveness of proximity as mate-guarding behaviour in reducing extra-pair fertilization in the Seychelles warbler

Extra-pair copulations (EPCs; copulations outside the pair bond) are widespread in birds and may result in extra-pair fertilizations (EPFs). To increase reproductive success, males should not only seek to gain EPFs, but also prevent their own females from gaining EPFs. Although males could reduce the number of EPCs by their mates, this does not necessarily mean that they reduce the number of EPFs; indeed several studies have found no association between EPCs and EPFs. Male Seychelles warblers (Acrocephalus sechellensis) follow their partner closely during the period when the pair female is most receptive (fertile period). We show that males that guarded their mates more closely were less likely to have extra-pair young in their nest. This study on the Seychelles warbler is the first to provide explicit experimental evidence that mate guarding is effective in reducing EPFs. First, in territories where free-living males were induced to stop mate guarding during the pair female's fertile period, extra-pair parentage was higher than in the control group. Second, in the experimental group, the probability of having an extra-pair nestling in the nest was positively associated with the number of days during the fertile period for which mate guarding was artificially stopped. Thus, male mate guarding was effective in reducing the risk of cuckoldry.     

The mating behaviour of tsetse flies (Glossina): a review

Abstract. The mode of reproduction of tsetse flies, by adenotrophic viviparity, is unusual among the Diptera and is associated with many unique aspects of the tsetse's mating system. Tsetse exist at relatively low densities in the environment but a combination of olfactory and visual stimuli brings males and virgin females together on or around host animals. The behavioural repertoire associated with mate location and identification, courtship and copulation is regulated by external physical and chemical stimuli as well as by internal physiological mechanisms. With a view to identifying stimuli that could be used to manipulate tsetse behaviour and exploited for control purposes, much progress has been made in recent years in elucidating the mating behaviour of tsetse and its regulatory mechanisms. This progress and the current state of understanding of tsetse mating behaviour is reviewed.     

Correlates of male mating success in two natural populations of the damselfly lschnura graellsii (Odonata: Coenagrionidae)

Abstract.

• 1 Two natural populations of Ischnura graellsii were studied in north-west Spain by means of mark-release-recapture techniques. Recaptured males were a random sample of the original marked population with regard to date of marking. At O Rosal a greater proportion of young males than old males disappeared after marking; at Lourizán recaptured males were larger than unrecaptured ones.
• 2 The number of matings observed in both populations showed great daily variation. Most of the variation is accounted for by climatic variables. Most males (56–65%) and many females (41–45%) were never observed to mate.
• 3 Male LMS was highly correlated with lifespan in both populations. At O Rosal, male LMS was also positively correlated with body length, and mated males were larger than unmated males. This surprising result for a non-territorial species was due to the positive correlation between date of marking and size. There was a positive correlation between body size and mobility for males at O Rosal, but mobility was not correlated with male LMS.
• 4 As predicted by sexual selection theory, the standardized variance in male LMS was greater than in female LMS. Variation in mature lifespan explained 16% of variance in male LMS at Lourizán and 28% at O Rosal.

     

Evidence for widespread sperm displacement ability among Zygoptera (Odonata) and the means for predicting its presence

Males of the coenagrionid damselflies Argia moesta, A. sedula and hchnura ramburii use similar penis morphology to remove and/or reposition sperm of previous males from the storage organs of females prior to inseminating them. Although the species vary in the degree to which sperm is removed from or packed into the spermatheca, in all three species, sperm is removed from the bursa copulatrix. Since sperm in the bursa probably has priority in fertilizing eggs in at least the first oviposition after mating, sperm precedence can be estimated as the percentage of sperm (by volume) in the bursa belonging to the last male to mate. Estimated sperm precedence for these species is approximately 71% for Argia sedula, 82% for I. ramburii and 93% for A. moesta. These results, combined with similar ones for other damselflies clearly indicate that the ability to displace sperm may be widespread among temperate-zone Zygoptera. Species with each of the four major variations in damselfly penis structure have now been shown to displace sperm using this morphology. The systematic distribution of these major variants suggests several origins of sperm displacement ability within the Zygoptera. Whether or not all damselflies are capable of sperm displacement depends on both the presence of micro-structures used in sperm removal or repositioning and on the presence of sperm of previous males in mating females. It is possible, therefore, to predict that sperm displacement occurs in a damselfly if (1) females mate more than once, (2) mating females store sperm in organs accessible to penis morphology, (3) the distal segment of the male penis has structures similar to those known to be involved in sperm removal or repositioning, and (4) oviposition occurs in tandem or with the male non-contact guarding his mate.     

Vibratory signals enhance mate-guarding in a water strider (Hemiptera: Gerridae)

Mating males of the water strider Gerris remigisproduce vibratory signals when-single males grasp mating pairs. When played through live females with dead males on their backs, these signals repelled mating attempts by single males. A previous study showed that male mate-guarding enhances female foraging effectiveness in this species. Thus male mate-guarding signals also enhance female foraging effectiveness.     

The ecology and electrophoretic analysis of the damselfly,Argia vivida hagen,living in a geothermal gradient

The ecology and electrophoretic properties of a damselfly, Argia vivida Hagen, inhabiting a geothermal gradient were studied. Monthly sampling of five sites revealed nymphal colonization along a 15–40°C thermal gradient; greatest densities occurred between 15–27°C. An electrophoretic analysis of proteins suggest that nymphs were adapted to a wide range of temperatures which was evidenced by differential activity of four enzyme systems (glucose-6-phosphate dehydrogenase, lactate dehydrogenase, leucine aminopeptidase, and tetrazolium oxidase). Evidence suggests the nymphs acclimated to different temperatures by altering the structure of important isozymes and expressed certain genetic features characteristic of individuals naturally found at a given temperature.Published with the approval of the Director of the University of Idaho Agriculture Experiment Station as Research Paper No. 78612.     

Diurnal changes and frequency dependence in male mating preference for female morphs in the damselfly Ischnura senegalensis (Rambur) (Odonata: Coenagrionidae)

Ischnura senegalensis females exhibit color dimorphism, consisting of an andromorph and a gynomorph, which might be maintained under a frequency-dependent process of mating harassment by mate-searching males. Males change their mating preference for female morph depending on prior copulation experience. Binary choice experiments between two female morphs were carried out in four local populations in the early morning (07.00–09.00 hours) and the afternoon (12.00–14.00 hours), times which mark the onset and the end of diurnal mating activity, respectively. According to the line census along the water's edge, the proportion of andromorphs in the female population varied from 21 to 67% throughout the survey period for four local populations. Males showed non-biased preference for female morphs in the early morning in each local population, while they chose the common morph in the afternoon. Male mating preference for female morphs was positively correlated to the proportion of female morphs in the population. If the selective mating attacks on the common female morphs inhibit their foraging and/or oviposition behavior, frequency-dependent male mating attacks might provide a selective force for maintaining the female color dimorphism in I. senegalensis .     

Influence of previous mating experience on future mating success in maleLucilia cuprina (Diptera: Calliphoridae)

Receptive and virginL. cuprina females were placed with a virgin male and an experienced male that had mated between one and five times previously. The experienced males secured significantly more matings than virgin males. Males with previous matings also gained experience in competing with males. Males directed mating attempts at each other, seemingly in the context of intrasexual competition. Experienced males directed more mating attempts at virgin males than vice versa. As their number of previous matings increased, experienced males made the first mating attempt at females more often and directed more mating attempts at females compared with virgin males. Females did not actively discriminate against experienced males, even though the proportion of matings secured on the first attempt by experienced males declined with increasing mating experience. Alternative behavioral explanations are discussed.     

Parthenogenesis did not consistently evolve in insular populations of Ischnura hastata (Odonata,Coenagrionidae)

1. The evolutionary advantages that have driven the evolution of sex are still very much debated, and a number of benefits of parthenogenesis over sexual reproduction have been proposed. In particular, parthenogenetic individuals are thought to exhibit higher probabilities of establishment following arrival in new, isolated habitats such as islands. 2. One notable example of parthenogenesis occurring in islands is the damselfly Ischnura hastata, an American species that has colonised the Azores archipelago, where the populations consist only of females. This is the only known example of parthenogenesis within the insect order Odonata. 3. Here, two island populations of I. hastata were studied, one in the Galapagos and one in Cuba, to test whether island colonisation is consistently associated with parthenogenesis in this species. Field capture–mark–recapture studies and laboratory rearing of field‐collected eggs were undertaken in both areas. 4. Sex ratios in the field were found to be heavily female‐biased among mature individuals; however, fertility rates of field‐collected eggs were high, and the sex ratios in the laboratory did not differ from 1 : 1. Data from laboratory rearing showed that shorter larval development times and shorter adult life spans in males result in protandry, which might explain the skewed sex ratios in the field. 5. These findings are consistent with sex differences in key demographic parameters which could predispose I. hastata to parthenogenesis. However, the Azores population of I. hastata remains the only documented case of asexual reproduction in this insect group.     

Ontogenic colour change,survival, and mating in the damselfly Agriocnemis pygmaea Rambur (Insecta: Odonata)

1. Damselflies often show intra-specific colour variation, which may represent genetic polymorphism or age-related (ontogenic) colour changes. 2. Such variation has distinct implications for the species' ecology and evolution. Colour variation in females of the damselfly Agriocnemis pygmaea was studied, which range from blue male-like individuals (andromorphs) to those with a distinct red colour (heteromorphs). From preliminary observations, it was hypothesised that this species exhibits ontogenic colour change from heteromorph to andromorph coloration. 3. Mark–recapture experiments and egg counts of dissected females suggested that immature females are heteromorphic and gradually begin to resemble males as they attain sexual maturity. 4. Reflectance spectra of field-caught individuals indicated that, although males are indistinguishable from andromorphs, they could be easily differentiated from heteromorphs. 5. Finally, field observations and mate choice experiments showed that males rarely attempt to mate with heteromorphic females and prefer andromorphs. Together, this study's results suggest that the observed colour variation in A. pygmaea females is ontogenic and is associated with sexual maturity.