Low Incidence Of Diapause Research Articles

Strangers in a strange land: do life history traits differ for alien and native colonisers of novel environments?

Do alien invasive species exhibit life history characteristics that are similar to those of native species that have become pests in their continent of origin? We compared eucalypt specialists that have become pests in Australian plantations (natives) to those that have established overseas (aliens) using 13 life history traits and found that although traits that support rapid population build-up were shared, overall, aliens and native colonisers differed significantly. Distance from source (New Zealand vs. other) had no significant effect, but species that established more than 50 years ago exhibited different life history traits from those that established within the last 50 years, possibly because of more effective quarantine. Native and alien eucalypt insect invaders differed predominantly in traits that facilitate long-distance movement (pathway traits), compared to traits that facilitate establishment and spread. Aliens had longer adult flight seasons, were smaller and more closely host-associated (cryptic eggs and larvae), had lower incidence of diapause (i.e. were more seasonally plastic) and more generations per year than natives. Thus, studies of species invasive within their country of origin can shed light on alien invasions.

Optimization of Orius majusculus release: photoperiodic sensitivity at different temperatures and storage of diapausing adults

The photoperiodic sensitivity and storage of Orius majusculus (Reuter) from Antalya was investigated to obtain data for the optimization of its release. In the current study, it was not possible to induce a high (up to 100%) incidence of diapause unless all the nymphal instars and adults were successively exposed (i.e. full exposure) to a short day length (11.5 h) at constant temperatures of 18 and 26 °C, and fluctuating temperatures of 10/26 °C. Hence an intermittent exposure to long day lengths, even for short periods of time (only during instars IV–V or adult stage), would avoid a high incidence of diapause at 10/26 °C and 26 °C. The response of O. majusculus nymphal instars and adults to a short day length with a low incidence of diapause under fluctuating temperatures suggests that greenhouses, where such temperatures prevail, provide an environment that is conducive to diapause prevention. The release of adults is a better approach than the release of nymphs, since the adults and their nymphs, until the eclosion of new adults, are expected to respond to short day lengths with a low incidence of diapause in greenhouses. When nymphs are released, on the other hand, a high incidence of diapause would be inevitable. Increasing the constant temperature to 30 °C at full exposure did not prevent diapause and consequently did not change the incidence of diapause. Storage of diapausing O. majusculus adults was possible for 1 month with a higher survival rate and fecundity than in a study based on the storage of nondiapausing adults at a lower temperature.

The Distribution and Geographic Variation in Diapause Capacity among Populations of Two Tetranychus Species (Acari: Tetranychidae) in East and Southeast Asia

The incidence of diapause in two species of spider mite, Tetranychus urticae and T. kanzawai, was determined for populations derived from various regions in East and Southeast Asia, at 3 temperatures under short-day conditions. The distribution of T. urticae was locally limited. It has been known that the T. urticae populations in northern Japan have a high capacity for diapause and the mites show a clinal decrease in diapause capacity. However, all populations examined in this study, including those from southern Japan, had very low capacity for diapause. T. kanzawai was one of the most common spider mites over the entire East Asia. In East Asia the mites occurred not only on cultivated plants but also on wild plants, but in Southeast Asia they were observed only on cultivated plants. Most populations derived from Japan (except those from the Okinawa Islands, which had low diapause capacity), Korea and South-central China had very high capacity for diapause, whereas populations from Thailand showed low incidence of diapause. The Taiwanese populations had very diversified diapause percentage among local populations. There was a conspicuous decrease in diapause expression with increasing temperature in populations from the Tanegashima and Yakushima Islands, China, Vietnam and Indonesia. Contrary to our expectation, the tropical populations from Indonesia and Philippines maintained a high capacity for diapause. Thus, T. kanzawai did not show any explicit clinal decrease in diapause capacity, as was observed in T. urticae.

Geographic variation in diapause induction under constant and changing conditions in Helicoverpa armigera

AbstractVariation in the incidence of diapause in local populations of Helicoverpa armigera (Hübner) and Helicoverpa assulta (Guenée) (Lepidoptera: Noctuidae) was examined in relation to changes in photoperiod and/or temperature during the larval period. Temperate zone populations of H. assulta, a native species in temperate Japan, showed a high incidence of diapause induction when only the photoperiod was decreased during the larval period, even at favorable temperatures. This photoperiod‐dependent response may allow H. assulta to foresee the beginning of autumn well in advance in the temperate zone, where temperature conditions are severe. In contrast, temperate zone populations of H. armigera, an invasive and polyphagous species mainly distributed in the subtropics, showed a high incidence of diapause only when both photoperiod and temperature decreased, whereas subtropical populations showed a very low incidence of diapause under the same conditions. Furthermore, both temperate zone and subtropical populations of H. armigera enter diapause under constant low temperatures at short‐day photoperiod. Thus, there is geographic variation in sensitivity to diapause‐inducing stimuli (changes in photoperiod and temperature) in H. armigera. This variation may be a part of the climatic adaptation achieved by H. armigera in Japan.

Effects of thermoperiods on diapause induction in the cabbage beetle, Colaphellus bowringi (Coleoptera: Chrysomelidae)

Abstract. The effects of thermoperiods on diapause induction in continuous darkness or under a 12 : 12 h LD photoperiod were investigated in the cabbage beetle, Colaphellus bowringi Baly, a typical short‐day species. The diapause response curves both at different constant temperatures and at the thermocycle of format CT x: (24 − x) h (16 : 28 °C) under continuously dark rearing conditions showed that the incidence of diapause depended mainly on whether or not the mean temperature was ≤20 °C or >20 °C. If the mean temperature was ≤20 °C, all individuals entered diapause; if >20 °C, the incidence of diapause declined gradually with increasing mean temperatures. The thermocycle (CT 12 : 12 h) with a series of different cryophases (8–22 °C) and thermophases (24–32 °C) under continuous darkness demonstrated a cryophase response threshold temperature of approximately 19 °C and a thermophase response threshold temperature of approximately 31 °C. Thermoperiodic amplitude (temperature difference between cryophase and thermophase) was shown to have a significant influence on diapause induction at the mean temperatures of 22, 23 and 24 °C, but not at ≥25 °C. Thermoperiodic responses under LD 12 : 12 h clearly showed that the incidence of diapause was influenced strongly by the photophase temperature. The thermoperiod under LD 12 : 12 h induced a much lower incidence of diapause than the thermoperiod with the same temperature in continuous darkness. The ecological significance of thermoperiodic induction of diapause in this species is discussed.

Diapause characteristics of two species of tetranychid mites (Acari: Tetranychidae) in southern Japan and Taiwan

As in other Tetranychus species, both T. kanzawai and T. urticae undergo reproductive diapause induced by short-days and low temperatures. This study compares the diapause characteristics of populations of these two species from Taiwan with those from Kagoshima (southern Japan) and the Okinawa islands (southwestern islands). Our previous study (Takafuji et al., 2001, Appl. Entomol. Zool. 36: 177–184) showed that most T. kanzawai populations from Kagoshima exhibited more than 90% diapause at 15°C–9L15D, but the incidence of diapause in populations from the Okinawa islands was very low, and some exhibited no diapause even at 15°C. The present study shows that populations from central Taiwan, including those from the lowlands, exhibited a lower incidence of diapause than populations from Kagoshima, but a higher incidence than populations from the Okinawa islands. These results imply that the gene flow among populations in the lowlands and mountains maintains a higher incidence of diapause in Taiwan, but the diapause characteristic may have been eliminated by warm temperatures on the Okinawa islands, on which there are no high mountains. On the other hand, all populations of T. urticae from Kagoshima, Okinawa and Taiwan similarly exhibited a very low incidence of diapause.

Effects of photoperiod on induction of diapause in Feltiella acarisuga (Diptera: Cecidomyiidae)

AbstractLarvae of the predatory gall midge Feltiella acarisuga (Vallot) diapaused as prepupae in tightly woven, brown, silk cells on leaf surfaces. Photoperiod alone, at day lengths from 16 to 8 h did not induce diapause at either 20 or 25 °C. A low incidence of diapause was induced by a combined photoperiod and thermoperiod of an 8-h day at 25 °C and a 16-h night at 15 °C. The incidence of diapause was higher under these conditions if the larvae were fed diapausing spider mites, Tetranychus urticae (Koch) (Acari: Tetranychidae). Because F. acarisuga only diapauses at daylengths equivalent to mid-winter, when its prey, T. urticae, is also in diapause, it can be used as a biological control agent for T. urticae in British Columbia greenhouses throughout most of the growing season.

Overwintering ecology of two species of spider mites(Acari: Tetranychidae) on different host plants.

The overwintering ecology of two species of spider mites was studied on three different host plants in central Wakayama Prefecture, southwestern Japan. Laboratory diapause-inducing experiments showed that populations of Tetranychus urticae on peas and chrysanthemums both had a very low inherent capacity for diapause, and the population on chrysanthemums continued development and reproduction throughout the winter. On the other hand, populations of T. kanzawai had a genetically strong diapause capacity, regardless of the host species on which they occurred. However, the proportion of field-induced diapause females was lower in the population occurring on Akebia quinata, an evergreen host that had ample fresh leaves throughout the winter, than the populations on peas and Clerodendrum trichotomum, a deciduous tree, the leaves of both of which deteriorated or defoliated in winter. The low incidence of diapause on A. quinata seemed due to weak diapause induction and/or earlier diapause termination in the plastic response to ample food conditions. On A. quinata, high proportions of eggs and immatures remained throughout the winter, suggesting that development and reproduction are possible throughout the winter in this area under ample food conditions.

A weak tendency to “obligatory” diapause inCoccinella septempunctata from southern Spain

Diapausing adults ofC. septempunctata were collected in November from hibernation quarters in the mountains Sierra de Grazalema in southern Spain. In their progeny, the incidence of non-ovipositing females under long day of 20L∶4D and 25°C was 24%. Thus the tendency to an “obligatory” onset of diapause was much lower than in populations from central Europe and France. The progeny appeared neutral to photoperiod, as a similar low incidence of diapause was also obtained at short day of 12L∶12D and 25°C.

Adult Locomotor Rhythmicity as "Hands" of the Maternal Photoperiodic Clock Regulating Larval Diapause in the Blowfly, Calliphora vicina

Some basic properties of the adult locomotor activity rhythm and of the maternal induction of larval diapause in Calliphora vicina are described. Diapause responses in Nanda-Hamner experiments indicate that circadian rhythmicity is involved in photoperiodic time measurement (PPTM). However, although the locomotor rhythm shows long-lasting changes in free-running period (aftereffects of photoperiod and constant light) and occasional "splitting," thereby indicating a structural complexity to the circadian system, the overt rhythm may be used as an indicator of phase relationships (or "hands") of the covert system involved in PPTM, within the framework of a simple external-coincidence model for the diapause clock. Thus, in light-dark (LD) cycles close to "resonance" with the circadian pacemaker(s) (T 24, LD 12:12; T 48, LD 12:36; and T 72, LD 12:60), light is restricted to the subjective day and diapause incidence is high. In T 36 (LD 12:24) and T 60 (LD 12:48), light falls into the subjective night and illuminates the postulated light-sensitive phase (phi i), and diapause incidence is low. Within the primary range of entrainment, light invades the late subjective night in T 20 (LD 12:8), illuminates phi i, and causes low incidence of diapause; however, it invades the early subjective night in T 30 (LD 12:18) and diapause remains high.

Influence of thermoperiod and photoperiod on reproductive diapause in Bruchidius atrolineatus (Pic) (Coleoptera, Bruchidae)

Abstract Bruchidius atrolineatus (Pic) is a common pest infesting cowpea seeds (Vigna unguiculata Walp) in Africa. In the Sahelian zone, the adults are in reproductive diapause during the dry season. Diapause induction depends on the climatic conditions during embryonic and post‐embryonic development. A strain of B. atrolineatus originating from the Niamey (13oN) was reared in different thermoperiodic and photoperiodic conditions. In the thermoperiodic regime 40:25oC, in continuous darkness, induction of diapause was dependent on the duration of the thermophase. Photoperiod could also influence diapause induction but the response depended on the temperature. When the beetles were reared in conditions of LD 12:12 h, 40:25oC, for seven generations, the proportion of diapausing adults decreased and their sensitivity to photoperiod increased. In LD 14:10 h, 40:25CC, the proportion of diapausing adults remained high regardless of the photoperiod. In these conditions, the first emerging adults were sexually active and were used for selection of a strain with a low incidence of diapause. After twelve generations, the proportion of diapausing beetles was lower than 5%. The responses of this selected strain to photo‐ and thermoperiods were reduced. The sensitivity of B. atrolineatus to photoperiod and thermoperiod could be controlled by genetic systems as observed in other insect species.

Thermoperiodic induction of diapause in the predacious mite, Amblyseius potentillae

The effect of temperature on the induction of diapause was studied in the phytoseiid mite Amblyseius potentillae. Photoperiodic induction of diapause was shown to be temperature dependent; at higher constant temperatures diapause incidence was virtually absent. When a photoperiod was applied in combination with a thermoperiod, diapause was induced only if the cool phase of the thermoperiod coincided with the scotophase; scotophase temperature appeared to be of much greater importance for diapause induction than photophase temperature. For the first time in a mite it was shown that diapause could be induced by a thermoperiod in continuous darkness. No diapause or only a very low incidence of diapause was found in continuous darkness when either the high, mean or low temperature of the thermoperiod was applied as a constant temperature throughout. A thermoperiodic response was found to be absent in continuous light. The thermoperiodic response curve determined for A. potentillae appeared to be closely similar to the photoperiodic response curve. Both the critical scoto- and cryophase were about 10 h in duration. Incidence of diapause was found to be dependent on the amplitude of the thermoperiod; except for the higher temperature range diapause incidence increased with increasing thermoperiod amplitude. Full induction of diapause was obtained with an amplitude of 4°C and above. No indication was found for the existence of a temperature threshold for thermoperiodic induction of diapause in A. potentillae.

Maternal influence on the incidence and duration of larval diapause in Calliphora vicina

ABSTRACT. The photoperiodic mechanism governing larval diapause in the blowfly Calliphora vicina R.‐D. (Diptera: Calliphoridac) is largely maternal. The critical daylength for adult flies at 20d̀C, and larvae derived from day 12 eggs and maintained in darkness at 11d̀C, is about 14.5 h/24. At short daylength (LD 12:12 h) and a range of temperatures, eggs laid on or before day 9 gave rise to a low incidence of diapause, whereas those laid on day 10 and later gave rise to a high incidence; the photoperiodic ‘counter’ therefore shows a temperature‐compensated mechanism for ‘accumulating’ successive short days. The rate of switching from non‐diapause to diapause progeny is hardly affected by the timing of protein meals, although an early supply of meat accelerates egg development and leads to an increasing proportion of early, non‐diapausing progeny. There is no evidence for a maternal effect preventing diapause induction in the first post‐diapause (‘spring’) generation of flies. Diapausing larvae terminate diapause spontaneously in darkness at 11d̀C after a variable period which is positively correlated with the incidence of diapause in the group. Diapause incidence and duration therefore are both determined maternally.

Hatchability of Eggs of Aedes taeniorhynchus (Diptera: Culicidae): Effects of Different Temperatures and Photoperiods during Embryogenesis

Eggs of Aedes taeniorhynchus (Wiedemann) were subjected to different photoperiod/ temperature combinations on days 0–5 postoviposition. At 22°C, those exposed on day 2 displayed the highest incidence of photoperiod-induced diapause. At 15°C, photophases <12 h produced a lower incidence of diapause when experienced by eggs from days 0–2 than from days 3–5 postoviposition. However, at both a constant 15 and 22°C and at a 21:5°C thermoperiod, percentage hatch tended to be inversely proportional to age for eggs that were 0–2 days old and directly proportional to age for those that were 3–5 days old on exposure to photoperiod. A combination of a 10.5:13.5 (L:D) photoperiod and 21:5°C (photophase/scotophase thermal regime) had the greatest effect when encountered by eggs 0–2 days postoviposition; the combination's effect on eggs that were 3–5 days old was similar to that of a 10:14 photoperiod and 15°C. Under a 11.3:12.7 photoperiod and a 24:9°C thermoperiod, a clearly defined hatching pattern was shown only by eggs subjected to the treatment 2 days after oviposition. A constant 5, 10, and 27°C suppressed the effect of photoperiod. Results suggest that photoperiod/temperature interactions were influential during embryogenesis.

The incidence of diapause in seventeen populations of the flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

Samples of Ephestia kuehniella were examined for diapause at 20 and 25°C in continuous darkness, continuous light and three other photoperiods. The samples came from five flour mills and five unheated stores in England, and from Scotland, Egypt, Finland and Japan, together with three laboratory reared stocks. Some larvae entered diapause in all but three of the English stocks, in all stocks from other countries, and in a 10-yr old laboratory stock from Japan but not in two other stocks reared in the laboratory for over 30 yr. In continuous darkness at 25°C, the incidence of diapause exceeded 10% in eleven stocks, 25% in eight, and 50% in three stocks, while in darkness at 20°C the proportions were usually much smaller. In other light regimes there was a much lower incidence of diapause, 10% being reached in only six experiments out of more than eighty. Markedly more larvae entered diapause when reared on the maize or wheat flour available in mills than on a nutritious laboratory diet of wheatfeed, glycerol and yeast.

Geographic variation and genetic aspects of reproductive diapause in Drosophila triauraria and D. quadraria

ABSTRACT. Geographic variation and genetic aspect of reproductive diapause were studied in Drosophila triauraria Bock &amp; Wheeler and D. quadraria Bock &amp; Wheeler, in relation to their quantitative response to photoperiods. D. quadraria from the subtropical region had no photoperiodic diapause. In D. triauraria strains, diapause was induced under LD 10:14 or 12:12, but not under LD 14:10 or longer photoperiods. Their diapause was induced more effectively and maintained longer by LD 10:14 than by LD 12:12. The duration of diapause was longer in a northern strain, but the diapause inducing process varied little among different geographical strains. Diapause incidence was 50% or lower in F1 hybrids between D. triauraria and D. quadraria and backcross progenies between F1 and D. quadraria, and about 70% in backcross progenies between F1 and D. triauraria under LD 10:14, but very low under LD 12:12. The lower incidence of diapause in these F; and backcross progenies is assumed to be due to the less efficient induction of diapause, since once diapause was induced in them, it was maintained for a long time, especially in the backcross progenies between F1 and D. triauraria. These experiments suggest that diapause induction and maintenance are different physiological processes controlled by different genetic systems.

Photoperiodic induction of pupal diapause in Sarcophaga argyrostoma: Temperature effects on circadian resonance

Larval cultures of the flesh-fly Sarcophaga argyrostoma maintained in circadian ‘resonance’ experiments produced a high incidence of pupal diapause when the period of the light cycle was close to ( T) 24, 48 or 72 hr, but a low incidence of diapause at T 36, 60 or 84 hr. Cultures pre-programmed for diapause by exposing pregnant females to long nights indicated the induction of non-diapause development at T 36, 60 and 84, whereas cultures pre-programmed for diapause-free development by exposing females to continuous light indicated the induction of diapause at T 24, 48 and 72. Raising the temperature reduced the heights of the diapause peaks whereas lowering the temperature raised them. With progeny from long-night-reared flies the lowest temperature tested (18°C) produced a result indistinguishable from an ‘hour-glass’ response, warning that ‘negative’ resonance experiments may merely indicate non-permissive conditions for demonstrating the involvement of circadian rhythmicity in insect photoperiodism. The results of the ‘resonance’ experiments and the effects of temperature are interpreted in terms of a multioscillator ‘external coincidence-photoperiodic counter’ model for the clock.

The effects of temperature and photoperiod on the induction of diapause in eggs of the Australian plague locust,Chortoicetes terminifera(Walker) (Orthoptera: Acrididae)

AbstractPhotoperiod was shown to be the principal factor regulating the induction of a facultative egg-diapause inChortoicetes terminifera(Wlk.). All developmental stages from first-instar nymphs to immature adults were sensitive to photoperiod. At constant photophases, the insect exhibited a short-day—long-day response, with the upper and lower critical photo-periods for induction approximating to LD 15·5: 8·5 and 11:13, respectively. These correspond to the range of photoperiods experienced by the insect under natural conditions. The maximum inductive response occurred at about the mid-point of this range, i.e. LD 13·5: 10·5. In experiments in which insects experienced a change in photophase at the end of the nymphal stage, the incidence of diapause varied with the direction of change (long to short or short to long) and indicated that diapause induction was prevented by an increase in photophase but enhanced when the photophase was reduced. The size of the inductive response associated with a decrease in photophase appeared to depend less on the size of the decrease than on its position within the inductive range, such that the maximum effects were observed when the sequence of light regimes were close to or spanned the most inductive constant photophase. Temperature was also important in determining the induction of diapause. In the upper portion of the inductive range (15·5 to 12·5 h light), insects subjected to high temperatures or to an increase in temperature during development showed a lower incidence of diapause than those subjected to low temperatures or to a decrease in temperature. In the lower portion of the inductive range, the effects of temperature were reversed, with high temperature or an increase in temperature being more inductive than low temperature or a decrease in temperature.

The Biology of Peristenus stygicus (Hymenoptera: Braconidae), a Newly Imported Parasite of Lygus Bugs 1 , 2

The fecundity, longevity and diapause of Peristenus stygicus Loan was studied. P. stygicus parasitizes the 1st to 4th instars of Lygus hesperus Knight. The number of parasite offspring decreased with an increase in host instar. However, the percent female parasite offspring increased with an increase in host instar. The fecundity of P. stygicus did not show a continuous increase as the host density increased. The number of offspring increased from a host density of 25–50 second instar Lygus and then leveled off at higher host densities. There was an inverse relationship between adult parasite longevity and temperature. Adult parasite longevity was greatly influenced by a carbohydrate source within its diet. Nearly all individuals entered a diapausing stage at a photoperiod of 12.75 h light. An intermediate incidence of diapause was observed at 13.5 h light, and a very low incidence of diapause was observed at 14 h light.

?Skeleton? photoperiods and the control of diapause and development in the flesh-fly,Sarcophaga argyrostoma

1. Larvae of the flesh-flySarcophaga argyrostoma were exposed to ‘skeleton’ photoperiods consisting of two unequal pulses of light (asymmetrical skeletons) or two equal pulses of light (symmetrical skeletons) per 24 h period. Asymmetrical skeletons (‘night interruption experiments’) revealed two apparently light-sensitive phases within the night, the second, occurring about 9 h after ‘dusk’ in all regimes, being thought to correspond to the photoinducible phase (Φi) of the photoperiodic oscillator (Fig. 1). 2. Symmetrical skeletons consisting of two 1 h pulses of light closely simulated the diapause-promoting effects of complete photoperiods of the same duration up to about 10 h. Skeletons longer than 16 h were again diapause-promoting in contrast to the diapause-averting (long day) effects of corresponding complete photoperiods. The incidence of diapause was reduced in the ambiguous symmetrical skeletons close to 12 h (in the ‘Bistability Zone’) (Fig. 3). 3. The ambiguity of symmetrical skeletons in the ‘Bistability Zone’ was eliminated by transferring cultures from continuous light (LL) into regimes consisting of two 1 h pulses placed 11 h apart. When the shorter interval (11 h) was ‘seen’ first after theLL-DD transition, long-day effects (low incidence of diapause) were observed; when the longer interval (15 h) was ‘seen’ first short-day effects (high diapause) were observed (Fg. 5). These results are consistent with the hypothesis that the photoperiodic oscillator is damped out by light periods of more than 12 h and resumes its motion on transfer to darkness.