The photoperiodic responses and phenology of an English strain of the pea aphid Acyrthosiphon pisum

Abstract

1. The response curves for the photoperiodic induction of the sexual forms (oviparae and males) differ significantly in an English clone of the pea aphid Acyrthosiphon pisum Hams. Male production is sharply peaked. The late summer scotophases (dark periods) that initiate male production are 1.0-1.5 h shorter than those that initiate ovipara production; the induction of males, but not oviparae, virtually ceases at scotophases longer than 12 h. This disparity suggests that there are two photoperiodic clocks.2. All ovipara-producing aphids switch spontaneously to virginopara production part-way through the progeny sequence, irrespective of photoperiod. This may confer the ability to overwinter parthenogenetically under favourable climatic conditions. Since males are always born last in the progeny sequence this possibility would be pre-empted unless the terminal male sequences were suppressed by long winter scotophases.3. The role of the photoperiodic response in determining the seasonal phenology was tested in the field by exposing a succession of laboratoryreared aphids to natural photoperiods, in late summer and autumn. Adult males and oviparae developed synchronously in early October, the difference in critical scotophase compensating for the late appearance of males in the progeny sequence. A large part of the 'civil twilight' is photoperiodically active.4. Clones propagated outdoors by isolating aphids in each generation from the terminal sequence of virginoparae did not survive the whole winter of 1985/86. The chances of survival were reduced by severe weather and by the inability of the photoperiodic system to 'turn off the production of early born oviparae which are, therefore, 'wasted'.

Inter- and intraclonal variability in the photoperiodic response and fecundity in the pea aphid Acyrthosiphon pisum (Hemiptera: Aphididae)

“…The age-dependent progeny patterns of apterae described in the present study are consistent with other reports (Kenten, 1955;Lamb & Pointing, 1975;Sharma et al, 1975;MacKay, 1987;Lees, 1989) and were previously discussed in detail by the author (Erlykova, 1997(Erlykova, , 1999. However, it must be noted that the tendency in this study for both apterae and alatae to produce initial and final batches of viviparae contrasts with the findings of MacKay et al (1983) and Vaz Nunes & Hardie (1996) who found no viviparae production at the end of progeny sequences of alatae.…”

“…The simultaneous analysis of several aphid clones sometimes revealed the existence of local interclonal variability in the photoperi odic response (Blackman, 1971;Eisenbach & Mittler, 1987;Takada, 1988;MacKay, 1989;Smith & MacKay, 1989aMittler & Wilhoit, 1990;Mittler & Gorder, 1991;Lamb & MacKay, 1997;Dedryver et al, 1998), but usually only a few photoperiods were used. The photope riodic response curves for male and ovipara production in the pea aphid Acyrthosiphon pisum (Harris) over the com plete range of photoperiods is known for one clone from Cambridge (Lees, 1989). The object of the present work was to estimate the interclonal variability in the photope riodic response of the green form of the pea aphid from the Leningrad Province, the northernmost population studied to date, and to determine the intraclonal differ ences in the responses shown by apterae and alatae.…”

“…However, the detailed reports are generally based on an analysis of single clones (Lees, 1963(Lees, , 1989Lamb & Pointing, 1975;Zaslavski & Fomenko, 1983, 1986MacKay, 1987). The simultaneous analysis of several aphid clones sometimes revealed the existence of local interclonal variability in the photoperi odic response (Blackman, 1971;Eisenbach & Mittler, 1987;Takada, 1988;MacKay, 1989;Smith & MacKay, 1989aMittler & Wilhoit, 1990;Mittler & Gorder, 1991;Lamb & MacKay, 1997;Dedryver et al, 1998), but usually only a few photoperiods were used.…”

Aphid sex pheromone components: Age-dependent release by females and species-specific male response

“…In this case, there may well be a temporal separation between the sexual forms. It has been found that the critical night length for the induction of oviparae in two English clones differs by 1.5 h (11 vs 9.5 h, Lees 1973Lees , 1989. In the field, M. viciae would produce oviparae some three weeks earlier than A. pisum.…”

Symbiont modifies host life-history traits that affect gene flow

“…The proximate cues resulting in wing induction are not fully understood, but include direct contact with other aphids, decreased plant nutritional quality, and exposure to natural enemies (Muller et al 1999;Weisser 2001;Mondor et al 2004Mondor et al , 2005Podjasek et al 2005). Sexual morphs are produced in response to conditions that precede the onset of winter in temperate climates, specifically, increasing dark phase of each day and decreasing temperature (Lees 1989;Via 1992).…”