Temperature modulation of photoperiodism: an adaptation for long-distance dispersal in the aphid, Acyrthosiphon pisum (Hemiptera: Aphididae)

2013 ◽  
Vol 145 (3) ◽  
pp. 302-316
Author(s):  
M.A.H. Smith ◽  
P.A. MacKay ◽  
R.J. Lamb
Keyword(s):  
Acyrthosiphon Pisum ◽  
Seasonal Pattern ◽  
Local Population ◽  
Late Summer ◽  
Photoperiodic Response ◽  
Day Length ◽  
Temperature Modulation ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Critical Photoperiod

AbstractVariation in the seasonal occurrence of asexual and sexual phenotypes of Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae) is quantified for a local population in southern Manitoba, Canada. To survive winter, summer asexual generations must produce a sexual generation in a timely way at the end of the season, so that females can lay overwintering eggs. This transition is controlled by day length, which varies in a fixed seasonal pattern with latitude, and the local pattern of day length selects for an appropriate photoperiodic response. Substantial variation in the timing of production of males and mating females occurs among locally collected genotypes. Some of the variation is due to the arrival of long-distance dispersers (1000 km or more), and some is consistent with shorter but still long-distance dispersal. Some of the variation is due to year-to-year changes in late summer temperature. The critical day length in nature, which corresponds to critical photoperiod, increases as the average temperature decreases. This temperature modulation is adaptive because it allows many genotypes to produce some sexual phenotypes before the end of the season, although their photoperiodic responses are characteristic of long-distance dispersers and inappropriate to local day lengths.

Temperature modulation of photoperiodism and the timing of late-season changes in life history for an aphid, Acyrthosiphon pisum

2011 ◽  
Vol 143 (1) ◽  
pp. 56-71 ◽  
Author(s):  
M.A.H. Smith ◽  
P.A. MacKay ◽  
R.J. Lamb
Keyword(s):  
Sexual Reproduction ◽  
Seasonal Changes ◽  
Acyrthosiphon Pisum ◽  
Late Summer ◽  
Day Length ◽  
Temperature Modulation ◽  
Four Seasons ◽  
Aphid Clone ◽  
Photoperiodic Responses

AbstractWhere winters are severe, aphids reproduce parthenogenetically and viviparously in summer, switch to sexual reproduction in late summer, and produce winter-hardy eggs by the end of the season. The role of day length and temperature in initiating seasonal changes from parthenogenetic to sexual reproduction by pea aphids, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), are described and the selection pressures that affect the timing of this transition are investigated. Over four seasons, a pea aphid clone was sampled from field cages through late summer in southern Manitoba, Canada, and reared in the laboratory to determine the phenotypes of progeny produced as the season progressed. The timing of transitions from one phenotype to another under natural day length and temperature, and the critical day lengths that caused the transitions, coincided with expectations from laboratory studies of photoperiodic responses. Males and mating females appeared later when the weather in August was warm than when it was cool. The timing of seasonal changes was adapted to minimize the physiological time to the end of the season, which maximized the number of asexual summer generations. Ambient temperature modulated the response to day length and fine-tuned the timing of sexual reproduction to adapt for annual variation in autumn weather.

Population ecology in an environmental mosaic: Cakile edentula on a gravel bar

1980 ◽  
Vol 58 (9) ◽  
pp. 1095-1100 ◽  
Author(s):  
Paul A. Keddy
Keyword(s):  
Population Ecology ◽  
Zostera Marina ◽  
Reproductive Output ◽  
Late Summer ◽  
Long Distance Dispersal ◽  
Seedling Density ◽  
Long Distance ◽  
Two Phase ◽  
Cakile Edentula ◽  
Gravel Bar

The population ecology of the annual plant Cakile edentula was studied on a gravel bar in Halifax County, Nova Scotia, where it grows in a two phase mosaic consisting of (1) open shingle or gravel and (2) thick mats of dead Zostera marina wrack. Cohorts of seedlings were marked and regularly counted in both habitats. Reproductive output and seed dispersal were also studied.There were marked differences in C. edentula ecology between the two habitats. In general, survivorship and reproductive output were both greater in shingle. However, caterpillar grazing in late summer was concentrated on shingle plants, with the eventual result that net reproductive output was greater in wrack. There was no evidence of seed movement between wrack and shingle.Seedlings of C. edentula often grew in dense clusters around the remains of the previous year's parent(s). In both habitats, C. edentula seedling density declined with distance from the centre of clusters. Reproductive output increased with distance in both habitats; survivorship increased with distance only in wrack. Distal fruit segments were dispersed further than proximal segments; thus seedlings derived from distal segments tended to grow further from the previous year's parent, and in turn had higher survivorship and reproductive output. Distal fruit segments are normally thought to function primarily for long-distance dispersal; on shingle beaches "long-distance dispersal" of less than a metre could significantly improve the reproductive success of a seedling.

Phenological variation in Heteropogon contortus and its relation to climate

1966 ◽  
Vol 14 (1) ◽  
pp. 35 ◽  
Author(s):  
JC Tothill
Keyword(s):  
Seasonal Pattern ◽  
Natural Populations ◽  
Late Summer ◽  
Day Length ◽  
Tropical Region ◽  
Wet Season ◽  
Early Maturity ◽  
Heteropogon Contortus ◽  
Rainfall Season ◽  
Eastern Australia

Heteropogon contortus Beauv. ex Roem. & Schult. (spear grass or tanglehead) exhibits conisiderable: morphological and phenoiogicai variation. Wniie the morphological variation is apparently unrelated to geographic distribution, the phenological variation appears to be closely associated with differences in climate. Flowering is largely governed by day length, but the seasonal pattern of rainfall distribution has selected only those day lengths which promote flowering within the rainfall season. In the tropical region of north-eastern Australia flowering occurs in late summer and short days, since the wet season prevails over the second half of the summer. When northern material is grown in uniform grass gardens south of this tropical region, late maturity still prevails; hence this behavioural pattern is genetically fixed. In the subtropics, on the other hand, adequate rain may fall over the entire potential growing season or any part of it. In the garden great variation of phenology marks the southern material. Furthermore, sampling within local populations may also show great variation from early maturity through to late. It is suggested that in Australia H. contortus is naturally a species of the semi-arid tropics. It has spread into the subtropics through its ability to match the extended but more uncertain rainfall season by producing types of differing day length response. This variation is fixed by the predominantly apomictic mode of reproduction, while the perenniality of the plants ensures survival over periods of unsuitable climate. A long-term equilibrium is therefore established between the flowering behaviour of the population and its climate. A knowledge of the patterns of behaviour within and between populations is likely to be Important for increased pastoral efficiency, firstly, in preventing natural populations from deteriorating towards earlier maturity, and secondly, in lengthening the productive season of pasture growth.

Comment on ‘Seagrass Viviparous Propagules as a Potential Long-Distance Dispersal Mechanism’ by A. C. G. Thomson et al.

2015 ◽  
Vol 39 (1) ◽  
pp. 290-293 ◽  
Author(s):  
Elizabeth A. Sinclair ◽  
Renae Hovey ◽  
John Statton ◽  
Matthew W. Fraser ◽  
Marion L. Cambridge ◽  
...  
Keyword(s):  
Long Distance Dispersal ◽  
Long Distance ◽  
Dispersal Mechanism
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