AN INTERACTION BETWEEN ENVIRONMENTAL TEMPERATURE AND GENETIC VARIATION FOR BODY SIZE FOR THE FITNESS OF ADULT FEMALEDROSOPHILA MELANOGASTER

Abstract

Abstract.-Drosophila and other ectotherms show geographic genetic variation in body size, with larger individuals at higher latitudes and altitudes. Temperature is implicated as an important selective agent because long-term laboratory culture of Drosophila leads to the evolution of larger body size at lower temperatures. In this paper, we tested the hypothesis that, in Drosophila melanogaster, larger size is favored at lower temperatures in part because of selection on adult females. We used replicated lines of D. melanogaster artificially selected for increased and decreased wing area with constant cell area. The resulting size differences between the selected lines were due solely to differences in cell number, and thereby were similar to the cellular basis of elinal variation in body size in nature. We examined life-history traits of adult females at 18 and 25°C. Rearing for two generations at the two temperatures did not affect the extent of the size differences between lines from the different selection regimes. There was a strong interaction between temperature and size selection for both survival and lifetime reproductive success, with larger females living significantly longer and producing more offspring over their lifetime only when reared and tested in the colder environment. There was also an increase in average daily progeny production in large-line females relative to the control and small lines again, only in the colder environment. Thus, the females from the large selection lines were relatively fitter at the colder temperature. At both experimental temperatures, especially the lower one, the small-line females rescheduled their progeny production to later ages. Larger body size may have evolved at higher latitudes and altitudes because of the advantages to the adult female of being larger at lower temperatures.

Body size, insulin/IGF signaling and aging in the nematode Caenorhabditis elegans

“…It has also been shown that Drosophila evolves a larger body size in response to colder environments. These large lines are longer-lived than small and control lines, but only when survival analyses are performed at the cold temperatures at which the large lines were originally selected (McCabe and Partridge, 1997). The larger lines also display increased daily progeny production, again, only at the cold temperature.…”

Latitudinal cline in weapon allometry and phenology of the European stag beetle

“…Indeed, a general consensus has not been reached to support the Bergmann's Rule for ectotherms: some authors report the presence of the converse-Bergmann (e.g., Schutze and Clarke 2008), others have stated that Bergmann's Rule cannot be considered a valid eco-geographical law for insects (Shelomi 2012), or Bergmann and converse-Bergmann could not even be mutually exclusive, being driven by different environmental causes (Blanckenhorn and Demont 2004). Using common garden experiments, several studies on insects (Anderson 1973, Cavicchi et al 1985, 1989, Partridge et al 1994 proved that body size increases in low-temperature conditions and that selection favours larger body size at low temperatures (McCabe andPartridge 1997, Reeve et al 2000). Furthermore, several studies which compared geographical variation and biometric traits of insects, have recorded a latitudinal correlation with body size (Capy et al 1993, Cushman et al 1993, Arnett and Gotelli 1999, Huey et al 2000, Stillwell et al 2007.…”

Developmental temperature, body size and male mating success in fruit flies, Drosophila melanogaster (Diptera: Drosophilidae)

“…flies that develop at cold temperatures are larger than those developing at warmer temperatures. The phenomenon of climate related adult body size shows clinal variation in Drosophila (Gibert et al, 2004) with larger individuals occurring at higher latitudes and altitudes (McCabe & Partridge, 1997;Trotta et al, 2010). Drosophila body size also varies seasonally and is inversely proportional to seasonal temperature (Tantawy, 1964;Kari & Huey, 2000).…”

“…In laboratory conditions, response of body size to rearing at different temperatures has also been studied: different species that significantly varied in their natural habitats attain larger size when reared at lower temperature (Powell et al, 2010). In addition to morphological traits, rearing temperature may affect some other characteristics, such as physiological (Crill et al, 1996), behavioral (Zamudio et al, 1995), and life history traits (McCabe & Partridge, 1997).…”