Evolution of increased larval competitive ability inDrosophila melanogasterwithout increased larval feeding rate

Abstract

Multiple experimental evolution studies on D. melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies. We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/029249 doi: bioRxiv preprint first posted online Oct. 15, 2015; 4 on D. ananassae and D. n. nasuta. Here, we show that long-term laboratory populations of D. melanogaster, descended from some of the populations used in the earlier studies, evolve essentially the same set of traits as the D. ananassae and D. n. nasuta crowdingadapted populations when subjected to a similar larval density at low absolute volumes of food. As in the case of D. ananassae and D. n. nasuta, and in stark contrast to earlier studies with D. melanogaster, these crowding-adapted populations of D. melanogaster did not evolve greater larval feeding rates as a correlate of increased competitive ability. The present results clearly suggest that the suite of phenotypes through which the evolution of greater competitive ability is achieved in fruitflies depends critically not just on larval density per unit volume of food, but also on the total amount of food available in the culture vials. We discuss these results in the context of an hypothesis about how larval density and the height of the food column in culture vials might interact to alter the fitness costs and benefits of increased larval feeding rates, thus resulting in different routes to the evolution of greater competitive ability, depending on the details of exactly how the larval crowding was implemented.All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

Evolution of increased adult longevity in Drosophila melanogaster populations selected for adaptation to larval crowding

“…Archana (2010) had found that the suit of larval traits that has evolved in our study populations is very different from the suit of larval traits that had evolved in the r and K populations (Mueller, 1988) or the CU and UU populations . Taken together, the results of Archana (2010), Sarangi et al (2015) and our study show that adaptation to larval crowding can occur through more than one set of mechanisms. Such alternative mechanisms of adaptation to crowding have been detected by multiple other studies (Joshi & Thompson, 1995;Joshi et al, 2001;Dey et al, 2012;Nagarajan et al, 2014).…”

“…However, consistent with the results of the previous studies, the selected larvae had increased competitive ability and larval survivorship under crowded conditions. Thus, the mechanisms that underlie adaptations to larval crowding in the populations of Archana (2010) and Sarangi et al (2015) are very different from those found in the populations of Mueller et al (1993). Therefore, as suggested by other studies (Joshi & Thompson, 1995;Joshi et al, 2001;Dey et al, 2012;Nagarajan et al, 2014), there are multiple ways of adapting to larval crowding.…”

“…We carried out this study on six populations of Drosophila melanogaster, three selected for adaptation to larval crowding (MCU 2-4) and three controls (MB 2-4), described in Archana (2010) and Sarangi et al (2015). The MB and MCU populations were originally derived in the laboratory of Prof. Joshi and were kindly provided to us in February 2011, at which point they had undergone over 75 generations of selection.…”

“…In a recent set of studies, Archana (2010) and Sarangi et al (2015) selected a fresh set of D. melanogaster populations for adaptation to larval crowding. They found a completely different set of larval traits evolving in their populations (compared to the studies of Mueller, 1988;Joshi & Mueller, 1996).…”

Evolutionary compromises to metabolic toxins: Ammonia and urea tolerance in Drosophila suzukii and Drosophila melanogaster

“…Due to the limited mobility of larvae [28,29], behavioural avoidance cannot prevent larval exposure to environmental toxins accumulating in the food, but physiological mechanisms help larvae to cope with toxic compounds [30,31]. Drosophila melanogaster populations reared under crowded larval conditions exhibit greater competitive ability [22,32] and increased resistance to both urea and ammonia [22,33]. While the response of D. melanogaster to high levels of urea and ammonia has already been studied [22,33], little is known about the effects in D. suzukii.…”