Reaction norms across and genetic parameters at different temperatures for thorax and wing size traits in Drosophila aldrichi and D. buzzatii

Abstract

Reaction norms across seven constant and one fluctuating temperature of development were measured for thorax length and several wing size traits for up to 10 isofemale lines of each of the cactophilic Drosophila species, D. aldrichi and D. buzzatii, originating from the same locality. Maximum thorax length was reached at different low to intermediate temperatures for the two species, whereas wing length was highest at the lowest temperature in both species. Various ratio parameters showed pronounced species differences. The reaction norm for the wing loading index (wing length/thorax length) decreased monotonically with temperature in both species, but was much steeper and spanned a wider range in D. aldrichi than in D. buzzatii, suggesting either that wing loading is not a good characterization of flight capacity or, more likely, that flight optimization does not occur in the same manner in both species. The vein ratio (distal length/proximal length of the third vein) increased with temperature in D. buzzatii but decreased in D. aldrichi. Wing development in the two species thus is very different, with the proximal part of the wing in D. buzzatii more closely allied to the thorax than to the distal part. Among line variation was significant for all traits in both species, and most pronounced for thorax length and the ratio parameters. Coefficients of variation were significantly different between the species for all traits, with those in D. aldrichi higher than in D. buzzatii. Genetic variance in plasticity was significant for all traits in D. buzzatii, but only for seven out of 12 in D. aldrichi. Additive genetic variances for all traits in both species were significantly larger than zero. Genetic correlations between thorax length and several wing length parameters, and between these and wing area, were positive and generally significant in both species. The genetic correlation between the distal and the proximal length of the third vein was not significantly different from zero in D. aldrichi, but negative and significant in D. buzzatii. Heritabilites varied significantly among temperatures for almost all traits in both species. Phenotypic variances were generally higher in D. aldrichi than in D. buzzatii, and commonly highest at the extreme temperatures in the former species. At the high temperature the genetic variances also were usually highest in D. aldrichi. The data clearly suggest that the process of thermal adaptation is species specific and caution against generalizations based on the study of single species.

Body Size and Wing Shape Measurements as Quality Indicators of Aedes aegypti Mosquitoes Destined for Field Release

“…Given that previous studies have suggested that this trait may influence dispersal ability, 32 and given the lower ratio in females from the sticky ovitraps, it would seem prudent to try to match ratios in released material with those from the field. Temperature manipulations may need to be monitored closely with changing seasons, as there is some evidence from our May sampling data and previous studies 73,74 that temperature could affect wing load.…”

Body size in Drosophila: genetic architecture, allometries and sexual dimorphism

“…Genetic correlations between body size-related traits are well documented in Diptera (for example, Atchley, 1988, 1990;David et al, 2006;De Moed et al, 1997;Loeschcke et al, 1999;Misra, 1966;Moreteau et al, 2003;Norry et al, 1997;Rohlf andSokal, 1972, Scheiner et al, 1991;Sisodia and Singh, 2001). Most studies reported that correlations among measurements of different body parts are usually positive indicating that cell proliferation and cell growth rates of different imaginal discs may be proportional during larval growth, providing a possible explanation to the apparent constraints that limit divergence from the fundamental body plan of flies.…”

Predicting the physiological performance of ectotherms in fluctuating thermal environments

“…Dramatic fluctuations in temperature occur daily in many environments, including ephemeral pools (Johns et al, 1981;Dadour et al, 2001;Niehaus et al, 2006), shallow soils (Shine and Elphick, 2001;Ashmore and Janzen, 2003;Georges et al, 2005) and tidal waters (Stillman and Somero, 2000;Podrabsky and Somero, 2004). Despite the ubiquity of thermal change, studies of development at constant temperatures greatly outnumber studies of development at fluctuating temperatures [for examples of the latter, see the following references (Siddiqui and Barlow, 1972;Qualls and Shine, 1998;Loeschcke et al, 1999;Pétavy et al, 2004;Niehaus et al, 2011a;Niehaus et al, 2011b)]. Instead, impacts of thermal fluctuations are usually inferred from a reaction norm, which describes the relationship between temperature and the phenotype.…”