Maternal and grandmaternal age effects on developmental instability and wing size in parthenogenetic Drosophila mercatorum

Abstract

Age is known to have a large effect upon fertility and survival. Here we study the impact of maternal and grandmaternal age on wing size and developmental instability (DI) in offspring using a parthenogenetic strain of Drosophila mercatorum. This enabled us to cancel out any genetic variance between individuals. The mean centroid size of the wings was estimated in offspring from four maternal/grandmaternal age groups. Further, DI was calculated by measuring phenotypic variability and correcting this index for the bias produced by the environmental variability. The offspring developed from eggs laid by mothers belonging to four different age groups with young (Y) or old (O) mothers and grandmothers. The age groups are: YY, YO, OY and OO, with the first letter referring to the age of the grandmother and the second letter to the age of the mother. We consider flies between three to six days of age as young and flies between 15 and 18 days of age as old. We found that environmental variability was present in this study and therefore the correction for its bias on phenotypic variability was shown to be necessary for a correct interpretation of the results. DI displayed, for most of the traits investigated, a significantly higher level in the OY and OO age groups, as compared to the YY and YO age groups. The mean centroid size of the wings were in almost all cases significantly different among the age groups with the highest mean value in the OY group for all traits. This investigation shows that offspring are affected by maternal age and that this effect can be transmitted maternally across more than one generation.

A Study of Canalization and Developmental Stability in the Sternopleural Bristle System of Drosophila Melanogaster

“…Andersen et al 2002Andersen et al , 2006Garnier et al 2006). One commonly used measure of DI is fluctuating asymmetry (FA), or the difference in value between paired bilateral traits, which is known to be elevated due to environmental stresses and genetic factors such as hybridization (Andersen et al 2002(Andersen et al , 2006(Andersen et al , 2008Kristensen et al 2003Kristensen et al , 2004Røgilds et al 2005;Pertoldi et al 2006a;Petavy et al 2006;Lens et al 2000;Soderman et al 2007;Krag et al 2009). The reason for the increased FA in intraspecific hybrids has been attributed to a breakdown in co-adapted gene complexes (Andersen et al 2002), whereas in interspecific hybrids increased FA has more often been attributed to genetic incompatibilities causing meiotic irregularities or physiological and developmental abnormalities (Andersen et al 2006;Burke and Arnold 2001;Pialek et al 2001;Rego et al 2006;Kurbalija et al 2010).…”

A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect?

“…The measurement error should be minimal compared to the level of variation of the (r − l) values [1,42] and there should not be antisymmetry and/or directional asymmetry, which will make the correction proposed in this paper inapplicable [43,44]. Potentially, there is a very promising application of fluctuating asymmetry as an indicator of environmental stress if we choose to apply the exact correction proposed in this paper on clonal organisms where no genetic substructure is present [45][46][47][48][49][50][51]. The absence of genetic substructure is allowing us to exclude one of the potential biases which is afflicting the fluctuating asymmetry indexes.…”

Possible Evolutionary Response to Global Change – Evolutionary Rescue?

“…In particular, studies have been conducted in the attempt to obtain more detailed knowledge on the potential of  2 p in an evolutionary context. A number of investigations have shown that  2 p is positively associated with the level of genetic and environmental stresses that individuals experience (Kristensen et al, 2004;Røgilds et al, 2005). Several studies have also tried to elucidate the effect of genetic variability ( 2 g) on  2 p (e.g.…”

“…Various modelling approaches have shown that to optimize fitness, phenotypic plasticity evolves by trading the adaptation to acquire resources against the costs of maintaining the potential for plasticity (Ernande & Dieckman, 2004). Plastic responses include changes in behavior, physiology, morphology, growth, life history and demography, and can be expressed either within the lifespan of an individual or across generations Røgilds et al, 2005). Two ways of adapting to environmental changes are therefore possible, by evolutionary or by plastic responses, including maternal transmission (trans-generational plasticity).…”