Regional Center for Talented Youth Belgrade II, Serbia, dijanachl@gmail.com
1.
clear sexual dimorphism in this species (Picture 2). There is significant interaction between sex and groups (Table 1).
Inbreeding, mating between close relatives, is a genomic stress that may disrupt the stability of the genome [1]. This phenomenon occurs in nature, especially in situations of habitat fragmentation caused by anthropogenic influence, global climate changes and rapidly growing pollution. In those cases, population could be isolated for a certain period, which would lead to mating closely genetically related individuals [1]. Inbreeding results in homozygosity, and has both positive and negative effects on whole range of traits, including morphological traits and fitness components [2].
The aim of this study was to evaluate influence of experimentally increased homozygosity, as genomic stress, after 14 generations of full-sib inbreeding treatment in laboratory conditions on Drosophila wings morphological traits.
Effect df MS F group sex
3
1
23606 37.7 ***
492693 787.2 *** group x sex 3 4089 6.5 ***
Error 481 626
Table 1. Two-way ANOVA on wing size (CS) of individuals from four groups and both sex
2.
In this experiment, highly inbred lines of D. subobscura, originating from two ecologically and topologically distinct habitats (Botanical Garden in Belgrade and Sicevo gorge) were used, knowing that they possess a certain degree of genetic differences due to their different evolutionary histories. Beside homozygotes from inbred lines, heterozygotes from direct and reciprocal crosses between these populations were used. For analysis of phenotypic variability of the wings males and females were separated.
The right wing of each fly was fixed and the digital photograph was taken. Images were landmarked with 13 landmarks (Picture 1). Wing size was examined using centroid size (CS) and shape was examined using weight matrix ( wm ). Differences in CS were tested with ANOVA, and the ones in wm with MANOVA.
Picture 2. Mean values of centroid size for all experimental groups and both sexes
MANOVA showed no difference in wing shape between experimental groups, as a result of different genes and genetic pathways involved in development of these wing morphological characteristic [3], and which is consistent with results of previous studies.
4.
Understanding nature of phenotypic variation is important aspect of evolutionary biology. One of the reasons why homozygous individuals have smaller wings may lie in fact that more recessive genes are expressed in phenotype than expected, which can lead to lower performances in individuals as well as in populations.
Another explanation is heterozygote superiority, theory which states that higher level of heterozygosity increases fitness of an individual, and since the wing size is closely related to a fitness of an individual, obtained results are in concordance with this theory.
5.
Picture 1. Right wing of D. subobscura with 13 landmarks
3.
The results for wing size showed significant difference between homozygote and heterozygote groups (Table 1).
Heterozygous individuals have larger wings than homozygous (Picture 2). Also, between sexes is significant difference: males have smaller wings than females, due to
[ 1 ] L. F. Keller, D. M. Waller, 2002: Inbreeding effects in wild populations. Trends in Ecology & Evolution, 17: 231.
[ 2 ] M. Lynch 1997: Inbreeding depression and outbreeding depression. In: Genetic effects of straying of non-native fish hatchery fish into natural populations. W. S. Grant (editor).
U.S. Dep. Commer., NOAA Tech Memo.
[ 3 ] V. P Carreira, I. M Soto, J. Mensch, J. J Fanara, 2011:
Genetic basis of wing morphogenesis in Drosophila : sexual dimorphism and non-allometric effects of shape variation.
BMC Developmental Biology, 11: 32.