Developmental instability in hybrids between Lychnis viscaria and Lychnis alpina (Caryophyllaceae)

Developmental instability shown by increased fluctuating asymmetry can be caused by either genetic or environmental stress. Genomic coadaptation and heterozygosity are the genetic factors that are commonly assumed to increase the level of developmental stability. Therefore, in hybrid populations the level of fluctuating asymmetry (FA) can be lower due to higher heterozygosity or higher due to disruption of coadapted gene complexes, depending on the degree of divergence between hybridizing taxa. Here I present data on FA in petals from hybrids between Lychnis viscaria (Caryophyllaceae) and Lychnis alpina and from parental species grown in a common garden environment. Petal asymmetry of hybrids was clearly higher than that of either parental species grown in common environment. Between the two parental species petal asymmetry did not differ. The mean size of the petals in hybrids was about the same as in L. viscaria, thus indicating no heterotic effect. Therefore, it seems that hybrids between L. viscaria and L. alpina do suffer from the disruption of coadapted gene complexes as indicated by higher developmental instability.