INHERITANCE AND FITNESS EFFECTS OF A PERICENTRIC-INVERSION AND A SUPERNUMERARY CHROMOSOME SEGMENT IN MUSCARI-COMOSUM (LILIACEAE)

The inheritance and the effects on fitness of a pericentric inversion and a supernumerary chromosome segment (SCS) involving the second chro mosome pair of Muscari comosum, have been analysed in an experimental population. Whereas the inversion is inherited in a Mendelian fashion through the female side, the SCS shows a powerful accumulation mechani sm (k = 0.796). Cases of nonrandom pollination were observed in homozy gous bulbs for the standard chromosomes (++) and also in those homozyg ous for the inverted chromosomes (ii), which may be caused by a certai n rate of self-pollination. The different karyotypes for both the inve rsion and the SCS showed similar values for several life-history trait s related to female fitness, such as bulb weight, number of fruits, nu mber of seeds and seed weight. However, plants carrying the inversion had heavier bulbs than those lacking it. The significance of these obs ervations is discussed in relation to the maintenance of the two types of polymorphism in natural populations.