While a great deal of effort has gone into determining the genetic basis of hybrid sterility
, the actual "phenotype" of hybrid male sterility has typically been ignored.
Genetics of morphological differences and hybrid sterility
between Drosophila sechellia and its relatives.
With such screening, hybrid sterility
genes of potential maintainers are not detectable due to the low pollen fertility resulting from lack of Rf under the cms background.
This seems like a very great number, and in fact it may be biased by extrapolation from studies of the X chromosome, which may be exceptional in regard to hybrid sterility
(Laurie 1997), as well as by the inclusion of genes causing hybrid sterility
that arise since speciation.
in Drosophila is known to be germ-cell autonomous (Dobzhansky and Beadle 1936), but spermatogenic defects in only a few studies have been characterized cytologically (Naveira and Fontdevila 1991; Pantazidis et al.
Kelly and Noor (1996) have further shown with autosome-autosome interactions that assuming an epistatic rather than additive source of hybrid sterility
restricts the conditions under which reinforcement will occur.
n] for `wide-compatibility'; the hybrids between this cultivar and many of indica type are free of hybrid sterility
(Ikehashi and Araki, 1986).
The marker, which is within 5 cM of the S-5 hybrid sterility
locus (Yanagihara et al.
Third, hybrid sterility
and inviability evolve at similar rates.
Instead, genetic analyses show that hybrid sterility
and inviability involve incompatibilities between two or more loci that behave as "complementary genes," that is, although these genes are deleterious when brought together with genes from another species, they are perfectly fit on their normal genetic backgrounds (Coyne 1992; Wu and Palopoli 1994; Orr 1995).
Work done to determine the basis of the hybrid sterility
(Goodpasture et al.
So far, genetic studies on hybrids between Drosophila species have demonstrated that sex chromosomes, and in particular the X chromosome, play a large role in hybrid sterility
and viability (Orr 1987, 1989; Orr and Coyne 1989; Wu 1992; Perez et al.