Cytoplasmic Inheritance in Culex

Abstract

FROM an analysis of non-reciprocal fertility in Aëdes scutellaris, Smith-White and Woodhill¹ drew the conclusion that this phenomenon must be due either to anomalous meiosis in the course of oogenesis, with polarized segregation of bivalents and the elimination of part of the paternal genom, or to cytoplasmic factors acting independently of the nucleus. They state that “There is no critical evidence enabling a choice between the two types of hypothesis”. Crossing relations in Aëdes scutellaris, as studied by Smith-White and Woodhill, are essentially similar to the more complex relations encountered in the Culex pipiens complex². Some geographically representative populations are fully fertile in both directions, whereas others, although morphologically indistinguishable, are almost completely isolated by inter sterility. In this case the limitations of a purely morphological species concept are obvious. A third group of populations is interfertile with the others in one direction only. Parthenogenesis, with pseudogamy, predetermination and multiple incompatibility genes can be excluded as causative mechanisms. These cases of strictly maternal inheritance can be explained only by the two hypotheses mentioned by Smith-White and Woodhill.