Evolution of maternal effects: past and present

It has been said that many original ideas reflect a convergence of related thought that coalesces into a unified representation of what many have been thinking. This is certainly true for the subfield of maternal effects evolution. The study of maternal effects has a long history. The first two papers reported in the ISI database dealing with the evolutionary significance of maternal effects were published in Proceedings of the National Academy of Science USA by Dobzhansky & Sturtevant (Dobzhansky 1935, ‘Maternal effect as a cause of the difference between the reciprocal crosses in Drosophila pseudoobscura’; Dobzhansky & Sturtevant 1935, ‘Further data on maternal effects in Drosophila pseudoobscura hybrids’). Surprisingly, given its authors, these papers have received little attention in the literature (a total of 12 citations for the Dobzhansky and Sturtevant paper), perhaps because of their relatively recent addition to electronically searchable databases, although the third paper in the list, by Walton & Hammond (1938), dealing with maternal effects in Shetland ponies, has been well cited (total of 228 citations) with an increasing rate of citation in the past decade. Overall, prior to 1987, ISI reports a total of 185 publications with ‘maternal effects’ as a keyword phrase. Between 1988 and 1997 this number jumped to 520 papers, while from 1998 to the present (November 2008) there have been at least 1397 publications on this topic. These numbers are underestimates, especially for the latter years, as they do not include the many keyword variants of relevant processes (e.g. maternal inheritance, maternal genetic effects, parental effects, epigenetic effects), or papers where the primary emphasis is in a different but related area, but they do reflect a dramatic increase in awareness following the late 1980s of the importance of maternal effects in the evolutionary process