Fig 1. General changes of embryonic gene expression between four Drosophila species.

A. In this paper we compare the genome-wide mRNA levels in blastoderm embryos of four Drosophila species D. melanogaster, D. yakuba, D. pseudoobscura and D. virilis. Pairwise comparisons of mRNA levels between one male replicate in different species show that mRNA levels are overall highly conserved. As a comparison, scatter plots of two male replicates are shown for each species. B. Spearman correlations between mRNA levels of the 22 tightly staged embryos of our dataset (2–3 males/2–3 females per species). Correlations decrease with increasing phylogenetic distance. C. Spearman correlations between mRNA levels of the seven unfertilized eggs (1–2 per species) and a representative embryo sample from each species (“Male replicate 2”). Correlations are highest within eggs and embryos than between eggs and embryos. For B and C, the Spearman correlations are shown in percentages (so ranging from 0 to 100). D. Correspondence analysis (COA) of expression levels in the single eggs and embryos. Values for pools of embryos were projected to the COA. The proportion of the variance explained by the first components of the correspondence analysis is indicated in parentheses. Samples separate along first axis mainly according to developmental stage while they separate along second axis mainly according to species.