Fig. 3.

Variable meiotic stability in Cardamine amara. (a) An example of stable and unstable diploid and autotetraploid DAPI-stained meiotic chromosomes (diakinesis and metaphase I). Unstable meiosis is characterized by multivalent formation and interchromosomal connections, so we use the proportion of bivalents to multivalents as a proxy to estimate stability. In this example, the stable and unstable diploids (left panels) pictured contain 8 and 4 bivalents, respectively, whereas the stable and unstable tetraploids (right panels) show 16 and 0 bivalents, respectively. Thus all chromosomes pictured in these “Stable” examples are present as bivalents, whereas in the “Unstable” examples, only the four with asterisks (*) are bivalents, whereas the rest are mulivalents. Scale bar corresponds to 10 µm. For a complete overview of all scored chromosome spreads see supplementary figure 5, Supplementary Material online. (b) Distribution of meiotic stability (calculated as proportion of stable and partly stable to all scored meiotic spreads) in diploid and autotetraploid individuals of C. amara. *** P < 0.001, GLM with binomial errors.