For the calculation of χ², the observed frequency (in parentheses) is compared to the expected frequency under the null hypothesis of a random distribution of TA-indel size (i.e., 1/3 of 3 n TA-indels and 2/3 of non-3 n TA-indels). NB, by definition, low-frequency TA-indels that are located within coding regions cannot contain in-frame stop codons. (NS) Not significant.

^aTA-indels located within coding regions that do not contain a TGA triplet in frame with the upstream coding region.

^bThe 42 experimentally determined P. tetraurelia IESs (Gratias and Bétermier 2001) are all located in coding regions.

^cTA-indels located within coding regions that contain at least one TGA triplet in frame with the upstream coding region.