Fig. 2

Determination of scores assigned for each similarity criterion based on their Δlog values i.e. [Δlog = log(control) − log(dark zone)] with the data obtained for the Apse reference situation (in blue). The calculation is shown in orange for Ochroconis in the Apse. The data (higher or lower) obtained for the other dark zones are positioned according to the different intervals of values, each corresponding to a given scale of gap with the Apse reference situation, resulting into a score between 0 and 1 (with increments of 0.1, according to the green gradient), whereas data for which the gap falls outside of the scale or with an opposite sign are represented in red (meaning that the difference in the number of sequences between the two rock surface conditions is greater than those indicated in the scale). The Δlog value are computed, and the fold change value between this Δlog value and the corresponding Δlog value for the Apse (i.e., ΔFold-change) is scored as 1 (when |Δfold change| is below one tenth of the Δlog value for the Apse), 0.9 (when |Δfold change| is between one and two tenths of the Δlog value for the Apse), …, and 0 (when |Δfold change| is above nine tenths of the Δlog value for the Apse). When the Δlog value is equal to 0.000 (framed in mauve), it means that the number of sequences is the same for both rock surface conditions (i.e. control and dark zone). Δlog values and score assignations are illustrated for Ochroconis and Pseudomonas criteria in all sample locations. The division factor (when counter-selection) or multiplication factor (when selection) for the number of sequences between the two rock surface conditions is indicated on the side, to facilitate reading