Fig. 1

Phylogeny, desiccation features, geographical origin and desiccation resistance of bdelloid species exposed to desiccation (with the exception of desiccation-sensitive R. macrura and R. rotatoria species). Phylogeny (Left) was reconstructed from Cox1 and 18S. The tree was calibrated using published substitution rates of Cox1 and 18S (see Methods). All clades have posterior probability support values = 1.0. Adineta vaga species was added as reference species with published genomic data (Flot et al. [27]). Mapped ancestral character reconstruction (ACE) was added on the phylogenetic tree for desiccation resistance. Color codes are white = desiccation-sensitive and gray = desiccation-tolerant. Bdelloids were classified in 2 groups associated with their exposure to desiccation: Group “Frequent” includes species isolated from habitats that experience frequent desiccation (at least 1 time per generation); Group “Null or rare” includes species sampled from habitats that rarely or never experienced desiccation (see Methods). Map (Center) was acquired from https://upload.wikimedia.org/wikipedia/commons/6/69/World_map_blank_gmt.svg. Illustration pictures credited to B. Hespeels and D. Fontaneto. Except for the two Rotaria species, all species were found to be desiccation tolerant. Comparison between the survival rate and the capacity to produce a fertile population of desiccation-resistant bdelloid species exposed to 24h of desiccation (Right) was visualized as a dotplot (● = average value with plot of Standard Deviation). Survival rate was evaluated 2 days post rehydration on a minimum of 3 replicates. Fertility rate was evaluated 1 month post isolation of rehydrated individuals on a minimum of 3 replicates (see Methods). For each replicate, 60 individuals were randomly isolated and individually placed in multi-well plates. Reproduction was evaluated by direct observation under a binocular stereoscope 30 days after rehydration/radiation. Effective reproduction was validated when at least 2 adults and 1 egg were observed per well. Letters indicate significant differences between groups: a significant difference (Tukey test p-value <0.05) between two conditions is observed when these conditions do not share any letter. Desiccation resistance data of A. vaga species was extracted from Hespeels et al. [20]