Table 1 The hypotheses tested.
Hypotheses | Mechanism | Prediction | Analyses | Acceptance |
|---|---|---|---|---|
‘Bridge’ hypothesis | Some seamounts of FNC had suitable conditions for the occurrence of our ingroup during periods of sea level decrease. The colonization was due to a long-lasting contact promoted by a stepping-stone bridge of emerging seamounts between FNI and the mainland. | Suitable areas below the present-day sea level will be available during periods of sea level as low as LGM. Signature of foundation followed by a gradual decline of gene flow with mainland populations along time | Paleomodeling (MaxEnt, Random Forest, ANN) Quantification of the transient-land bridges in FNC (PleistoDist R package) Coalescent Analyses (ABC) ‘Model 1’ (Fig. 2) | Yes |
Long-distance dispersal | Long-distance dispersal of few mainland individuals | severe short-term colonization of FNI, according to the classical founder event model Absence of suitable areas below the present-day sea level during periods of sea level as low as LGM | Coalescent Analyses (ABC) ‘Model 2’ (Fig. 2) Paleomodeling (MaxEnt, Random Forest, ANN) | No |
Rapid adaptive divergence of C. insularis after the colonization of FNI | The new insular environment may play selective pressures in the colonizing population. | Signatures of divergent selection between C. insularis and C. fernambucensis | Outlier loci detection (BayeScan, PCAdapt) | Yes |
