Corals from each of the three regions, although morphologically very similar, clustered weakly as separate groups (Fig. 3) suggesting slight morphological divergence is occurring between corals in the three isolated regions.
Of course, morphological divergence isn't the same as speciation.
Formally, this tests whether the angles between two assemblages' Mmax axes, 2-D planes, and 3- and 4-D spaces of morphological divergence are more different than the angles between two random samples of either single assemblage.
Similar morphological plasticity in other dinosaurian groups (e.g., hadrosaurids) has typically been interpreted in relation to behavior, although often behavior and morphological divergence are correlated with phylogeny [46], and it can be difficult to tease apart the influences of phylogeny and behavior on morphology.
To confirm that regional differences in rainforest-ecotone morphological divergence were due to greater deforestation in West Africa, and not to a persistent historical pattern, we collected morphological data from historical specimens of A. virens deposited at the Natural History Museum at Tring, United Kingdom (Table S3, details in Text S1).
The sexual selection hypothesis states that morphological differences in male genitalia are related to variation in fertilization success and that morphological divergence is driven by sexual selection [ 3].
Speciation without morphological divergence is usually linked to selection promoting morphological invariance or to the use of nonvisual mating signals [ 1].
Despite the importance of character displacement for inferring the role of selection in morphological evolution however, replicated instances of sympatric morphological divergence are understudied.
Finally, we assess genetic variation among our study populations to test whether the patterns of morphological divergence are congruent with patterns of genetic divergence.
Our results suggest that morphological divergence is not driven by subtle drift in specificity of TFs, but primarily caused by cis-regulatory changes (Carroll, 2000; Levine and Tjian, 2003), with some contribution from relatively large shifts in binding specificities of specific TFs.
