Data from: Long-term stasis and short-term divergence in the phenotypes of microsnails on oceanic islands

Phenotypic divergence is often unrelated to genotypic divergence. An
extreme example is rapid phenotypic differentiation despite genetic
similarity. Another extreme is morphological stasis despite substantial
genetic divergence. These opposite patterns have been viewed as reflecting
opposite properties of the lineages. In this study, phenotypic radiation
accompanied by both rapid divergence and long-term conservatism is
documented in the inferred molecular phylogeny of the micro land snails
Cavernacmella (Assimineidae) on the Ogasawara Islands. The populations of
Cavernacmella on the Sekimon limestone outcrop of Hahajima Island showed
marked divergence in shell morphology. Within this area, one lineage
diversified into types with elongated turret shells, conical shells and
flat disc-like shells without substantial genetic differentiation.
Additionally, a co-occurring species with these types developed a much
larger shell size. Moreover, a lineage adapted to live inside caves in
this area. In contrast, populations in the other areas exhibited no
morphological differences despite high genetic divergence among
populations. Accordingly, the phenotypic evolution of Cavernacmella in
Ogasawara is characterized by a pattern of long-term stasis and periodic
bursts of change. This pattern suggests that even lineages with phenotypic
conservatism could shift to an alternative state allowing rapid phenotypic
divergence.