Spira mirabilis in Heterostegina: evolutionary and ecological perspectives

Morphometric analysis of the marginal spiral outline of Heterostegina populations belonging to the ocalana-matteuccii lineage reveals that it fully fit with a logarithmic spiral identified by two variables: the initial radius (IRex) and the radius increase (Rinc). Spirals tend to become more looser through time as observable also in well-known Mediterranean lineages. Rinc tends to increase along a phyletic line leading to the definition of a...