Development of anchialine cave habitats and karst subterranean estuaries since the last ice age
van Hengstum, P.J., Cresswell, J.N., Milne, G.A. and Iliffe, T.M.
Extinction models generally predict that coastal and neritic fauna benefit during sea-level rise
(transgression), whereas sea-level retreat (regression) diminishes their suitable habitat area and
promotes evolutionary bottlenecks. Sea-level change also impacts terrestrial island biogeography, but
it remains a challenge to evidence how sea-level rise impacts aquatic island biogeography, especially
in the subterranean realm. Karst subterranean estuaries (KSEs) occur globally on carbonate islands
and platforms, and they are populated by globally-dispersed, ancient ecosystems (termed anchialine).
Anchialine fauna currently exhibit a disjunct biogeography that cannot be completely explained by
plate tectonic-imposed vicariance. Here we provide evidence that anchialine ecosystems can experience
evolutionary bottlenecks caused by habitat reduction during transgression events. Marine-adapted
anchialine fauna benefit from habitat expansion during transgressions, but fresh- and brackish-adapted
fauna must emigrate, evolve to accommodate local habitat changes, or are regionally eliminated.
Phanerozoic transgressions relative to long-term changes in subsidence and relief of regional lithology
must be considered for explaining biogeography, evolution, local extirpation or complete extinction of
anchialine fauna. Despite the omission of this entire category of environments and animals in climate
change risk assessments, the results indicate that anchialine fauna on low-lying islands and platforms
that depend upon meteoric groundwater are vulnerable to habitat changes caused by 21st century sealevel