Population dynamics of Ervilia castanea (Montagu, 1803) hints at
evolutionary processes shaping north-east Atlantic insular sandy
habitats
Abstract
Volcanic oceanic islands are some of the Earth’s most geologically and
ecologically dynamic habitats, where continuous volcanic activity and
erosion lead to the formation of habitats that drastically change
throughout their ontogeny. Shallow-water sandy habitats, specifically,
repetitively disappeared and regenerated due to seasonal oceanographic
and climatic eustatic sea-level variations. For its inhabitants, these
events translate into populations being cyclically removed or passing by
drastic reductions in population size, where the outcome often depends
on the specific life-history modes of the species, determining their
dispersal, colonization potential and, ultimately, their survival
ability. Therefore, population genetic patterns of marine shallow-water
infaunal species can provide powerful clues of such outcomes, as well as
how specific geological and ecological settings determine the genetic
structure of the species. We herewith test the population structure of
the marine infaunal bivalve Ervilia castanea (Montagu, 1803) in the
sandy habitats of the Azores and Madeira Archipelagos (Northeast and
Central Atlantic Ocean), by comparing insular populations with
conspecifics from the nearest continental shores in mainland Europe.
Little to no genetic structure was observed between insular populations
with both nuclear microsatellites and the mitochondrial cytochrome c
oxidase subunit I. Moreover, deviations in the Hardy-Weinberg
Equilibrium of insular populations suggests the exitance of archipelago
specific processes. The high dispersal ability of E. castanea combined
with the ephemeral nature of oceanic shallow-water sandy habitats likely
made each population to be composed of individuals from multiple
sources. High prevalence of null alleles, gene duplication hint at the
potential occurrence of recent polyploidization events that require
further investigation. Moreover, we found evidence of hyperdiversity
among the markers used which may constrain the detection of more
detailed patterns. We herewith demonstrate the uniqueness of insular
environmental settings and inquire further into the evolutionary and
biogeographic patterns of marine shallow-water infaunal species from
volcanic oceanic islands.