In an attempt to unravel the possible relationships among coastal stability,
genetic variability and orientation behaviour in the sandhopper Talitrus saltator, we
have screened four subpopulations of this species. Sandhoppers along 3 km of a
dynamic sand beach were studied for orientation performance (i.e. adherence to the
seaward theoretical escape direction (TED)) and sequence variation for a fragment
of the mitochondrial (mt) gene encoding for the cytochrome oxidase subunit I (COI).
The sampling sites differed in the stability of the shoreline (from severely eroded to
accreting). Analysis of molecular variance (AMOVA) revealed significant subdivisions
among the four locations. The subpopulation sampled at the most eroded
point showed no haplotype diversity and had the highest scatter in orientation.
Genetic diversity increased with decreasing erosion. Orientation performances were
best where the beach is in dynamic equilibrium, and were progressively more scattered
at the accreting points. Multiple linear regression analyses demonstrated that
the variables and factors that affected orientation significantly were daytime, global
solar radiation, sex of individuals and haplotype diversity. Environmental factors
are likely to influence sandhopper behaviour on a short and medium time scale (i.e.
from single individual life span to a few generations). The data also suggest that temporal
stability of the shoreline has a positive effect on the genetic variability of the
resident sandhopper populations.
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