Environmental Engineering Reference
In-Depth Information
Uhen 2010). One example is the harbour porpoise,
Phocoena phocoena
, which
is currently distributed throughout cold to temperate coastal waters of the
North Pacifi c, the North Atlantic and the Black Sea, being absent in the
Mediterranean (Read 1999). The south-eastern part of the distribution range
in the North Atlantic is of particular interest in regard to recent climate
change, as it covers the biogeographic transition between arctic/boreal
species and subtropical species (Southward et al. 1995). Fontaine et al.
(2010) used data previously obtained from 10 microsatellite loci (Fontaine
et al. 2007) to test whether the genetic divergence observed among harbour
porpoises populations in the Northeast Atlantic is compatible with the
recent changes reported in the seascape and marine assemblages, or is more
likely owing to ancient vicariance processes. Their results showed that the
isolation of porpoises in Iberian waters from those further north occurred
approximately 300 years ago, matching with a warming trend that started
after the Little Ice Age period and with the ongoing retreat of cold-water
fi shes from the Bay of Biscay. Results of Fontaine et al. (2010) work show how
past climate change can produce population fragmentation. In this context,
it is expected that future increases in sea water temperature, a predicted
impact for the ongoing climate change, will force this marine predators to
adapt to the changing spatial distribution of their prey, as they did in the
past. The survival of the current genetic units will depend upon the ability
of this top predator to adapt to rapidly changing habitat conditions.
The dusky dolphin,
Lagenorhynchus obscurus
, is another species for
which prey availability played an important role along its evolutionary
history. The species is widely distributed in the Southern Hemisphere, with
a disjoint distribution restricted to temperate and sub-Antarctic waters
(Würsig et al. 1997). Dusky Dolphins eat a wide diversity of prey, including
Southern Anchovy, and mid-water and benthic prey such as squid and
laternfi shes, species tightly associated with temperate ocean sea surface
temperatures. The species is thought to be particularly vulnerable to broad-
scale changes in the marine environment because of their high positions in
marine food chains (Bannister et al. 1996) and has been suggested that its
timing of foraging may be seasonal and be correlated with the movements
of their prey (Bannister et al. 1996, Würsig et al. 1997). Previous studies
on the genetics and distribution of dolphin genera
Cephalorhynchus
and
Lagenorynchus
(Pichler et al. 2001, Cassens et al. 2003) have suggested that
the dusky dolphin dispersed in the Southern Hemisphere eastward from
Peru via a linear, temperate dispersal corridor provided by the circumpolar
west-wind drift. Harlin-Cognato et al. (2007) using a multi-locus approach
analysis, that included mitochondrial and nuclear sequence data, proposed
the alternative hypothesis that the phylogeographic history of the dusky
