[OANNES Foro] Anchovies go north and west without losing diversity: post-glacial range expansions in a small pelagic fish

[Mario Cabrejos]

Journal of Biogeography

 <http://onlinelibrary.wiley.com/doi/10.1111/jbi.2014.41.issue-6/issuetoc>
Volume 41, Issue 6, pages 1171–1182, June 2014

Article first published online: 23 JAN 2014

DOI: 10.1111/jbi.12275


 


 


Anchovies go north and west without losing diversity: post-glacial range
expansions in a small pelagic fish


1.     Gonçalo Silva, John B. Horne and Rita Castilho*

Centre of Marine Sciences, CCMAR/CIMAR Associate Laboratory, University of
Algarve, Gambelas, Faro, Portugal. * Correspondence: E-mail:
<mailto:rcastil en ualg.pt> rcastil en ualg.pt


 


Abstract


Aim


As part of an emerging effort to understand the role played by climatic
fluctuations in shaping the geographical distributions and abundances of
marine organisms, we examined the genetic patterns of leading-edge
populations in the European anchovy, Engraulis encrasicolus, and its
American counterpart, the morphologically similar silver anchovy, Engraulis
eurystole, in the North Atlantic Ocean.


Location


Adults were collected from the western Atlantic, eastern Atlantic (from
Norway to Ghana) and western Mediterranean.


Methods


A 1045 bp fragment of the mtDNA cytochrome b gene was sequenced (n = 312)
and nine microsatellite loci were genotyped (n = 462) for anchovies from 13
locations across the temperate North Atlantic. Populations were surveyed for
diversity and differentiation with a range of summary statistics.
Multivariate discriminant analysis of principal components was employed to
detect the number of genetic clusters in the data and assign individuals to
populations based on their microsatellite genotypes. Historical demographic
inferences – mismatch distributions and Bayesian skyline plots – were used
to observe population size changes relating to climatic oscillations.


Results


Two mitochondrial clades were recovered, consistent with previous studies of
E. encrasicolus, in which the frequency of each clade varied by latitude.
Four genetic clusters corresponding loosely to large geographical regions
were identified with microsatellite data. The north-western Atlantic E.
eurystole was not reciprocally monophyletic for either mtDNA or
microsatellite analyses and is probably conspecific with E. encrasicolus.
Genetic diversity peaked in Iberian populations, but differences in genetic
diversity were only statistically significant for the least diverse
population, Tangier. The indications of demographic expansion were more
pronounced in the southern clade and both mtDNA clades exhibited genetic
diversity and expansion imprints that are likely to be older than climatic
oscillations of the recent Pleistocene.


Main conclusions


The highly mobile nature of anchovies has allowed them to track their
optimal thermal physiological conditions during the extreme climate shifts
of the Last Glacial Maximum and avoid wholesale population reductions and
genetic bottlenecks. Both north-eastern and north-western Atlantic were
probably rapidly recolonized after the Last Glacial Maximum by large numbers
of anchovies, such that leading-edge populations retained the genetic
diversity of parent populations.

 



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