| Abstract |
Mesopelagic fish comprise the most abundant group of vertebrates in the marine environment
as well as in the total biosphere. They are small sized species, which inhabit the mesopelagic
zone, usually found at depths of 100-1000 m. Despite their unique biological and ecological
traits, this group of species has not been studied extensively. Genetic studies regarding these
species have been particularly scarce. The present study investigates the intraspecific genetic
diversity of four species of mesopelagic fish (Maurolicus muelleri Gmelin, 1789, Benthosema
glaciale Reinhardt, 1837, Hygophum benoitι Cocco, 1838, Myctophum punctatum
Rafinesque, 1810), collected from the Greek Seas (Corinthian Gulf, Saronic Gulf, North
Aegean Sea, North Euboean Gulf, Cretan Sea, Ionian Sea). For this purpose three
mitochondrial genes (COI, 12S, 16S) and the internal transcribed spacer ITS2 from 265
specimens were amplified and sequenced. The obtained sequences were used in order to study
the genetic diversity of different populations and the existence of geographical patterns of
differentiation of the four species in Greece. Moreover, we studied the phylogeography of
these species by co-analyzing the haplotypes from the present study and the available
published sequences from different areas of their distribution. The results revealed shared
haplotypes with high frequencies as well as haplotypes private to populations from all the
sampling sites with low frequencies. Among the three main sampling sites (Corinthian Gulf,
Saronic Gulf, N. Aegean), the lowest genetic diversity was found in the populations from the
Saronic Gulf, which could be attributed to the smaller population sizes in this area.
Indications of genetic differentiation between all populations were found in the majority of
the studied locus. H. benoiti specimens from the Corinthian Gulf were highly differentiated
from the specimens from the Saronic Gulf and the North Aegean. This suggests that the
limited connection between the Corinthian and the open sea, could act as a barrier to gene
flow and that H. benoiti potentially has additional adaptations compared to the other species,
limiting the distance of passive transfer by the currents. The phylogeographic analysis of each
species revealed lack of phylogeographic structure and population subdivision with a few
exceptions which need to be further studied. However, it is necessary to analyze more
sequencies from the whole geographical range of each species as well as apply highly
polymorphic molecular markers, in order to clarify recent population events and draw safe
conclusions.
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Πρότυπα γενετικής ποικιλότητας μεσοπελαγικών ιχθύων στις ελληνικές θάλασσες
