Investigating evolution o f closely related, sym patric cryptic species
using com plete m itoch on drial DNA
Grosemans Tara, Sofie Derycke and Tom Moens
Marine Biology section, Faculty o f Science, Biology D epartm ent, U niversity o f Ghent,
Krijgslaan 281 (S8), 9000 Gent, Belgium
E-mail: tara.qrosem ans@ uqent.be
C ryptic species are organism s w ith very sim ilar m orphology but d is tin c t genetic make-up. They can
be found in many animal groups, but typ ica lly in organism s fo r which chem ical recognition is more
im p o rta n t than visual recognition fo r m ating. If the cryptic species are living in sym patry (in the
same area), reproduction could, in theory, s till be possible and hence, gene flo w w ill occur. Gene
flo w w ill in h ib it fu rth e r d iffe re n tia tio n o f the species and thus spéciation. Why spéciation does or
does not occur, is not always clear and investigating the genes th a t are under selection w ill provide
more insights in the spéciation process.
Genetic differences can be detected by com paring the genom es o f the species. These genetic
differences can be as large as those observed in species w ith clear m orphological d istinctions. The
position o f the gene in the genome or alteration in the genes by m utation, are a few exam ples o f
these genetic differences. Four cryptic species o f the marine nem atode L itod itis m a rin a species
com plex are held in m onospecific cultures. Recent research found th a t these fo u r species cannot
interbreed, but th ey do co-occur. Therefore reproductive barriers m ust exist between the d iffe re n t
subspecies. N ext-generation sequencing allows to sequence com plete genomes instead o f a few
genes and enables to differen tia te between the nucleotides and the position o f the genes in the
genome. By com paring the m itochondrial genomes o f closely related species, we can investigate
which genes are under selection and which are im p o rta n t fo r the spéciation and evolution o f the
cryptic species.
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