Study
sheds new light on a fundamental question in evolutionary biology
Date: March 4, 2019
Source: Helmholtz Centre for Ocean Research Kiel
(GEOMAR)
For a new
species to evolve, two things are essential: a characteristic -- such as a
colour -- unique to one species and a mating preference for this
characteristic. For example, individuals from a blue fish species prefer blue
mates and individuals from a red fish species prefer red mates. If the two
species interbreed, the process of sexual recombination is expected to destroy
the coupling between colour and mate preferences and form red individuals with
a preference for blue mates and vice versa. This will prevent the two species
from diverging, and this is one of the reasons why it has been thought for a
long time that new species can only evolve in absolute isolation, without
interbreeding.
However,
the dynamics of this process depend on the exact number and location of genes
underlying species characteristics and mate preferences, the strength of
natural selection acting on these genes, and the amount of interbreeding
between species. In a new study, Professor Oscar Puebla from GEOMAR Helmholtz
Centre for Ocean Research Kiel in Germany together with colleagues from the
Smithsonian Tropical Research Institute in Panama have found that natural
selection can couple the evolution of genes for colour pattern and mate
preferences when species still interbreed. The study has been published today
in the international journal Nature Ecology and Evolution.
"To
address this question, the first challenge was to identify an animal group in
which species are still young and interbreed, with clear species
characteristics, and in which the bases of reproductive isolation are well
understood," Oscar Puebla explains. The hamlets, a group of closely
related reef fishes from the wider Caribbean, constitute exactly such a group.
The hamlets are extremely close genetically, differ essentially in terms of
colour pattern, and are reproductively isolated through strong visually-based
mate preferences.
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