Huyghe, F.

Kochzius, M.

Open Marine Archive

 - 55 -  
Connectivity of Amphiprion akallopisos (Skunk Clown Fish) in the 
Indian Ocean 
Huyghe Filip and Marc Kochzius
 
Department of Biology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium 
E-mail: fhuyghe@vub.ac.be 
Like many coral reef associated organisms, Amphiprion akallopisos, which lives in mutualistic 
symbiosis with two species of giant sea anemones, is unable to migrate from one coral reef to 
another during its adult life stage. Dispersal between reefs in the patchy coral reef environment is 
assured during the pelagic larval stage. Because small pelagic larvae are extremely difficult to track 
in the open ocean, population genetics is a useful technique to evaluate gene flow and connectivity 
between populations of coral reef associated organisms. Amphiprion akallopisos has a disjunct 
distribution, occurring in the Western Indian Ocean (WIO) and the Eastern Indian Ocean (EIO) but not 
in the Central Indian Ocean (CIO). The WIO and EIO populations are separated by more than 4500km 
of open ocean. In this study, a 337 base pair long sequence of the Control Region of the 
mitochondrial DNA is used as a genetic marker to study population genetics and connectivity both 
between and within the WIO and EIO populations. A total of 263 samples from 17 different sites in 
the WIO and the EIO have been collected and analysed. Strong population structure (ф
st
=0.28; 
P<0.001), strong differentiation (ф
ct
=0.61; P<0.001), and low gene flow between the EIO and the 
WIO populations was observed. A haplotype network was created in which 76 haplotypes were 
identified. Not one of these haplotypes simultaneously occurred in individuals sampled in the EIO 
and the WIO populations. This further confirms the genetic differentiation between both 
populations already observed using F-statistics. Within both the WIO and EIO populations, low 
population structure was observed. Selective neutrality tests indicate that the WIO population 
underwent a population expansion. The EIO population was identified as the source population 
based on higher genetic diversity. Two possible explanations exist for the disjunct distribution of 
A. akallopisos. In the first hypothesis, the WIO was directly colonized from the EIO. However, it is 
rather improbable that larvae would be able to cross the large distance between both populations 
during a pelagic stage of less than 2 weeks. Furthermore, our results indicate low gene flow 
between WIO and EIO populations, making this scenario unlikely. In the second hypothesis, 
A. akallopisos migrated from the EIO towards the WIO in a stepwise manner. Suitable sea anemone 
habitat occurs in the CIO but is occupied by another species, Amphiprion nigripes, in this region. It 
is currently unclear whether A. akallopisos disappeared from the CIO due to competition with 
A. nigripes or whether A. nigripes evolved as a new species out of a common ancestor with 
A. akallopisos as a result of isolation of the CIO from the other two regions. 


Connectivity of <i>Amphiprion akallopisos</i> (Skunk Clown Fish) in the Indian Ocean

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