Rugged adaptive landscapes shape a complex, sympatric radiation.

Area of Science:

• Evolutionary biology
• Speciation research
• Ecology and adaptation

Background:

• Disruptive ecological selection can drive speciation without physical isolation.
• Ecologically distinct species are expected to show weak initial genetic differentiation.
• Assortative mating and strong selection may counteract gene flow.

Purpose of the Study:

• To investigate evidence for disruptive ecological selection in a natural system.
• To examine the role of ecological specialization in fish radiation.
• To assess the adaptive landscape in an incipient species radiation.

Main Methods:

• Studied sympatric, incipient radiation of 'sharpfin' sailfin silverside fishes.
• Analyzed adaptive morphological differences linked to ecological specialization.
• Assessed reproductive isolation between differently adapted morphs.
• Examined individual fitness and variation in key morphological characters.

Main Results:

• Found evidence for multiple disruptive ecological selection regimes.
• Demonstrated adaptive morphological divergence driven by ecological specialization.
• Observed significant, though incomplete, reproductive isolation between morphs.
• Confirmed disruptive selection shapes a rugged adaptive landscape.

Conclusions:

• Disruptive ecological selection promotes divergence and speciation in sympatric populations.
• Ecological specialization is a key driver of adaptive radiation.
• Lake Matano's 'sharpfin' silverside fish radiation provides a model for studying speciation under disruptive selection.