Digest: Mediating the Impact of Integration in Malagasy Cichlids.

Biology has a fruitful history of studying the evolution of traits in relative isolation. Recently, researchers have urged for a more holistic perspective, arguing that a solid comprehension of how traits interact will greatly enhance our understanding of global patterns of biodiversity (e.g. Kane & Higham 2016). Some traits covary with each other such that a change in one is associated strongly with a change in the other; this pattern is known as integration. Integration is thought to constrain evolution by limiting the pool of potential forms. Conversely, modularity refers to the relative independence of traits, and is thought to elevate rates of diversification, because it allows organisms to "mix and match" traits, thus opening up a wider swath of potential morphologies. Most sets of traits exist somewhere along this continuum from completely integrated to completely modular. Integration may arise at a functional level if common selective pressures act on multiple traits that influence some aspect of performance. Integration may also arise on a molecular level, through overlapping genetic architecture or a shared developmental precursor. This article is protected by copyright. All rights reserved.