Preface: Advances in cichlid research: behavior, ecology, and evolutionary biology

Abstract

With about 1,300validlydescribedspecies,butatleast2,200 species known, cichlid fishes (Cichlidae) repre-sent the second most species-rich family of freshwaterfishaftertheCyprinidae(2,700describedspecies),andaccount for about 13% of extant freshwater fishdiversity. They are naturally distributed from Centraland South America, across Africa to Madagascar, andsouthern India. Throughout this distributional range,they have repeatedly demonstrated their capacity offorming adaptive radiations—explosive speciationwith niche partitioning—generating an outstandingvariation of body shapes, color patterns, behavior, andecomorphological specializations (e.g., Schliewenet al., 1994; Danley & Kocher, 2001; Joyce et al.,2005; Barluenga et al., 2006; Muschick et al., 2012;Lo´pez-Ferna´ndez et al., 2013). This extraordinarydiversity and an often stunning pace of speciationmakes cichlid fishes particularly well suited forstudying the factors and mechanisms underlyingpopulation differentiation, diversification, and spe-ciation. They are now well established among theprime model systems in evolutionary biology research(Kocher, 2004; Seehausen, 2006). With the develop-ment of an increasing number of genetic and genomicresources, including the recent sequencing of severalcichlid genomes (Brawand et al. 2014), cichlids willreceive even greater attention in future evolutionaryand ecological research.This special issue comprises sixteen studies with aparticular focus on behavior, ecology, and/or evolu-tionary biology of cichlid fishes. Together, theyadvance our knowledge of the mechanisms generatingand maintaining the tremendous diversity of thisfreshwater fish family.Over the last few decades, a multitude of studieshave employed various approaches to shed light on thefactors responsible for the stunning diversity withinthis family. An elaborate reproductive behavior and ahighly developed pharyngeal jaw have long beenrecognized as important key factors for the cichlids’evolutionary success (Liem, 1973; Keenleyside,