Speciation is the evolution of reproductive isolation that can be achieved by genetic, geographical and ecological processes. Ecological factors play roles in rapid speciation such as adaptive radiation and sympatric speciation. However, ecological factors (e.g., strong selection) alone are not sufficient for causing speciation. Recent theoretical arguments on speciation have shown that genetic architecture underlying traits substantially influence the probability of speciation. Thus, genomic studies are inevitable to understand speciation mechanisms fully.

Theoretical studies have shown that genetic factors such as genetic variations, the number of loci, the effects of mutations, pleiotropy, linkages and interactions among genes are important factors promoting or disturbing speciation processes. By detecting these genetic factors, we can argue why some groups of species speciate more rapidly or what factors disturbing or promoting speciation. In addition, by detecting genes or DNA sites relating to traits for speciation, we can detect whether or not the substitution of these genes or sites were influenced by selection or genetic drift.

Here, I will discuss how and what genetic information is important to understand the cause of speciation, taking examples of recent studies.