Analysis of Hybrid Zones

摘要: Hybrid zones are, roughly speaking, narrow regions in which genetically distinct populations meet, mate, and produce hybrids. They are often only a few hundred meters wide yet may be several kilometers long. found variety of organisms: Tables 1 2 list about 150 reasonably clear examples, there is spatial transition between two hybridizing forms. Such widespread striking phenomenon requires explanation; more importantly, it offers us ways understanding the nature origin species. First, hybrid pose interesting questions for taxonomist, they contrast views species: as set delimited by genetic barriers to gene exchange; maintained particular stable equilibrium selection. Second, range genotypes zone can used analyze differences selective forces that separate taxa involved. This allow some inferences way these evolved and, extrapolation, fully isolated species diverge from each other. Finally, models parapatric speciation, Wright's "shifting balance," involve formation, move­ ment, modification zones. must understood before plausibility judged. After clarifying our terminology, we will summarize relevant theory then see how this make field data. A notable increase number detailed studies occurred over