Thisisthesecondeditionandistwicethesizeofthefirstone.Thematerialonrecombinationandthesteppingstonemodelhavebeengreatlyexpanded,therearemanyresultsformthelastfiveyears,andtwonewchaptersondiffusionprocessesdevelopthatviewpoint.Thisbookiswrittenformathematiciansandforbiologistsalik