Chapter V 



-73— 



Types of Areas 



There is no doubt that vicarious species may arise not only as a 

 result of autopolyploidy but also from various other causes. Thus 

 they may arise as a result of hybridization, likewise frequently accom- 

 panied by an increase in chromosome number (allopolyploidy), in which 

 case the hybrids very often have areas that are not identical to the 



TETRAPLOIDS 

 • qII forms known f-o be Utraptoid. 

 X forms not mvtsHgated but probsb/y fetrjp/o^, 

 DIPLOIDS 

 ro Ssp.grsolis O Ssp »ls»frcs O Ssp s^b»phyf/s 



A van mollis 

 FORMS NOT INVCSTIGA7£D BUT PfJOBABL^ 

 lU Ssp 3ustriaca 



ffl Ssp. ktrneri 



^ i Ssp- ^ucstphshcs 

 {Ssp. t€nuifof,s 



DIPLOID 



Q nr psrui'foJiA 



Fig 9 — Distribution of diploid and tetraploid forms of Biscutdla laevi- 

 gata. (After Manton). 



areas of the initial species, sometimes not coinciding in any part (see 

 CUSTAFSSON, 193s). Lastly, vicarious species may arise as a conse- 

 quence of the differentiation of an initial form at one time widely dis- 

 tributed. Owing to changes in climatic and other habitat conditions 

 in ditterent parts of an originally continuous area, the initial form 



