CHAPTER 12 



The Amphipioids 



12.1: Amphiploldy and Implications 



New species can arise suddenly In interspecific hybridization and 

 doubling of the chromosomes. Such an act in nature separates the 

 new amphiploid, a potential species, from its parental progenitors. 

 New amphiploid species are able to invade new habitats, an invasion 

 not possible by either parent. A new ecological range, as well as re- 

 productive isolation from all other species, is acquired. More data 

 are now at hand from amphipioids produced in the laboratory, be- 

 cause colchicine has provided an effective method for making the poly- 

 ploids after the interspecific hybridization has been made. Principles 

 of theoretical and practical value can be developed. 



Not all autoploids and am])hiploids separate into clear-cut cate- 

 gories since certain of their characteristics tend to overlap.^- Many 

 amphipioids produced by colchicine show autoploid characteristics.^! 

 The genetic and cytological changes that take place in later genera- 

 tions of propagation among such amphipioids are difficult to interpret 

 when there is interchange between the two parental genomes. A 

 classification designed by Clausen, Keck, and Heisey sought to visual- 

 ize how a gradual merger between autoploids and amphipioids obtains 

 if a number of cases \ue compared. Table 12 in their paper places 

 amphipioids in positions from the upper left-hand corner to the lower 

 right, in a gradient from autoploid to amphi))loid.-i The conclusions 

 incorporated in this chart were made after analyzing natural and 

 experimentally produced amphipioids. 



While the limits between some autoploitls and amphipioids are 

 not clearly defined, the requirements for the success of an amjihiploid 

 as a new species are extremely sharp, almost to the jjoint of bemg 

 restrictive. Limits aj^pear to be set that cannot be violated, that is, if 

 the new plants are to succeed in nature. We should consider whether 

 the requirements for success in agricultural situations are not equally 

 restrictive. The requirements may be somewhat different, but new 



[ 252 J 



