MAN AS A MAKER OF NEW PLANTS — ANDERSON 469 



from apiana were all in the direction of S. mellifera. These "sub- 

 apianas" graded into plants closely resembling the first-generation 

 hybrids raised by Epling. There were a few "sub-meZfo'/eras" sim- 

 ilar to those we had detected along the pathway on the mountainside 

 and a few plants which on our index scored as typical melliferas. 

 However, in the field none of them looked quite average. Dr. Anderson 

 and I had to work in St. Louis on pressed and pickled material pre- 

 viously collected in California. Had we been able to go back and add 

 characters such as flower color and flower pattern to our battery of 

 measurable differences between S. mellifera and S. apiana, I believe 

 we could have demonstrated that the entire plot was colonized with 

 hybrids and mongrels, most of them first or second or third back- 

 crosses from the original hybrids to one or the other species. 



The results indicate that hybrids are being constantly produced on 

 this mountainside, but one does not ordinarily find them, because there 

 is no niche into which they can fit. The native vegetation had a long 

 evolutionary history of mutual adaptation. Plants and animals have 

 gradually been selected which are adapted to life with each other like 

 pieces of a multidimensional jigsaw puzzle. It is only when man, or 

 some other disruptive agent, upsets the whole puzzle that there is any 

 place where something new and different can fit in. If a radical vari- 

 ant arises, it is shouldered out of the way before it reaches maturity. 

 In a radically new environment, however, there may be a chance for 

 something new to succeed. Furthermore, the hybrids and their 

 mongrel descendants were not only something new ; they varied great- 

 ly among themselves. If one of them would not fit into the strange 

 new habitat, another might. Though virtually all of them had been 

 at a selective disadvantage on the mountainside, a few of them (aided 

 and abetted no doubt by the vigor which is characteristic of these and 

 many other hybrids) were now at a selective advantage. They con- 

 sequently flowed in and occupied the old olive orchard to the virtual 

 exclusion of the two original species. 



Furthermore, to take up an important fact about which biology as 

 yet knows very little, the habitat among the olives was not only some- 

 thing new ; it was open. It was not full of organisms which had been 

 selected to fit together. Remember that for the mountainside, on 

 those rare occasions where a first-generation hybrid plant had been able 

 to find a foothold, virtually none of its highly variable descendants 

 was able to persist. Such species crosses can father hundreds if not 

 thousands of distinguishably different types of mongrel descendants. 

 Only along the pathway had any of these been able to find a place for 

 themselves and then only those that differed but slightly from Salvia 

 mellifera. Hybridization does not advance in closed habitats. 



