364 W. HOVANITZ 



ORIGINS 



Genetically speaking, the point of origin of any species, genus, or 

 family can be any location inhabited by the genetically aberrant 

 individual ancestor. Origins can ordinarily be determined only by 

 circumstantial evidence and thus are no more certain than the evi- 

 dence used. Inferences on the origin of any group depend on the 

 distributional pattern of the group, particularly on its isolation, and 

 on the number of forms that have remained isolated in a particular 

 area. 



It has been seen that for the American butterflies an Old World 

 origin can plausibly be postulated for all those types having a 

 northern range, as they all have affinities in Eurasia. However, it 

 could be proposed with similar plausibility that these forms origi- 

 nated in North America and dispersed into Eurasia. Moreover, 

 since all these northern types also have affinities in the American 

 tropics, it is possible that they originated in the tropics or at least 

 from the tropical forms. It seems probable that the tropical forms as 

 we know them have originated in the American tropics. The degree 

 of differentiation of the New World butterfly fauna from the faunas 

 of Eurasia and the African-Australian region increases progressively 

 in proportion to the distance from Bering Straits. This suggests long 

 and great isolation of the American tropical fauna from the faunas 

 of the Old World tropics. Such continuity as exists is only through 

 the few northern types. 



Primary origins, whether of the northern or the tropical groups of 

 butterflies, can seldom be securely determined, or even plausibly 

 suggested. Secondary origins or centers for butterfly types, however, 

 are indicated for various regions, including the zones of endemism 

 already discussed. In the North American temperate region there 

 has been an extensive development of characteristic subgenera in 

 such genera as Colias, Argynnis, Melitaea, Oeneis, Satyrus, Pieris, 

 Limenitis, Plebejiis, and Glaucopsyche. Colias and Argynnis give 

 evidence of other secondary origins in the temperate zones of South 

 America. The tremendous development of satyrid genera in the 

 Andes is unique, as is the development of a number of genera in 

 several families on the Altiplano of Peru and Bolivia. The Caribbean 

 region shows relatively little endemism, but four genera are re- 

 stricted thereto. 



By analogy and by theory it seems plausible to postulate that 



