SERUM PROTEINS OF SALAMANDERS OF AMBYSTOMA JEFFERSONIANUM COMPLEX AND ORIGIN OF TRIPLOID SPECIES OF THIS GROUP

A serum protein characteristic of the diploid Ambystoma jeffersonianum and another characteristic of the diploid A. laterale both occur in the triploids A. platineum and A. tremblayi. In A. platineum. the jeffersonianum-type protein stains more intensely than the laterale-type protein; in A. tremblayi. the laterale-type protein stains more intensely. These data suggest that A. tremblayi and A. platineum have, respectively, 2:1 and 1:2 ratios of A. laterale and A. jeffersonianum chromosomes. This interpretation is compatible with other morphological data. Origin of the triploids by fertilization, by males of each species, of unreduced ova produced in a hybrid female by mitosis unaccompanied by cytokinesis prior to meiosis invokes a minimal number of features to account for the origin and maintenance of the triploid species. Males of A. laterale mate preferentially with females of A. laterale. and with decreasing frequency, with females of A. tremblayi, A. platineum, and A. jeffersonianum. Males of A. jeffersonianum mate preferentially with females of A. jeffersonianum, and with decreasing frequency, with females of A. platineum and A. tremblayi. The geographical association of A. platineum with A. jeffersonianum, and of A. tremblayi with A. laterale. probably represents sorting on the basis of mating preference.