The structure of the lineage Archidiskodon - Mammuthus in Eurasia and peculiarities of its evolution
Deinsea , Volume 6 - Issue 1 p. 103- 118
An original method was proposed to study the elephants of the Archidiskodon- Mammuthus lineage (using materials from numerous Eurasian localities). As a result, a multidimensional model was created for the lineage. The enamel thickness and plate frequency of the last molars of the taxa known in the lineage were analyzed. The model is a multiple-level structure of adaptive peaks and depressions, organized like ‘Wright's symbolic picture’. Generally, it reflects anagenesis and canalized selection associated with the progressing increase of cold and aridification of Quaternary climates. Also, it illustrates the microevolutionary process. The discreteness of adaptive peaks reflects the selection of optimal phenotypes and intraspecific variability. The sequences of adaptive peaks in thin-enamel and thick-enamel limits of distribution (all along the lineage) are entirely new elements making the structure different from traditional gradualistic model. The data complex allows us to interpret these forms as ‘adaptations’ to alternating glacial and interglacial conditions. An analysis of regional graphs shows: (1) transcontinental spreading of the majority of phenotypes (forms); (2) chronological, geographical (clinal), and paleogeographical variability; (3) two speciation ‘directions’ at different stages of the lineage development; and (4) the possibility of comparing depressions with the variability limits of different ranged taxa. The method provides new information on lineage development in general, and on microevolutionary and macroevolutionary processes.