AFFINITIES OF TAMAULIPAN MAMMALS
Owing to the differences in climate from one region to another, the flora and fauna also differ, especially in the southern part of the state as compared with the northern part.
For expressing the taxonomic resemblance of mammalian faunas having nearly equal numbers of taxa, Burt (1959:139) recommended the following formula: C × 100/(N1 + N2 - C) (where C is the number of taxa common to the two faunas, N1 is the number of taxa in the smaller fauna, and N2 is the number of taxa in the larger fauna). For non-flying mammals the resemblance of the Tamaulipan fauna to that of Texas, adjacent to the north, and Veracruz, adjacent to the south, is as follows:
Genera.—Texas 65 per cent, Veracruz 60 per cent.
Species.—Texas 45 per cent, Veracruz 39 per cent.
For bats the resemblance of the Tamaulipan fauna to those of Texas and Veracruz is as follows:
Genera.—Texas 40 per cent, Veracruz 51 per cent.
Species.—Texas 24, Veracruz 39.
Table 1.—Number of Genera and Species of Non-introduced Land Mammals in Three States.