Most studies concerning frugivory and endozoochory
center on avian and mammalian systems (Braun and Brooks, 1987) partly because they are viewed as the most important dispersers of seeds of modern gymnosperms and angiosperms (Fleming and Lips, 1991); however, reptiles also can play an important selective force in evolution of angiosperms (Tiffney, 1986).
Ecological correlates of endozoochory by herbivores.
Two groups of seeds stood out with regard to their tentative potential to withstand anaerobic digestion; those with a water-impermeable seed coat and those adapted to dispersal via endozoochory.
In analogy with selection of specific seed traits that accommodate dispersal by ants, birds or wind, Janzen (1984) proposed that grazers could exert a selective force to accommodate endozoochory by herbivorous mammals, such that seeds would become more resistant to anaerobic digestion.
Attempts were made to correlate seed survival to certain seed characteristics, such as seed size, weight, and shape (ecological correlates); if successful, dispersal distance and spatial distribution patterns of species due to endozoochory could be simulated (e.