Evolutionary problems and global solutions

Abstract

Abstract Some of the foregoing challenges, controversies, and paradoxes of evolutionary biology can be tested and resolved by analysing global, regional, and local experiments of convergent evolution originating due to shared ecological stresses on unrelated taxa. One of the most dramatic experiments of convergent evolution in nature is the evolution of subterranean mammals across the planet (Fig. 2.1, colour figure section). This global experiment originated mainly in Oligocene times, following drastic Eocene—Oligocene climatic changes of aridization, causing remarkable biotic evolution (Prothero and Berggren, 1992). These have driven representatives of several mammalian orders and families to partial or total life in the underground adaptive zone (Van Valen, 1971), a process that continued later throughout Neogene times. Currently, subterranean mammals involve three orders (marsupials, insectivores, and rodents), or four orders if the order Insectivora is partitioned on molecular grounds and the two African families (golden moles and tenrecs) are placed in a new order. The African superordinal clade now includes six orders of placental mammals (Stanhope et al., 1998; De Jong, 1998); 11 families; and at least 250 species (Nevo, 1979, 1995d), but probably many more based on the new evidence of molecular biology, chromosomal evolution, and behavioural ecology (e.g. Nevo, 1991). The stressful life underground resulted in diverse adaptive strategies to cope with the unique physical and biotic environmental conditions of the subterranean ecotope (Dubost, 1968; Pearson, 1959; Nevo, 1979, 1991, 1995d; Nevo and Reig, 1990). Convergent evolution in subterranean mammals intimately coupled regressive evolution of molecular, genetic, morphological, physiological, and behavioural characters with distinct parallel progressive evolutionary phenomena in all the above organizational levels.