Rare ecomorphological convergence on a complex adaptive landscape: Body size and diet mediate evolution of jaw shape in squirrels (Sciuridae) : CONVERGENCE ON A COMPLEX ADAPTIVE LANDSCAPE

Interactions between a large community of vertebrate frugivore-granivores (including 7 species of large canopy birds, 19 species of rodents, 7 species of ruminants, and 6 species of monkeys), and 122 fruit species they consume, were studied for a year in a tropical rainforest in Gabon.The results show how morphological characters of fruits are involved in the choice and partitioning of the available fruit spectrum among consumer taxa. Despite an outstanding lack of specificity between fruit and consumer species, consideration of simple morphological traits of fruits reveals broad character syndromes associated with different consumer taxa. Competition between distantly related taxa that feed at the same height is far more important than has been previously supposed. The results also suggest how fruit characters could have evolved under consumer pressure as a result of consumer roles as dispersers or seed predators. Our analyses of dispersal syndromes show that fruit species partitioning occurs more between mammal taxa than between mammals and birds. There is thus a bird-monkey syndrome and a ruminant-rodent-elephant syndrome. The bird-monkey syndrome includes fruit species on which there is no pre-dispersal seed predation. These fruits (berries and drupes) are brightly colored, have a succulent pulp or arillate seeds, and no protective seed cover. The ruminant-rodent-elephant syndrome includes species for which there is pre-dispersal predation. These fruits (all drupes) are large, dull-colored, and have a dry fibrous flesh and well-protected seeds.

G. G. Simpson, one of the chief architects of evolutionary biology's modern synthesis, proposed that diversification occurs on a macroevolutionary adaptive landscape, but landscape models are seldom used to study adaptive divergence in large radiations. We show that for Caribbean Anolis lizards, diversification on similar Simpsonian landscapes leads to striking convergence of entire faunas on four islands. Parallel radiations unfolding at large temporal scales shed light on the process of adaptive diversification, indicating that the adaptive landscape may give rise to predictable evolutionary patterns in nature, that adaptive peaks may be stable over macroevolutionary time, and that available geographic area influences the ability of lineages to discover new adaptive peaks.