Adaptive Radiations, Ecological Specialization, and the Evolutionary Integration of Complex Morphological Structures

Abstract

The evolutionary integration of complex morphological structures is a macroevolutionary pattern in which morphogenetic components evolve in a coordinated fashion, which can result from the interplay among processes of developmental, genetic integration, and different types of selection. We tested hypotheses of ecological versus developmental factors underlying patterns of within-species and evolutionary integration in the mandible of phyllostomid bats, during the most impressive ecological and morphological radiation among mammals. Shape variation of mandibular morphogenetic components was associated with diet, and the transition of integration patterns from developmental to within-species to evolutionary was examined. Within-species (as a proxy to genetic) integration in different lineages resembled developmental integration regardless of diet specialization, however, evolutionary integration patterns reflected selection in different mandibular components. For dietary specializations requiring extensive functional changes in mastication patterns or biting, such as frugivores and sanguivores, the evolutionary integration pattern was not associated with expected within-species or developmental integration. On the other hand, specializations with lower mastication demands or without major functional reorganization (such as nectarivores and carnivores), presented evolutionary integration patterns similar to the expected developmental pattern. These results show that evolutionary integration patterns are largely a result of independent selection on specific components regardless of developmental modules.

Studying morphological integration and modularity at multiple levels: concepts and analysis

“…Genetic integration has mostly been compared to static phenotypic integration, reflecting the importance of the genetic and phenotypic covariance matrices in quantitative genetic theory [67,71,73]. Evolutionary integration has been compared to static within-taxon integration [16,25,95] and ontogenetic variation [35,85,87,88], and through links to ecological variables such as diet or direct biomechanical arguments, functional considerations have also been incorporated [63,113]. Systematic multilevel studies incorporating more than two levels simultaneously are rare.…”

Shape analysis of odontocete mandibles: Functional and evolutionary implications

“…Furthermore, GM can be used in phylogenetic analyses to determine the extent of "phylogenetic signal" in the observed shape variation (e.g., Cardini, 2003;Meloro et al, 2008;Young, 2008;Monteiro and Nogueira, 2009). …”

Biting disrupts integration to spur skull evolution in eels

“…The origin of one of these integrationdisrupting innovations may therefore act as a catalyst of morphological diversification, allowing structures to evolve independently of one another, to accumulate differences among species at a faster rate and to reach more extreme forms 1,3,4,15,17 . Few empirical studies, however, have connected such innovations-and their associated changes in the strength of functional integration-with shifts in evolutionary integration (that is, correlations between evolutionary change in structures or suites of structures 9,11 ), rates of evolution and morphospace occupation (but see related studies by Monteiro et al 22 and Claverie and Patek 23 ).…”