Quantitative Genetics, Pleiotropy, and Morphological Integration in the Dentition of Papio hamadryas

Variation in the mammalian dentition is highly informative of adaptations and evolutionary relationships, and consequently has been the focus of considerable research. Much of the current research exploring the genetic underpinnings of dental variation can trace its roots to Olson and Miller's 1958 book Morphological Integration. These authors explored patterns of correlation in the post-canine dentitions of the owl monkey and Hyopsodus, an extinct condylarth from the Eocene. Their results were difficult to interpret, as was even noted by the authors, due to a lack of genetic information through which to view the patterns of correlation. Following in the spirit of Olson and Miller's research, we present a quantitative genetic analysis of dental variation in a pedigreed population of baboons. We identify patterns of genetic correlations that provide insight to the genetic architecture of the baboon dentition. This genetic architecture indicates the presence of at least three modules: an incisor module that is genetically independent of the post-canine dentition, and a premolar module that demonstrates incomplete pleiotropy with the molar module. We then compare this matrix of genetic correlations to matrices of phenotypic correlations between the same measurements made on museum specimens of another baboon subspecies and the Southeast Asian colobine Presbytis. We observe moderate significant correlations between the matrices from these three primate taxa. From these observations we infer similarity in modularity and hypothesize a common pattern of genetic integration across the dental arcade in the Cercopithecoidea

Caste-specific morphological modularity in the ant tribe Camponotini (Hymenoptera, Formicidae)

Background: The morphological structures of organisms form tightly integrated but mutually independent character complexes (modules) linked through common development and function. Even though their abundance, diversity, and complex caste systems make camponotine ants ideal subjects to research developmental modularity and phenotypic integration, no studies investigating these phenomena have been conducted in this taxonomic group. This study attempts to identify and visualize integrated character complexes in 14 taxa from the genera Camponotus and Colobopsis using statistical analyses of morphometry. Results: The identified modules differ between castes: Minor workers have small heads and long extremities, while major workers have enlarged heads modified for defence, and short, thick appendages; extremities (legs and antennae) are strongly correlated in both worker castes. Gynes show weaker integration of extremities, but a strong correlation of mesosoma and eyes, and highly variable median ocellus size. Gynes infested by mermithid nematodes exhibit reduction of gyne-specific characters and altered patterns of phenotypic integration. Conclusion: The integrated character complexes described herein can largely be interpreted as functional, caste-specific modules related to behavioural ecology and task allocation within ant colonies. This modular nature of the body plan is hypothesized to facilitate the evolution of novel phenotypes and thus contributes to the tremendous evolutionary success of ants. The study of these modules can help to further elucidate the evolution and ontogeny of castes in camponotine ants, as well as the effects of parasite infestation on the phenotype.© The Author(s) 201

Genome growth and the evolution of the genotype-phenotype map

Genome growth and the evolution of the genotype-phenotype ma

Birds have peramorphic skulls, too: anatomical network analyses reveal oppositional heterochronies in avian skull evolution

In contrast to the vast majority of reptiles, the skulls of adult crown birds are characterized by a high degree of integration due to bone fusion, e.g., an ontogenetic event generating a net reduction in the number of bones. To understand this process in an evolutionary context, we investigate postnatal ontogenetic changes in the skulls of crown bird and non-avian theropods using anatomical network analysis (AnNA). Due to the greater number of bones and bone contacts, early juvenile crown birds have less integrated skulls, resembling their non-avian theropod ancestors, including Archaeopteryx lithographica and Ichthyornis dispars. Phylogenetic comparisons indicate that skull bone fusion and the resulting modular integration represent a peramorphosis (developmental exaggeration of the ancestral adult trait) that evolved late during avialan evolution, at the origin of crown-birds. Succeeding the general paedomorphic shape trend, the occurrence of an additional peramorphosis reflects the mosaic complexity of the avian skull evolution