Thiotrophic bacterial symbiont induces polyphenism in giant ciliate host Zoothamnium niveum.

Evolutionary theory predicts potential shifts between cooperative and uncooperative behaviour under fluctuating environmental conditions. This leads to unstable benefits to the partners and restricts the evolution of dependence. High dependence is usually found in those hosts in which vertically transmitted symbionts provide nutrients reliably.

A threshold model for polydactyly.

We present a cellular automaton-based model for threshold behaviors in vertebrate digit patterning and polydactyly formation. The rules of the model follow classical reactor-diffusion algorithms. Yet it is not physical diffusion that is taken as the required natural agent but the propagation of cellular states, which can be represented by the same differential equations.

MORPHOMETRIC CORRELATION PATTERNS OF ADULT BIRDS (FRINGILLIDAE: PASSERIFORMES AND COLUMBIFORMES) MIRROR THE EXPRESSION OF DEVELOPMENTAL CONTROL GENES.

Stimulated by the rapid progress in developmental genetics, recent approaches to evolutionary theory focus on the interface function of developmental processes in the study of genotype-phenotype mapping. From this viewpoint, the main result of the present analysis is that the expression patterns of developmental control genes are reflected in the infraspecific correlation patterns of phenotypic characters in the adult stage. The study is based on 42 logarithmically scaled skeletal measurements of two avian clades, finches (43 species, n = 313) and pigeons (27 species, n = 219).