Chromosomal speciation and reticulate evolution: Testing phylogenetic hypotheses with compatibility and parsimony

Abstract

Compatibility analysis and classic Wagner parsimony methods were contrasted in studying patterns and processes of karyotypic evolution in Italian Alpine chromosomal races of the house mice Mus domesticus and the cosmopolitan black rats of the subgenus Rattus. Evidence from the field suggests that hybridization and polymorphism retention constitute a common event during speciation. It has been attempted to explain character conflicts (homoplasies) through reticulate evolution. This can be represented in a tree if the biogeography of taxa is sufficiently known, and, mostly important, if hybrid offspring does not bear chromosomal rearrangements with monobrachial homology. This special kind of structural heterozygosity produces hybrid sterility and therefore is testimonial of full speciation, i.e. complete reproductive isolation. Compatibility method proves to depict scenarios of successions of events involving hybridization which are more consistent with a ≪parsimonious≫ idea of evolution as historical process.