describe Rapid chromosomal evolution in mice on the island of Madeira.
Step 1
The origin of species due to chromosome speciation is connected with the phenomenon of sibling species. Some rodents like Mus Linnaeus, Ctenomys Blainville demonstrate broad chromosome variability at the species and intraspecies level without a morphological difference.
Step 2
Madeira is a small volcanic island in the Atlantic Ocean. The region is inhabitable by humans and their interdependency. House mice (Mus musculus domesticus) had a sudden chromosomal diversity in Madeira island. The evolution is independent of adaptative processes, depending rather on geographic isolation and genetic drift. The evolution of animal species present on Madeira island has produced examples of adaptative radiation. Natural selection is the underlying process that has been responsible for these adaptative radiations. This leads to enhanced rates of speciation, as well as non-adaptative processes playing a major part.
The extreme topography of Madeira island has not allowed the movement of the mouse population between valleys, which led to extensive chromosomal radiation. Six different chromosomal races of the mouse have been established on Madeira island. These races got split from each other by mountain barriers. The races reduced diploid numbers respective to the standard for the species (2N = 40) that has its own to the presence of numerous Robertsonian chromosome fusional fusions. Each of these has resulted from the joining of a pair of the standard chromosome. This fusion has been found in wild house mice, but all the six races on the island carrying the Robertsonian chromosome differentiated from each other.
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