Chromosomal Mechanisms in the Evolution of Chiropteran Karyotype Chromosomal Tables of Chiroptera

ABSTRACT

Chromosomal mechanisms involved in the evolution of the karyotype were examined in Chiroptera. In particular the Robertsonian process of centric fusion-fission was thoroughly studied. On the basis of karyological and morphological observations, the Authors aim to demonstrate that the Robertsonian change does not proceed in a single direction; it just provides a cytological basis for the onset of a genetic barrier. The importance of other chromosomal changes in the karyotypic evolution of Chiroptera has also been pointed out. A complete table of karyological data in Chiroptera is provided.

SUMMARY

The chiropteran karyotype was revealed vary not only between the families making up the order but also within the families and even remarkably within the genera too. Therefore we have made use as well of personal observations as of available data of recent literature in order to discuss the chromosomal changes involved in the karyotypic evolution of Chiroptera.

The Robertsonian process of centric fusion-fission is often openly involved in the karyotypic transformation of families and genera (European Vespertilionidae, non-European species of genus Pipistrellus, genus Rhinolophus, etc.).

As regards the direction of Robertsonian change (fission or fusion) it seems to move indifferently in both directions in the karyotypic evolution of Chiroptera.

The comparison, between karyological and morphological data, dental formulae, pointing out the primitivity or the specialization of different forms shows that specialized forms have karyotypes formed by a totality of acrocentrics as well as by a totality of metacentrics. We consider as casual the direction of the Robertsonian change. This does not represent the moment of speciation, but rather provides only a karyological barrier. Natural selection works on the two different genie pools, which have been separated by such a barrier.

The evolutionary success and the « Robertsonian direction » result indeed from the operation of natural selection, but remain unrelated to the Robertsonian situation (fission or fusion).

Non-Robertsonian changes are also involved in the karyotypic evolution of Chiroptera: pericentric inversion, nullisomy, and tetrasomy.

It is difficult nevertheless to state with any certainty the presence of such changes, if a karyometric evaluation has not been carried out.

The karyological data available about Chiroptera do not suffice till now to ascertain the interrelationships among the different families belonging to this order.