BASE-COMPOSITIONAL BIASES AND THE BAT PROBLEM - III - THE QUESTION OFMICROCHIROPTERAN MONOPHYLY

Using single-copy DNA hybridization, we carried out a whole genome stu dy of 16 bats (from ten families) and five outgroups (two primates and one each dermopteran, scandentian, and marsupial). Three of the bat s pecies represented as many families of Rhinolophoidea, and these alway s associated with the two representatives of Pteropodidae. All other m icrochiropterans, however, formed a monophyletic: unit displaying inte rrelationships largely in accord with current opinion. Thus noctiliono ids comprised one clade, while vespertilionids, emballonurids, and mol ossids comprised three others, successively more closely related in th at sequence. The unexpected position of rhinolophoids may be due eithe r to the high AT bias they share with pteropodids, or it may be phylog enetically authentic. Reanalysis of the data with varying combinations of the five outgroups does not indicate a rooting problem, and the in clusion of many bat lineages divided at varying levels similarly disco unts long branch attraction as an explanation for the pteropodid -rhin olophoid association. If rhinolophoids are indeed specially related to pteropodids, many synapomorphies of Microchiroptera are called into q uestion, not least the unitary evolution of echolocation (although thi s feature may simply have been lost in pteropodids). Further, a rhinol ophoid-pteropodid relationship-if true-has serious implications for th e classification of bats. Finally, among the outgroups, an apparent si ster-group relation of Dermoptera and Primates suggests that flying le murs do not represent the ancestors of some or all bats; yet, insofar as gliding of the type implemented in dermopterans is an appropriate m odel for the evolution of powered mammalian flying, the position of Cy nocephalus in our tree indirectly strengthens the argument that true f light could have evolved more than once among bats.