A reexamination of Lipotyphla and Afrotheria based on both molecular and morphological analyses.

摘要

Recent molecular studies have supported removal of Chrysochloridae and Tenrecidae from Order Lipotyphla (=Insectivora) and their placement into a new order, Afrosoricida (=Tenrecoidea), within Afrotheria. These results imply that chrysochlorids and tenrecids are more closely related to paenungulates (proboscideans, sirenians, and hyracoids), macroscelidids, and tubulidentates than to definitive lipotyphlans: erinaceids, soricids, talpids, and solenodontids. This relationship is in strong opposition to the most recent phylogenetic analyses based on morphological data from the fossil and extant records. This project attempts to resolve this conflict by performing a comprehensive review of Liptyphla and Afrotheria, integrating both molecular and morphological evidence in order to clarify their relationships.; On a morphological basis lipotyphlans are thought to be near the base of the placental radiation; alternatively, molecular systematists believe afrotherians represent one of the most ancient radiations, being only slightly more derived than xenarthrans. The determination of the proper basal eutherian taxon will have profound ramifications on character coding and establishing new character polarity in studies of mammalian evolution. For example, Afrotheria as the true basal taxon suggests multiple origins of hooves in mammalian evolution, thus making Ungulata polyphyletic. More importantly the degree of similarity observed between fossil paenungulates and fossil condylarths would be the result of an almost unprecedented amount of morphological convergence.; A comprehensive morphological dataset was compiled consisting of 114 characters for 87 taxa representing almost every extant genus of lipotyphlan and all afrotherian genera. Molecular sampling diversity was also expanded for two genes, Bmi1-3'UTR and Bdnf, with the addition of original sequence data for lipotyphlan groups neglected previously. These datasets were analyzed individually and in concert as part of a "total evidence" analysis. Further "total evidence" analyses were performed with the complete molecular data sets from Murphy et al., 2001 a, b and a partial morphological data set from Asher et al., 2003. Afrotheria was recovered in the "total evidence" analyses, but with only molecular characters supporting the group unambiguously. Neither Afrotheria nor Lipotyphla received consistent support from both lines of evidence. Tenrecoidea, Eulipotyphla, and a new superorder Afroungulata do receive support from both molecular and morphological data.; Without support from both molecular and morphological data, Lipotyphla as currently defined, can not be considered a natural group. Afrotheria is rejected on the same basis. What has clearly emerged is that the dissolution of the lipotyphlan mammals into two separate natural groups, tenrecoids and eulipotyphlans, is justified and defensible along both morphologic and molecular lines of evidence.