Terrestrialization, Miniaturization and Rates of Diversification in African Puddle Frogs (Anura: Phrynobatrachidae)

Terrestrialization, the evolution of non-aquatic oviposition, and miniaturization, the evolution of tiny adult body size, are recurring trends in amphibian evolution, but the relationships among the traits that characterize these phenomena are not well understood. Furthermore, these traits have been identified as possible “key innovations” that are predicted to increase rates of speciation in those lineages in which they evolve. We examine terrestrialization and miniaturization in sub-Saharan puddle frogs (Phrynobatrachidae) in a phylogenetic context to investigate the relationship between adaptation and diversification through time. We use relative dating techniques to ascertain if character trait shifts are associated with increased diversification rates, and we evaluate the likelihood that a single temporal event can explain the evolution of those traits. Results indicate alternate reproductive modes evolved independently in Phrynobatrachus at least seven times, including terrestrial deposition of eggs and terrestrial, non-feeding larvae. These shifts towards alternate reproductive modes are not linked to a common temporal event. Contrary to the “key innovations” hypothesis, clades that exhibit alternate reproductive modes have lower diversification rates than those that deposit eggs aquatically. Adult habitat, pedal webbing and body size have no effect on diversification rates. Though these traits putatively identified as key innovations for Phrynobatrachus do not seem to be associated with increased speciation rates, they may still provide opportunities to extend into new niches, thus increasing overall diversity

Studies on the differential inhibition of glutathione conjugate formation of (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide and 1-chloro-2,4-dinitrobenzene in V79 Chinese hamster cells.

V79 Chinese hamster cells have previously been shown to lack the capacity to detoxify the mutagenic and carcinogenic compound (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide [(+)-anti-BPDE] by Pi class glutathione transferase (GSTPi)-catalysed conjugation with GSH, although these cells contain such an enzyme [Romert, Dock, Jenssen and Jernström (1989) Carcinogenesis 10, 1701-1707; Swedmark, Romert, Morgenstern and Jenssen (1992) Carcinogenesis 13, 1719-1723; Swedmark and Jenssen (1994) Gene 139, 251-256]. Previous findings also indicate that these results do not depend on an inactive GSTPi enzyme, since V79 cells conjugate 1-chloro-2, 4-dinitrobenzene (CDNB) with GSH, but more likely on (a) factor(s) that inhibit(s) V79 GSTPi selectively [Swedmark, Jernström and Jenssen (1996) Biochem. J. 318, 533-538]. The present study demonstrates that both human and V79 recombinant GSTPi enzymes are inhibited with respect to conjugating (+)-anti-BPDE, but not CDNB, after pre-incubation with V79-cell extract, but not with MCF-7-cell extract. In addition, it was found that the inhibition is dependent on the amount of cell extract present and that the factor(s) is heat-resistant and has a molecular mass of less than 10 kDa, suggesting that the factor(s) is (are) non-proteinaceous in nature