Among UF’s renowned team of extinction experts is David Blackburn, whose appreciation for frogs has led to his work on a groundbreaking new study. A paper published in July in the Proceedings of the National Academy of Sciences shows that although frogs have been around for longer than dinosaurs, most of the world’s 6,700-plus living species of frogs evolved after a mass extinction 66 million years ago made way for new biodiversity.
This was a fun collaboration with Peng Zhang's lab at Sun Yat-Sen University! https://t.co/6WB5QlxAzw— David C. Blackburn (@davidcblackburn) July 3, 2017
Perhaps best known among mass extinctions, if not actually the most devastating, is the one that killed the dinosaurs. This event, called the Cretaceous–Tertiary extinction (K–T for short, to remind you that “Cretaceous” has a hard C), or more precisely the Cretaceous–Paleogene (K–Pg) extinction, caused a global die-off of 75 percent. Evolutionarily, these closed doors allowed others to open. Frogs, a highly adaptive type of creature, occupied many new niches, especially those created by a bloom of angiosperms, or flowering plants. Frogs took to the trees, which well suited their reproductive and self-defense needs.
This new analysis shows that the frog family tree's new crop of branches spread out from the extinction event between the Cretaceous and Paleogene periods — the K–Pg boundary, formerly called K–T — not 100 million years ago. The results were surprising to both the researchers and the scientific community, because previous mitochondrial DNA analysis traced major extant frog lineages to about 35 million years earlier than the K–T extinction, in the middle of the Mesozoic era.
Frogs also took on very different forms, with some retaining the commonly known tadpole stage and others evolving direct development, in which minuscule frogs hatch out of the eggs. They now occupy a wide range of habitats, from semi-arid regions of Africa to the super-humid South American rainforests, from clumps of leaves on the forest floor to the tops of trees.
"Except for a small handful of species, all other North American frogs are 'post-dinosaur' colonists. If you could travel back to the time of T. rex in North America, there would be frogs, but the chorus you would hear at night would have been nothing like you'd hear today. They're not even the same families." – David Blackburn
6,700+ species of extant frogs (55 families )
200 million years ago: frogs first appeared
88 percent of living species stemmed from post-K–T explosion in 3 lineages (Hyloidea, Microhylidae and Natatanura)
95 genes sampled in this study, from 156 species (within 44 out of the 55 living families) and combined with previous research on additional 145 species
David Blackburn is the Associate Curator of Herpetology at the Florida Museum of Natural History and an Affiliate Professor of Biology in the College of Liberal Arts and Sciences. He also is part of the Tropical Conservation and Development program, the School of Natural Resources and Environment, and the Center for African Studies.
Herpetology classes were offered again in Spring 2017 for the first time in a decade, taught by Blackburn and fellow biology professor Harvey Lillywhite. Add herpetology to your UF education.
Yan-Jie Feng et al. Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary. PNAS, 2017 DOI: 10.1073/pnas.1704632114