No ecological opportunity signal on a continental scale? Diversification and life-history evolution of African true toads (Anura: Bufonidae).
The niche-filling process predicted by the "ecological opportunity" (EO) model is an often-invoked mechanism for generating exceptional diversity in island colonizers. Whether the same process governs lineage accumulation and trait disparity during continental colonization events is less clear. Here, we test this prediction by investigating the rate dynamics and trait evolution of one of Africa's most widespread amphibian colonizers, the true toads (Bufonidae). By reconstructing the most complete molecular phylogeny of African Bufonidae to date, we find that the diversification of lineages in Africa best conforms to a constant rate model throughout time and across subclades, with little support for EO. Evolutionary rates of life-history traits have similarly been constant over time. However, an analysis of generalists and specialists showed a shift toward higher speciation rates associated with habitat specialization. The overall lack of EO signal can be interpreted in a number of ways and we propose several explanations. Firstly, methodological issues might preclude the detection of EO. Secondly, colonizers might not experience true EO conditions and due to the size, ecological heterogeneity and age of landmasses, the diversification processes might be more complex. Thirdly, lower speciation rates of habitat generalists may have affected overall proliferation of lineages.
Department of Environmental Science (Biogeography), University of Basel, 4056, Basel, Switzerland. christoph.liedtke@ebd.csic.es.|Ecology, Evolution and Developmental Group, Department of Wetland Ecology, Estación Biológica de Doñana (CSIC), 41092, Sevilla, Spain. christoph.liedtke@ebd.csic.es.
H Christoph
HC
Liedtke
Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, 07743, Jena, Germany.
Hendrik
H
Müller
Museum für Naturkunde Berlin, Leibniz Institute for Evolution and Biodiversity Science, 10115, Berlin, Germany.
Mark-Oliver
MO
Rödel
Tropical Biodiversity Section, MUSE-Museo delle Scienze, Trento, 38123, Italy.
Michele
M
Menegon
Cameroon Herpetology-Conservation Biology Foundation, P.O. Box 8218, Yaoundé, Cameroon.
LeGrand Nono
LN
Gonwouo
Museum für Naturkunde Berlin, Leibniz Institute for Evolution and Biodiversity Science, 10115, Berlin, Germany.
Michael F
MF
Barej
Institute of Vertebrate Biology, Czech Academy of Sciences, Brno, Czech Republic.
Václav
V
Gvoždík
Natural History Museum of Geneva, Department of Herpetology and Ichthyology, C.P. 6434, 1211 Geneva 6, Switzerland.
Andreas
A
Schmitz
Biodiversity and Conservation Biology Department, University of the Western Cape, Bellville, 7535, South Africa.
Alan
A
Channing
Department of Environmental Science (Biogeography), University of Basel, 4056, Basel, Switzerland.
Peter
P
Nagel
Department of Environmental Science (Biogeography), University of Basel, 4056, Basel, Switzerland.|Department of Life Sciences, University of Roehampton, London, SW15 4JD, United Kingdom.
Simon P
SP
Loader
D000818:Animals; D044822:Biodiversity; D049628:Body Size; D002025:Bufonidae / Q000145:classification* / Q000235:genetics / Q000502:physiology*; D049810:Genetic Speciation; D000071421:Life History Traits; D010063:Ovum / Q000502:physiology; D010802:Phylogeny; D012098:Reproduction; D017422:Sequence Analysis, DNA
Amphibia; BAMM; bGMYC; disparity; evolutionary rate dynamics; molecular phylogeny