The “Bateman gradient” or “Bateman slope” is an important measure in sexual selection research, and describes the number of additional offspring an individual can expect to produce for each additional mating. A key insight has been that Bateman slopes are often steeper in males than in females, dating back to Bateman’s original experiments in Drosophila. However, applying these measures to natural populations is not straightforward. We contribute to a debate on how this should best be done in this week’s issue of Science. The exchange arose from an original Report by John Byers and Stacey Dunn from the University of Idaho (USA) published in November last year, in which they analyse a long-term dataset on sexual selection in pronghorn. In a Technical Comment written together with several colleagues here in Bielefeld (Rudy Jonker, Klaus Reinhold, Fritz Trillmich, Tim Schmoll and Holger Schielzeth, plus Tamás Székely from the University of Bath and Rob Freckleton from the University of Sheffield, UK), we point out some difficulties we see with this analysis, and the original authors reply to us, plus two additional Technical Comments by Göran Arnqvist and Patrick Bergeron and colleagues, in an accompanying Response.
Ramm SA, Jonker RM, Reinhold K, Székely T, Trillmich F, Schmoll T, Schielzeth H & Freckleton RP. 2013. Comment on "Bateman in nature: Predation on offspring reduces the potential for sexual selection". Science, 340:549. doi:10.1126/science.1233298