Core elements of a TPB paper.

The subject matter of Theoretical Population Biology lies at the intersection between mathematics and biology, and we seek papers that contain elements of both fields. Many ways exist to report contributions that combinemath and biology;we receive submissions that span the full range from math with relatively little biology to biology with relatively little math. Beyond high-quality science and relevance to the scope of the journal, what features are we seeking for manuscripts submitted to TPB? To help prospective authors, this editorial describes core elements of typical TPB papers, as exemplified by some of the articles we published in 2013. First, TPB papers are biologically motivated. They aspire to address problems in biology through a theoretical approach. Perhaps the effect of one biological phenomenon on another is of interest, and a study might be framed in terms of exploring the relationship conceptually and mathematically (Nilsen et al., 2013; Van Cleve and Lehmann, 2013; Wittmann et al., 2013). An empirical phenomenon observed in a specific organism or group of organisms might generate a need for a model (Della Rossa et al., 2013; Lončarić and Hackenberger, 2013; Mathias and Chesson, 2013; Turner et al., 2013). A comparison of, or analysis of the relationship between, two or more models might be of interest (Huillet and Möhle, 2013; Lambert and Stadler, 2013; Walters and Kendal, 2013). A project might seek to understand a new aspect of an important model in an established area of theory, or to extend a theoretical framework to accommodate additional biological phenomena or more general assumptions (Geoghegan and Spencer, 2013; Messinger and Ostling, 2013; Schreiber and Killingback, 2013; Sverdlov and Thompson, 2013). These scenarios all have in common that the biology drives the theory. Second, TPB papers are mathematically substantial. A new configuration of assumptions might be used to build a model and analyze its mathematical properties (Barton et al., 2013; Huang et al., 2013), or new techniquesmight be presented for the analysis of model features (Bansaye and Lambert, 2013; Steinrücken et al., 2013b). Under the assumptions of a model, new theoretical results might be obtained (Good and Desai, 2013; Schraiber et al., 2013), existing results enhanced through new derivations or connections (Cohen, 2013; Tazzyman and Bonhoeffer, 2013), or new features computed numerically or by simulation (Carja et al., 2013; Fogarty et al., 2013). A statisticalmethod for data analysismight be devised under the assumptions of amodel (Slatkin, 2013; Steinrücken et al., 2013a), or the mathematical or computational properties of such a method might be evaluated (Bryc et al., 2013; Cowell, 2013). In each case, the theory or methodological insight required for the advance is nontrivial. Third, results in TPB papers are formulated in relation to the biological phenomena. Ideally, the exposition—and especially abstracts, results sections, and figures—enables both theorists