| Cooperation and competition between relatives SA West, I Pen, AS Griffin Science 296 (5565), 72-75, 2002 | 925 | 2002 |
| Inclusive fitness theory and eusociality P Abbot, J Abe, J Alcock, S Alizon, JAC Alpedrinha, M Andersson, ... Nature 471 (7339), E1-E4, 2011 | 545 | 2011 |
| Geographical patterns of adaptation within a species’ range: interactions between drift and gene flow M Alleaume‐Benharira, IR Pen, O Ronce Journal of evolutionary biology 19 (1), 203-215, 2006 | 333 | 2006 |
| A guide to sexual selection theory B Kuijper, I Pen, FJ Weissing Annual Review of Ecology, Evolution, and Systematics 43 (1), 287-311, 2012 | 244 | 2012 |
| Adaptive sex allocation in birds: the complexities of linking theory and practice J Komdeur, I Pen Philosophical Transactions of the Royal Society of London. Series B …, 2002 | 221 | 2002 |
| An evolutionary perspective on self-organized division of labor in social insects A Duarte, FJ Weissing, I Pen, L Keller Annual review of ecology, evolution, and systematics 42 (1), 91-110, 2011 | 213 | 2011 |
| Sanctions and mutualism stability: when should less beneficial mutualists be tolerated? SA West, ET Kiers, I Pen, RF Denison Journal of Evolutionary Biology 15 (5), 830-837, 2002 | 203 | 2002 |
| Climate-driven population divergence in sex-determining systems I Pen, T Uller, B Feldmeyer, A Harts, GM While, E Wapstra Nature 468 (7322), 436-438, 2010 | 183 | 2010 |
| Three epigenetic information channels and their different roles in evolution N Shea, I Pen, T Uller Journal of evolutionary biology 24 (6), 1178-1187, 2011 | 168 | 2011 |
| Towards a unified theory of cooperative breeding: the role of ecology and life history re-examined I Pen, FJ Weissing Proceedings of the Royal Society of London. Series B: Biological Sciences …, 2000 | 168 | 2000 |
| The evolution of sex ratios and sex-determining systems T Uller, I Pen, E Wapstra, LW Beukeboom, J Komdeur Trends in Ecology & Evolution 22 (6), 292-297, 2007 | 125 | 2007 |
| Sex ratios under asymmetrical local mate competition: theory and a test with parasitoid wasps DM Shuker, I Pen, AB Duncan, SE Reece, SA West The American Naturalist 166 (3), 301-316, 2005 | 117 | 2005 |
| The information value of non-genetic inheritance in plants and animals S English, I Pen, N Shea, T Uller PloS one 10 (1), e0116996, 2015 | 116 | 2015 |
| Genomic conflict in scale insects: the causes and consequences of bizarre genetic systems L Ross, I Pen, DM Shuker Biological Reviews 85 (4), 807-828, 2010 | 116 | 2010 |
| Optimal sex allocation: steps towards a mechanistic theory I Pen, FJ Weissing Sex ratios: concepts and research methods, 26-45, 2002 | 115 | 2002 |
| Caribbean mangroves and seagrass beds as daytime feeding habitats for juvenile French grunts, Haemulon flavolineatum MC Verweij, I Nagelkerken, SLJ Wartenbergh, IR Pen, G van der Velde Marine Biology 149, 1291-1299, 2006 | 110 | 2006 |
| Segregation distortion and the evolution of sex-determining mechanisms M Kozielska, FJ Weissing, LW Beukeboom, I Pen Heredity 104 (1), 100-112, 2010 | 109 | 2010 |
| Parental energy expenditure in relation to manipulated brood size in the European kestrel Falco tinnunculus C Deerenberg, I Pen, C Dijkstra, BJ Arkies, GH Visser, S Daan Zoology-Analysis of Complex Systems 99 (1), 39-48, 1995 | 103 | 1995 |
| Sex-ratio optimization with helpers at the nest I Pen, FJ Weissing Proceedings of the Royal Society of London. Series B: Biological Sciences …, 2000 | 97 | 2000 |
| When is incomplete epigenetic resetting in germ cells favoured by natural selection? T Uller, S English, I Pen Proceedings of the Royal Society B: Biological Sciences 282 (1811), 20150682, 2015 | 91 | 2015 |