Causes and consequences of lifetime fitness variation in male Collared Lizards displaying alternative social ontogenies

We combined behavioral and genetic parentage data recorded over a decade to test the causes and fitness consequences of some first-year males defending breeding territories whereas others delayed defense until Year-2. Ours was an interesting study population because individuals displayed long-term philopatry to habitat patches differing in structural features that influenced the success of breeding tactics. Territorial longevity was under strong selection that enhanced lifetime male fitness. Among males that survived to a second breeding season, Year-1 fitness was a strong predictor of lifetime fitness, and individuals that defended territories during Year-1 achieved higher first season fitness than those postponing defense. Nonetheless, the proportion of non-territorial first-year males remained relatively stable, suggesting that more than one social ontogeny is maintained in this population. Variation in habitat structural complexity appeared to play a key role in the maintenance of delayed territory defense. Surreptitious travel and mating via the network of sub-surface crawlspaces characterizing complex habitats allowed non-territorial males to achieve higher lifetime reproductive success than their counterparts in simple habitats lacking such interconnected crawlspaces. More frequent territory acquisition by larger first-year males, most of which hatched from first clutches, suggested that first-year territory acquisition was driven by the robust physiological condition, perhaps stemming from the increased time to forage and grow experienced by these males prior to their first spring breeding season. Our results demonstrate that combining lifetime genetic parentage with behavioral data on individuals is a powerful paradigm for investigating variation in individual behavior and social system evolution.