Poor conditions in early life directly affect survival, but also may indirectly affect the fitness of survivors by influencing physiological or behavioral characteristics that relate to lifetime reproductive potential (e.g., longevity, fecundity). Although numerous studies have examined how poor food quality or quantity in early life affect an individual species’ fitness throughout life, a synthesis of these studies is lacking. To increase our ability to draw general conclusions from the existing literature, we conducted a meta-analysis. Our preliminary ISI Web of Science search included the following terms: food quality AND “early life” OR young OR larva* AND fitness. Of 232 results, 16 studies fit our search criteria providing a total 84 responses. Responses were categorized as ‘condition,’ ‘learning,’ ‘survival’, ‘reproductive success,’ and ‘locomotor abilities.’ We calculated an effect size (Hedge’s g) for each response and a weighted mean for all responses, as well as for each response category. If the 95% confidence interval of the weighted mean for a given response category overlapped with zero, we determined that poor food in early life did not influence that response.
Our preliminary results indicated that poor early life food quality negatively affects fitness throughout life for a broad range of species, particularly through reproductive success and survival. The weighted mean for overall effect size was -0.15 (± 0.06, 95% CI, n = 84); the weighted means for reproductive success and survival were -0.20 (± 0.08, n = 15) and -0.17 (± 0.14, n = 15), respectively. Funnel plots showed little evidence for publication bias. Although our results validate our hypothesis that early life food can affect fitness later in life, the mean effect sizes were small. Therefore, we are conducting a broader ISI Web of Science search to include more studies to further verify our results. Additionally, we will examine if factors such as taxonomic group, the age or stage at which food was limited, or the number of effect sizes drawn from a single study influences the effect size.