Meta-analysis reveals that density-dependent growth, survival, and their trade-off vary systematically among habitats and taxa

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Recent advances posit that density dependence plays a substantial role in the eco-evolutionary dynamics of life-history evolution, wherein fast-paced life histories (high fecundity, lower growth, short lifespan) perform better at lower densities while slower paced life histories (lower fecundity, higher growth, longer lifespan) are favoured in populations with strong density dependence. However, no meta-analysis has quantified systematically the importance of environmental factors on the occurrence, strength, and shape of density-dependent growth, survival, and their trade-off across animals. We processed 7214 papers from 1979 to 2021, resulting in 786 correlational effect sizes from 309 studies across 210 species. Systematic differences were detected among habitats (lentic, lotic, marine, or terrestrial) that were consistent with mechanisms of competition; studies in lotic environments were consistent with interference competition for food, whereas lentic and marine environments were consistent with exploitative competition. The shape of density dependence (linear, logarithmic, exponential, unimodal, non-significant) was context-dependent across animals. Density-dependent growth and survival covaried positively in fishes, herptiles, and invertebrates, but were unrelated in birds and mammals, suggesting context-dependent trade-offs. Collectively, our results reveal that the strength of density-dependent growth and survival varies more systematically across animals than their shape, relying on key habitat and taxonomic considerations.