Comparative analysis of larval growth in Lepidoptera reveals instar-level constraints

1. Juvenile growth trajectories evolve via the interplay of selective pressures on age and size at maturity, and developmental constraints. In insects, the moulting cycle is a major constraint on larval growth trajectories. 2. Surface area to volume ratio of a larva decreases during growth, so renewal of certain surfaces by moulting is likely needed for the maintenance of physiological efficiency. A null hypothesis of isometry, implied by Dyar’s Rule, would mean that the relative measures of growth remain constant across moults and instars. 3. We studied ontogenetic changes and allometry in instar-specific characteristics of larval growth in 30 lepidopteran species in a phylogenetic comparative framework. 4. Relative instar-specific mass increments (RMI) typically, but not invariably, decreased across instars. Ontogenetic change in RMIs varied among families with little within-family variation. End-of-instar growth deceleration (GD) became stronger with increasing body size across insta...1. 幼体生长轨迹的演化，源于成熟时年龄与体型所受选择压力与发育限制之间的相互作用。在昆虫中，蜕皮周期是制约幼虫生长轨迹的核心约束因素。 2. 幼虫在生长过程中，其表面积与体积之比会逐渐降低，因此通过蜕皮更新部分体表面，或为维持生理效率所必需。由戴尔法则（Dyar's Rule）推导得出的等生长零假设，意味着在各蜕皮周期与龄期内，生长的相对度量始终保持恒定。 3. 本研究基于系统发育比较框架，对30种鳞翅目物种的幼虫生长龄期特异性特征展开分析，探究其个体发育变化与异速生长规律。 4. 龄期特异性相对体重增量（RMI）通常（但并非绝对）会随龄期增加而降低。RMI的个体发育变化在各科之间存在显著差异，但科内变异极小。龄末期生长减速（GD）会随着各龄期的体型增大而愈发显著……