Center for Bottomland Hardwoods Research, Oxford, MS 38655, USA.
Biol Rev Camb Philos Soc. 2011 Feb;86(1):225-47. doi: 10.1111/j.1469-185X.2010.00146.x.
The amount of energy allocated to growth versus other functions is a fundamental feature of an organism's life history. Constraints on energy availability result in characteristic trade-offs among life-history traits and reflect strategies by which organisms adapt to their environments. Freshwater mussels are a diverse and imperiled component of aquatic ecosystems but little is known about their growth and longevity. Generalized depictions of freshwater mussels as 'long-lived and slow-growing' may give an unrealistically narrow view of life-history diversity which is incongruent with the taxonomic diversity of the group and can result in development of inappropriate conservation strategies. We investigated relationships among growth, longevity, and size in 57 species and 146 populations of freshwater mussels using original data and literature sources. In contrast to generalized depictions, longevity spanned nearly two orders of magnitude, ranging from 4 to 190 years, and the von Bertalanffy growth constant, K, spanned a similar range (0.02-1.01). Median longevity and K differed among phylogenetic groups but groups overlapped widely in these traits. Longevity, K, and size also varied among populations; in some cases, longevity and K differed between populations by a factor of two or more. Growth differed between sexes in some species and males typically reached larger sizes than females. In addition, a population of Quadrula asperata exhibited two distinctly different growth trajectories. Most individuals in this population had a low-to-moderate value of K (0.15) and intermediate longevity (27 years) but other individuals showed extremely slow growth (K = 0.05) and reached advanced ages (72 years). Overall, longevity was related negatively to the growth rate, K, and K explained a high percentage of variation in longevity. By contrast, size and relative shell mass (g mm⁻¹ shell length) explained little variation in longevity. These patterns remained when data were corrected for phylogenetic relationships among species. Path analysis supported the conclusion that K was the most important factor influencing longevity both directly and indirectly through its effect on shell mass. The great variability in age and growth among and within species shows that allocation to growth is highly plastic in freshwater mussels. The strong negative relationship between growth and longevity suggests this is an important trade-off describing widely divergent life-history strategies. Although life-history strategies may be constrained somewhat by phylogeny, plasticity in growth among populations indicates that growth characteristics cannot be generalized within a species and management and conservation efforts should be based on data specific to a population of interest.
生物体将能量分配用于生长和其他功能的比例是其生活史的基本特征。由于能量供给的限制，生物在生活史特征之间会产生特有的权衡，这反映了生物适应其环境的策略。淡水贻贝是水生生态系统中多样化且受到威胁的组成部分，但人们对其生长和寿命知之甚少。一般来说，淡水贻贝被描述为“寿命长、生长缓慢”，这可能会对其生活史多样性产生不切实际的狭隘看法，这种看法与该类群的分类多样性不一致，并且可能导致制定不适当的保护策略。我们使用原始数据和文献资料，研究了 57 种淡水贻贝和 146 个种群的生长、寿命和体型之间的关系。与普遍的描述相反，寿命跨度接近两个数量级，范围从 4 年到 190 年，von Bertalanffy 生长常数 K 也跨越了类似的范围（0.02-1.01）。在不同的进化群中，寿命和 K 存在差异，但这些特征在群中也有广泛的重叠。寿命、K 和体型在种群之间也存在差异；在某些情况下，种群之间的寿命和 K 差异可达两倍甚至更多。在某些物种中，雌雄两性的生长存在差异，雄性通常比雌性体型更大。此外，一种叫 Quadrula asperata 的贻贝种群表现出两种截然不同的生长轨迹。该种群的大多数个体的 K 值（0.15）和中等寿命（27 年）较低，但其他个体的生长速度极慢（K = 0.05），寿命很长（72 年）。总的来说，寿命与生长率 K 呈负相关，K 可以解释寿命的大部分变化。相比之下，体型和相对壳质量（g mm⁻¹壳长）对寿命的变化解释很小。当对物种间的系统发育关系进行数据校正后，这些模式仍然存在。路径分析支持这样的结论，即 K 是影响寿命的最重要因素，它通过对壳质量的影响直接或间接地影响寿命。物种内和物种间的年龄和生长差异很大，这表明淡水贻贝的生长分配具有高度的可塑性。生长和寿命之间的强烈负相关关系表明，这是描述广泛不同生活史策略的一个重要权衡。尽管生活史策略可能在一定程度上受到系统发育的限制，但种群间的生长可塑性表明，不能在一个物种内对生长特征进行概括，管理和保护工作应该基于对感兴趣的种群的具体数据。
