Roberts Wade R, Siepielski Adam M, Alverson Andrew J
Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America.
PLoS Biol. 2024 Aug 8;22(8):e3002733. doi: 10.1371/journal.pbio.3002733. eCollection 2024 Aug.
A principal goal in ecology is to identify the determinants of species abundances in nature. Body size has emerged as a fundamental and repeatable predictor of abundance, with smaller organisms occurring in greater numbers than larger ones. A biogeographic component, known as Bergmann's rule, describes the preponderance, across taxonomic groups, of larger-bodied organisms in colder areas. Although undeniably important, the extent to which body size is the key trait underlying these patterns is unclear. We explored these questions in diatoms, unicellular algae of global importance for their roles in carbon fixation and energy flow through marine food webs. Using a phylogenomic dataset from a single lineage with worldwide distribution, we found that body size (cell volume) was strongly correlated with genome size, which varied by 50-fold across species and was driven by differences in the amount of repetitive DNA. However, directional models identified temperature and genome size, not cell size, as having the greatest influence on maximum population growth rate. A global metabarcoding dataset further identified genome size as a strong predictor of species abundance in the ocean, but only in colder regions at high and low latitudes where diatoms with large genomes dominated, a pattern consistent with Bergmann's rule. Although species abundances are shaped by myriad interacting abiotic and biotic factors, genome size alone was a remarkably strong predictor of abundance. Taken together, these results highlight the cascading cellular and ecological consequences of macroevolutionary changes in an emergent trait, genome size, one of the most fundamental and irreducible properties of an organism.
生态学的一个主要目标是确定自然界中物种丰度的决定因素。体型已成为丰度的一个基本且可重复的预测指标，较小的生物个体数量比较大的生物更多。一个被称为伯格曼法则的生物地理成分描述了在不同分类群中，体型较大的生物在较寒冷地区占优势的现象。尽管体型无疑很重要，但它在多大程度上是这些模式背后的关键特征尚不清楚。我们在硅藻中探讨了这些问题，硅藻是单细胞藻类，因其在碳固定和通过海洋食物网的能量流动中的作用而具有全球重要性。利用来自一个具有全球分布的单一谱系的系统基因组数据集，我们发现体型（细胞体积）与基因组大小密切相关，基因组大小在不同物种间相差50倍，且由重复DNA数量的差异驱动。然而，定向模型表明，对最大种群增长率影响最大的是温度和基因组大小，而非细胞大小。一个全球宏条形码数据集进一步确定基因组大小是海洋中物种丰度的一个有力预测指标，但仅在高纬度和低纬度的较寒冷地区，基因组较大的硅藻占主导，这一模式与伯格曼法则一致。尽管物种丰度受到无数相互作用的非生物和生物因素的影响，但仅基因组大小就是丰度的一个非常有力的预测指标。综上所述，这些结果突出了一种新兴特征——基因组大小（生物体最基本且不可简化的属性之一）的宏观进化变化所带来的一系列细胞和生态后果。
