Diversity across organisational scale emerges through dispersal ability and speciation dynamics in tropical fish

AbstractBackgroundBiodiversity exists at different levels of organisation: e.g., individual, population, species, and community. These levels of organisation all exist within the same system, with diversity patterns emerging across organisational scale through several key processes. Despite this inherent interconnectivity, observational studies reveal that diversity patterns across levels are not consistent. However, the underlying mechanisms for variable continuity in diversity across levels remain elusive. To investigate these mechanisms, we apply a spatially explicit simulation model to reconstruct the global diversification of tropical reef fishes at both the population and species levels through emergent population-level processes.ResultsWe find significant relationships between the population and species levels of diversity which vary dependent on both the measure of diversity and the spatial partitioning considered. In turn, these population-species relationships are driven by modelled biological trait parameters, especially the divergence threshold at which populations speciate.ConclusionsTo explain variation in multi-level diversity patterns, we propose a simple, yet novel, population-to-species diversity partitioning mechanism through speciation which disrupts continuous diversity patterns across organisational levels. We expect that in real-world systems this mechanism is driven by the molecular dynamics that determine genetic incompatibility, and therefore reproductive isolation between individuals. We put forward a framework in which the mechanisms underlying patterns of diversity across organisational levels are universal, and through this show how variable patterns of diversity can emerge through organisational scale.

摘要：背景
生物多样性存在于多个组织层次，例如个体、种群（population）、物种与群落。这些组织层次共存于同一系统中，多样性格局会随组织尺度（organizational scale）经由若干关键过程逐步形成。尽管存在这种内在关联性，但观测研究表明，不同层次的多样性格局并不一致。然而，跨层次间多样性的可变连续性的潜在机制仍未明晰。

为探究此类机制，我们采用空间显式模拟模型（spatially explicit simulation model），通过涌现的种群水平过程，重建热带礁鱼类在种群与物种水平的全球多样化进程。

结果
我们发现，多样性的种群水平与物种水平之间存在显著关联，且该关联因多样性测度指标与所考虑的空间分区方式而异。进一步分析表明，这些种群-物种关联由模拟设定的生物学性状参数所驱动，尤其是种群发生物种形成（speciation）时的分化阈值。

结论
为解释多水平多样性格局的变异规律，我们提出了一种简洁却新颖的种群-物种多样性分区机制：通过物种形成过程打破跨组织层次的连续性多样性格局。我们推测，在现实生态系统中，该机制由决定遗传不相容性（genetic incompatibility）、进而决定个体间生殖隔离（reproductive isolation）的分子动力学所驱动。我们提出了一个理论框架，认为跨组织层次的多样性格局背后的机制具有普适性，并借此展示了多样性的可变格局如何随组织尺度产生。