By OCAdmin in Research highlights on

Hsiao-Pei Lu & Chih-hao Hsieh

Institute of Oceanography, National Taiwan University

A study in the East China Sea, led by Dr. Hsiao-Pei Lu and Prof. Chih-hao Hsieh, shows for the first time that diversity of marine bacteria community is strongly affected by macro-evolutionary constraints. This study is published (January, 2019) in The ISME Journal.

A core objective in community ecology is to assess and explain how species diversity varies along environmental gradients. Many theories trying to explain observed diversity–environment relationships consider mainly resource availability and species interactions, focusing on contemporary ecological processes in shaping local community diversity. However, it is increasingly recognized that local communities may bear imprints of macro-scale effects, such as speciation, long-distance dispersal, and historical events, which also contribute to form foundations of species diversity patterns. While the influences of evolutionary constraints on community diversity have been demonstrated for plants and animals, little attention has been paid to examine whether and how macro-evolutionary drivers can constrain contemporary diversity patterns of microorganisms.

To fill this knowledge gap, the research team proposes a conceptual model integrating processes at (a) short-term, local-scale and (b) long-term, broad-scale for the interpretation of species diversity patterns, emphasizing the potential influences of past evolutionary processes (i.e. phylogenetic divergence and adaptation) on present diversity–environment relationships (Figure 1). For bacteria which have evolved for >3.5 billion years and occupy wide variety of habitats on Earth, how bacterial lineages diverged and distributed in the past might exert strong constraints on their present diversity patterns. Specifically, the local species diversity should be critically influenced by the imprints of phylogenetic niche conservatism and unequal diversification rates among bacterial deep (i.e. phylum-level) lineages. The team used bacterioplankton community datasets from the East China Sea and global oceans as an example to demonstrate that species diversity of marine bacterioplankton communities is predictable with only phylum-level composition, due to macro-evolutionary constraints (Figure 2).

This work reveals species-pool effects on local community diversity of microorganisms, and the proposed conceptual model would lead to a more comprehensive understanding of the origin and variation of microbial community diversity.

Reference:

Hsiao-Pei Lu, Yi-Chun Yeh, Fuh-Kwo Shiah, Gwo-Ching Gong & Chih-hao Hsieh. Evolutionary constraints on species diversity in marine bacterioplankton communities. The ISME Journal, Online Published: 03 January 2019. https://www.nature.com/articles/s41396-018-0336-1

Figure 1. A conceptual model integrating processes at (a) short-term, local-scale and (b) long-term, broad-scale for the interpretation of species diversity patterns. Here, three hypothetical cases illustrate the potential confines of past evolutionary processes (i.e. phylogenetic divergence and adaptation) on present species diversity patterns along environmental gradients. Notably, the specific diversity-environment relationship may differ depending on the taxonomic groups and environmental variables of consideration in each case. This figure is from Fig. 1 of the published paper.

Figure 2. High correlation between observed and predicted species richness, using bacterioplankton communities of the East China Sea (ECS) as an example. For each ECS bacterioplankton community, the pie chart shows the phylum composition. The species richness of a local ECS community is predictable with a known phylum composition plus the information of global-seawater species pool, highlighting an important influence of evolutionary constraints on local community diversity. This figure is from Fig. 3 of the published paper.