New publication from Zhang et al. in Ecology Letters: Species Assembly Is Lineage Specific: Phylogenetic Divergent Species Aggregate in Some Lineages but Segregate in Others

Phylogenetic divergence between species may weaken both negative and positive biotic interactions. Whether, as a result, divergent species aggregate or segregate remains unclear. These interactions differ among lineages, and without immigration, the effects of interactions might be overridden by dispersal limitation. We studied changes in co-occurrence across 5 years for 1770 pairs of grassland species drawn primarily from four major lineages (families), reducing dispersal limitation by seed addition. Across all lineages, changes in co-occurrence were almost unrelated to phylogenetic divergence, partly reflecting opposing relationships within two groups of families: Fabaceae/Poaceae, where more divergent species segregated, versus Asteraceae/Apiaceae, where they aggregated. Dispersal limitation through lack of immigration existed, without eliminating divergence effects. We conclude that species assembly differed between major lineages, with spatial aggregation in Asteraceae/Apiaceae possibly reflecting limiting similarity, whereas segregation in Fabaceae/Poaceae may reflect mutualist incompatibility or asymmetric competition. These processes could feedback on within-lineage diversification.

FIGURE 1 | Conceptual scenarios linking phylogenetic divergence to species aggregation. The phylogenetic divergence within the underlying species pool is illustrated on the right, where two families are shown (dark green vs. light green branches). Divergence (branch lengths and trait differences) is largest between families and also varies within each family. In panels A–D, each local community (field plot) is schematically represented by a single focal species pair (one horizontal row), illustrating the expected pattern of aggregation or segregation across plots under the corresponding scenario. (A) Larger phylogenetic divergence can promote functional trait divergence among species (leaf and plant shapes), reducing symmetric competition and increasing isolation from specialist enemies, thereby facilitating aggregation. (B) Alternatively, phylogenetic divergence can limit recruitment of shared mutualists and increase competitive asymmetry, promoting aggregation among species that have diverged little. (C) Community assembly is entirely stochastic, for example, due to dispersal limitation, and therefore aggregation or segregation are unrelated to phylogenetic divergence. (D) Relationships between phylogenetic divergence and aggregation exist (for the reasons explained above) but with different signs in different families. In panel D, within the dark-green family (phylogram), the least divergent species aggregate (top), whereas within the light green family, the most divergent species aggregate (middle, bottom).

Reference:

Zhang, K., A. J. Fergus, L. Barbe, B. Schmid, E. Allan, et al. 2026. Species Assembly Is Lineage Specific: Phylogenetic Divergent Species Aggregate in Some Lineages but Segregate in Others. Ecology Letters 29:e70402. https://doi.org/10.1111/ele.70402.