Species Assembly Is Lineage Specific: Phylogenetic Divergent Species Aggregate in Some Lineages but Segregate in Others

Abstract

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.

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