Abstract
AbstractAimMany clades display the macroevolutionary pattern of a negative relationship between standing diversity and diversification rates. Competition among species has been proposed as the main mechanism that explains this pattern. However, we currently lack empirical insight into how the effects of individual‐level ecological interactions scale up to affect species diversification. Here, we investigate a clade that shows evidence for negative diversity‐dependent diversification in the fossil record and test whether the clade's modern communities show a corresponding signal of interspecific competition.LocationWorld's oceans.Time periodHolocene.Major taxa studiedPlanktonic Foraminifera (Rhizaria).MethodsWe explore spatial and temporal ecological patterns expected under interspecific competition. Firstly, we use a community phylogenetics approach to test for signs of local competitive exclusion among ecologically similar species (defined as closely related or of similar shell sizes) by combining species relative abundances in seafloor sediments. Secondly, we analyse whether population abundances of co‐occurring species covary negatively through time using sediment trap time‐series spanning 1–12 years.ResultsThe great majority of the assemblages are indistinguishable from randomly assembled communities, showing no significant spatial co‐occurrence patterns regarding phylogeny or size similarity. Through time, most species pairs correlated positively, indicating synchronous rather than compensatory population dynamics.Main conclusionsWe found no detectable evidence for interspecific competition structuring extant planktonic Foraminifera communities. Species co‐occurrences and population dynamics are likely regulated by the abiotic environment and/or distantly related species, rather than intra‐clade density‐dependent processes. This interpretation contradicts the idea that competition drives the clade's macroevolutionary dynamics. One way to better integrate community ecology and macroevolution is to consider that diversification dynamics are influenced by groups that interact ecologically even when distantly related.
Highlights
Ecological interactions play an important role in shaping the diversity of life across space and time
An alternative approach to test whether the negative dependent diversification (DDD) pattern is a result of upward causation from competition among individuals is to contrast macroevolutionary and present‐day community ecology dynamics (Voje, Holen, Liow, & Stenseth, 2015; Weber et al, 2017)
The temporal scale we study ranges from weeks to millennia
Summary
Ecological interactions play an important role in shaping the diversity of life across space and time. Interspecific competition has often been proposed to have a consistent negative effect across ecological and geological time scales, generating the pattern of a negative relationship between species diversity and diversification rates (Rabosky, 2013). An alternative approach to test whether the negative DDD pattern is a result of upward causation from competition among individuals is to contrast macroevolutionary and present‐day community ecology dynamics (Voje, Holen, Liow, & Stenseth, 2015; Weber et al, 2017) This approach involves investigating whether the ecological interactions among most (if not all) extant species of a clade (clade‐wide) support interspecific competition, and are consistent with the clade's observed DDD pattern. If competing species coexist, population sizes of competitors are expected to show a negative relationship
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