When fossil clades ‘compete’: local dominance, global diversification dynamics and causation

Abstract

Examining the supposition that local-scale competition drives macroevolutionary patterns has become a familiar goal in fossil biodiversity studies. However, it is an elusive goal, hampered by inadequate confirmation of ecological equivalence and interactive processes between clades, patchy sampling, few comparative analyses of local species assemblages over long geological intervals, and a dearth of appropriate statistical tools. We address these concerns by reevaluating one of the classic examples of clade displacement in the fossil record, in which cheilostome bryozoans surpass the once dominant cyclostomes. Here, we analyse a newly expanded and vetted compilation of 40 190 fossil species occurrences to estimate cheilostome and cyclostome patterns of species proportions within assemblages, global genus richness and genus origination and extinction rates while accounting for sampling. Comparison of time-series models using linear stochastic differential equations suggests that inter-clade genus origination and extinction rates are causally linked to each other in a complex feedback relationship rather than by simple correlations or unidirectional relationships, and that these rates are not causally linked to changing within-assemblage proportions of cheilostome versus cyclostome species.

Paleozoic origins of cheilostome bryozoans and their parental care inferred by a new genome-skimmed phylogeny

“…This is in contrast to other empirical studies based on different taxa, which suggest that larva dispersal modes or geographic range sizes associated with them directly influence diversification rates ( 46 ). Rather, it could be “external” factors, such as the macroevolutionary influence from a competing clade, the cyclostomes, which drove their diversification ( 13 ), as suggested by a character-independent model of speciation and extinction ( Table 1 ). Alternatively, an unmeasured trait that is associated with brooding/nonfeeding larvae could be responsible for differential rates of diversification in cheilostomes (table S7).…”

“…They represent c. 80% of the phylum’s living species diversity ( 12 ). Likewise, there are c. 7900 described fossil cheilostome species documented in a recent data compilation, where this number is a considerable underestimate of true fossil richness based on models that account for incomplete sampling in the fossil record ( 13 ). Their benthic, largely sessile and encrusting life habit allows us to investigate spatial competition frozen in geological time ( 14 ), and their modular and polymorphic nature permits the estimation of key biological parameters, including fitness components ( 15 ) beyond ecological time scales.…”

Enhancing georeferenced biodiversity inventories: automated information extraction from literature records reveal the gaps

“…While the portion of TMO data that is derived from the taxonomic literature may be less plagued by taxonomic misidentifications, the same cannot be easily argued for faunal lists or ecological surveys, much of which DB data is based on. However, in our experience, broad inferences based on synoptic, large-scaled databases tend to change significantly with different models, more so than data updates ( Sepkoski, 1993 ; Liow, Reitan & Harnik, 2015 ; Lidgard et al, 2021 ).…”

“…Many species await description; Gordon et al (2019) suggest that there are over 6,400 known cheilostome species without commenting on nomenclatural status, suggesting that there are up to 600 known species that need naming. Yet, a recent study, based on bryozoans, comparing datasets with taxonomic synonyms and without, found that synonymization does not contribute to qualitative changes in broad scale inferences ( Lidgard et al, 2021 ). Our machine-classifier is currently unable to extract location information for 21% of the species that were detected in our corpus of published works ( Fig.…”

The end of the line: competitive exclusion and the extinction of historical entities

“…The import of interspecific competition in both evolution and ecology has long been recognized [1,2], but the capacity for biotic interactions at the organism and population level to impact directly upon species richness remains an open question [3][4][5][6][7][8][9].…”