Decoupling of local and regional dominance in trilobite assemblages from Northwestern Argentina: new insights into Cambro-Ordovician ecological changes

WAISFELD, B.G.; BALSEIRO, D.

LETHAIA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 49 p. 379 - 392

0024-1164

p { margin-bottom: 0.25cm; line-height: 120%; }Components of biodiversity are strongly scale-dependent, but the relativeimportance of the patterns that operate at different scales and thelinks between them have been overlooked. In order to disentangle theecological structure of Cambro- Ordovician trilobite assemblagesfrom the Argentine Cordillera Oriental at different scales, weexplore patterns of abundance, dominance, and occupancy across theonshore-offshore profile, and through three time intervals:Furongian, earliest late Tremadocian (Tr2), latest middleFloian-earliest late Floian (Fl2-Fl3). At the regional scale, singletaxa are overwhelming dominant in the Furongian (Parabolina) and inthe earliest late Tremadocian (Leptoplastides). Several dominantsoccur in the Floian, but just one (Famatinolithus) attains highoccupancy and, rarely, high dominance. In contrast, only theFurongian records highly dominated local assemblages, whereasdominance distinctly decreases among Tr2 and Fl-Fl3 ones. Thus, whenboth scales of analysis are combined, an unexpected scenario becomesevident: Tr2 assemblages resemble those of the Furongian at theregional scale, but mirror those of the Floian at the local scale.These results highlight a decoupling in local versus regionalstructures triggered by an earlier switch in dominance in localcommunities and a delayed change at the regional scale.Interestingly, this decrease in local dominance matches previousanalyses accounting for a coeval step up in local evenness,suggesting that the Tr2 appears as a pivotal interval in thereorganization of communities in the Cordillera Oriental. Thisscenario emphasizes that biogeographical regions witnessed differentregional scale processes, and suggests that scaling local andregional patterns provides new insights to unravel the history ofbiodiversity among benthic communities.