Ecological fidelity and spatiotemporal resolution of arthropod death assemblages from rodent middens in the central Atacama Desert (northern Chile)

Abstract

Evaluating the magnitude and direction of biases affecting the ecological information captured by death assemblages is an important prerequisite for understanding past, present, and future community-environment relationships. Here, we establish the ecological fidelity and spatiotemporal resolution of an overlooked source of fossil remains: the soil arthropod assemblages found in rodent middens (that span from the present to >44,420 cal yr BP) collected in the central Atacama Desert of northern Chile. We evaluated the “live-dead agreement” across four sources of soil arthropod data; two contemporary surveys of live communities (i.e., live), and two sources of death assemblages (i.e., dead). Although live-dead agreements and diversity indices are highly variable among samples (live and dead assemblages), our results consistently demonstrate that an average fossil midden (i) better captures the structure and composition of living communities than species richness per se; (ii) offers a spatially-resolved picture of those communities at local scales; and (iii) is only weakly affected by time-averaging. The fine spatiotemporal resolution of fossil midden records in the Atacama, and most likely other areas of the world where rodent middens occur offers ecological information on the structure and composition of fossil arthropod assemblages potentially over many thousands of years. This information is reliable enough to establish historical baselines before past and ongoing anthropogenic impacts.