Environmental predictors and invertebrate morphotypes in caves of Iuiú, Bahia, Brazil

In caves, the absence of natural light in deeper regions starkly contrasts
with the entrance areas, which still exhibit a light gradient extending
into the cave interior. This interplay with the structural gradient of the
environment potentially exerts distinct influences on invertebrate
communities residing in different cave light zones. To investigate this,
we formulated a hypothesis positing that communities within distinct cave
light zones respond differently to habitat structure and microclimatic
conditions. Our approach involved a spatial multi-scale sampling of
invertebrates and the application of statistical analyses to contrast the
responses of communities inhabiting photic and aphotic zones. Photic zone
richness is influenced by factors such as air moisture, resource
availability, root presence, and shelter diversity. In contrast, the
richness of communities in aphotic zones is shaped by resource
availability, the presence of roots, branches, and distance from the cave
entrance. As expected, the richness in the photic zone surpasses that of
the deeper regions, highlighting the challenges faced by invertebrates
attempting to establish themselves in the aphotic zone. The species
composition of faunal communities varied predictably from the entrance to
the aphotic zone, and the three most important factors driving this
variation were geographic distance, humidity, and distance from the
entrance. The composition between these cave zones differs significantly,
primarily due to the high number of obligate cave species predominantly
inhabiting the aphotic region. Indeed, communities associated with
different cave zones exhibit distinct responses to resource,
microclimatic, and structural variables.