Are expanding rolled leaves of aroids used as shelter sites by arthropods? Effects of leaf size and environmental context

In nature, leaf rolls form during the expansion of young leaves of some plant species but their importance as shelter structures for arthropods is unknown. We examined the role of expanding rolled leaves of aroid species as shelter sites for arthropods and evaluated the effect of leaf size and environmental context (natural forest vs pastures) on the occupation of these leaves. In a Mexican tropical rainforest, arthropods were sampled from 25 fully expanded and 25 expanding rolled leaves of each of three aroid species (Rhodospatha wendlandii, Dieffenbachia oerstedii, and Spathiphyllum ortgiesii), that differ in the size of their leaves. In addition, for D. oerstedii we also collected leaves from a pasture area. We recorded 120 arthropods (44 in expanded and 76 in rolled leaves) from 53 unique morphospecies (21 and 38). Average arthropod abundance was greater in rolled leaves compared with expanded leaves. Average arthropod species richness and abundance, and colonization frequency were lower in the aroid species with smaller leaves (R. wendlandii). Although we found no significant effects of habitat type on arthropods in rolled leaves of D. oerstedii, 3.4 times more individuals (34) and 2.11 times more morphospecies (19) were found in the rolled leaves in the forest compared with those in pasture (10 and 9). This study demonstrates that expanding rolled leaves of aroids, despite being an ephemeral resource, represent suitable leaf shelters used by a diverse arthropod fauna, and that leaf size and environmental context are important factors that affect the colonization of these leaves by arthropods.