Species, hybrid and genotype effects on leaf litter curling, and their extended consequences for spiders and soil moisture dynamics

Background and aims: Subtle morphological traits, such as leaf litter curling, may have unexpected legacy effects on ecosystems. We tested the hypotheses that litter curling is influenced by plant species, hybridization and genotype, and has extended consequences for associated organisms and soil processes. Methods: A novel litter curling index (LCI) was used to characterize the curling of leaf litter from 11 plant species (including shrubs, trees and a forb) in natural field sites and of two Populus species (P. fremontii James, P. angustifolia S. Watson), their F₁ hybrids and replicated P. angustifolia genotypes from a common garden. Surveys of dominant, litter-dwelling spiders (Agelenidae), and a soil drying experiment, were used to test the potential extended ecological consequences of litter curling. Results: Five results emerged. (1) LCI ranged 15-fold among plant species in natural sites. (2) LCI nearly doubled from P. fremontii to P. angustifolia, while average LCI for F₁ hybrids was intermediate (although not statistically different from P. fremontii). (3) LCI exhibited broad-sense heritability (H ² = 0.42) among P. angustifolia genotypes. (4) Abundance of spider webs was positively associated with increasing litter curl across the Populus hybrid system (R ² = 0.35). (5) After 57 days of drying, flat litter contained 1.4 times higher moisture than curled litter, which translated to wetter soil beneath flat litter. Conclusion: Litter curling has a genetic basis, which has legacy effects on other trophic levels and soil moisture dynamics that may shape the ecology and evolution of complex communities.