Niche theory suggests that the coexistence of ecologically similar species at the same site requires some form of resource partitioning that reduces or avoids interspecific competition. Here, we investigated the temporal and spatial niche differentiation of two sympatric congeneric spiders,Peucetia rubrolineataandP. flava, inhabitingTrichogoniopsis adenantha(Asteraceae) plants along an altitudinal gradient in various shaded and open areas in an Atlantic forest in Serra do Japi, SP, Brazil. In theory, the coexistence of twoPeucetiaspecies could be explained by: (1) temporal segregation; (2) differential use of the branches of the plant; (3) differential use of specific parts of the branches of the plant; (4) differential distribution in shaded and open areas; and (5) differential altitudinal distribution of the twoPeucetiaspecies. With respect to temporal niche, we observed that the two spider species had a similar age structure and similar fluctuation in abundance throughout the year. With respect to micro-habitat use, in both species, different instars used different plant parts, while the same instars of both species used the same type of substrate. However, the twoPeucetiaspecies segregated by meso-habitat type, withP. rubrolineatapreferringT. adenanthaplants in shaded areas andP. flavapreferring those in open areas. Our results support the hypothesis of niche partitioning begetting diversity, and highlight the importance of analysing habitat use at multiple scales to understand mechanisms related to coexistence.

Bacterial cell walls are essential barriers that protect bacteria against the onslaught of potentially lethal molecules from the outside. Small molecule therapeutics, proteins from bacterial foes, and host immune proteins must navigate past a dense layer of bacterial biomacromolecules (e.g., capsular proteins, teichoic acids, and anchored proteins) to reach the peptidoglycan (PG) layer of Gram-positive bacteria. A subclass of molecules (e.g., antibiotics with intracellular targets) must also permeate through the PG (in a molecular sieving manner) to reach the cytoplasmic membrane. In the case of Staphylococcus aureus (S. aureus), teichoic acids are the major biopolymers that decorate bacterial cell surfaces. Despite the biological and therapeutic importance of surface accessibility, systematic analyses in live bacterial cells have been lacking. We describe a novel live cell fluorescence assay that reports on the permeability of molecules to and within the PG scaffold. The assay has robust reproducibility, is readily adoptable to any Gram-positive organism, and is compatible with high-throughput sample processing. Analysis of the factors controlling permeability to S. aureus and the methicillin resistant MRSA revealed that molecular flexibility plays a central role in molecular permeability. Moreover, teichoic acids impeded permeability of molecules of a wide range of sizes and chemical composition.