Search

Transcending pairwise interactions in ecological networks remains a challenge. 1,2,3,4,5 Higher-order interactions (HOIs), the modulation of a pairwise interaction by a third species, 6 are thought to play a particularly important role in stabilizing coexistence and maintaining species diversity. 7,8,9,10,11,12 However, HOIs have so far only been demonstrated in models 9,10,11,12,13,14 or isolated experimental systems including only a few interacting species. 7,8,15 Their ubiquity and importance at a community level in the real world remain unknown. We hypothesized that a complex network of HOIs could be constantly modifying pairwise interactions and shaping ecological communities and that consequently the outcome of pairwise interactions would be a product of many influences from distinct sources. Using field experiments, we tested how multiple interactions within a diverse arthropod community associated with the tropical shrub Baccharis dracunculifolia D.C. (Asteraceae) were modified by the removal of ant species or live or hatched insect galls (a non-trophic engineering effect) of the dominant galler species. We revealed an extensive hidden network of HOIs modifying each other and the "visible" pairwise interactions. Most pairwise interactions were affected indirectly by the manipulation of non-interacting taxonomic groups. The pervasiveness of these interaction modifications challenges pairwise approaches to understanding interaction outcomes and could shift our thinking about the structure and persistence of ecological communities. Investigating coexistence mechanisms involving interaction modulation by HOIs may be key to elucidating the underlying causes of the stability and persistence of ecological communities. [Display omitted] • Higher-order interactions (HOIs) are interaction modulations by a third species • HOIs have so far only been demonstrated in models or simple empirical systems • We reveal an extensive network of HOIs in a diverse arthropod field community • This pervasiveness of HOIs challenges pairwise approaches in community ecology Barbosa et al. reveal with field experiments an extensive hidden network of higher-order interactions (HOIs) modifying the visible pairwise interactions in a diverse arthropod community. The pervasiveness of HOIs challenges pairwise approaches to understanding interaction outcomes and may shift our thinking on community structure and persistence. [ABSTRACT FROM AUTHOR]

Summary: The exploitation ecosystems hypothesis suggests that food chain length increases along gradients of increasing primary productivity. Recent results provide compelling new evidence for this from an arctic–alpine ecosystem. [Copyright &y& Elsevier]

Summary Defining specific cellular and molecular mechanisms in most obesity-related diseases remains an important challenge. Here we report a serendipitous finding that consumption of a high-fat diet (HFD) greatly increased the occurrence of skin lesions in C57BL/6 mice. We demonstrated that HFD induced the accumulation of a specific type of CD11c + macrophages in skin preceding detectable lesions. These cells primed skin to induce IL-1β and IL-18 signaling, which further promoted the cytokines IFN-γ- and IL-17-mediated skin inflammation. Mechanistically, epidermal fatty acid binding protein (E-FABP) was significantly upregulated in skin of obese mice, which coupled lipid droplet formation and NLRP3 inflammasome activation. Deficiency of E-FABP in obese mice decreased recruitment of CD11c + macrophages in skin tissues, reduced production of IL-1β and IL-18, and consequently dampened activation of effector T cells. Furthermore, E-FABP-deficient mice are completely resistant to HFD-induced skin lesions. Collectively, E-FABP represents a molecular sensor triggering HFD-induced skin inflammation. [ABSTRACT FROM AUTHOR]

Summary: Species-rich tropical communities are expected to be more specialized than their temperate counterparts [1–3]. Several studies have reported increasing biotic specialization toward the tropics [4–7], whereas others have not found latitudinal trends once accounting for sampling bias [8, 9] or differences in plant diversity [10, 11]. Thus, the direction of the latitudinal specialization gradient remains contentious. With an unprecedented global data set, we investigated how biotic specialization between plants and animal pollinators or seed dispersers is associated with latitude, past and contemporary climate, and plant diversity. We show that in contrast to expectation, biotic specialization of mutualistic networks is significantly lower at tropical than at temperate latitudes. Specialization was more closely related to contemporary climate than to past climate stability, suggesting that current conditions have a stronger effect on biotic specialization than historical community stability. Biotic specialization decreased with increasing local and regional plant diversity. This suggests that high specialization of mutualistic interactions is a response of pollinators and seed dispersers to low plant diversity. This could explain why the latitudinal specialization gradient is reversed relative to the latitudinal diversity gradient. Low mutualistic network specialization in the tropics suggests higher tolerance against extinctions in tropical than in temperate communities. [ABSTRACT FROM AUTHOR]

Cell adhesion and communication are interdependent aspects of cell behavior that are critical for morphogenesis and tissue architecture. In the skin, epidermal adhesion is mediated in part by specialized cell-cell junctions known as desmosomes, which are characterized by the presence of desmosomal cadherins, known as desmogleins and desmocollins. We identified a cadherin family member, desmoglein 4, which is expressed in the suprabasal epidermis and hair follicle. The essential role of desmoglein 4 in skin was established by identifying mutations in families with inherited hypotrichosis, as well as in the lanceolate hair mouse. We also show that DSG4 is an autoantigen in pemphigus vulgaris. Characterization of the phenotype of naturally occurring mutant mice revealed disruption of desmosomal adhesion and perturbations in keratinocyte behavior. We provide evidence that desmoglein 4 is a key mediator of keratinocyte cell adhesion in the hair follicle, where it coordinates the transition from proliferation to differentiation. [Copyright &y& Elsevier]