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Conventionally, the size, shape, and biomechanics of cartilages are determined by their voluminous extracellular matrix. By contrast, we found that multiple murine cartilages consist of lipid-filled cells called lipochondrocytes. Despite resembling adipocytes, lipochondrocytes were molecularly distinct and produced lipids exclusively through de novo lipogenesis. Consequently, lipochondrocytes grew uniform lipid droplets that resisted systemic lipid surges and did not enlarge upon obesity. Lipochondrocytes also lacked lipid mobilization factors, which enabled exceptional vacuole stability and protected cartilage from shrinking upon starvation. Lipid droplets modulated lipocartilage biomechanics by decreasing the tissue’s stiffness, strength, and resilience. Lipochondrocytes were found in multiple mammals, including humans, but not in nonmammalian tetrapods. Thus, analogous to bubble wrap, superstable lipid vacuoles confer skeletal tissue with cartilage-like properties without “packing foam–like” extracellular matrix. 

Abstract Spatial partitioning is a classic hypothesis to explain plant species coexistence, but evidence linking local environmental variation to spatial sorting, demography and species' traits is sparse. If co‐occurring species' performance is optimized differently along environmental gradients because of trait variation, then spatial variation might facilitate coexistence.We used a system of four naturally co‐occurring species ofClarkia(Onagraceae) to ask whether distribution patchiness corresponds to variation in two environmental variables that contribute to hydrological variation. We then reciprocally sowedClarkiainto each patch type and measured demographic rates in the absence of congeneric competition. Species sorted in patches along one or both gradients, and in three of the four species, germination rate in the ‘home’ patch was higher than all other patches.Spatially variable germination resulted in the same three species exhibiting the highest population growth rates in their home patches.Species' trait values related to plant water use, as well as indicators of water stress in home patches, differed among species and corresponded to home patch attributes. However, post‐germination survival did not vary among species or between patch types, and fecundity did not vary spatially.Synthesis. Our research demonstrates the likelihood that within‐community spatial heterogeneity affects plant species coexistence, and presents novel evidence that differential performance in space is explained by what happens in the germination stage. Despite the seemingly obvious link between adult plant water‐use and variation in the environment, our results distinguish the germination stage as important for spatially variable population performance.