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Abstract Over 125 million years of ant-plant interactions have culminated in one of the most intriguing evolutionary outcomes in life history. The myrmecophyteDuroia hirsuta(Rubiaceae) is known for its mutualistic association with the antMyrmelachista schumanniand several other species, mainlyAzteca, in the north-western Amazon. While both ants provide indirect defences to plants, onlyM. schumanninests in plant domatia and has the unique behaviour of clearing the surroundings of its host tree from heterospecific plants, potentially increasing resource availability to its host. Using a 12-year survey, we asked how the continuous presence of either onlyM. schumannior onlyAztecaspp. benefits the growth and defence traits of host trees. We found that the continuous presence ofM. schumanniimproved relative growth rates and leaf shearing resistance ofDuroiabetter than trees withAzteca. However, leaf herbivory, dry matter content, trichome density, and secondary metabolite production were the same in all trees. Survival depended directly on ant association (> 94% of trees died when ants were absent). This study extends our understanding of the long-term effects of strict ant-plant mutualism on host plant traits in the field and reinforces the use ofD. hirsuta–M. schumannias a model system suitable for eco-co-evolutionary research on plant–animal interactions. 

Increases in the abundance of woody species have been reported to affect the provisioning of ecosystem services in drylands worldwide. However, it is virtually unknown how multiple biotic and abiotic drivers, such as climate, grazing, and fire, interact to determine woody dominance across global drylands. We conducted a standardized field survey in 304 plots across 25 countries to assess how climatic features, soil properties, grazing, and fire affect woody dominance in dryland rangelands. Precipitation, temperature, and grazing were key determinants of tree and shrub dominance. The effects of grazing were determined not solely by grazing pressure but also by the dominant livestock species. Interactions between soil, climate, and grazing and differences in responses to these factors between trees and shrubs were key to understanding changes in woody dominance. Our findings suggest that projected changes in climate and grazing pressure may increase woody dominance in drylands, altering their structure and functioning. 

A high-resolution map of ant diversity allows an assessment of how well biodiversity centers overlap across taxa. 

No abstract available. 

Interactions among grazing pressure, climate, soil properties, and biodiversity affect ecosystem services provided by drylands.