Butterflies closer to the equator have been shown to evolve shared wing patterns faster than their relatives at higher latitudes. That gradient reframes tropical diversity as an active process, shaped ...

We describe a gradient of potential HIV transmission from HIV-infected persons to their partners and thence to uninfected populations. The effect of this newly discovered transmission gradient is to ...

The decrease in liana diversity with increasing latitude has been indicated as the major physiognomic difference between tropical and temperate forests’ ecosystem. Despite the robustness of this ...