invasive or just happy at home?

there are several well entrenched stands of jerusalem artichokes out there...and always kept company be lamb's quarters wherever they go...i have rarely seen one without the other and since plants don't appear spontaneously i am assuming the sunchokes attract something that is depositing the lamb's quarters' seeds..while ;lamb's quarters are another native and fairly ubiquitous they still seem always to grow in tandem, resisting the jerusalem artichokes habit of relentlessly shading out anything that tries to take root anywhere near them...there must be some advantage...but for which? more research.