I've just come across Mark Hansen's Becoming as Creative Involution?:Contextualizing Deleuze and Guattari's Biophilosophy---an attempt to unpack and clarify the genealogy of Deleuze'schanging, though lifelong, engagement with Bergson. Essentially,after starting off from a point of seemingly perfect convergence between philosophy and biology--Bergson's notion of the élan vital--Deleuze drives an ever-widening wedge between thebiological notions he appropriates from neo-evolutionism and what he increasingly comes to view as a model of creative evolution too fundamentally bound up with both humanism and a residual representationalism. Hansen argues that:

what compels Deleuze to distance himself from creative evolution and from a certain Bergson is his (paradoxically very Bergsonian) philosophical aim of furnishing a metaphysics for contemporaryscience, that is, a metaphysics of the virtual....Against such a metaphysics, I shall insist, against such metaphysics and with the support of contemporary biologists, that a certain priority be granted processes of actualization.