<P> More recently, the panarchy theories of adaptive capacity and resilience promoted by C.S. Holling and Lance Gunderson have revived interest in the theory, and use it as a way of integrating social systems, economics and ecology . </P> <P> Writing in 2002, Reznick and colleagues reviewed the controversy regarding r / K selection theory and concluded that: </P> <P> The distinguishing feature of the r - and K - selection paradigm was the focus on density - dependent selection as the important agent of selection on organisms' life histories . This paradigm was challenged as it became clear that other factors, such as age - specific mortality, could provide a more mechanistic causative link between an environment and an optimal life history (Wilbur et al. 1974; Stearns 1976, 1977). The r - and K - selection paradigm was replaced by new paradigm that focused on age - specific mortality (Stearns, 1976; Charlesworth, 1980). This new life - history paradigm has matured into one that uses age - structured models as a framework to incorporate many of the themes important to the r--K paradigm . </P>

K-selected species and r-selected species demonstrate two different