Changes in yearly means of Warwick's W statistic (ABC curves) over 35 years in the Chicago Area Waterway System. Positive values are considered indicative of un-disturbed environments (i.e., fewer larger individuals) whereas negative values indicate more disturbance (i.e., highly abundant small individuals), values near zero are non-conclusive. Lines represent significant piecewise regressions (minimum of 3-yr spans; α = 0.05). Different shapes represent groups with significantly different (A = circles vs. B = squares) or shared (AB = diamonds) means (α = 0.05).