Rings, circles, and null-models for point pattern analysis in ecology Thorsten Wiegand 1 , and Kirk A. Moloney 2 1 Department of Ecological Modelling, UFZ-Centre for Environmental Research, PF 500136, 04301 Leipzig, Germany, email: towi@oesa.ufz.de , Fax: (**49) 341-235 3500; 2 Department of Botany, 143 Bessey Hall, Iowa State University, Ames, Iowa 50011-1020, email: kmoloney@iastate.edu , Fax.(**01) 515- 294 1337. Please send all correspondence concerning this manuscript to Thorsten Wiegand