BIOGEOGRAPHY OF MILKWEED BUTTERFLIES (NYMPHALIDAE, DANAINAE) AND MIMETIC PATTERNS ON TROPICAL PACIFIC ARCHIPELAGOS

Distributions of danaine butterfly species and associated mimetic patt erns were compared among fifteen archipelagos of the tropical Pacific Ocean, and within five major archipelagos (the Bismarcks, Fiji, East a nd West Solomon Islands, and Vanuatu). Using both simple and stepwise linear regression analysis, variation in the total number of danaine s pecies and number of mimetic patterns was assessed with respect to isl and size, isolation and elevation. Relative to interarchipelago distri butions, the distribution of danaine species and number of mimetic pat terns on islands within archipelagos exhibited less dependence upon in terisland distance and island area. Geographical features influencing the number of mimetic patterns were similar to those of danaines as a whole. Analysis of residuals from stepwise linear repression suggested that factors influencing danaine distributions were different from th ose for nondanaine butterflies. This result is consistent with the hyp othesis of enhancement of danaine species establishment through Muller ian mimicry, although other factors such as host plant availability an d similar habitat use may also be important. (C) 1996 The Linnean Soci ety of London