The reproductive phenology of three sympatric species of columnar cacti on Curacao

The phenological response by three sympatric species of columnar cacti of the semi-arid island of Curacao (Stenocereus griseus, Subpilocereus repandus, and Pilosocereus lanuginosus) to recent rainfall was investigated during 21 months. Rainfall is the climatic cue most likely to affect bud formation on Curacao, and each species of cactus responded differently to it. Pilosocereus lanuginosus started budding immediately after rainfall, whereas Stenocereus griseus responded negatively with abortions and cessation of bud production within 2-3 weeks after rain. Subpilocereus repandus showed no response to rain within one month. Despite a long period of temporal overlap (81% overlap) between the budding/flowering activity of Subpilocereus repandus and that of Stenocereus griseus, buds and/or flowers on Stenocereus griseus appeared more than a month earlier than on Subpilocereus repandus. The effect of plant size on phenology and how anthropogenic disturbance may affect cactus resource availability to nectar-feeders and frugivores were also examined. The larger the individual tree within a species, the more flowers were produced and the earlier the tree started to flower. Thus, the indiscriminate removal of columnar cacti for urban development can drastically affect the timing and availability of resources to threatened pollinators and other nectar-feeders, as well as to frugivores and omnivores. (C) 2001 Academic Press.