LIMITATIONS TO NATURAL PRODUCTION OF LOPHOPHORA WILLIAMSII (CACTACEAE) I. REGROWTH AND SURVIVORSHIP TWO YEARS POST HARVEST IN A SOUTH TEXAS POPULATION Martin Terry Keeper Trout Bennie Williams Sul Ross State University Cactus Conservation Institute Cactus Conservation Institute Department of Biology P.O. Box 561 P.O. Box 561 Alpine, Texas 79832, U.S.A. Alpine, Texas 79831, U.S.A. Alpine, Texas 79831, U.S.A. mkterryaiw@sbcglobal.net Teodoso Herrera Norma Fowler Rio Grande Native American Church The University of Texas at Austin P.O. Box 460346 Department of Integrative Biology C0930 San Antonio, Texas 78246, U.S.A. 1 University Station Austin, Texas 78712, U.S.A. ABSTRACT Lophophora williamsii (peyote) is a cactus whose crowns are commercially harvested for religious use as an ingested psychoactive sacrament by members of the Native American Church. Over the past quarter century peyote has become progressively less available, due in part to improper harvesting techniques and excessive harvesting. Since anatomical aspects of the regrowth of peyote and best harvesting practices were explicated in a previous study (Terry & Mauseth 2006), the principal focus in the present study was to determine the effects of harvest- ing where only best practices were employed. We assessed the effects of (1) harvesting per se (a single harvesting event evaluated after two years), (2) repeated harvesting (two harvesting events two years apart), and (3) not harvesting at all. After two years, the once-harvested group had a 90% survival rate and the unharvested control group had a 98% survival rate, a difference that was not statistically signifi- cant. The above-ground volume of the unharvested plants was significantly larger than that of the regrown harvested plants. While the re- grown harvested plants had on average more crowns, their crowns were significantly smaller, in comparison to those of the unharvested plants. After two years, the surviving plants in the harvested group were divided into two subgroups, one of which was harvested for a sec- ond time. The other subgroup consisted of plants that had been harvested only once (at the start of the study) and were not reharvested. The weights of the crowns obtained in the second harvest were significantly lower than the weights of the crowns obtained in the first harvest from the same plants two years earlier. The net effect of a single harvesting was a reduction of plant above-ground volume by almost 80% after two years of regrowth. These data reflect what is occurring on a massive scale in habitat where peyote is commercially harvested. The annual numbers of crowns being harvested have not yet decreased drastically, due to the increased number of crowns produced as regrowth in response to harvesting. But the average size of the crowns in the regulated peyote market has decreased markedly due to too-early har- vesting of immature regrowth crowns. These results—with emphasis on the conspicuous reduction in mean size of individuals—are typi- cal of overharvested populations of wild-collected species, such as ginseng. The conclusion for conservation management is that reducing the frequency of harvesting of wild peyote would allow regrowth crowns to mature in size—thus reducing the number of crowns per dose required for sacramental consumption. It would also allow regrowth crowns to mature sexually, which would effectively de-suppress the production of seed for the next generation. RESUMEN Lophophora williamsii (peyote) es una cactácea, cuyos tallos se cosechan comercialmente para uso religioso como un sacramento psicoactivo ingerido por miembros de la Native American Church. En el último cuarto de siglo, el peyote se ha hecho progresivamente menos dis- ponible, debido por una parte al uso de técnicas inapropiadas de cosecha y por otra a la práctica de cosechar en exceso. Ya que los aspectos anatómicos del recrecimiento del peyote y las mejores prácticas de cosecharlo fueron explicados en un estudio previo (Terry y Mauseth 2006), el enfoque principal en el estudio presente era determinar los efectos de cosechar utilizando solamente las mejores prácticas. Evalu- amos los efectos de (1) cosechar de por sí (un solo evento de cosechar evaluado después de dos años), (2) cosechar repetidamente (dos even- tos de cosechar, el segundo dos años después del primero), y (3) no cosechar. Después de los dos años, el grupo cosechado una sola vez mostró una tasa de supervivencia de un 90% y el grupo no cosechado mostró una tasa de supervivencia de un 98%, tal diferencia no fue es- tadísticamente significativa. El tamaño de la porción por encima del suelo de las plantas del grupo control fue significativamente mayor que el de las plantas que volvieron a crecer después de la cosecha. Mientras que las plantas cosechadas y vueltas a crecer tuvieron más coronas en el promedio, sus coronas fueron más pequeñas que las del grupo no cosechado—ambas diferencias fueron también significativas. J. Bot. Res. Inst. Texas 5(2): 661 – 675. 2011