The Pollination Ecology of Sclerocactus brevihamatus ssp. tobuschii (Cactaceae) in the Edwards Plateau Region of west-central Texas

The Tobusch fishhook cactus (Sclerocactus brevihamatus ssp. tobuschii) (Cactaceae) is an endangered species endemic to the Edwards Plateau region of west-central Texas. This study’s objectives were to provide information on pollination ecology by comparing pollinator effectiveness among floral visitors and determining the breeding system and floral attraction system. Research was conducted on two field sites located in Kimble and Kerr Counties and on greenhouse specimens from Val Verde and Edwards Counties during the reproductive period (February-July) of 2014 and 2015. Honey bees (Apidae) were determined to be the most frequent and effective pollinators, followed by halictid bees (Halictidae). Fruit set results from pollination treatments and pollen-ovule (P/O) ratios support the reports from previous studies that this species is primarily self-incompatible. The flowers are protandrous with anther dehiscence occurring in the bud. Lastly, pollen was determined to be the primary floral reward.