Effectiveness and Importance of Pollinators to the Star Cactus (Astrophytum Asterias) (Report‪)‬

In the past decade, it has become clear that effective management of populations of rare plants must include understanding community-level processes that affect these populations (Sipes and Tepedino, 1995; Corbet, 1997; Timmerman-Erskine and Boyd, 1999; Wall et al., 2003). Interactions between plants and their pollinators are of particular importance as many endangered plants are dependent on pollinators for reproduction and maintenance of viable populations (Nabhan and Flemming, 1993; Kearns and Inouye, 1997; Kearns et al., 1998; Spira, 2001; Wall et al., 2003). Studies of pollination are especially important for rare species of plants that are self-incompatible or that do not reproduce asexually (Bond, 1994). Understanding which flower visitors are the most effective and important pollinators of these plants is crucial to their recovery. Management decisions, such as designation of critical habitat or use of pesticides on nearby lands, may need to take into account needs of pollinators to ensure long-term survival of populations (Sipes and Tepedino, 1995; Havens, 1999). Astrophytum asterias is a rare species federally listed as endangered in 1993 and listed as endangered by the state of Texas in 1997 (United States Fish and Wildlife Service, 2003). Astrophytum asterias also is included in Appendix I of CITES (Convention on International Trade of Endangered Species). While surveys are ongoing, A. asterias currently is known to occur only on 14 properties in Starr County, Texas, and at 9 small sites in neighboring Mexican states of Tamaulipas and Nuevo Leon (Martinez-Avalos et al., 2004). Historically, A. asterias occurred over a larger portion of southern Texas and northern Mexico, but habitat destruction and modification along with overexploitation by collectors have greatly reduced the range of the species (United States Fish and Wildlife Service, 2003).