Assessing regional differences in predation of endangered species: Implications from Texas populations of the endangered star cactus (Astrophytum asterias) Adam W. Ferguson a, * , Richard E. Strauss a , Anna W. Strong b , Sandra J. Birnbaum c , Jackie M. Poole c , Gena K. Janssen d , Paula S. Williamson b a Department of Biological Sciences, Box 43131, Texas Tech University, Lubbock, TX 79409, USA b Department of Biology, Texas State University-San Marcos, San Marcos, TX 78666, USA c Texas Parks and Wildlife Department, 4200 Smith School Road, Austin, TX 78744, USA d Janssen Biological, Austin, TX 78749, USA article info Article history: Received 2 October 2011 Received in revised form 22 May 2012 Accepted 31 May 2013 Available online Keywords: Astrophytum asterias Endangered Species Act Herbivory Mortality Recovery plan Threat assessment abstract Understanding threats to endangered species is one of the most critical components of implementing a successful recovery plan. For the endangered star cactus Astrophytum asterias, both mammalian and insect herbivory have been documented as a major threat to populations in Mexico. Herein, we focus on populations of A. asterias in Texas, examining how mortality threats differ from populations found in Mexico as well as among sites within Texas. Our study supports insect and mammalian herbivory as a major threat to A. asterias in Texas, with reductions in population sizes ranging between 16 and 54%. However, our study highlights that both regional and local differences can influence rates of mortality even in a range-restricted species such as A. asterias and highlights the need to assess threats at both of these levels for effective development and implementation of endangered species recovery plans. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The U.S. Endangered Species Act of 1973 (ESA; United States Code, 1973) requires that a recovery plan be developed for every species listed as threatened and endangered. The objective of these species specific plans is to assist in the recovery of listed species such that their populations become self-sustaining and no longer threatened with extinction (Clark et al., 2002). Despite this mandate, researchers and policy-makers alike have identified short-comings associated with these recovery plans (Clark et al., 2002; Foin et al., 1998; National Research Council, 1995; Schemske et al., 1994; Tear et al., 1995). Clark et al. (2002) identified that threats to species had received insufficient attention in re- covery plans and that those plans that linked recovery goals to species specific biological information were more likely to improve the species’ status. For endangered plants of arid systems, identifying which threat is most critical to long-term population persistence can be difficult (Valverde et al., 2004). Despite this difficulty, particular groups of plants tend to share suites of similar threats. For arid-land cacti, these threats often include over-collection for the horticultural trade (McIntosh et al., 2011), habitat disturbance (Martorell and Peters, 2005), and disease or predation (Martínez-Ávalos et al., 2007). Although documentation of individual threats at the species-specific level are available for several arid-land cacti (Godínez-Álvarez et al., 2003 and references therein), very few species have been examined for regional and or local differences in relation to specific threats such as predation. Without a detailed understanding of how threats may differ among proximal or distant populations of arid-land, endangered plants, construction of effective recovery plans will remain a challenge. * Corresponding author. Tel.: þ1 806 742 2715; fax: þ1 806 742 2963. E-mail addresses: adam.w.ferguson@ttu.edu, adamwferguson@gmail.com (A.W. Ferguson), rich.strauss@ttu.edu (R.E. Strauss), as47@txstate.edu (A.W. Strong), sandy.birnbaum@tpwd.texas.gov (S.J. Birnbaum), jackie.poole@ tpwd.texas.gov (J.M. Poole), gkjanssen@austin.rr.com (G.K. Janssen), pw04@ txstate.edu (P.S. Williamson). Contents lists available at SciVerse ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jaridenv.2013.05.018 Journal of Arid Environments 97 (2013) 143e149