AbstractLittle is known about the c

Abstract
Little is known about the causes of mortality in natural populations of threatened cactus species.
In particular we focus on the endangered Astrophytum asterias in four populations where most
individuals of the species are found. At two sites one of each vegetation type (Tamaulipan thornscrub
[TS] and Piedmont thornscrub [PT]) we measured individual mortality by three causes: the plant
pathogen Phytophtora infestans, a cerambicid beetle and the terrestrial squirrel Spermophilus
mexicanus. We found that damage by the combination of pathogen and herbivore meant a reduction
of more than 50% in population size. From these factors, the most important cause of death was
S. mexicanus followed by the cerambicid beetle in TS and P. infestans in PT. Mortality was
concentrated in the small size categories, even though large size plants were also affected albeit to a