A study of the growth, reproduction, and mortality of Echinomastus mariposensis (Cactaceae) in Big Bend National Park, Texas

Echinomastus mariposensis is globally rare and federally listed as a threatened species but can be common within known localities in the northern Chihuahuan Desert. To satisfy criteria for de-listing this species, permanent monitoring plots were established in Big Bend National Park in 1994, and those plots have been revisited by researchers in subsequent years. These data revealed general trends in growth, such as a steady increase in diameter of approximately five millimeters per year until growth plateaued at diameter of 50--60 millimeters. Additionally, the diameter of these cacti tended to decrease one to two years prior to mortality. Correlations of fruit production, fruit abortion, juvenile establishment, and weather indicate that hotter summers, colder winters, and decreased rainfall may inhibit the reproductive output of this species. Mortality observations indicate that adult cacti are more likely to perish than those still at a juvenile stage.