What can the demography of Astrophytum ornatum tell us of its endangered status?

The Cactaceae are prominent members of national and international endangered species lists. This is true for even those that have not been studied in any significant detail, and given the need to assess these species there is still a general lack of information. Demographic studies in the Cactaceae have highlighted several threats some of which are clearly human induced (disturbance), and others that have a biological component (e.g. low survival rates of seedlings). We modelled the population dynamics of Astrophytum ornatum (the southernmost representative of Astrophytum) in one population in central Mexico, during a three year period. We constructed two size classified transition matrices and determined the growth rate (λ), as well as the stochastic log growth rate. We simulated changes in the matrix elements that correspond to the seed bank and the seed-seedling transition as these were the most important bottlenecks to population growth. In both years, the growth rate indicates a declining population, which will face serious problems in the next 2 to 3 decades. The simulations show that the seed bank is not as important as the seed-seedling transition. Any program that aims to restore A. ornatum populations needs to enhance seedling establishment.

► Many Cactaceae are endangered and little is known of their population dynamics.
► Astrophytum ornatum is one of four species of the endangered genus.
► Matrix models under a common R framework were used to assess risk.
► All scenarios showed a decreasing population with an extinction risk in <30 years.
► Recruitment and habitat specificity are quite likely the main population bottlenecks.