Demographic analysis of Agave angustifolia (Agavaceae) with an emphasis on ecological restoration

Abstract

We studied the demography of two populations of Agave angustifolia, one in a preserved tropical dry forest (Xochicalco), and the other one in a pastureland area used for cattle grazing (Tembembe), to test whether populations are likely to thrive on the deteriorated habitats left after cattle ranching. Seed germination and seedling survival experiments were carried out in different natural microsites (i.e. under tree canopies and in open microsites). We built Lefkovitch matrices and carried out prospective (elasticity) and retrospective (Life Table Response Experiments) analyses for both populations. Numerical simulations were performed to project the effect of inflorescences harvest and seedling introduction. Seedling survival and seed germination were highest in Tembembe. Population growth rate was slightly higher in Tembembe (lambda = 1.268) than in Xochicalco (lambda = 1.208). Prospective and retrospective analyses showed that stasis and growth contributed most to population growth rate and that the differences between the two populations were accounted for a lower fecundity and stasis in Xochicalco compared to Tembembe. Simulations of inflorescence harvest showed that lambda dropped below unity only when all inflorescences were eliminated. The simulated introduction of seedlings produced a substantial rise in lambda. As the lambda values reflect thriving populations at both sites, we suggest that this species could be successfully used in restoration programs.

Integral Projection Models and Sustainable Forest Management of Agave inaequidens in Western Mexico

“…Only in the population Pino Real, λ values, in both study periods, had values slightly below the equilibrium, suggesting a decreasing trend, but these values were not far from the unity. Similarly as found in other works with Agave species of semiarid zones of Mexico ( Illsley et al., 2007 ; Jiménez-Valdés et al., 2010 ; Torres et al., 2015a ; Arias-Medellín et al., 2016 ), survival and growth are the vital rates that mostly contribute to λ in A. inaequidens , but in this study we found that fecundity also showed a significant contribution to λ, a fact that can be explained based on findings by Metcalf et al. (2003) .…”

“…Studies on monocarpic perennial plants have been carried out for several species ( Metcalf et al., 2003 ; Metcalf et al., 2006 ), which emphasize that the reproductive strategy of these plants is directly related to the individuals size, larger plants yielding larger numbers of seeds and likewise increasing the number of seedlings. Case studies using matrix models of Agave species under human exploitation are relatively scarce [e.g., Agave cupreata ( Illsley et al., 2007 ), A. marmorata ( Jiménez-Valdés et al., 2010 ), A. potatorum ( Torres et al., 2015a ), and A. angustifolia ( Arias-Medellín et al., 2016 )], compared with the large number of species used. However, the few studies available for this genus allow identifying some general demographic patterns.…”

Demographic consequences of mutualism disruption: Browsing and big‐headed ant invasion drive acacia population declines

“…We simulated four species interaction scenarios based on the 2 × 2 combination of P. megacephala invasion and exposure to LMH. For tree populations exposed to LMH in uninvaded areas, we expected population growth rates ( λ ) not to differ statistically from 1.0 (i.e., population stability, inferred via bootstrapped confidence intervals of stochastic λ [e.g., Arias‐Medellín et al, 2016; Layton‐Matthews et al, 2018]) over the course of 4 years (Figure 1, Scenario 1). This scenario represents a pre‐invasion (reference) population, which serves as a control for comparisons to our other treatments.…”

Comparative study of steroidal sapogenins content in leaves of five Agave species

“…Its natural populations are small and decimated due to mature individuals (7–8 years old) being harvested just before flowering to produce mezcal in artisanal distilleries 7 In this region, the species A. angustifolia Haw. is also collected, which is characterized by its grayish‐green leaves, 60–120 cm long, with thorns on the edges of the leaves and a dark thorn at the tip 8 …”