1 Stage projection (Lefkovitch) matrices for 21 species of woody plants and 45 herbaceous perennials were extracted from the plant demographic literature or compiled from published data. 2 Each matrix was divided into six regions representing: 1, recruitment of seeds to the seed pool; 2, recruitment of seedlings or juveniles from current seed production; 3, clonal growth; 4, retrogression, due to plants decreasing in size or reverting in stage; 5, stasis, (survival from one year to the next in the same stage class); 6, progression to later stage classes. 3 Matrix analysis was used to calculate the finite rate of increase X for each population and to calculate the elasticities of each transition coefficient in the matrices. Elasticities were summed within each of the six regions of the matrix to give measures (E1 -E69 respectively) of the importance of each component of the life cycle to X and fitness. 4 Herbs as a group differed significantly from woody plants in most of these components. Seedling recruitment was more important in herbs than woody plants. Retrogression occurred only in herbs, particularly those with a tuber. Stasis occurred in nearly all species, but was most important in woody plants. Progression was more important than fecundity in almost all species. 5 Trade-offs among life cycle components were determined from correlation matrices of r (= ln X) and elasticities E1 -E6 for the whole sample and for herbs and woody plants separately. As a whole, r was positively correlated with elasticities for fecundity (E1 + E2) and growth (E3 + E6) and negatively correlated with survival (E4 + E15). In clonal herbs, fecundity and clonal growth were negatively correlated. 6 The division of elasticities into three major components (growth, G = E3 + E6; fecundity, F = E1 + E2; and survival, L = E4 + E5) allowed us to construct triangular plots in G-L-F space. This was done separately for iteroparous forest herbs, iteroparous herbs from open habitats, semelparous herbs and woody plants. Each of these four groups occupied a distinct position in G-L-F space. Within woody plants, shrubs of fire-prone habitats occupied the end of the distribution with the lowest survival elasticity. 7 It is argued that the demographic approach to the classification of distinct ecological groups offers new insights into the relationship between life history and habitat.

Priming has proved to enhance seed germination, but most of the research dealing with this topic has been carried out with cultivated species. The potential applications that this process has on wild species, which can be useful for restoration, are usually overlooked. This study analyses the germination response after natural priming and hydropriming of Penstemon roseus and Castilleja tenuiflora, two perennial herbs growing in a protected area known as ‘Parque Ecológico de la Ciudad de México’. Photoblastism was evaluated for both species. Seeds were exposed to a hydration/dehydration cycle and then placed in germination chambers to determine responses to hydropriming. To identify the effects of natural priming, seeds were buried in natural conditions and then recovered every two months and placed in germination chambers. Germination percentages and rates were then quantified. Both species proved to have permeable seed coats. Penstemon roseus seeds are positive photoblastic whereas C. tenuiflora seeds are indifferent to light. Priming methods increased C. tenuiflora germination rates, but they did not affect germination capacity. For P. roseus, priming methods did not improve germination rates, and germination capacity of recovered seeds decreased after the rainy season, suggesting that P. roseus forms a short-term, transient, seed bank. The germination strategies of these two species allow them to occupy suitable microsites for germination and establishment. These responses can be helpful in developing restoration programmes based on the accelerated establishment of native and characteristic successional species.

Castilleja tenuiflora is a facultative root hemiparasitic plant that has colonized a disturbed lava field in central Mexico. To determine the effects of hemiparasitism on the population dynamics of the parasite, we identified a set of potential hosts and quantified their effects on the vital rates of C. tenuiflora during 2016–2018. Connections between the roots of the hemiparasite and the hosts were confirmed with a scanning electron microscope. Annual matrices considering two conditions (with and without potential hosts) were built based on vital rates for each year, and annual stochastic finite rate growth rates (λs) were calculated. Plants produced more reproductive structures with hosts than without hosts. A Life Table Response Experiment (LTRE) was performed to compare the contributions of vital rates between conditions. We identified 19 species of potential hosts for this generalist hemiparasite. Stochastic lambda with hosts λs = 1.02 (CI = 0.9999, 1.1) tended to be higher than without them λs = 0.9503 (CI = 0.9055, 0.9981). The highest elasticity values correspond to survival. LTRE indicated that the most important parameters are survival and fecundity; the total contribution of fecundity (0.0192) to the difference in growth was three times lower than that of survival (0.0603). Piqueria trinervia was the most abundant host, and C. tenuiflora had a higher lambda with it than with other species. Individuals can grow alone, but hosts can have a positive effect on the vital parameters of C. tenuiflora and on λ.

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