Coryphantha werdermannii

Structure and identification

The stem is solitary, ovoid or columnar, with shallow fibrous roots. In the young stage, thin white lateral spines cover small tubercles. As the plant enters the adult stage, tubercle arrangement and size change, lateral spine number increases, and stronger, dark central spines appear. Clustered upper spines cover the woolly apex. Flowers are broad and yellow. [Dicht and Lüthy 2005, p. 169–170]

Habitat and variation

The monograph documents sites in the Cuatro Ciénegas valley in Coahuila, on gravelly slopes and plains. Later demographic studies concern specific populations in this valley. Their results separate conditions for the appearance of small plants from adult survival and reproduction, relating them to local human pressure. [Dicht and Lüthy 2005, p. 169–170; 2011, p. 510–515; 2015, p. 74–80] [Portilla-Alonso and Martorell 2011, p. 169–170; 2011, p. 510–515; 2015, p. 74–80] [Martorell et al. 2015, p. 169–170; 2011, p. 510–515; 2015, p. 74–80]

Recruitment and survival in Cuatro Ciénegas

In 2005–2006, three populations in the Cuatro Ciénegas valley were tracked, with samples of 87, 101 and 124 plants. Habitats differed in the intensity of long-term human impact. In a field experiment, 1000 seeds were sown in each population. By January 2006, only four seedlings had appeared, two at each of two more transformed sites. None were found at the least transformed site. The small number of seedlings limited estimation of recruitment, the addition of new individuals to a population. [Portilla-Alonso and Martorell 2011, pp. 510–512, Table 1–3]

Models with six plant size classes showed different mechanisms of population change. At the least transformed site, seedling appearance was important. At the moderately transformed site, population persistence depended more on the survival of adult plants, damaged by cattle among other causes. At the most transformed site, growth was limited. Forecast results changed with assumptions about rare recruitment. Observations covered one annual interval and three different sites. [Portilla-Alonso and Martorell 2011, pp. 512–515]

A broader study published in 2015 combined density and reproductive data from demographic models with models of potential range. Density was positively associated with signs of grazing and the proportion of bare soil, and negatively with shrub cover. Human activity was also associated with fewer reproductive structures. Simulations indicated greater sensitivity of population growth to the loss of adult plants than to the loss of a similar proportion of seeds. The relationship between density and grazing remains a habitat observation, while the simulations describe effects under the assumed parameters. [Martorell et al. 2015, p. 74–79, tab. 1–3, ryc. 2–4]

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