Name and distribution
Epithelantha ilariae is an accepted species in POWO, native to Nuevo León in Mexico. Donati and Zanovello published the name in 2010. [2-WWW]
Climate at the boundary of two vegetation formations
Aquino and colleagues describe E. ilariae near the transition from the Chihuahuan Desert to Tamaulipan thornscrub. Annual rainfall assigned to its sites in the climate grid used was about 544 mm, higher than in the environments of most other species analysed. This is a description of the climate of the sites derived from maps. [Aquino et al. 2021, pp. 4525–4527, Fig. 4]
In the comparison of soil categories, E. ilariae sites were associated with typical kastanozems. In the tree based on plastid DNA, the species belonged to a lineage including E. bokei, E. micromeris and E. spinosior, among others. Rainfall differences indicate environmental variation even among closely related members of the genus. [Aquino et al. 2021, p. 4524–4527, ryc. 2–4]
A long flower opening in the evening
The flower of Epithelantha ilariae was the longest in the 2019 study. It measured 17–18 mm from the base of the pericarpel to the tip of the longest tepal. The key also distinguished evening flower opening. There were fewer than 40 spines per areole, without the persistent projections characteristic of E. bokei. Combining flower-opening time with flower length allowed E. ilariae to be separated from species with smaller daytime flowers. [Aquino et al. 2019, p. 606, 610, 612, 615; ryc. 5G–H]
The morphological study covered 15 adult plants from three sites in Nuevo León. The DNA samples formed a distinct sister lineage to the remaining members of the first of the two major Epithelantha groups. Flower structure and position in the tree provided consistent evidence for the species' distinctness. Evening opening alone does not establish the pollinator's identity, which was not tracked in this study. [Aquino et al. 2019, p. 601, 605–607, 612, 614; tabela 5, ryc. 3]