Thanks for the info about CICY. Actually, I wasn’t aware of this organization. It seems like a great resource! I hadn’t seen a live picture of Echeandia campechiana previously.
I do see the resemblance between potato tree flowers (Solanum species) and Echeandia luteola. It’s the fused anthers like you say. About half of Echeandia species have fused anthers and the other half have free anthers. Aside from the fused anthers, other characteristics are rather different. Echeandia is a fairly typical monocot, with flowers that have 6 “tepals” (3 petals and 3 sepals that all look pretty similar) and narrow, slightly fleshy leaves. Dicots like Solanum species don’t have the three-fold symmetry of monocots. Solanum has 5 petals and much more “leaf-like” leaves.
The relationship to rain lilies (Zephyranthes) is actually a lot closer. Both Echeandia and Zephyranthes are within the Asparagales order of monocots. Even so, they’re really distant relatives, with their last common ancestor being about 120 million years ago.
Echeandia is a much closer cousin to Agave species such as Agave fourcroydes
(Henequen) and Agave sisalana (Sisal). The two genera probably diverged less than 40 million years ago and maybe as recently as 20 million years.
Robert Cruden was the botanist who described most species of Echeandia, including the two on the Yucatan Peninsula. In 1999 he divided the roughly 80 species into two subgenera. Both E. luteola and E. campechiana are in Echeandia subgenus Mscavea, which he named after Marion Stilwell (M.S.) Cave, a research collaborator at U.C. Berkeley. Cruden distinguished Mscavea species from subgenus Echeandia species as follows:
In contrast, in subgenus Mscavea, the flowers open late in the morning or the afternoon, 24 of 25 species have narrowly elliptical inner tepals, and, in 22 of 23 species for which I have reasonable data, the maximum width of the inner tepal was 4.5 mm. Most of the species have white flowers (22/25), two have cream-colored flowers, one has orange flowers, and one, possibly two, species include orange- or yellow-flowered populations.
Cruden specifically says that E. luteola flowers open in the early afternoon. He doesn’t mention a flowering time for E. campechiana but you should probably expect it also to be closed up in the mornings. I don’t know that either species is weather-dependent, and typically Echeandia plants will have many flowers on the stem, in groups of 2 or more, with individual flowers maturing successively from the lowest ones to the tip. In terms of where to find these plants, E. luteola might be anywhere in a forested area in the northern half of the peninsula. Like CICY indicates, E campechiana has mostly been recorded in Campeche state, but (based on that one record from near Sayil) you might come across it in the Puuc region as well.
Turning to the Iris family plants, I realize that the one iNat observation of Eleutherine latifolia on the peninsula is way south in Campeche state, so forget about that one! Alophia silvestris and Cipura campanulata are both native to Yucatan. Both seem to flower for much of the year, with a peak in July–September, so you certainly could come across them. Whether or not you come across any of these plants I’ll be interested to see your observations!