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Riparian species colonize habitats induced by disturbance along the hydrologic Churince System in Cuatro Cienegas (Coahuila, Mexico), like sinkholes and the river and lacustrine dry beds, the dry riverbank, and the surrounding flatland. Among the colonizers of newly opened habitats, dominant species are scarce. They include Samolus ebracteatus var. coahuilensis, a perennial sprawling, hydrophilous herb that can form clones; Flaveria chlorifolia, an erect gypsovage perennial herb that can also grow as a shrub; and Eustoma exaltatum, a herb that usually behaves as an annual, but can also behave as a short-lived perennial. The life cycles and population dynamics of these species reflect short- and long-term responses to these heterogeneous, unpredictable, and disturbed habitats. Two main strategies of the life cycle of F. chlorifolia and E. exaltatum are key for their survival, especially in bare zones where abiotic conditions are harder: deciduous leaves which are lost during the cold season after producing flowers and fruits, and regrowth of new branches and leaves from their basal stem. The capacity of E. exaltatum to shift from an annual life cycle to a short-lived perennial when conditions allow it depends on root development and regrowth. S. ebracteatus var. coahuilensis is not completely deciduous and perennates through the activation of under or above ground meristems, and, as F. chlorifolia, it can produce underground leaves that emerge afterwards. The maintenance of living stems is crucial for the survival of individuals and permanence of these populations. |
