Advantages of vivipary in Echinocactus platyacanthus , an endemic and protected Mexican cactus species

Vivipary is the germination of seeds within a fruit before they are shed from the parent plant. Vivipary occurs in a broad range of habitats and species including cacti. The advantages of vivipary in Cactaceae have been poorly studied. Echinocactus platyacanthus is a viviparous endemic and endangered cactus from Mexico. In this study, we determined the vivipary incidence and its benefits in this species. We collected mature fruits of this plant from the fields of two municipalities, Guadalcázar and Vanegas, located in the southern part of the Chihuahuan Desert in San Luis Potosí, México. The seeds in these fruits were classified into three categories: (1) non-viviparous (N-V; from fruits without viviparous seeds), (2) non-viviparous from viviparous plant (N-V-V; from fruits without germinated seeds belonging to a plant with at least one fruit with germinated seeds), and (3) viviparous (V-V, from fruits that contain at least one germinated seed). We evaluated seed germination under three water potential treatments (0, −0.2, and −0.4 MPa). Vivipary incidence was independent of the site. However, we found higher germination of N-V-V and V-V seeds than N-V seeds. Our findings suggest an advantage of viviparous (N-V-V and V-V) phenotypes in germinability, which increases the possibilities of survivorship of wild E. platyacanthus populations and contributes to their natural regeneration in arid environments.