Endangered globose cactus Melocactus lanssensianus P. J. Braun depends on lizards for effective seed dispersal in the Brazilian Caatinga

Effective seed dispersal is essential to plant reproductive success. In this study, we evaluated the fruiting phenology, fruit traits, and seed dispersal of the endangered globose cactus Melocactus lanssensianus in the Brazilian Caatinga over 1-year period. We carried out monthly phenological monitoring, focal observations, and germination experiments, to identify the effective seed dispersers of this cactus. M. lanssensianus exhibited a continuous, non-seasonal fruiting pattern, with peaks during both the dry and rainy seasons. We observed seed dispersal by Tropidurus semitaeniatus and T. hispidus lizards. In 116 h of focal observations, lizards made 76 visits during different times of day, with a mean dispersal distance of 5 m. Both lizard species showed more frugivory interactions in the dry season, with peak visits in water-stressed months. We collected 132 intact and viable seeds from 29 fecal samples, specifically from T. semitaeniatus (N?=?20 scats; 122 seeds) and from T. hispidus (N?=?9 scats; 10 seeds). Germination experiments with seeds consumed by T. semitaeniatus, washed seeds and control seeds revealed that 85% of seeds found in T. semitaeniatus feces germinated compared to 41% of the control seeds. Frequency, pattern of visits and germination rates indicate T. semitaeniatus is an effective seed disperser of M. lanssensianus. Continuous production of fleshy fruits and environmental conditions of the Caatinga ecosystem favor the close dependent mutualistic interaction reported here.