Ombrohydrochory in Thismia panamensis (Standley) Jonk: a mycoheterotrophic species in Brazilian Cerrado forests.

Species of the genus Thismia Griff. are small herbs, considered mycoheterotrophic due to an intimate relationship with fungi. They are achlorophyllous, with complex floral structure but little information on reproductive strategies. This study evaluated structural and ecological aspects associated with the dispersal of seeds of Thismia panamensis (Standley) Jonk. The study was carried out in a forest fragment in the Brazilian Cerrado. During the reproductive period, 36 individuals were monitored for spatial distribution of the population and their fruits were collected. Samples were subjected to light microscopy and microtomography techniques, in addition to an experiment to evaluate seed dispersal by water droplets. Thismia panamensis is up to 8-cm tall, with a tuberous root and stem, without leaves. Its fruit is dehiscent, cup-shaped, 5 ± 1 mm in diameter, containing 219.33 ± 106.70 seeds, with an average length of 0.55 ± 0.07 mm. The seeds are exposed, and their coat has a thin and lignified wall. Accumulation of secretions was observed inside the fruits. The innermost cell layer of the ovary showed typical characteristics of aquiferous parenchyma. Water splash experiments showed that the seeds reached an average distance of 44.04 ± 26.58 cm. Each splash contained, on average, 1.50 ± 1.23 seeds, with 75% of the splashes containing a single seed. A total of 239 seeds were counted in the 163 splashes evaluated. The data show potential seed dispersal by ombrohydrochory in T. panamensis, favouring its maintenance in the study area and reflecting its clumped spatial distribution.