European pond turtles (Emys orbicularis) as alternative dispersers of “water-dispersed” waterlily (Nymphaea alba)

Abstract

Nymphaea alba (white waterlily) is an aquatic plant adapted to dispersal by water. This study assesses the potential of Emys orbicularis (European pond turtle) to disperse seeds undamaged and to contribute to dispersal between isolated water bodies, which cannot be achieved by the standard hydrochorous mode of dispersal. We investigated the effect of seed passage through the turtles' digestive tract on seed viability and germination over a 2-y period. The effect of gut passage differed between seeds germinated in light and in darkness. In light, gut passage delayed germination, both within the first year and between years, but total germination at the end of the study did not differ from that of control seeds. In darkness, gut passage delayed germination within the first year, but accelerated it in the long term, and total germination was higher than that for control seeds. Emys orbicularis can be regarded as a legitimate disperser of Nymphaea alba. The turtles move between different water bodies and can disperse seeds when they do so, which is essential for the colonization or re-colonization of isolated water bodies.