Dung longevity influences the fate of endozoochorically dispersed seeds in forest ecosystems Bogdan Jaroszewicz and Ewa Pirożnikow Abstract: Many studies show large discrepancies between the potential (studied in the greenhouse) and realized (studied in the field) effects of endozoochory. The influence of environmental conditions on the fate of endozoochorically dispersed seeds and subsequent plant establishment is still not well understood. We addressed this issue by studying the viable seed content of the dung of European bison (Bison bonasus L.) by means of seedling germination in the greenhouse and in two forest habitats in Białowieża Primeval Forest. The number of seedlings and the number of plant species that emerged from 1 L of feces were positively correlated with dung longevity. Generative shoots were produced by plants only in coniferous forest. Their number was positively correlated with dung longevity and with light availability. Germination of seeds from bi- son feces was higher in coniferous forest than in deciduous forest but did not differ between open- and closed-canopy plots within the same habitat. We conclude that (i) seed germination and plant establishment after endozoochorous dispersal is in- fluenced by dung longevity; (ii) the number of generative shoots produced by endozoochorously dispersed plants is influ- enced by dung longevity and light availability; (iii) seeds of some plant species, present in dung, stay viable for at least 3 years. Key words: European bison, Bison bonasus, Białowieża Forest, plant establishment, generative success. Résumé : Plusieurs études montrent de grands écarts entre les effets potentiels de l’endozoochorie (études en serres) et réa- lisés (études sur le terrain). On ne comprend pas toujours très bien l’influence des conditions environnementales sur le sort des graines dispersées par endozoochorie et l’établissement subséquent des plantes. L’auteur a examiné cette question en étudiant le contenu en graines viables de fèces de bison européen (Bison bonasus L.), en faisant germer les graines en serre et dans deux habitats forestiers de la forêt primitive de Bialowieza. Le nombre de plantules et le nombre de plantes qui ont émergé à partir de 1 litre de fèces montrent une corrélation positive avec la longévité des fèces. Ce n’est que dans la forêt de conifères qu’il y a eu production de tiges génératives. On observe une corrélation positive entre leur nombre et la longé- vité des fèces ainsi que la disponibilité de la lumière. Une plus forte germination des graines à partir des fèces de bison sur- vient dans la forêt de conifères que dans la forêt feuillue, mais ne diffère pas entre les parcelles sous une canopée ouverte ou fermée, dans le même habitat. L’auteur conclut que (i) la longévité des fèces influence la germination des graines et l’é- tablissement des plantes, suite à la dispersion par endozoochorie; (ii) la longévité des fèces et la disponibilité de la lumière influencent le nombre de tiges génératives produites par les plantes dispersées par endozoochorie; (iii) les graines de certai- nes espèces de plantes présentes dans les fèces demeurent viables pendant au moins 3 ans. Mots‐clés : bison européen, Bison bonasus, forêt de Białowieża, établissement des plantes, succès génératif. [Traduit par la Rédaction] Introduction Viable seeds of many grassland (e.g., Malo and Suárez 1995a; Eycott et al. 2007) and forest (e.g., Schmidt et al. 2004; Eycott et al. 2007; Jaroszewicz et al. 2009) plant species are found in the dung of large herbivores. The potential impor- tance and role of endozoochory in plant dispersal has been widely studied and discussed (e.g., Myers et al. 2004; Cosyns and Hoffmann 2005; Eycott et al. 2007). The role of endozoo- chory in the shaping of vegetation is considered by many au- thors to be underestimated (e.g., Heinken et al. 2002; Schmidt et al. 2004; Eycott et al. 2007). These papers are based on studies of seed germination carried out in greenhouse condi- tions, which are assumed to be favourable for most plant spe- cies. They provide information on the potential magnitude of endozoochorous dispersal, which overestimates the real role of herbivores in plant dispersal, measured by the rate of plant es- tablishment in the field (Pakeman and Small 2009). The discrepancy in species composition and number of seedlings emerging from herbivore dung between greenhouse and field conditions is rarely addressed. There are a limited number of studies directly addressing the effect of endozoo- chory by large herbivores upon actual ecosystems (Eichberg et al. 2007; Gower 2008; Jaroszewicz et al. 2008; Pakeman Received 10 May 2011. Accepted 12 September 2011. Published at www.nrcresearchpress.com/cjb on 1 November 2011. B. Jaroszewicz. Białowieża Geobotanical Station, Faculty of Biology, University of Warsaw, 19 Sportowa Street, 17-230 Białowieża, Poland. E. Pirożnikow. Institute of Biology, University of Białystok, 20B Świerkowa Street, 15-950 Białystok, Poland. Corresponding author: Bogdan Jaroszewicz (e-mail: b.jaroszewicz@uw.edu.pl). 779 Botany 89: 779–785 (2011) doi:10.1139/B11-069 Published by NRC Research Press Botany Downloaded from www.nrcresearchpress.com by Dr. Bogdan Jaroszewicz on 11/14/11 For personal use only.