Germination success of temperate grassland species after passage through ungulate and rabbit guts

Abstract

Summary Dispersal of endozoochorous seed involves uptake by a herbivore and exposure to different kinds of digestive fluids during passage through the gastrointestinal tract. Assessment of the ecological significance of endozoochory therefore requires examination of the survival rate of seeds during this phase. A feeding experiment was conducted with seeds of 19 plant species that are important constituents of temperate semi‐natural grasslands and five animal species (two ruminants, two colon fermenters and a caecum fermenter). Mean retention time of germinable seeds was determined and seed characteristics that might affect germination success were examined. Gut‐passed seeds had a much lower germination success (0–26%) than non‐gut‐passed seeds either sown directly on dung (2–79%) or bare soil (7–89%). Relative germination success differed considerably between both plant and animal species. This may result from complex, herbivore‐specific interactions between animal behaviour (chewing, digestion) and seed characteristics. Germination success was positively related to seed longevity and, remarkably, also to seed mass and seed shape. Retention time of germinable seeds varied from c . 12 hours (rabbit) to 72 hours (ungulates), potentially allowing long‐distance seed dispersal. This study highlights both the complex interaction between animal species and seed characteristics and the considerable differences in germination success of gut‐passed seeds, which exist between plant species. The loss of seed germinability after gut passage calls into question the ecological significance of endozoochory, although the costs of other dispersal mechanisms remain to be tested.