title: Effects of bird ingestion on seed germination of Sorbus commixta.
abstract: To determine the effects of ingestion by birds on seed germination, we performed germination experiments in the field and laboratory with Sorbus commixta. The germination of four groups of seeds was compared: ingested seeds, seeds defecated in feces after feeding of fruits to birds; extracted seeds, seeds deliberately extracted from the fruit pulp; juiced seeds, seeds plus the juice of the pulp after seeds had been deliberately extracted from the pulp; intact seeds, seeds in untreated intact fruits. In the laboratory, intact and juiced seeds hardly germinated, but ingested and extracted seeds germinated. Thus, the pulp and its juice appeared to inhibit germination, but seeds could germinate without ingestion by birds once the seeds had been manually extracted from the pulp. In the field, intact fruits did not germinate in the first spring, because the seed was still covered with pulp. The pulp of intact seeds decomposed during the first summer, and thus, the seeds had the potential to germinate during the second spring. In fact, most intact seeds do not germinate during the second spring either, since they lose their viability during the first summer. Thus, under natural conditions, most seeds of Sorbus commixta cannot germinate without bird ingestion.
authors.affiliation: Department of Forest Science, Faculty of Agriculture, Laboratory of Silviculture, Hokkaido University, Sapporo 060-8589, Japan, , , , , , JP.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Yagihashi
authors.affiliation: Department of Bioenvironment, Faculty of Agriculture, Yamagata University, Tsuruoka 997-8555, Japan Fax: +81-235-28-2928; e-mail: hayasida@tds1.tr.yamagata-u.ac.jp, , , , , , JP.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Hayashida
authors.affiliation: Department of Forest Science, Faculty of Agriculture, Laboratory of Silviculture, Hokkaido University, Sapporo 060-8589, Japan, , , , , , JP.
authors.forename: Toshizumi
authors.initials: T
authors.lastname: Miyamoto
keywords: Fruit pulp; Inhibition of germination; Key words Bird ingestion