Mountain-climbing bears protect cherry species from global warming through vertical seed dispersal.
In a warming climate, temperature-sensitive plants must move toward colder areas, that is, higher latitude or altitude, by seed dispersal [1]. Considering that the temperature drop with increasing altitude (-0.65°C per 100 m altitude) is one hundred to a thousand times larger than that of the equivalent latitudinal distance [2], vertical seed dispersal is probably a key process for plant escape from warming temperatures. In fact, plant geographical distributions are tracking global warming altitudinally rather than latitudinally, and the extent of tracking is considered to be large in plants with better-dispersed traits (e.g., lighter seeds in wind-dispersed plants) [1]. However, no study has evaluated vertical seed dispersal itself due to technical difficulty or high cost. Here, we show using a stable oxygen isotope that black bears disperse seeds of wild cherry over several hundred meters vertically, and that the dispersal direction is heavily biased towards the mountain tops. Mountain climbing by bears following spring-to-summer plant phenology is likely the cause of this biased seed dispersal. These results suggest that spring- and summer-fruiting plants dispersed by animals may have high potential to escape global warming. Our results also indicate that the direction of vertical seed dispersal can be unexpectedly biased, and highlight the importance of considering seed dispersal direction to understand plant responses to past and future climate change.
Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: naoeshoji@affrc.go.jp.
Shoji
S
Naoe
Research Institute for Humanity and Nature, 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto 603-8047, Japan; Center for Ecological Research, Kyoto University, Hirano 2-509-3, Otsu, Shiga 520-2113, Japan.
Ichiro
I
Tayasu
Lake Biwa Environmental Research Institute, 5-34 Yanagasaki, Ohtsu, Shiga 520-0022, Japan.
Yoichiro
Y
Sakai
Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
Takashi
T
Masaki
College of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-8510, Japan.
Kazuki
K
Kobayashi
College of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-8510, Japan.
Akiko
A
Nakajima
Rakuno Gakuen University, Ebetsu, Hokkaido, 069-8501, Japan. (Previously: College of Bioresource Sciences, Nihon University, Japan).
Yoshikazu
Y
Sato
Department of Forest Science, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan. (Previously: Ibaraki Nature Museum, Japan).
Koji
K
Yamazaki
Laboratory of Biodiversity Science, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
Hiroki
H
Kiyokawa
Tokyo University of Agriculture and Technology, 3-5-8 Saiwai, Fuchu, Tokyo, 183-8509, Japan.
Shinsuke
S
Koike
D000818:Animals; D057232:Global Warming; D010103:Oxygen Isotopes / Q000032:analysis*; D012621:Seasons; D058614:Seed Dispersal; D013696:Temperature; D001503:Ursidae / Q000145:classification
D010103:Oxygen Isotopes