Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada.
Department of Biology, University of British Columbia, Kelowna, BC, Canada.
PLoS One. 2024 Nov 6;19(11):e0311809. doi: 10.1371/journal.pone.0311809. eCollection 2024.
Berries are a staple of bear diets during late summer and fall in the southern Rocky Mountains, enabling bears to build up fat reserves and prepare to enter torpor during winter. In turn, bears can benefit fruiting shrubs through dispersal of their seeds. Bears are highly mobile species and seed passage through their guts (endozoochory) can influence seed germination in three ways: deinhibition (removal of germination inhibiting compounds), scarification (mechanical or chemical alteration) and fertilization (enhancement of germination from increased nutrients). We conducted a germination experiment to assess the ways each mechanism of bear endozoochory affects germination success of huckleberry (Vaccinium membranaceum.) in the southern Canadian Rocky Mountains. The potential for bears to act as long-distance seed dispersers was also investigated, using a combination of available literature on bear gut retention times and movement data of 74 GPS radio-collared grizzly bears. Deinhibition had a positive significant impact (28.5% germination for the Seeds from Berry treatment compared to 0.2% for Whole Berry at 60 days), while scarification and fertilization did not have detectable positive effects on huckleberry germination success. These results suggest that the removing germination-inhibiting compounds in berry pulp is the primary mechanism through which endozoochory can increase germination in huckleberry seed. We estimated that 50% of the seeds defecated by bears in the region are dispersed 1.1 km away from feeding places (and up to 7 km). The surfaces covered by the seed shadow was up to 149.6 km2, demonstrating that bears can act as effective vectors of seeds over long distances. Endozoochory bolsters the germination success of seeds from fruiting shrubs, and enables seeds to spread to new locations using bears as dispersal agents. Development, resource extraction, and climate change may disrupt the beneficial relationship between bears and huckleberries, where huckleberries help bears gain fat, and bears help spread huckleberry seeds-a process that may become increasingly important as climate change alters habitats.
浆果是落基山脉南部黑熊夏季和秋季饮食的主要组成部分，使它们能够积累脂肪储备，并准备在冬季进入冬眠状态。反过来，熊可以通过传播种子使结果的灌木受益。熊是高度移动的物种，其肠道内的种子传播（内动物传播）可以通过三种方式影响种子萌发：去抑制（去除萌发抑制化合物）、刻蚀（机械或化学改变）和施肥（通过增加养分增强萌发）。我们进行了一项萌发实验，以评估每种熊内动物传播机制对南加拿大落基山脉蔓越莓（ Vaccinium membranaceum.）萌发成功率的影响。还利用关于熊肠道保留时间的现有文献和 74 只 GPS 无线电项圈灰熊的运动数据的组合，研究了熊作为长距离种子传播者的潜力。去抑制作用具有积极的显著影响（与整个浆果相比，Berry 处理的种子在 60 天时的萌发率为 28.5%，而 Whole Berry 为 0.2%），而刻蚀和施肥对蔓越莓萌发成功率没有可检测的积极影响。这些结果表明，去除浆果果肉中的萌发抑制化合物是内动物传播通过增加蔓越莓种子萌发的主要机制。我们估计，该地区 50%的熊粪便中的种子在距离觅食地 1.1 公里的地方被传播（最远可达 7 公里）。种子阴影覆盖的面积最大可达 149.6 平方公里，这表明熊可以作为远距离种子的有效传播媒介。内动物传播促进了结果灌木种子的萌发成功率，并使种子能够在熊作为传播媒介的情况下传播到新的位置。发展、资源开采和气候变化可能会破坏熊和蔓越莓之间的互利关系，在这种关系中，蔓越莓帮助熊获得脂肪，而熊帮助传播蔓越莓种子——随着气候变化改变栖息地，这一过程可能变得越来越重要。
