Seed predation and dispersal by animals of an endangered endemic species Pinus dabeshanensis

doi:10.17520/biods.2023401

Abstract

Abstract:

Aim: Pinus dabeshanensis, an endemic species in the Dabieshan Mountains, has significant scientific values for studying the taxonomy, phylogenetic relationships, and distribution of the genus Pinus. Currently, the wild population of P. dabeshanensis is severely limited in natural regeneration and is critically endangered. Here, we explored the potential effects of seed predation and dispersal by animals on the regeneration of P. dabeshanensis.
Methods: First, we investigated the seed production of P. dabeshanensis by focusing all the adult trees in two 1-ha plots (n = 88). Second, by tracking the fate of 2,000 seeds, we compared the seed predation and dispersal by animals between P. dabeshanensis and three sympatric tree species. These included two dominant native species, Castanea seguinii and Quercus serrata, and an introduced species Pinus armandii that is a sister species of P. dabeshanensis, which all mainly depend on scatter-hoarding animals for seed dispersal. Third, we compared the visitation frequency of potential seed predators and dispersers between P. dabeshanensis and its sympatric species by using camera-trap surveys.
Results: The results showed that: (1) The seed production of P. dabeshanensis was low, with only 312 cones produced by 21 of the 88 adult trees surveyed, and the seed abortion rate reaching 51.89% ± 0.07% (mean ± SE). (2) A total of 146 cones were collected to assess the seed predation by birds, and 90 of them were pecked by birds which was significantly more than un-pecked cones (n = 56), with an average pecking intensity of 8.94% ± 0.55%. (3) Small rodents and ground-dwelling birds (e.g., Garrulus glandarius) were the main visitors to the seeds in the forest ground, and visitation frequency varied significantly among different tree species. Specifically, for P. dabeshanensis, birds visited the seeds more frequently (n = 77) than rodents (n = 46). (4) Seeds of C. seguinii were harvested the fastest, followed by Q. serrata and P. dabeshanensis, while P. armandii were harvested the slowest. (5) Of the 2,000 seeds released in the forest, 157 seeds were successfully dispersed, including 96 P. armandii seeds and 57 P. dabeshanensis seeds, which were significantly more than C. seguinii (3 seeds) and Q. serrata (1 seed). (6) The seed dispersal distance of C. seguinii was 13.9 ± 4.0 m (mean ± SE), followed by P. dabeshanensis (7.3 ± 0.8 m), P. armandii (3.8 ± 0.4 m) and Q. serrata (1.5 m, only one seed was successfully dispersed).
Conclusion: In conclusion, both rodents and birds are potential seed dispersers of P. dabeshanensis. Compared to sympatric tree species, P. dabeshanensis does not suffer heavy seed predation or limited seed dispersal, indicating that seed predation pressure and seed dispersal limitation do not explain the poor natural regeneration of P. dabeshanensis. In addition, our results suggest that the low seed production and high abortion rate may be important factors hindering the natural regeneration of P. dabeshanensis.

Key words: Pinus dabeshanensis, animal dispersers, seed dispersal, natural regeneration, plant animal interaction

Yang Ding, Yingqun Feng, Jinyu Zhang, Bo Wang. Seed predation and dispersal by animals of an endangered endemic species Pinus dabeshanensis[J]. Biodiv Sci, 2024, 32(3): 23401.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2023401

https://www.biodiversity-science.net/EN/Y2024/V32/I3/23401

Figures/Tables 5

Fig. 1 Comparison of the proportion of visiting frequency of the potential seed predators and dispersers among the four plant species. Different lowercase letters represent significant differences in the proportion of visiting frequency of animals between tree species (P < 0.05). PD, Pinus dabeshanensis; PA, Pinus armandii; CS, Castanea seguinii; QS, Quercus serrata.

Table 1 Summary of the main seed predators and dispersers of the four plant species

动物类群 Animal species	红外相机独立触发事件次数 No. of independent encounter events of the camera traps
动物类群 Animal species	大别山五针松 Pinus dabeshanensis	华山松 Pinus armandii	茅栗 Castanea seguinii	枹栎 Quercus serrata
啮齿动物 Rodents	46	45	114	116
其他哺乳动物 Other mammals	35	90	25	40
松鸦 Garrulus glandarius	68	56	45	63
燕雀 Fringilla montifringilla	6	11	13	9
山斑鸠 Streptopelia orientalis	1	2	6	2
白冠长尾雉 Syrmaticus reevesii	1	0	0	12
怀式虎斑地鸫 Zoothera aurea	1	1	3	2
勺鸡 Pucrasia macrolopha	0	2	1	0

Fig. 2 Survival curve of experimental seeds after being released in the forest

Fig. 3 Seed fates of the four species after being released in the forest. Numbers of seeds are shown in the figure.

Fig. 4 Seed fates of the four plant species. (a) Seed harvested vs. ignored; (b) Removed vs. eaten in situ; (c) Eaten after being removed vs. successfully dispersed; (d) Dispersal distance (mean ± SE) of the successfully dispersed seeds. Different lowercase letters represent significant differences between species (P < 0.05). PD, Pinus dabeshanensis; PA, Pinus armandii; CS, Castanea seguinii; QS, Quercus serrata.

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