Sex ratio and gender-dependent neighboring effects in Podocarpus nagi, a dioecious tree
Sex ratio and gender-dependent neighboring effects in Podocarpus nagi, a dioecious tree
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DOI：
10.1007/s11258-005-2210-2
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发表时间：
2005-04
期刊：
影响因子：
1.7
通讯作者：
Satoshi Nanami;H. Kawaguchi;T. Yamakura
中科院分区：
文献类型：
--
作者：
Satoshi Nanami;H. Kawaguchi;T. Yamakura
本文分析了黄山竹柏的性比、生长速率和个体间距。日本奈良市米卡萨。胸径≥ 5cm的生殖树的性比明显偏雄。< 20 cm和≥ 50 cm径级的性比偏向雄性，而20 ≤胸径< 50 cm径级的性比不偏离1：1。生长速率与树的大小在男性，但不是在女性。雄性的早熟和活力表明，两性之间的生殖成本差异导致了性别比的偏差。对生殖树位置的随机标记试验表明，在< 30 cm的级中，雌雄个体随机分布，且相互独立。在≥ 30 cm的类别中，雄性动物明显聚集，而雌性动物随机分布。男性和女性表现出明显的排斥，即，性别的空间隔离内和间性的影响，拥挤的增长率的邻居是显着的女性，但不为男性。最大的竞争干扰观察到在5米的距离，这大约对应于大的男性和大的男性和女性之间的显着排斥距离的集群的半径。这些结果表明，性别差异的敏感性局部拥挤有关的性别依赖的空间格局的形成。形成女性排斥男性团块和男性偏向的性别比例可能会加剧男性附近的再生的概率下降，这一物种的种子传播范围有限，从而促进与其他物种共存。
We analyzed sex ratio, growth rates, and spacing among individuals ofPodocarpus nagi, a dioecious tree, on Mt. Mikasa, Nara City, Japan. The sex ratio of reproductive trees ≥ 5 cm in stem diameter at breast height (dbh, 130 cm above ground level) was significantly male-biased. The sex ratio was male-biased in the < 20 cm and ≥ 50 cm size classes, while it did not depart from 1:1 in the 20 ≤ dbh < 50 cm class. Growth rate varied with tree size in males but not in females. The precocity and vigor of males suggests that differences in reproductive costs between sexes induce the biased sex ratio. Random labeling tests on the positions of reproductive trees showed that in the < 30 cm class, males and females were distributed randomly and independently from each other. In the ≥ 30 cm class, males were significantly clumped, whereas females were randomly distributed. Males and females showed significant repulsion, i.e., a spatial segregation of sexes. Both intra- and intersexual effects on the growth rate of crowding by neighbors were significant for females, but not for males. Maximum competitive interference was observed at a distance of 5 m, which corresponded approximately to the radius of clumps of large males and to the significant repulsive distance between large males and females. These results suggest that sexual differences in sensitivity to local crowding are related to the formation of gender-dependent spatial patterns. Formation of female-repulsive male clumps and a male-biased sex ratio may intensify the decreased probability of regeneration near males, as suggested by the limited seed-dispersal range of this species, thereby promoting coexistence with other species.