Density-dependent adult recruitment in a low-density tropical tree.
Density-dependent adult recruitment in a low-density tropical tree.
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DOI：
10.1073/pnas.1800353115
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发表时间：
2018-10-30
影响因子：
11.1
通讯作者：
Hubbell SP
中科院分区：
文献类型：
--
作者：
Kellner JR;Hubbell SP
在种群动态中，一类重要的负反馈是宿主特异性敌人的活动，它们不成比例地杀死了它们常见的地方的个体。这种机制被称为Janzen-Connell假说，被认为是热带森林中大量物种的决定因素。一个关键的假设，但未经检验的假设是，密度依赖的死亡率之间的幼树减少成年招聘的概率。在这里，我们表明，成人招聘是负密度依赖于低密度的树人口使用高分辨率遥感的时间序列。然而，这种密度依赖性不足以稳定成年人口的规模，这在规模上显着增加。Janzen-Connell假说是一个众所周知的解释，解释了为什么热带森林有大量的树种。一个基本的预测的假设是，成年招聘的概率是在高同种成年密度的地区，介导的密度依赖性死亡率在少年生命阶段的模式。虽然有强有力的证据表明，在许多树种的种子，幼苗和树苗遭受同种密度依赖性死亡率，没有研究表明，成年树招聘是负密度依赖性。密度依赖的成年人招聘是必要的Janzen-Connell机制，以调节树木种群。在这里，我们报告密度依赖的成人招聘的Handroanthus guayacan，风分散的新热带树冠树种的人口。我们使用高分辨率的遥感数据，以跟踪个别树木的能力，花在巴拿马的低地潮湿的森林景观，并分析这些数据在贝叶斯框架类似的捕获-再捕获分析。我们独立量化的概率成年树招聘和检测，成年招聘是负密度依赖。成年人招募的年化概率为3.03%-1年。尽管在成虫补充中检测到负密度依赖性，但这不足以稳定H.瓜亚坎，在观察的十年中，其规模大大增加。
An important class of negative feedbacks in population dynamics is the activity of host-specific enemies that disproportionately kill individuals in locations where they are common. This mechanism, called the Janzen–Connell hypothesis, has been proposed as a determinant of the large number of species in tropical forests. A critical but untested assumption of the hypothesis is that density-dependent mortality among juvenile trees reduces the probability of adult recruitment. Here, we show that adult recruitment is negatively density dependent in a low-density tree population using time series from high-resolution remote sensing. However, this density dependence was not strong enough to stabilize the size of the adult population, which increased significantly in size. The Janzen–Connell hypothesis is a well-known explanation for why tropical forests have large numbers of tree species. A fundamental prediction of the hypothesis is that the probability of adult recruitment is less in regions of high conspecific adult density, a pattern mediated by density-dependent mortality in juvenile life stages. Although there is strong evidence in many tree species that seeds, seedlings, and saplings suffer conspecific density-dependent mortality, no study has shown that adult tree recruitment is negatively density dependent. Density-dependent adult recruitment is necessary for the Janzen–Connell mechanism to regulate tree populations. Here, we report density-dependent adult recruitment in the population of Handroanthus guayacan, a wind-dispersed Neotropical canopy tree species. We use data from high-resolution remote sensing to track individual trees with proven capacity to flower in a lowland moist forest landscape in Panama and analyze these data in a Bayesian framework similar to capture–recapture analysis. We independently quantify probabilities of adult tree recruitment and detection and show that adult recruitment is negatively density dependent. The annualized probability of adult recruitment was 3.03% ⋅ year−1. Despite the detection of negative density dependence in adult recruitment, it was insufficient to stabilize the adult population of H. guayacan, which increased significantly in size over the decade of observation.
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