Anthropogenic disturbance driving population decline of a dominant tree in East Asia evergreen broadleaved forests over the last 11,000 years

Abstract

Current biodiversity loss is generally considered to have been caused by anthropogenic disturbance, but it is unclear when anthropogenic activities began to affect biodiversity loss. One hypothesis suggests it began with the Industrial Revolution, whereas others propose that anthropogenic disturbance has been associated with biodiversity decline since the early Holocene. To test these hypotheses, we examined the unique vegetation of evergreen broadleaved forests (EBLFs) in East Asia, where humans have affected landscapes since the early Holocene. We adopted a genomic approach to infer the demographic history of a dominant tree (Litsea elongata) of EBLFs. We used Holocene temperature and anthropogenic disturbance factors to calculate the correlation between these variables and historical effective population size of L. elongata with Spearman statistics, and integrated the maximum‐entropy niche model to determine the impact of climate change and anthropogenic disturbance on fluctuation in its effective population size. We identified 9 well‐defined geographic clades for the populations of L. elongata. Based on the estimated historical population sizes of these clades, all the populations contracted, indicating persistent population decline over the last 11,000 years. Demographic history of L. elongata and human population change, change in cropland use, and change in irrigated rice area were significantly negatively correlated, whereas climate change in the Holocene was not correlated with demographic history. Our results support the early human impact hypothesis and provide comprehensive evidence of that early anthropogenic disturbance may contribute to the current biodiversity crisis in East Asia.题目:早期人类活动导致东亚亚热带常绿阔叶林优势种在过去11,000年间有效种群大小的持续衰退摘要当前生物多样性丧失的主因普遍被认为是人类活动的干扰, 但人类活动何时开始导致地球生物多样性的丧失这一重大的科学问题仍不清楚。一些学者的研究认为, 生物多样性的丧失始于工业革命; 另一些研究者则发现, 人类活动导致的生物多样性下降至少可以追溯到全新世早期。为了检验这两种假说, 我们聚焦于东亚亚热带地区, 该地区的土地开发、作物驯化已至少有近万年的历史。本研究立足东亚亚热带地区的特征植被类型, 即亚热带常绿阔叶林(EBLFs), 选取其优势树种樟科木姜子属黄丹木姜子(Litsea elongata)为研究对象, 基于基因组重测序方法研究黄丹木姜子种群在万年尺度下的动态历史。通过生态位模拟, 相关性分析等方法推测全新世气候变化, 人类活动因素(人口增长变化, 耕地面积变化, 灌溉稻作面积变化)与黄丹木姜子有效种群大小波动之间的相关性。研究结果发现, 依据地理分布范围, 黄丹木姜子的种群可划分为9大地理分支, 种群动态历史揭示其9大分支在11,000年以来有效种群大小持续下降的历史过程。相关性分析发现, 有效种群大小在11,000年以来的下降与东亚亚热带地区人口增长变化, 耕地面积变化, 灌溉稻作面积变化呈现显著的负相关, 而与全新世期间的气候变化则不呈现相关性。本研究结果支持早全新世人类活动干扰的假说, 并且为东亚地区早期人类活动与当今生物多样性危机的关联机制提供了全新的证据和认识。关键词:早期人类活动, 气候变化, 亚热带常绿阔叶林, 全新世, 种群动态历史, 基因组重测序This article is protected by copyright. All rights reserved