Conservation Genomic Analysis of the Asian Honeybee in China Reveals Climate Factors Underlying Its Population Decline

SIMPLE SUMMARY: The Asian honeybee is an important pollinator in Asia that plays a vital role in maintaining biodiversity. Based on field surveys and personal observations, Asian honeybee populations in China were reported to be undergoing significant decline in 2005. However, a more recent survey revealed that its populations are stable and even slightly increased in some regions of China. Therefore, the status of declining Asian honeybee populations in China is still unclear. In this study, taking advantage of the abundant genomic data for Asian honeybees, we employed conservation genomics methods to understand the declining status of Asian honeybee populations in China and identify the causing factors. We found that most of the Asian honeybee populations of China showed a relatively stable population size during recent years, however, the population in Bomi, Tibet was in a serious decline and low temperatures and strong ultraviolet radiation should have synergistically led to this decline. Our study provides insights into the dynamic changes of Asian honeybee populations in China and identifies climate factors that underlie its population decline, which are valuable for the conservation of this important pollinator. ABSTRACT: The Asian honeybee, Apis cerana, is one of the most important native pollinators in Asia. Asian honeybees were believed to be under significant decline in China based on a report in 2005. On the contrary, a recent survey revealed that Asian honeybee populations in China are stable and even slightly increased in some regions. Therefore, the declining status of A. cerana populations in China is still unclear. Taking advantage of the abundant, publicly available genomic data for Asian honeybees in China, we employed conservation genomics methods to understand if Asian honeybee populations in China are declining and what the underlying climate factors are. We reconstructed the changes of effective population size (Ne) within the recent past for 6 population groups of Asian honeybees and found out that only one of them (population in Bomi, Tibet) showed a consistently declining Ne from the last 100 generations to 25 generations. Selective sweep analysis suggests that genes related to the tolerance of low temperatures and strong ultraviolet radiation are under selection in the declining population, indicating that these two climate factors most likely underlie the decline of BM populations during the recent past. Our study provides insights into the dynamic changes of Asian honeybee populations in China and identifies climate factors that underlie its population decline, which is valuable for the conservation of this important pollinator.