Title：
Genome sequences and population genomics provide insights into the demographic history, inbreeding, and mutation load of two 'living fossil' tree species of Dipteronia
Authors：
Corresponding
Author：
Yu Feng, Hans Peter Comes, Jun Chen, Shanshan Zhu, Ruisen Lu, Xinyi Zhang, Pan Li, Jie Qiu, Kenneth M. Olsen*, Yingxiong Qiu*
Pubyear：
2024
Title of
Journal：
The Plant journal
Paper
Code：
Volume：
117
Number：
Page：
177–19
Others：
Classification：
Source：
Abstract：
‘Living fossils’, that is, ancient lineages of low taxonomic diversity, represent an exceptional evolutionary
heritage, yet we know little about how demographic history and deleterious mutation load have affected
their long-term survival and extinction risk. We performed whole-genome sequencing and population geno_x0002_mic analyses on Dipteronia sinensis and D. dyeriana, two East Asian Tertiary relict trees. We found largescale genome reorganizations and identified species-specific genes under positive selection that are likely
involved in adaptation. Our demographic analyses suggest that the wider-ranged D. sinensis repeatedly
recovered from population bottlenecks over late Tertiary/Quaternary periods of adverse climate conditions,
while the population size of the narrow-ranged D. dyeriana steadily decreased since the late Miocene, especially after the Last Glacial Maximum (LGM). We conclude that the efficient purging of deleterious mutations in D. sinensis facilitated its survival and repeated demographic recovery. By contrast, in D. dyeriana,
increased genetic drift and reduced selection efficacy, due to recent severe population bottlenecks and a
likely preponderance of vegetative propagation, resulted in fixation of strongly deleterious mutations,
reduced fitness, and continuous population decline, with likely detrimental consequences for the species’
future viability and adaptive potential. Overall, our findings highlight the significant impact of demographic
history on levels of accumulation and purging of putatively deleterious mutations that likely determine the
long-term survival and extinction risk of Tertiary relict trees
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