Pinus kesiya and its sister species Pinus yunnanensis form savanna and forest communities in tropical and subtropical Southeast Asia (SEA). Their ranges overlap in southern Yunnan and have a wide zone of contact. To date, range-wide investigation across the pine species in SEA has not been performed. How Quaternary climate oscillations affected the geographic genetic structure and introgression among species remains unclear. 

In a study published in Journal of Systematics and Evolution, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) tried to infer how the Quaternary climate change affected the evolutionary process and range shifts in two pine species.  

The researchers investigated the population genetic structure and diversity, by surveying mitochondrial (mt) DNA and chloroplast (cp) DNA variation in 690 individuals from a broad distribution range in Southeast Asia. They then reconstructed historical species distributions under past climates using ecological niche modeling to understand the historical changes in species distribution. 

“The study, for the first time, revealed the spatial heterogeneity of diversity in two dominant pine species in SEA. The two pines showed different genetic geographic structure,” said GAO Jie of XTBG. 

They found that the past climate change resulted in a contrasting patterns of populations history in the two pine species and a large introgression zone between them. Range shifts caused by Quaternary glacial-interglacial climate oscillations created secondary contact zones between the two species, leading to a zone of introgression with complex genetic composition. 

They further found that the pine populations in SEA are at risk of population decline and extirpation due to climate change and habitat fragmentation. The researchers suggested that in situ and ex situ conservation based on genetic, ecological, and demographic inference, could maximize the maintenance of the existing genetic diversity in the long run and allow the pine species to adapt to new environmental threats. 

“Our results suggest that the Quaternary climate history in SEA strongly shaped the diversity and evolutionary trajectories of pine species in the region,” said GAO Jie. 

Contact 

GAO Jie Ph.D 

Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China   

E-mail: gaojie@xtbg.org.cn