# Multiple Glacial Refugia and Complex Postglacial Dynamics of Primula sikkimensis (Primuaceae) in the Heterogeneous Qinghai‐Tibet Plateau

## TL;DR

This study explores how climate changes shaped the genetic diversity and evolution of a plant species in the Qinghai-Tibet Plateau.

## Contribution

The study reveals distinct glacial refugia and postglacial gene flow mechanisms influencing genetic diversity in an alpine endemic species.

## Key findings

- Primula sikkimensis persisted in separate glacial refugia in the Hengduan Mountains and eastern Himalayas during the Last Glacial Maximum.
- Postglacial range expansions involved gene flow from secondary contact and hybridization, boosting genetic diversity and adaptability.
- These dynamics highlight evolutionary responses to Quaternary climate changes in alpine species.

## Abstract

The Qinghai‐Tibet Plateau (QTP) is a global biodiversity hotspot where Quaternary climatic oscillations profoundly shaped the evolution of endemic alpine flora. Understanding how genetic diversity and structure in these species responded to past climate change is crucial for deciphering regional evolutionary mechanisms. Using chloroplast and nuclear genome data of 958 samples from 48 populations, we evaluated the genetic diversity and population structure of Primula sikkimensis. We then investigated the lineage differentiation and dynamics of species by combining an Approximate Bayesian Computation procedure and species distribution modeling. Our study indicates that
P. sikkimensis
maintained separate glacial refugia in the Hengduan Mountains and eastern Himalayas during the Last Glacial Maximum (LGM). Our results suggest that postglacial range expansions onto the inner QTP plateau were accompanied by gene flow arising from both intraspecific secondary contact between previously isolated populations and interspecific hybridization events, which collectively enhanced genetic diversity and adaptive capacity in plateau populations. Our findings underscore the critical role of postglacial population dynamics and gene flow in shaping genetic diversity and adaptive potential of alpine endemics like
P. sikkimensis
, highlighting evolutionary responses to Quaternary climate change on the QTP.

Primula sikkimensis persisted in distinct glacial refugia within the Hengduan Mountains and eastern Himalayas during the Last Glacial Maximum. Subsequent postglacial range expansions onto the Qinghai–Tibet Plateau were accompanied by secondary contact and interspecific hybridization, collectively enhancing genetic diversity and adaptive capacity. These results demonstrate the pivotal role of refugial persistence and postglacial gene flow in shaping evolutionary responses of alpine endemics to Quaternary climatic oscillations.