Genetic Variation and Population Structure of Rhododendron anthopogon Along an Altitudinal Gradient: A Case Study from Himalaya

Abstract

High-altitude regions like the Himalaya, where various slopes are present on a very small spatial scale, are one of the best natural laboratories for investigating how genetic diversity and population structure are distributed across altitudinal gradients. In this study, we investigate the magnitude of genetic diversity and population structure of Rhododendron anthopogon D.Don along an altitudinal gradient in the Kashmir Himalaya. We used the start codon targeted (SCoT) marker to evaluate the genetic diversity and differentiation between different populations across five sites along an altitudinal gradient ranging from 3200 to 4000 m (amsl). Our results demonstrate that the magnitude of genetic diversity differs among the populations of R. anthopogon along the altitudinal gradient. We observed a decreasing trend in genetic diversity with increasing altitude from site-1 to site-3 (3200 to 3600 m), and an increasing trend from site-4 to site-5 (3601 to 4000 m). Furthermore, we also observed the highest genetic diversity at upper altitude (site-5) and the lowest at mid-altitude (site-3). Our results reveal a high genetic differentiation (G_st = 0.7349) and a low gene flow (N_m = 0.1804) among the populations. Analysis of molecular variance (AMOVA) reveals 71% variation among the populations and 29% variation within the populations. We also reveal positive associations between geographic and genetic distances, indicating isolation by distance effect across all altitudes. STRUCTURE and cluster analysis divided all the populations of R. anthopogon into five clusters according to their geographical location. Overall, the study adds to our understanding that altitude is the major driver of genetic variation and differentiation between populations of R. anthopogon which may help increase its range under ongoing projected climate change. Our study also reveals that populations at higher altitudes are not genetically isolated, suggesting that they might be an essential source for migration in the era of climate change.