Genetic diversity analysis in disjunct populations of Rhododendron arboreum from the temperate and tropical forests of Indian subcontinent corroborate Satpura hypothesis of species migration

Abstract

Rhododendron arboreum of the family Ericaceae represents one of the ancient relict tree species of the genus showing extreme disjunction in the Indian subcontinent. It is represented by two sub-species viz., ssp. arboreum Smith in the forests of north-eastern India (temperate) and spp. nilagiricum (Zenker) Tagg distributed in the southern Western Ghats (tropical) of India with apparently no distribution in the intervening plains. 35 Samples corresponding to different locations in the tropical montane forests of Nilgiris and temperate forests of northeast India were analyzed for distribution of genetic variation using 25 random primers. Relatively high genetic diversity was measured in the temperate populations (Ht = 0.21; Nm = 1.13) than tropical Rhododendrons. The hierarchical analysis of molecular variance showed that among the total variance, 25% is residing within populations while 63% of variance is among regions apparently revealing that disjunct distribution has structured genetic differentiation pattern in this species. Grouping of samples was in conformity with their spatial distribution, which was confirmed by UPGMA cluster analysis and PCA scatter plot. The taxon with its unique distribution pattern and wide cross compatibility between sub-species is however threatened by low genetic variation and gene flow that catalyses it's shifting towards genetic drift and hence long-term conservation strategies need to be formulated particularly for the tropical Rhododendron sub-species. Among the various hypotheses and theory proposed to explain the Malayan affinity in the flora and fauna of Western Ghats, Satpura hypothesis based on dispersal model of distribution largely explains the discontinues distribution of R. arboreum.

Genetic diversity and population structure of Rhododendron simsii (Ericaceae) as revealed by microsatellite markers

“…In this study, the gene flow was estimated to be 1.3525, which should effectively counteract population differentiation. Similarly, relatively frequent gene flow was previously reported among R. arboreum populations (Nm = 1.13) (Kuttapetty et al 2014).…”

“…The level of genetic variation within R. simsii populations (84.34%) was slightly lower than previously reported for other Rhododendron species, such as R. jinggangshanicum (93.13%, p < 0.001) distributed on Jinggangshan Mountain (Li et al 2015), R. decorum (85.11%, p < 0.001) sampled from southwest China (Wang et al 2013b), and R. concinnum (85.3%, p < 0.001) collected from Qinling Mountains (Zhao et al 2012). However, only 25% of the genetic variance was harboured within R. arboreum populations (Kuttapetty et al 2014). In relation to chloroplast (trnS-trnG and trnL-trnF) and nuclear (RPB2-i) loci, moderate levels of genetic differentiation (cpDNA: N ST = 0.125; G ST = 0.114 and nuclear DNA: N ST = 0.261; G ST = 0.152) has been found in 17 wild R. delavayi populations sampled from southwest China (Sharma et al 2014).…”

Out of Borneo: biogeography, phylogeny and divergence date estimates ofArtocarpus(Moraceae)

“…An Indo-Malayan influence in the flora and fauna of southern India has long been recognized (Hora, 1944(Hora, , 1949, and there are many examples of extant plant taxa present in the wet tropical forests of the Western Ghats and northeastern India, but absent from the more arid central Indian region (Bahulikar et al, 2004;Apte et al, 2006;Banu et al, 2009;Kuttapetty et al, 2014). Recent analysis of fossil flora from the Deccan Intertrappean beds in central India suggests that the wet tropical forests, similar to present-day forests of the Western Ghats and north-east India, were flourishing in central India during the late Cretaceous into the Oligocene (Kapgate, 2013).…”

Distribution pattern of the genus Rhododendron in Bhutan Himalayan range

“…Chandra et al [23] also spotted R. arboreum below 1000 m in Indian Himalayan region. Kuttapety et al [24] reported that annual mean temperature was found to be an ecological factor that defined the survival of R. arboreum var. cinnamomeum and R. arboreum var.…”