Microsatellite Marker Analysis Reveals the Complex Phylogeographic History of Rhododendron ferrugineum (Ericaceae) in the Pyrenees

Abstract

Genetic variation within plant species is determined by a number of factors such as reproductive mode, breeding system, life history traits and climatic events. In alpine regions, plants experience heterogenic abiotic conditions that influence the population's genetic structure. The aim of this study was to investigate the genetic structure and phylogeographic history of the subalpine shrub Rhododendron ferrugineum across the Pyrenees and the links between the populations in the Pyrenees, the Alps and Jura Mountains. We used 27 microsatellite markers to genotype 645 samples from 29 Pyrenean populations, three from the Alps and one from the Jura Mountains. These data were used to estimate population genetics statistics such as allelic richness, observed heterozygosity, expected heterozygosity, fixation index, inbreeding coefficient and number of migrants. Genetic diversity was found to be higher in the Alps than in the Pyrenees suggesting colonization waves from the Alps to the Pyrenees. Two separate genetic lineages were found in both the Alps and Pyrenees, with a substructure of five genetic clusters in the Pyrenees where a loss of genetic diversity was noted. The strong differentiation among clusters is maintained by low gene flow across populations. Moreover, some populations showed higher genetic diversity than others and presented rare alleles that may indicate the presence of alpine refugia. Two lineages of R. ferrugineum have colonized the Pyrenees from the Alps. Then, during glaciation events R. ferrugineum survived in the Pyrenees in different refugia such as lowland refugia at the eastern part of the chain and nunataks at high elevations leading to a clustered genetic pattern.

Using metabarcoding to reveal and quantify plant-pollinator interactions

“…If the number of sequences mirrors the number of pollen grains then, the number of ITS1 and trnL sequences would scale across insect taxa in the same order as their carrying capacities; (2) If, when considering a target plant species (here R. ferrugineum ), there is a relationship between the number of pollen grains in the pollen loads and the number of conspecific ITS1 and trnL sequences. Overall, we would expect a quite similar trend as for total pollen analysis even if the proportion of R. ferrugineum in pollen loads is usually lower in Diptera (0.29–0.55) than in Hymenoptera (0.61–0.89; but see Bombus pascuorum: 0.4135. Honeybees and bumblebees are indeed usually reported as the main R. ferrugineum pollen carriers in R. ferrugineum heathlands in the Pyrenees29 and in the Alps36, while Diptera usually display much smaller R. ferrugineum pollen loads; (3) If there is a positive correlation between the number of visits (all visitors pooled) received by a plant species and the number of its ITS1 and trnL sequences.…”

“…From a previous study based on 522 visitors in 17 R. ferrugineum heathlands distributed across the Pyrenees35 we have a good picture of the carrying capacity of insect taxa. The average number of pollen grains in individual pollen loads can be ranked: Hymenoptera ( Apis mellifera  ≈  Bombus lucorum  ≈ other wild bees; from 2100 to 2500 pollen grains >  Bombus pascuorum (≈800 grains) >  Diptera ( Syrphidae  ≈ 500 grains >  Empididae  ≈ 80 grains) and Lepidoptera (≈20 grains).…”

Molecular Biogeography of the High Mountain Systems of Europe: An Overview

“…Maps based on Google Maps are rare, but have been shown, e.g. for Rhododendron ferrugineum with five (Charrier et al 2014) and Cardamine alpina with a number of lineages that is difficult to quantify (Lihová et al 2008).…”

“…they are derived from the same refugia as the nearby Alpine populations (e.g. Pauls et al 2006;Schmitt et al 2006;Mardulyn et al 2009;Triponez et al 2011;Alvarez et al 2012;Charrier et al 2014). Exceptions to this rule are the caddisfly Drusus discolor with a genetic lineage restricted to Jura, Vosges and Black Forest (Pauls et al 2006) and the butterfly Erebia manto with the genetically strongly differentiated taxon vogesiaca endemic to the Vosges (Schmitt et al 2014).…”

Isolation and characterization of 19 novel microsatellite loci in Rhododendron aureum and Rhododendron brachycarpum (Ericaceae)

“…Seorak population, the mean N A was 7.3, the H o and H e ranged from 0.120 to 0.880 and 0.113 to 0.914, respectively. The values of H e did not deviate from the previously reported ones from genus Rhododendron (Naito et al, 1999;Hirao et al, 2006;Tan et al, 2009;Wang et al, 2013;Charrier et al, 2014). Three R. aureum loci (RA85, RA88, and RA114) and one R. brachycarpum locus (RA85) deviated from HWE.…”