Population structure and adaptive variation of Helichrysum italicum (Roth) G. Don along eastern Adriatic temperature and precipitation gradient

Tonka Ninčević,Martina Grdiša,Filip Varga,Zlatko Šatović,Zlatko Liber,Marija Jug-Dujaković,Dejan Pljevljakušić

doi:10.1038/s41598-021-03548-6

Abstract

Immortelle (Helichrysum italicum (Roth) G. Don; Asteraceae) is a perennial plant species native to the Mediterranean region, known for many properties with wide application mainly in perfume and cosmetic industry. A total of 18 wild H. italicum populations systematically sampled along the eastern Adriatic environmental gradient were studied using AFLP markers to determine genetic diversity and structure and to identify loci potentially responsible for adaptive divergence. Results showed higher levels of intrapopulation diversity than interpopulation diversity. Genetic differentiation among populations was significant but low, indicating extensive gene flow between populations. Bayesian analysis of population structure revealed the existence of two genetic clusters. Combining the results of FST - outlier analysis (Mcheza and BayeScan) and genome-environment association analysis (Samβada, LFMM) four AFLP loci strongly associated with the bioclimatic variables Bio03 Isothermality, Bio08 Mean temperature of the wettest quarter, Bio15 Precipitation seasonality, and Bio17 Precipitation of driest quarter were found to be the main variables driving potential adaptive genetic variation in H. italicum along the eastern Adriatic environmental gradient. Redundancy analysis revealed that the partitioning of genetic variation was mainly associated with the adaptation to temperature oscillations. The results of the research may contribute to a clearer understanding of the importance of local adaptations for the genetic differentiation of Mediterranean plants and allow the planning of appropriate conservation strategies. However, considering that the identified outlier loci may be linked to genes under selection rather than being the target of natural selection, future studies must aim at their additional analysis.

Highlights

The Mediterranean basin area is one of the largest biodiversity hotspots in the world[1]
Molecular analyzes of the genetic diversity and structure of H. italicum populations from the eastern Adriatic coast using AFLP markers revealed high intrapopulation diversity and low differentiation between populations as well as the population structure characterized by a pattern of isolation by distance
Overexploitation has been observed in all three species but may have most affected the genetic diversity of T. cinerariifolium, the species that has been extensively collected over long periods

Summary

Introduction

The Mediterranean basin area is one of the largest biodiversity hotspots in the world[1]. Detection of outlier loci is a population-level analysis based on estimates of population genetic differentiation (FST), whereas genome-environment analysis examines correlations between population allele frequencies and environmental variables[27,28,29]. Using these methods, local adaptation along environmental gradients was studied in several plant species: Eruca sativa Mill.[30]; Eucalyptus camaldulensis Dehnh.[31]; Abies alba Mill.[32]; Liriodendron chinense (Hemsl.) Sarg.[21]; Geropogon hybridus (L.) Sch.Bip.[33]; Diplotaxis harra (Forssk.) Boiss.[34], Populus tremula L.35, and Festuca pallescens (St.-Yves) P arodi[36]

Methods

Results

Conclusion