Genetic structure of coast redwood (Sequoia sempervirens [D. Don] Endl.) populations in and outside of the natural distribution range based on nuclear and chloroplast microsatellite markers.

Natalie Breidenbach,Konstantin V Krutovsky,Oliver Gailing,Berthold Heinze

doi:10.1371/journal.pone.0243556

Abstract

Coast redwood (Sequoia sempervirens) naturally growing in southern Oregon and northern California is one of the few conifer tree species that are polyploid. Despite its unique ecological and economic importance, its population genetic structure is still insufficiently studied. To obtain additional data on its population genetic structure we genotyped 317 samples collected from populations in California (data set C) and 144 trees growing in a provenance trial in France (data set F) using 12 nuclear (five random nuclear genomic nSSRs and seven expressed sequence tag EST-SSRs) and six chloroplast (cpSSRs) microsatellite or simple sequence repeat (SSR) markers, respectively. These data sets were also used as reference to infer the origin of 147 coast redwood trees growing in Germany (data set G). Coast redwood was introduced to Europe, including Germany as an ornamental species, decades ago. Due to its fast growth and high timber quality, it could be considered as a potential commercial timber species, especially in perspective to climate warming that makes more regions in Germany suitable for its growing. The well performing trees in colder Germany could be potential frost resistant genotypes, but their genetic properties and origin are mostly unknown. Within the natural range in southern Oregon and northern California, only two relatively weak clusters were identified, one northern and one southern, separated by the San Francisco Bay. High genetic diversity, but low differentiation was found based on the 12 nuclear SSR markers for all three data sets F, C and G. We found that investigated 147 German trees represented only 37 different genotypes. They showed genetic diversity at the level less than diversity observed within the natural range in the northern or southern cluster, but more similar to the diversity observed in the southern cluster. It was difficult to assign German trees to the original single native populations using the six cpSSR markers, but rather to either the northern or southern cluster. The high number of haplotypes found in the data sets based on six cpSSR markers and low genetic differentiation based on 12 nuclear SSRs found in this study helps us study and better understand population genetic structure of this complex polyploid tree and supports the selection of potential genotypes for German forestry.

Highlights

Climate change can negatively affect the growth of certain native species in Central Europe [1], increased precipitation and temperature in winter expected in some regions in Germany [2] can make the environment more suitable for growing certain non-native tree species in these regions
The main objectives of this study were to 1) compare genetic population structure resolution based on nuclear (EST-simple sequence repeat (SSR) together with nuclear simple sequence repeat (nSSR)) vs. chloroplast microsatellite markers, 2) study genetic diversity based on expressed sequence tag SSR (EST-SSR), nSSRs and chloroplast SSR (cpSSR) within and outside the natural distribution range, and 3) assign trees growing in Germany to the original populations
Douhovnikoff and Dodd [31] partitioned 135 Russell Reserve trees into 17 watersheds according to their original geographic location and the GPS data (Fig 1) for population genetic structure analysis based on six nSSR markers [31]

Summary

Introduction

Climate change can negatively affect the growth of certain native species in Central Europe [1], increased precipitation and temperature in winter expected in some regions in Germany [2] can make the environment more suitable for growing certain non-native tree species in these regions. To secure German timber production and the growing demand for wood products in Europe, more non-native tree species should be tested for potential introduction. The predicted altitudinal shift in the distribution of woody species [1,6] due to climate change would make Germany more suitable for species adapted to the Mediterranean climate, such as coast redwood that has already been introduced to Europe as an exotic species [7]. Coast redwood was introduced into several countries with similar climatic conditions for timber production, such as France [13], New Zealand [14] and China [15]

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