Simultaneous evaluation of the effects of geographic, environmental and temporal isolation in ecotypic populations of Solidago virgaurea

Our plain-English summary of Simultaneous evaluation of the effects of geographic, environmental and temporal isolation in ecotypic populations of Solidago virgaurea, by S. Sakaguchi, K. Horie, N. Ishikawa, et al (The New Phytologist, 2017).

The study

• Authors: S. Sakaguchi, K. Horie, N. Ishikawa, A.J. Nagano, M. Yasugi, H. Kudoh, M. Ito
• Journal: The New Phytologist
• Published: 2017;216(4):1268-1280
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Early stages of ecological speciation can create populations with an ecology and reproduction timing distinct from those of related populations. Landscape genetic models incorporating environmental heterogeneity and population-specific reproductive traits enable the processes of population genetic differentiation to be inferred. We investigated genome-wide genetic variation in ecotypic populations of Solidago virgaurea sensu lato, a herbaceous plant inhabiting a wide range of habitats (woodlands, serpentine barrens and alpine grasslands) and displaying remarkable variation in flowering time. Simultaneous evaluation of environmental factors revealed an overwhelming effect of soil type differences on neutral genetic differentiation, compared with elevational differences. This result probably reflects the abrupt environmental changes generated by geological boundaries, whereas mountain slopes exhibit clinal changes, facilitating gene exchange between neighbouring populations. Temporal isolation was positively associated with genetic differentiation, with some early-flowering serpentine populations having allele frequencies distinct from adjacent nonserpentine populations. Overall, this study highlights the importance of ecological processes and of evolution of flowering time to promote genetic differentiation of S. virgaurea populations in a complex landscape.

© 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

In plain English

This study looked at a wild flowering plant, Solidago virgaurea sensu lato, on Hokkaido Island, Japan. It is not a study of people, and the article does not mention asbestos. In 2014 the authors recorded the month flowering began in 49 populations growing on serpentine or nonserpentine soils and at different altitudes. They also typed 3385 genetic markers (SNPs) in 150 plants. A statistical model predicted that populations on serpentine soil began flowering about 1.3 months earlier than those on nonserpentine soil. The model also predicted flowering about 0.75 months earlier for each 1000 m increase in altitude. Genetic differences between plants were linked to how far apart they grew (r = 0.207), to soil type (r = 0.064) and to difference in flowering time (r = 0.171). They were not significantly linked to altitude. Some serpentine populations were genetically distinct from nearby nonserpentine ones, while others were not. The authors concluded that differences in flowering time reduced gene exchange within and among these plant types. They noted small samples, about three plants per population, and incomplete coverage of the island.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Field survey and population (landscape) genetic study of wild plant populations, using genome-wide genetic markers
• Who was studied: 150 individual plants of Solidago virgaurea sensu lato from 49 populations on Hokkaido Island, Japan, collected in field surveys in 2014
• Exposure: Not an asbestos or human exposure study. The factors studied were soil type (serpentine or nonserpentine), altitude and flowering time, together with geographic distance.
• Main results:
  • Among the 49 populations, the model predicted that a population on serpentine soil begins flowering about 1.3 months earlier than a population on nonserpentine soil
  • The model predicted that a population 1000 m higher in altitude flowered 0.75 months earlier. The table gives the altitude estimate as 7.5E-04 per metre, which is 0.75 per 1000 m.
  • The 150 plants were genotyped at 3385 SNP markers
  • Genetic distance between plants increased with geographic distance (Mantel test r = 0.207, P = 0.001)
  • Altitude difference was not significantly correlated with genetic distance (Mantel r = 0.102, P = 0.991; with geography controlled, r = 0.098, P = 0.984)
  • With geography controlled, genetic distance was significantly correlated with soil type difference (r = 0.057, P = 0.001) and with flowering time difference (r = 0.162, P = 0.001)
  • Among serpentine population pairs only, flowering time difference was correlated with genetic distance (r = 0.106, P = 0.001). Among nonserpentine pairs it was not (r = 0.047, P = 0.146).
  • In the best redundancy analysis model (soil type and flowering time, with geography controlled), the constrained components explained 8.78% of the genetic variance
  • Three genetic clusters were assigned to specific serpentine populations in the central area
  • Other serpentine populations and the alpine populations shared regional genetic clusters with surrounding nonserpentine populations
• The authors' conclusion: The authors concluded that reproductive isolation due to variation in flowering time reduced gene exchange within and among the plant ecotypes. They also emphasized the importance of how fast the environment changes over space.
• Limitations the authors state:
  • Small sample size per population (mean 3.06 individuals per population)
  • Population sampling did not cover the whole island
  • It remains unclear whether similar-looking populations share one origin or evolved separately

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Serpentine Group.

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