Genetic variation in horizontally transmitted fungal endophytes of pine needles reveals population structure in cryptic species

Ryoko Oono, François Lutzoni, A. Elizabeth Arnold, Laurel Kaye, Jana M. U'Ren, Georgiana May, Ignazio Carbone

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

Premise of the study: Fungal endophytes comprise one of the most ubiquitous groups of plant symbionts, inhabiting healthy leaves and stems of all major lineages of plants. Together, they comprise immense species richness, but little is known about the fundamental processes that generate their diversity. Exploration of their population structure is needed, especially with regard to geographic distributions and host affiliations. Methods: We take a multilocus approach to examine genetic variation within and among populations of Lophodermium aus-trale, an endophytic fungus commonly associated with healthy foliage of pines in the southeastern United States. Sampling focused on two pine species ranging from montane to coastal regions of North Carolina and Virginia. Key results: Our sampling revealed two genetically distinct groups within Lophodermium australe. Our analysis detected less than one migrant per generation between them, indicating that they are distinct species. The species comprising the majority of isolates (major species) demonstrated a panmictic structure, whereas the species comprising the minority of isolates (cryptic species) demonstrated isolation by distance. Distantly related pine species hosted the same Lophodermium species, and host species did not influence genetic structure. Conclusions: We present the first evidence for isolation by distance in a foliar fungal endophyte that is horizontally transmitted. Cryptic species may be common among microbial symbionts and are important to delimit when exploring their genetic structure and microevolutionary processes. The hyperdiversity of endophytic fungi may be explained in part by cryptic species without apparent ecological and morphological differences as well as genetic diversification within rare fungal species across large spatial scales.

Original languageEnglish (US)
Pages (from-to)1362-1374
Number of pages13
JournalAmerican journal of botany
Volume101
Issue number8
DOIs
StatePublished - Aug 2014

Keywords

  • Diversity
  • Foliar fungal endophyte
  • Lophodermium
  • Pinus
  • Rhytismataceae
  • Speciation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Plant Science

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