DNA sequences from Miocene fossils: anndhFsequence ofMagnolia latahensis(Magnoliaceae) and anrbcLsequence ofPersea pseudocarolinensis(Lauraceae)

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Abstract
We report a partialndhFsequence (1528 bp) ofMagnolia latahensisand a partialrbcLsequence (699 bp) ofPersea pseudocarolinensisfrom the Clarkia fossil beds of Idaho, USA (Miocene; 17–20 million years [my] BP). ThendhFsequence fromM. latahensiswas identical to those of extantM. grandiflora,M. schiediana,M. guatemalensis, andM. tamaulipana. Parsimony analysis of thendhFsequence ofM. latahensisand previously reportedndhFsequences for Magnoliaceae placedM. latahensiswithinMagnoliaas a member of the Theorhodon clade. This result is reasonable considering that: (1) the morphology ofM. latahensisis very similar to that of extantM. grandiflora, and (2) a recent molecular phylogenetic study of Magnoliaceae showed that the maximum sequence divergence ofndhFamong extant species is very low (1.05% in subfamily Magnolioideae) compared with other angiosperm families. We reanalyzed the previously reportedrbcLsequence ofM. latahensiswith sequences for all major lineages of extant Magnoliales and Laurales. This sequence is sister toLiriodendron, rather than grouped with a close relative ofM. grandifloraas predicted by morphology and the results of thendhFanalysis, possibly due to a few erroneous base calls in the sequences. TherbcLsequence ofP. pseudocarolinensisdiffered fromrbcLof extantPerseaspecies by 3–6 nucleotides and fromrbcLof extantSassafras albidumby two nucleotides. Phylogenetic analyses ofrbcLsequences for all major lineages of Magnoliales and Laurales placed the fossilP. pseudocarolinensiswithin Lauraceae and as sister toS. albidum. These results reinforce the suggestion that Clarkia and other similar sites hold untapped potential for molecular analysis of fossils.
Funding Information
  • National Science Foundation (DEB‐0090283)