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. 2014 Aug 5;369(1648):20140001.
doi: 10.1098/rstb.2014.0001.

Speciation on a local geographic scale: the evolution of a rare rock outcrop specialist in Mimulus

Kathleen G Ferris  1 , Jason P Sexton  2 , John H Willis  3
Affiliations

Speciation on a local geographic scale: the evolution of a rare rock outcrop specialist in Mimulus

Kathleen G Ferris et al. Philos Trans R Soc Lond B Biol Sci. .

Abstract

Speciation can occur on both large and small geographical scales. In plants, local speciation, where small populations split off from a large-ranged progenitor species, is thought to be the dominant mode, yet there are still few examples to verify speciation has occurred in this manner. A recently described morphological species in the yellow monkey flowers, Mimulus filicifolius, is an excellent candidate for local speciation because of its highly restricted geographical range. Mimulus filicifolius was formerly identified as a population of M. laciniatus due to similar lobed leaf morphology and rocky outcrop habitat. To investigate whether M. filicifolius is genetically divergent and reproductively isolated from M. laciniatus, we examined patterns of genetic diversity in ten nuclear and eight microsatellite loci, and hybrid fertility in M. filicifolius and its purported close relatives: M. laciniatus, M. guttatus and M. nasutus. We found that M. filicifolius is genetically divergent from the other species and strongly reproductively isolated from M. laciniatus. We conclude that M. filicifolius is an independent rock outcrop specialist despite being morphologically and ecologically similar to M. laciniatus, and that its small geographical range nested within other wide-ranging members of the M. guttatus species complex is consistent with local speciation.

Keywords: Mimulus filicifolius; Mimulus guttatus; Mimulus laciniatus; genetics; local speciation; rock outcrops.

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Figures

Figure 1.
Figure 1.
Geographical distributions of M. guttatus (indigo, green, purple and orange), M. nasutus (green, purple and orange), M. laciniatus (purple) and M. filicifolius (orange). Mimulus guttatus' distribution encompasses the ranges of the other three taxa. (Online version in colour.)
Figure 2.
Figure 2.
PCA of M. guttatus (indigo, G), M. nasutus (green, N), M. laciniatus (purple, L) and M. filicifolius (orange, F) genetic diversity at the CYCA locus. (a) A plot of genetic pc scores at the CYCA locus along axes PC1 and PC2. (b) A plot of genetic pc scores at the CYCA locus along axes PC1 and PC3. (Online version in colour.)
Figure 3.
Figure 3.
PCA of M. guttatus (indigo, G), M. nasutus (green, N), M. laciniatus (purple, L) and M. filicifolius (orange, F) genetic diversity on a concatenated alignment of six M. nasutus-based EST loci, Mg1–6. (a) A plot of genetic pc scores for the concatenated Mg loci along axes PC1 and PC2. (b) A plot of genetic pc scores for the concatenated Mg loci along axes PC1 and PC3. (Online version in colour.)
Figure 4.
Figure 4.
Maximum-likelihood gene tree at the CYCA locus of M. guttatus (indigo, g), M. nasutus (green, n), M. laciniatus (purple, I) and M. filicifolius (orange, BR) populations. Myec refers to the outgroup M. yecorensis. (Online version in colour.)
Figure 5.
Figure 5.
Maximum-likelihood gene tree at the Mg2 locus of M. guttatus (indigo, g), M. nasutus (green, n), M. laciniatus (purple, I) and M. filicifolius (orange, BR) populations. Mgvf refers to the outgroup M. glabratus. (Online version in colour.)
See this image and copyright information in PMC

References

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