Source: http://2018.botanyconference.org/engine/search/index.php?func=detail&aid=219
Timestamp: 2019-04-20 16:31:59+00:00

Document:
Botany 2018 - A remarkable population of <em>Vaccinium</em> (Ericaceae) from San Bruno Mountain, California: hybrid or new species?
Fritsch, Peter , Simison, W. Brian , Cruz, Boni , Schneider, Edward , Allshouse, Douglas D. .
A remarkable population of Vaccinium (Ericaceae) from San Bruno Mountain, California: hybrid or new species?
A population of Vaccinium from San Bruno Mountain in San Mateo County, California has been identified as V. cespitosum since its initial collection in 1961. The morphology of the plants in this population is consistent with a placement in V. section Myrtillus, the section to which V. cespitosum belongs; however, they differ from V. cespitosum and all other species of north-temperate V. section Myrtillus in several characters, most notably their evergreen habit and well developed calyx lobes. Because many of the character states of these plants are known in either V. cespitosum or V. ovatum, the only two species of Vaccinium documented from San Bruno Mountain, we initially hypothesized that the population is a hybrid between them. To test this, we employed DNA sequence data from the nrITS region and plastid matK and ndhF regions to assess phylogenetic placement as well as patterns of sequence identity and ITS polymorphic site additivity. Results confirmed the sectional placement as based on morphology. ITS yielded no instances of polymorphism resulting from additive contributions from the putative parental sequences, and the plastid haplotype was unique relative to those of the putative parents. The plants appear to be distinct from and non-intermediate between V. cespitosum and V. ovatum in their thinner branchlets, shorter pedicels, and ciliate versus eciliate calyx lobes. Taken together, the data weigh against hybrid status for the population. Resolution within the V. section Myrtillus clade is too low for inferring the closest relative of the plants, but in their well developed calyx lobes and pubescent filaments they match only the Polynesian species of the section. They clearly differ from these species, however, by the combination of slightly articulated and shorter pedicels with caducous bracteoles, shorter flowers, consistently 5-locular ovaries, and smaller fruits. They also differ by the absence of extended bundle sheath cells in their terminal leaf veinlets, which are also generally absent in the rest of V. section Myrtillus, and larger leaf veinlet areole size. We consider the totality of the data to suggest species status for these plants. The population occupies a total of only ca. 200 m2 with the number of individuals uncertain because of clonal growth. More precise phylogenetic relationships of these plants must await the application of additional DNA sequence data.

References: V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V.