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Electrophoretic Analysis of Diversity and Phylogeny of Pinus brutia and Closely Related Taxa

Informally Refereed

Abstract

Rangewide samples from mature natural stands of Pinus brutia Ten. subsp. brutia, subsp. stankewiczii (Sukaczew) Nahal, subsp. pithyusa (Stevenson) Nahal, and subsp. eldarica (Medw.) Nahal from throughout the eastern Mediterranean display a continuum of allozyme variation for 30 loci. Ten geographic samples of subsp. brutia from Greek islands of the eastern Aegean Sea, and from Turkey, Cyprus, and Iraq have a mean expected heterozygosity of 0.12 (range from 0.10 to 0.14) and similar allelic variation suggesting that they share a common gene pool with minor geographic differentiation. Subspecies stankewiczii, a narrow endemic of the Crimea, has expected heterozygosity equal to the mean for subsp. brutia populations; subsp. eldarica has the lowest expected heterozygosity (0.08) among these closely related pines. Pines of the P. brutia group are polymorphic for many loci that are monomorphic and are presumed fixed in a widespread parapatric close relative, P. halepensis Mill. Consequently, they have nearly three times more variation than P. halepensis. Of all the subspecies sampled, stankewiczii has allozyme traits most like those expected in a progenitor of the entire P. brutia-P. halepensis complex. Its allele frequencies resemble subsp. brutia and it has a moderate frequency for an allele that is fixed in P. halepensis but which is sparse or lacking in other samples of the P. brutia group. Subspecies pithyusa's allele frequencies resemble those of subsp. stankewiczii and several subsp. brutia populations. Subspecies eldarica's allozyme similarities to the easternmost subsp. brutia populations and reduced diversity provide evidence of its derivation from subsp. brutia. Allele frequencies of Quetta pine (a provenance from a P. brutia-like naturalized race in southwestern Asia) closely match those of subsp. eldarica and provide evidence of its derivation from subsp. eldarica. Genetic distances between P. brutia and P. halepensis average 0.35 for Nei's unbiased distance and 0.47 for Cavalli-Sforza and Edwards's chord distance. Allozyme characteristics support the hypothesis that P. halepensis was derived from progenitors similar to pines of the extant P. brutia group mainly by fixation of alleles that are still polymorphic in pines of the group.

Citation

Conkle, M. T.; Schiller, G.; Grunwald, C. 1988. Electrophoretic Analysis of Diversity and Phylogeny of Pinus brutia and Closely Related Taxa. Systematic Botany 13(3): p. 411-424
https://www.fs.usda.gov/research/treesearch/32856