A PCR-RFLP marker distinguishing Ophiostoma clavigerum from morphologically similar Leptographium species associated with bark beetles

Ophiostoma clavigerum, carried by Dendroctonus ponderosae and Dendroctonus jeffreyi, has morphological characteristics that are similar to other Ophiostoma and Leptographium species. The partial β-tubulin gene of 45 strains belonging to seven species was amplified by PCR and digested by the restriction enzyme HinfI. The specific restriction fragment length polymorphism obtained for O. clavigerum provided the means for its reliable identification. We are also reporting that O. clavigerum ascocarps have short necks; this fact has not been shown previously.Key words: Ophiostoma clavigerum, Leptographium, β-tubulin gene, RFLP, bark beetle.

Allozyme diversity and gene flow in Ophiostoma clavigerum (Ophiostomatales: Ophiostomataceae), the mycangial fungus of the Jeffrey pine beetle, Dendroctonus jeffreyi (Coleoptera: Scolytidae)

Genetic variation within and among 10 California populations of Ophiostoma clavigerum (Robinson-Jeffrey & Davidson) Harrington associated with the mycangia of Dendroctonus jeffreyi Hopkins was assessed using allozymes. Gene diversity was uniformly low across all populations, averaging 1.4%. Only 2 of 19 gene loci assayed were polymorphic. The three most southerly populations (two from the San Bernardino Mountains in southern California and one from the southern tip of the Sierra Nevada Mountains) were the most differentiated; however, all populations exhibited very low genetic distance. Several factors alone, or in combination could be responsible for the low genetic diversity observed in these populations including (i) a rarity of sexual recombination, (ii) a history involving genetic bottlenecks, and (iii) selection for a mutualistic association with the host beetle.

Allozyme diversity and gene flow in the bark beetle, Dendroctonus jeffreyi (Coleoptera: Scolytidae)

Genetic variation within and among 10 California populations of the Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins, was assessed using allozymes. Of 21 loci assayed, 6 were polymorphic in at least one population. Average heterozygosity across all populations and loci was 4%. Genetic distance among the populations ranged from 0.001 to 0.060. The two most southern populations were the most differentiated. At two loci, alleles were present in the southern populations that were not present in any northern populations. The southern populations were also lacking an allele at one locus that was present in all northern populations. Geographic isolation is apparently responsible for allowing the divergence of the southern populations. A dendrogram estimating the relationships among the 10 populations was developed using restricted maximum likelihood. Evidence of inbreeding was found, which in these beetles may be closely tied to population size and dispersal behavior.