Sampling 426 plants from 271 populations of Eriophyllum lanatum, a western North American species complex, revealed 195 diploid (x = 8), 61 tetraploid, ten hexaploid, and five octoploid populations. Polyploids were ∼400% more frequent in taxonomic intermediates. One to four supernumerary chromosomes were found in 13% of the populations. Artificial hybridizations were made in 58 of the 65 possible diploid-level combinations involving the ten varieties of E. lanatum and E. confertiflorum var. confertiflorum. Aberrations, mostly failure to pair normally, were observed in diakinesis or M(1) cells of progeny in 23 of 99 crosses. Studies of pollen stainability in cotton blue-lactophenol and other fertility indicators in 886 F(1)'s from 191 crosses involving 81 populations showed that strong (22-40% pollen stainability) to weak (60-76% pollen stainability) barriers to interbreeding existed among diploids of the E. lanatum varieties and among them and E. confertiflorum var. confertiflorum. Pollen stainability was much higher in progenies of tetraploid, hexaploid, and octoploid intra- and interspecific crosses involving E. confertiflorum var. tanacetiflorum, E. jepsonii, and E. latilobum than in diploid ones, supporting the hypothesis that polyploidy has mainly served to stabilize the products of intervarietal and interspecific hybridizations.
Meiotic analyses of 176 plants from 130 populations of Eriophyllum confertiflorum var. confertiflorum showed that diploids (n = 8) and tetraploids were about equally frequent and that hexaploids and octoploids were rare. Supernumerary chromosomes were found in 14% of the individuals; other meiotic aberrations were uncommon. Eriophyllum confertiflorum var. tanacetijlorum is octoploid. Migration from southwest North America, tolerance of aridity, and spontaneous origin ofpolyploids may explain the nonrandom distribution of cytotypes in E. confertiflorum var. confertiflorum. Artificial intravarietal crosses of E. confertiflorum var. confertiflorum yielded vigorous, bivalent-forming progeny with mean pollen stainabilities of 41%-96% and 88°/lr-90%at the diploid and tetraploid levels, respectively. Tetraploid x diploid crosses gave triploids in one case and tetraploids in another. The progenies of some artificial crosses between distant populations of E. confertiflorum var. confertiflorum had significantly lower rates of germination and pollen viability.
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