Genetic studies of dissimilar parapatric populations in northern bishop pine (Pinus muricata)
| Authors: | Connie I. Millar |
| Year: | 1985 |
| Type: | Dissertations |
| Station: | Pacific Southwest Research Station |
| Source: | Ph.D. dissertation. University of California. |
Abstract
Reported here are the results of studies on the unusually abrupt genetic transition that occurs in several traits in continuous bishop pine stands of northern Sonoma County, California. The genetic nature of this anomalous cline was investigated using allozyme, common garden, crossability, and controlled-soil analyses. Data from these analyses allowed a preliminary interpretation on the evolutionary relationships of the pines of this region.
Initially, seeds were collected from 78 green foliaged trees in 8 stands south of the transition at Sea Ranch, from 27 blue, green or intermediate foliaged trees in 3 transition stands, and from 96 blue foliaged trees in 8 stands north of Sea Ranch. Allozyme frequencies in maternal trees of alleles at one locus (Got2) differed significantly between the blue population (average frequency of allele 1, .96) and green population (average frequency of allele 1, .24). The frequencies changed over 2 km in a steep cline at Sea Ranch that coincided with the transition in foliage color.
The Got2 allele frequencies in the pollen grains that effected fertilization of the analysed seeds differed significantly from maternal allele frequencies in green stands south of Sea Ranch. The frequencies differed in a pattern that suggested unidirectional gene flow via pollen from north (blue) to south (green): south of Sea Ranch, the frequency of Gotl was lower in pollen than in maternal trees. The gene flow explanation was corroborated by the north-northwestern direction of prevailing winds along the coast during the pollination season.