Parameters and Consequences of Introgression in Salvia apiana x S. mellifera (Lamiaceae)

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Abstract
Introgression was studied in Salvia apiana and S. mellifera in two respects. First, a geographical survey was made to determine characteristic parameters of variation and the nature and extent of hybridization. Secondly, published and unpublished introgression data collected over a timespan of 30 years were analyzed to determine the stability of an introgressed population. Environmental data were assayed to assist in the interpretation of morphological variation in flower structure. Pollen viability was investigated for both species and their hybrids and found to be high in both parental and introgressed individuals. Computer analyses were used to test relationships between characters, to calculate descriptive statistics, and to identify any time-related changes. Results of the geographical studies in S. mellifera showed no statistically significant variation due to environmental or geographical factors, whereas populations of S. apiana showed statistically significant variation, indicating a topocline. Data from this study of introgression were compared to Anderson and Anderson''s original data of 1952. Progressive gene infiltration (introgression) and long term maintenance of introgression was documented. Further, it was demonstrated that at three different sites introgressed populations persist in the absence of one of the parental species, S. apiana in each case.