Physiological Evidence of Hybridization and Reticulate Evolution in Phlox Maculata

A comparative physiological analysis was conducted on a hybrid swarm involving P. maculata subsp. maculata and P. glaberrima subsp. interior . The population contained an array of segregates and introgressants. Hybrids displayed a high degree of heterogeneity in their physiological attributes, some characters being intermediate to, similar to, or transgressing those of the parental taxa. For example, both net photosynthetic rates and net photosynthetic/dark respiratory ratios were enhanced in the hybrids, and the level of enhancement was associated with the level of morphological intermediacy. Conversely, no enhancement was noted in either respiration rates or foliar fresh weight/ovendry weight ratios of the hybrids. Because of physiological imbalance, about one‐third of the hybrids were eliminated early in their development. Representatives of P. maculata subsp. pyramidalis , a putative stabilized derivative of hybridization between the above two parental species, were intermediate in most physiological features and closely resembled some natural hybrids. The data verify that the physiological features of subspecies pyramidalis can be assembled through recombination of the P. maculata and P. glaberrima genomes.