RESPONSE TO SELECTION ON AUTOGAMY IN PHLOX.

Area of Science:

• Evolutionary biology
• Plant reproductive biology
• Genetics

Background:

• Plant breeding systems, including self-incompatibility and self-compatibility, are crucial for reproductive success and population dynamics.
• Understanding the genetic basis and flexibility of these systems is key to predicting evolutionary trajectories.
• Phlox species offer a valuable model for studying the genetic control of reproductive traits.

Purpose of the Study:

• To investigate the genetic flexibility of breeding systems in Phlox species.
• To determine the effects of artificial selection on autogamy and self-compatibility.
• To identify the genetic mechanisms underlying shifts in plant reproductive strategies.

Main Methods:

• Two cycles of artificial selection were applied to wild populations of self-incompatible Phlox drummondii and self-compatible Phlox cuspidata.
• Selection aimed to increase or decrease autogamous fruiting (self-pollination).
• A pseudo-self-compatible P. drummondii cultivar was also subjected to selection for both increasing and decreasing autogamy.

Main Results:

• Breeding systems in Phlox were found to be genetically flexible and adaptable to selection.
• Artificial selection effectively modified autogamous fruiting and self-compatibility levels.
• Self-pollen-pistil compatibility appeared to be the primary trait influenced by selection.

Conclusions:

• The genetic architecture of breeding system shifts, particularly increasing autogamy, is highly flexible.
• Observed continuous variation suggests modification of the self-incompatibility reaction by modifier genes, rather than simple S-locus allele segregation.
• Phlox species demonstrate a capacity for rapid evolutionary adaptation of their reproductive systems.