MIXED MATING SYSTEMS IN HAWAIIAN BIDENS (ASTERACEAE)

Area of Science:

• Evolutionary Biology
• Plant Reproductive Biology
• Ecology

Background:

• Floral traits significantly influence plant breeding systems, affecting gene flow and population genetic structure.
• Understanding mating systems is crucial for predicting species' evolutionary trajectories and conservation needs.

Purpose of the Study:

• To investigate the floral mechanisms and mating systems of 11 Hawaiian Bidens species.
• To quantify outcrossing rates and the contribution of different mating events (autogamy, geitonogamy, biparental inbreeding) to the overall selfing rate.
• To evaluate the effectiveness of gynodioecy as an outcrossing mechanism in relation to population structure and mating system components.

Main Methods:

• Studied floral features related to breeding systems in 11 Hawaiian Bidens species.
• Quantified outcrossing rates across 15 populations using genetic markers (implied).
• Assessed apparent selfing rates in female and hermaphroditic individuals within seven gynodioecious populations.

Main Results:

• All 11 studied species displayed mixed mating systems, combining protandry, male sterility, self-compatibility, and geitonogamy.
• Outcrossing rates varied significantly among populations, averaging 0.65 (ranging from 0.43 to 0.88).
• Gynodioecy increased outcrossing by an average of 9% in studied populations, with biparental inbreeding varying among populations.

Conclusions:

• The efficiency of gynodioecy is contingent upon the outcrossing rate of hermaphrodites, female frequency, and population genetic substructuring.
• Autogamy, geitonogamy, and consanguineous mating contributed to the realized selfing rate (43%) in hermaphrodites.
• Hawaiian Bidens species demonstrate a complex interplay of floral mechanisms leading to mixed mating systems and variable outcrossing levels.