High outcrossing rates in a self-compatible and highly aggregated host-generalist mistletoe

Area of Science:

• Plant reproductive strategies
• Population genetics
• Ecological interactions

Background:

• Plants face inbreeding risks, especially those with mass flowering and aggregated distributions like mistletoes.
• Bird pollinators can facilitate self-pollination within mistletoe individuals and host trees.
• The influence of spatial distribution on mating systems and genetic structure in mistletoes is not well understood.

Purpose of the Study:

• To investigate the mating system and spatial distribution effects on the genetic structure of Dendrophthoe pentandra.
• To determine if self-incompatibility mechanisms are present in hermaphroditic mistletoes.
• To understand how ecological factors influence outcrossing rates and genetic diversity.

Main Methods:

• Utilized microsatellite markers and progeny arrays to analyze genetic structure in four mistletoe populations.
• Conducted manual pollination experiments to assess self-compatibility.
• Characterized fine-scale spatial genetic structure within host trees.

Main Results:

• Dendrophthoe pentandra was found to be self-compatible, contrary to initial hypotheses.
• Outcrossing rates were higher than expected across all studied populations.
• Spatial genetic structure was linked to distances between host trees, not within them.

Conclusions:

• Bird pollination and seed dispersal, coupled with post-dispersal processes, promote outcrossing in mistletoes.
• These mechanisms maintain high genetic diversity despite high local densities and potential self-compatibility.
• Ecological factors significantly shape the mating system and genetic makeup of mistletoe populations.