Mating patterns and pollinator mobility are critical traits in forest fragmentation genetics

Abstract

Most woody plants are animal-pollinated, but the global problem of habitat fragmentation is changing the pollination dynamics. Consequently, the genetic diversity and fitness of the progeny of animal-pollinated woody plants sired in fragmented landscapes tend to decline due to shifts in plant-mating patterns (for example, reduced outcrossing rate, pollen diversity). However, the magnitude of this mating-pattern shift should theoretically be a function of pollinator mobility. We first test this hypothesis by exploring the mating patterns of three ecologically divergent eucalypts sampled across a habitat fragmentation gradient in southern Australia. We demonstrate increased selfing and decreased pollen diversity with increased fragmentation for two smallinsect-pollinated eucalypts, but no such relationship for the mobile-bird-pollinated eucalypt. In a meta-analysis, we then show that fragmentation generally does increase selfing rates and decrease pollen diversity, and that more mobile pollinators tended to dampen these mating-pattern shifts. Together, our findings support the premise that variation in pollinator form contributes to the diversity of mating-pattern responses to habitat fragmentation.

Effects of converting natural forests to coniferous plantations on fruit and seed production and mating patterns in wild cherry trees

“…This result indicates that floweringtree density, an inverse of the distance between the trees, affects mate diversity (Eckert et al 2010;Breed et al 2013). The flowering-tree density seems to be positively related to the number of mates within a mating range.…”

“…The flowering-tree density seems to be positively related to the number of mates within a mating range. A positive effect of tree density on mate diversity was also detected in insect-pollinated Eucalyptus species, although this effect was confounded with the effect of forest loss (Breed et al 2013). Our findings in P. verecunda demonstrate that the flowering-tree density affects mate diversity independently of landscape properties.…”

“…Loss of forest habitats has frequently been associated with decreased plant density and increased selfing rate, biparental-inbreeding rate, and correlated paternity in animal-pollinated plants (Breed et al 2013). The forest loss resulted in increases in both biparental-inbreeding rate and correlated paternity in P. virginiana, because relatives were more aggregated spatially in fragmented forests than in a continuous forest (Suarez-Gonzalez and Good 2014).…”

“…Pollen dispersal distance sometimes increases in patches with reduced plant density (Llorens et al 2012;Cô rtes et al 2013) and between fragmented patches because of changes in pollinator movements in the matrix (Kamm et al 2010). In constrast, landscape disturbances decrease mate diversity (Breed et al 2013). Not only the size but also the shape of patches affects mating patterns (Llorens et al 2013).…”

“…However, independent comparisons between continuous and fragmented forests in multiple regions have revealed a consistent effect of fragmentation on reproductive performance in these regions (Aizen and Feinsinger 1994;Mimura et al 2009). Patterns observed at multiple sites with different landscape properties within a region also demonstrate the effects of landscape properties on reproductive performance, which can be estimated using statistical models (Llorens et al 2012;Breed et al 2013). The spatial independence of sites and the separation of factors confounded with the sites are crucial when fitting the models to observed patterns.…”