From pollen dispersal to plant diversification: genetic consequences of pollination mode

Abstract

Summary Pollinators influence patterns of plant speciation, and one intuitive hypothesis is that pollinators affect rates of plant diversification through their effects on pollen dispersal. By specifying mating events and pollen flow across the landscape, distinct types of pollinators may cause different opportunities for allopatric speciation. This pollen dispersal‐dependent speciation hypothesis predicts that pollination mode has effects on the spatial context of mating events that scale up to impact population structure and rates of species formation. Here I consider recent comparative studies, including genetic analyses of plant mating events, population structure and comparative phylogenetic analyses, to examine evidence for this model. These studies suggest that highly mobile pollinators conduct greater gene flow within and among populations, compared to less mobile pollinators. These differences influence patterns of population structure across the landscape. However, the effects of pollination mode on speciation rates is less predictable. In some contexts, the predicted effects of pollen dispersal are outweighed by other factors that govern speciation rates. A multiscale approach to examine effects of pollination mode on plant mating system, population structure and rates of diversification is key to determining the role of pollen dispersal on plant speciation for model clades.

Incomplete reproductive isolation and low genetic differentiation despite floral divergence across varying geographic scales inCastilleja

“…Because reproductive traits directly influence mating patterns (Wessinger, 2021) and fitness (and therefore are under strong selection), they are well‐suited to studying how selection and gene flow generate species divergence (Nosil and Crespi, 2004; Rice and Pfennig, 2010). Among angiosperms, flowers exhibit a stunning diversity of floral forms, colors, scents, and mechanisms by which they shape the reproductive success and genic exchange of plants (Armbruster, 2014).…”

Restored and remnant Banksia woodlands elicit different foraging behavior in avian pollinators

“…The morphological (e.g., large‐bodied) and behavioral traits of these generalist bird pollinators facilitates their access to more distant resources, supporting their existence in fragmented landscapes (Hagen et al., 2012 ; Yates et al., 2007 ). These traits decrease the risk of failure in the delivery of pollinator services (Wessinger, 2020 ). However, as habitat loss intensifies, particularly in urban ecosystems, the distance between remnants increases, reducing bird mobility because of their high resource requirements (Hagen et al., 2012 ).…”

“…More than 349,000 animal species forage on flowers worldwide, with over 87% of angiosperms relying on animal‐mediated pollination for sexual reproduction and genetic recombination (Kearns & Inouye, 1997; Ollerton, 2017; Ollerton et al., 2011). The behavior of pollinators during pollination has fundamental consequences for plant mating and determines the maximum frequency and diversity of mating opportunities (Harder & Barrett, 1996; Minnaar et al., 2019; Wessinger, 2020). There is ample evidence that habitat loss, alteration, and disturbance can negatively impact pollinators and plant–pollinator interactions (Bennett et al., 2020).…”

“…However, behavioral differences in species dominance relations can result in aggressive chases between honeyeaters (Armstrong, 1991 ; Ford, 1979 ; McFarland, 1986 ; Ramsay, 1989 ) and increase pollinator flights. This increases pollen carryover and the frequency of long‐distance pollen dispersal events within and among plant populations (Phillips et al., 2014 ; Wessinger, 2020 ).…”

5S-IGS rDNA in wind-pollinated trees (FagusL.) encapsulates 55 million years of reticulate evolution and hybrid origins of modern species

“…5S-IGS data to study complex history of wind-pollinated trees The permeability of species boundaries sets apart wind-and insect-pollinated, common tree genera. A recent study on genetic consequences of pollination mode (Wessinger, 2021) showed that wind pollination leads to reduced population genetic structure. For example, in one insect-and one wind-pollinated species of Chamaedorea (Arecaceae) in Mexico, the wind-pollinated species showed less isolation by distance as compared to the insect-pollinated species; the same was true in two common shrubs co-occurring in Mediterranean scrub, Pistacia lentiscus (wind-pollinated) and Myrtus communis (insect-pollinated).…”