Pollen as the link between floral phenotype and fitness

Abstract

Pollen plays a key role in plant reproductive biology. Despite the long history of research on pollen and pollination, recent advances in pollen-tracking methods and statistical approaches to linking plant phenotype, pollination performance, and reproductive fitness yield a steady flow of exciting new insights. In this introduction to the Special Issue "Pollen as the Link Between Phenotype and Fitness," we start by describing a general conceptual model linking functional classes of floral phenotypic traits to pollinationrelated performance metrics and reproductive fitness. We use this model as a framework for synthesizing the relevant literature, highlighting the studies included in the Special Issue, and identifying gaps in our understanding and opportunities for further development of the field. The papers that follow in this Special Issue provide new insights into the relationships between pollen production, presentation, flower morphology, and pollination performance (e.g., pollen deposition onto stigmas), the role of pollinators in pollen transfer, and the consequences of heterospecific pollen deposition. Several of the studies demonstrate exciting experimental and analytical approaches that should pave the way for continued work addressing the intriguing role of pollen in linking plant phenotypes to reproductive fitness.

Pollen and Floral Organ Morphology of 18 Oil-Tea Genotypes and Its Systematic Significance

“…8. The pollen shape could be reflected by the polar axis length (P), equatorial axis length (E), and polar axis/equatorial axis value (P/E) [9,12,32]. According to the pollen shape, eighteen oil-tea genotypes had three types in the equatorial view: oblong, spherical, and oblate, and had two types in the polar view: a triangular and subcircular shape (Table 5), which is consistent with the results of Lin et al [33] and Chen et al [34].…”

Dillenia (Dilleniaceae) pollen heteromorphy and presentation, and implications for pollination by bats

“…The mechanical fit between flowers and pollinators influences pollen competition and seed set. For example, the bodies of pollinators acting as male-male competition 'arenas' may affect pollen transfer efficiency and floral evolution (Minaar & Anderson, 2021;Minnaar et al, 2019;Opedal et al, 2023). Bilateral symmetry, fused corollas, horizontal orientation and reduced stamen numbers improved the precision of pollen placement on honeybees and bats in Thailand (Stewart et al, 2022).…”

Sexually concordant selection on floral traits despite greater opportunity for selection through male fitness

“…First, there is substantial uncertainty in how the rate of pollinator visitation and pollen removal translates into siring success through pollen export (Ellis & Johnson, 2010; Minnaar et al ., 2019; but see Nilsson et al ., 1992). Therefore, while studies linking floral traits to pollen removal are informative about floral function (Opedal et al ., 2023), these studies may not be directly informative about selection through siring success (Minnaar et al ., 2019; Christopher et al ., 2020). Second, selection on floral traits of self‐compatible species may also be mediated by the occurrence of either autonomous or pollinator‐facilitated self‐pollination (Barrett, 2002; Teixido & Aizen, 2019).…”

“…Understanding pollinator‐mediated selection is often facilitated by explicit consideration of trait functions and functional‐mechanical interactions among traits involved in pollen import and export (Opedal, 2021; Opedal et al ., 2023). While trait functions are increasingly well understood regarding pollen import and female reproductive success, additional complications arise when considering both sex functions and the roles of self‐ vs cross‐fertilization (Gerber, 1985; Barrett, 2002; Karron & Mitchell, 2012; Briscoe Runquist et al ., 2017).…”