2.2 Reproductive aspect
Seasonal synchronisation of flowering is often closely linked to vegetative phenology. This has several obvious benefits, apart from those incidental to optimal timing with respect to climatic factors. Among the benefits, close synchronisation helps assure adequate pollen when the female structures are receptive. Also, by all occurring early enough, this assures sufficient time for fruits and seeds to develop and mature before either summer drought or autumn cold disrupt such processes. Moreover, brief but differentiated flowering seasons can also provide reproductive barriers between species that are interfertile but whose hybrids may not be ecologically fit; however, such barriers have broken down in some eucalypt species grown as exotics where their flowering seasons differ from those in native habitats (Eldridge et al. 1993). This synchrony can mean very seasonal food supplies for animal pollinators, but very short seasons can be made good by other, sympatric species having differentiated flowering seasons − as with various eucalypt species (Eldridge et al. 1993). A further but probably very incidental benefit of flowering synchrony may be creating a brief superabundance for herbivores, which we will consider later.
Masting, namely heavy flowering and seed production in some years, with little or none in between (e.g. Kelly 1994; Kelly and Sork 2002), is a phenomenon involving the timing of flowering. Its postulated biotic significance is as a means of alternating between occasional predator satiation and more frequent predator avoidance. However, it is not actually a seasonal phenomenon, nor really ontogenetic, so it is not considered further.
Timing of flowering has been reported as a minor factor in complex interactions involving transmission of pathogens by pollinators (Biere and Antonovics 1996; McArt et al. 2014), but is not considered further in this connection.
Pathogens as putative drivers
The role of pathogens as potential evolutionary drivers of seasonal phenology appears to have been especially under-researched. Cases we consider involve: potential roles of pathogens in governing the deciduous growth habit; the seasonal timing of spring flushing in a widely distributed conifer; two closely related Pinus species with overlapping distributions but markedly different seasonal timing of vegetative and reproductive processes; and an oak species in what is effectively an altitudinal transect. Briefly considered also is how pathogens can modify phenotypically some processes that are normally parts of seasonal phenology.