Mass flowering and flowering asynchrony characterise a seasonal herbaceous community in the Western Ghats

Abstract

Flowering synchrony within a community may be facilitated by climatic factors and by ecological interactions that promote shared pollination services. In contrast, flowering asynchrony is promoted when there is inter-species competition for pollinators. In this multiyear study, we analyse the flowering phenology of a seasonal, herbaceous community (Kaas plateau) in Western Ghats, India to identify environmental constraints that may influence flowering synchrony. We addressed the questions: (a) Is flowering seasonality correlated with climatic factors? (b) Is there evidence for flowering synchrony within the community? (c) Do plant-pollinator interactions shift with flowering phenology? In Kaas, we recorded flowering phenology of 76 herbaceous species and found that climatic factors influenced their flowering phenology. We also identified the community to be composed of a few mass flowering (MF) species ([~]30%) and several non-mass flowering (nMF) species ([~]70%). Using two novel synchrony indices, temporal overlap (SItemp) and synchrony in abundance (SIabd), we also identified higher asynchronous flowering within the community than expected. Notably, species sharing the same floral colour, showed marked absence of synchrony, thus suggesting that competition and not pollinator-mediated facilitation drives flowering asynchrony within Kaas. Finally, pollination networks were observed to shift with flowering abundances within the community. Our findings reveal that even seasonal landscapes like the laterite plateaus, despite their short flowering season that last only 4-5 months, exhibit an overall asynchronous flowering phenology. And, the synchronous flowering for which the Kaas plateau is famous, was noted to be mostly due to a few mass flowering species that alter across years.