A handbook for standardised measurements of plant reproductive traits: from pollen grain to seedling

A lack of standardised sampling protocols prevents functional traits from expressing their full potential to advance plant ecology, biogeography, and evolutionary biology. Handbooks providing protocols for standardised measurements of plant functional traits allow researchers to tackle large-scale ecological questions but have traditionally focused on vegetative traits such as leaves, stems and roots. This handbook provides standardised protocols for 58 reproductive traits of flowers (10 traits), fruits (6 traits), seeds (36 traits) and seedlings (6 traits). It is the first effort to standardise sampling for relevant reproductive traits to better understand processes, such as pollination, frugivory, seed dispersal, seed longevity, germination, and seedling establishment. The protocols were designed to embrace the global diversity of ecological contexts experienced by flowers, fruits, seeds, and seedlings and incorporate methods for temperate to tropical, dry to moist and fire-prone to fire-sensitive ecosystems. We offer general guidelines for sampling, storing, and processing reproductive traits. Before laying out the protocol, we briefly describe each trait functionality, trade-offs, and sources of variability to give a broad context. Standardised protocols to estimate reproductive plant traits will unlock the full potential of plants to mitigate land-use and climate-change impacts, and support restoration of degraded ecosystems.