Connecting relative differences in floral phenology to reproductive success Público
Schiffer, Anne (Spring 2020)
Published
Abstract
Flowering phenology is critical for plant fitness due to both abiotic and biotic drivers of reproductive success. On the abiotic side, an individual’s flowering time can influence the potential for frost damage and the soil moisture available for seed development. In terms of the biotic drivers, relative differences in blooming time may impact pollinator visitation rates and availability of pollen donors. However, it is still unclear how individual flowering time and drivers of reproduction impact plant fitness for phenologically distinct species. In this study, I analyzed the impact of relative differences in flowering time on the fecundity of individuals within a population. I collected floral phenology and seed set data for individuals of three subalpine plant species (Mertensia fusiformis, Delphinium nuttallianum, Potentilla pulcherrima) in the Colorado Rocky Mountains. To address the abiotic and biotic drivers of reproduction, I calculated changes in soil moisture, included the density of conspecific individuals, and conducted a pollen limitation experiment to isolate pollination function. Additionally, I accelerated snowmelt to simulate the variability of blooming time caused by climate change. My statistical models assessed the effects of relative blooming time, soil moisture, conspecific flower density, and pollination treatment on individual fecundity for the three species. I found that off-peak blooming is beneficial for reproductive success in some species, but the direction of flowering compared to the population peak is species-specific. Off-peak blooming in our earliest-blooming species, Mertensia, had marginally significant negative effects on seed production. The flowering time of early season species is constrained by abiotic and biotic factors, which could result in increased seed production for individuals that bloom with the population peak. For individuals of Delphinium, our mid-season species, it was reproductively advantageous to flower later than the population peak. However, individuals of Potentilla, our late-blooming species, increased seed production when they flowered earlier than the population peak. Blooming earlier or later than the population peak may have enabled individuals to avoid competition while still receiving pollination service. Over time, selection can act on those relative differences in floral phenology and reproductive success, possibly resulting in changes in population size and/or altered community composition.
Table of Contents
Introduction .................................................................................................................................. 1
Methods ......................................................................................................................................... 5
Results .......................................................................................................................................... 11
Discussion .................................................................................................................................... 19
References .................................................................................................................................... 25
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