Ison J.L.,University of Illinois at Chicago |
Ison J.L.,Wittenberg University |
Wagenius S.,Plant Conservation and Biology
Journal of Ecology | Year: 2014
Summary: In small fragmented plant populations, reproductive failure due to pollen limitation is often attributed to spatial isolation of individuals. While flowering time has been shown to affect seed set, its role in pollen limited fragmented populations is less understood. In this study, we quantified near-neighbour distances, flowering phenology, and how they interact to affect seed set in individual plants. We followed the daily flowering phenology of over 2400 heads on over 500 Echinacea angustifolia individuals and quantified the resulting seed set during three consecutive flowering seasons. The study was conducted in an experimental plot where we randomized planting locations to eliminate spatial patterns of mate availability which are common in fragmented populations of Echinacea, a self-incompatible plant. We found that individual flowering time had a larger and more consistent effect on seed set than did spatial location. Seed set in the earliest flowering plants exceeded seed set in the latest by 46-70% in all three years. The role of spatial isolation, characterized both by individual distance to conspecific plants and by location in the plot, was less consistent and showed a weaker relationship with seed set than did flowering phenology. The most isolated plants set 20-27% less seed than the least isolated plants in 2005-2006 with no difference in 2007. In one year, we quantified seed set by floret position within a flowering head. We found significant positional effects; however, effects due to flowering time were much greater. These results were more consistent with the pollen limitation hypothesis than the resources limitation hypothesis. Synthesis. Our results illustrate that flowering time and distance to neighbouring conspecifics can cause reproductive failure in fragmented populations, even in the absence of mate limitation caused by mating incompatibility. These findings suggest that flowering time may be an underappreciated contributor to reproductive failure in small fragmented populations. Our results illustrate that flowering time and distance to neighbouring conspecifics can cause reproductive failure in fragmented populations, even in the absence of mate limitation caused by mating incompatibility. These findings suggest that flowering time may be an underappreciated contributor to reproductive failure in small fragmented populations. © 2014 British Ecological Society.
Ison J.L.,University of Illinois at Chicago |
Ison J.L.,Wabash College |
Wagenius S.,Plant Conservation and Biology |
Reitz D.,Carleton College |
Ashley M.V.,University of Illinois at Chicago
American Journal of Botany | Year: 2014
Premise of the study: Although spatial distance is considered the primary factor in determining plant mating patterns, flowering time and synchrony are also likely to be important. Methods: We quantified the relationships of both distance and fl owering phenology to the probability of mating between individual plants. In an experimental plot, we followed daily fl owering phenology in Echinacea angustifolia, a self-incompatible perennial pollinated by solitary bees. We assigned paternity to 832 of 927 seedlings from 37 maternal plants using 11 microsatellite loci. Potential pollen donors included the experiment plot's 202 fl owering plants and a nearby plot's 19 flowering plants. For each maternal plant sampled, we examined the pollen pool by quantifying correlated paternity and the effective number of pollen donors. Key results: Significantly more pollinations occurred between neighboring and synchronous plants than expected under random mating, with distance being more important than fl owering synchrony. The distance pollen moved varied over the course of the season, with late fl owering plants mating with more distant plants compared to early or peak fl owering plants. All maternal plants had a diverse set of mates (mean number of effective pollen donors = 23.7), and the composition of the pollen pools overlapped little between maternal plants. Conclusion: Both distance and flowering synchrony influenced pollination patterns in E. angustifolia. Our results suggest that pollen movement between incompatible mates and fl owering asynchrony could be contributing to the reduced seed set observed in small E. angustifolia remnants. However, we also found that individual plants receive pollen from a diverse group of pollen donors. © 2014 Botanical Society of America.