Fire is an important determinant of habitat structure and biodiversity across ecosystems worldwide. In fire-dependent communities, similar to the North American prairie, fire suppression contributes to local plant extinctions. Yet the demographic mechanisms responsible for species loss have not been directly investigated. We conducted a 21-y longitudinal study of 778 individual plants of Echinacea angustifolia, a widespread perennial species with chronically limited mating opportunities, to explore how fire affects reproduction. In a large preserve, with management units on different burn schedules, we investigated Echinacea mating scenes, which quantify isolation from potential mates and overlap in the timing of flowering, to determine the extent to which fire influences the potential for sexual reproduction. We demonstrate that fire consistently increased mating opportunities by synchronizing reproductive effort. Each fire occurred during fall or spring and stimulated flowering in the subsequent summer, thus synchronizing reproduction among years and increasing the proximity of potential mates after a fire. Greater within-season flowering synchrony in postfire mating scenes further increased mating potential. The improved postfire mating scene enhanced reproduction by increasing pollination efficiency. Seed set in scenes postfire exceeded other scenes by 55%, and annual fecundity nearly doubled (88% increase). We predict the reproductive benefits of synchronized flowering after fire can alleviate mate-finding Allee effects, promote population growth, and forestall local extirpation in small populations of Echinacea and many other prairie species. Furthermore, the synchronization of flowering by burning may improve mating opportunities, reproduction, and the likelihood of persistence for many other plant species in fire-dependent habitats.

The timing and synchrony of mating activity in a population may vary both within and among years. With the exception of masting species, in which reproductive activity fluctuates dramatically among years, mating synchrony is typically studied within years. However, opportunities to mate also vary among years in nonmasting iteroparous species. We demonstrate that studying only within-year flowering synchrony fails to accurately quantify variation in mating opportunity in an experimental population ([Formula: see text]) of a nonmasting species, Echinacea angustifolia. We quantified individuals' synchrony of flowering within and among years and partitioned the contribution of each measure to mean daily mating potential, the number of potential mates per individual per day, averaged over every day that it flowered during the 11-year study period. Individual within- and among-year synchrony displayed wide variation and were weakly correlated. In particular, among-year synchrony explained 39% more variation in mean daily mating potential than did within-year synchrony. Among-year synchrony could have underappreciated significance for mating dynamics in nonmasting species.

1. Species that persist in small populations isolated by habitat destruction may experience reproductive failure. Self-incompatible plants face dual threats of matelimitation and competition with co-flowering plants for pollination services. Such competition may lower pollinator visitation, increase heterospecific pollen transfer and reduce the likelihood that a visit results in successful pollination. 2. To understand how isolation from mates and competition with co-flowering species contribute to reproductive failure in fragmented habitat, we conducted an observational study of a tallgrass prairie perennial Echinacea angustifolia. We quantified the isolation of focal individuals from mates, characterized species richness and counted inflorescences within 1 m radius, observed pollinator visitation, collected pollinators, quantified pollen loads on pollinators and on Echinacea stigmas, and measured pollination success. Throughout the season, we sampled 223 focal plants across 10 remnant prairie sites. 3. We present evidence that both co-flowering species and isolation from mates substantially limit reproduction in Echinacea. As the flowering season progressed, the probability of pollinator visitation to focal plants decreased and evidence for pollen-limited reproduction increased. Pollinators were most likely to visit Echinacea plants from low-richness floral neighbourhoods with close potential mates, or plants from high-richness neighbourhoods with distant potential mates. Frequent visitation only increased pollination success in the former case, likely because Echinacea in high-richness floral neighbourhoods received low-quality visits. 4. Synthesis. In Echinacea, reproduction was limited by isolation from potential mates and the richness of co-flowering species. These aspects of the floral neighbourhood influenced pollinator visitation and pollination success, although conditions that predicted high visitation did not always lead to high pollination success. These | 1357

Habitat fragmentation produces small, spatially isolated populations that promote inbreeding. Remnant populations often contain inbred and outbred individuals, but it is unclear how inbreeding relative to outbreeding affects the expression of functional traits and biotic interactions such as herbivory. We measured a suite of 12 functional traits and herbivore damage on three genotypic cross types in the prairie forb, Echinacea angustifolia: inbred, and outbred crosses resulting from matings within and between remnant populations. Inbreeding significantly affected the expression of all 12 functional traits that influence resource capture. Inbred individuals had consistently lower photosynthetic rates, water use efficiencies, specific leaf areas, and had higher trichome numbers, percent C, and percent N than outbred individuals. However, herbivore damage did not differ significantly among the cross types and was not correlated with other leaf functional traits. Leaf architecture and low physiological rates of the inbred compared to outbred individuals imply poorer capture or use of resources. Inbred plants also had lower survival and fitness relative to outbred plants. Our results show that inbreeding, a phenomenon predicted and observed to occur in fragmented populations, influences key functional traits such as plant structure, physiology and elemental composition. Because of their likely role in fitness of individuals and ecological dynamics plant functional traits can serve as a bridge between evolution and community or ecosystem ecology.

Rare species serve important ecosystem functions, including community resilience to global change. Yet rare species are disappearing globally because of anthropogenic activities such as fire suppression. Prescribed burning is a widespread management approach that can reduce invasive plant presence, recycle nutrients, and restore species diversity. However, the effects of prescribed burning on rare plants are not well understood. We analyzed the population dynamics of 67 rare, native plant species in response to prescribed burning using the Chicago botanic garden's Plants of Concern dataset. This dataset includes rare plant populations concentrated in the northeast part of Illinois, and a few populations in Indiana and Wisconsin, United States. We evaluated the effects of burning by comparing the percent change in population size in the short‐term (1–2 years) and long‐term (3–4 years) after prescribed burning, to the percent change in population size not following burns. In a global model with all species, we did not detect the effects of burning on percent change in population size. In species‐level analyses, we detected burn effects for most species for which we had the statistical power to detect possible burn responses, although the direction of their responses was mixed. Five species responded consistently between short‐ and long‐term datasets, and four species had mixed responses, with most responding positively over the short‐term and negatively over the long‐term. We complemented this analysis with a literature review of fire responses for available species. Our literature review revealed more responses to burning than what we found from our analyses; however, most of this evidence does not compare burned and unburned populations directly and should be treated cautiously. Through community science monitoring efforts, we were able to compile one of the largest studies of burn effects on rare plants to date, but continued monitoring is necessary to fully evaluate how prescribed burning impacts rare plant species.