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Successful management of rare plant species requires understanding of reproductive life history. To assess reproductive attrition, the status of all reproductive units (expressed in seven stages) on 40 plants at The Nature Conservancy's Keel Mountain Preserve (Madison County, Alabama) was recorded throughout 4 yr (2009–12). Floral herbivory by Lepidopteran larvae (Geometridae) and abortion of reproductive units was common, with few flower buds (< 12%) producing mature fruits and the greatest attrition occurring during the smallest flower bud stage. Reproductive output was positively correlated with peak growth season rainfall (April–June); plants produced more fruits in wet years (2009 and 2011) than in drought years (2010 and 2012). Postdispersal achene predation assessed in a high-density Clematis area and a low-density Clematis area reached 15% after 1 wk and increased to 30% after 4 mo but did not significantly differ between high-density and low-density areas. Germination was documented by planting achenes in cages in high-density and low-density areas. Seeds remained dormant the first year and germinated in significantly greater amounts the second year (23%) compared to the third year (9%) after planting. Germination did not differ between high-density and low-density areas. This study documented high levels of floral herbivory, demonstrated the importance of growing season rainfall, revealed moderate levels of postdispersal achene predation, and confirmed the existence of a short-lived seed bank. Land managers can use these results to design management strategies to boost reproductive success of plants in declining or small populations.
In pyrogenic ecosystems, fire often plays an integral part in plant population dynamics. For a subset of plant species in such ecosystems, fire is connected to seed set and/or germination, resulting in postfire recruitment episodes. We investigated the relationship between fire and seed set in the perennial forb Liatris ohlingerae (Asteraceae), one of many species endemic to the pyrogenic Lake Wales Ridge ecosystem of central Florida. Our study focused on comparisons of seed production and invertebrate damage to flowers across L. ohlingerae populations in locations encompassing a range of intervals since fire, between 1 mo and 9 yr prior to the study. We found that the estimated seed set was significantly higher in populations burned less than 1 yr prior to the study than in all other populations. Both low invertebrate damage and high seed production rates contributed to this trend in the populations burned < 1 yr prior to the study. Previous research has demonstrated that germination of L. ohlingerae seeds is higher and seed predation is lower in more recently burned patches, so it is likely that the pulse of seed production observed in recently burned populations would carry through to the seedling stage. The processes behind the observed increase in fecundity remain unknown, and their characterization will likely be valuable for continued efforts to conserve L. ohlingerae. Because invertebrate damage did not significantly influence seed production, it need not be prioritized for conservation management.
Roads have the potential to serve as dispersal corridors for invasion into pristine habitats for invasive exotic species. However, undisturbed habitats may also resist such invasion. Torpedograss (Panicum repens L.) is an aggressive invasive grass in many parts of the world and, although most problematic in lakes and ponds, frequently occurs in roadsides and in other disturbed habitats. We studied torpedograss dynamics along roadsides adjacent to upland habitats in south-central Florida to determine whether observed tiller population growth rates differed among roadside populations adjacent to different habitats. We also examined seasonal growth and persistence patterns of this invasive species in sand roads, quantifying torpedograss density, growth, and panicle production at 10 roadside sites every other month for 14 mo. Four populations were adjacent to disturbed habitats (pastures or disturbed Florida scrub) containing established populations of torpedograss, while six populations were adjacent to undisturbed Florida scrub lacking torpedograss. Population growth rates were negative in most roadsides neighboring undisturbed scrub, and positive when neighboring disturbed habitats. Tiller density, tiller height, and panicle production were all greatest in late summer, and tiller density increased with temperature and relative humidity. We observed no evidence of recruitment from seed. We never found any invasion of undisturbed Florida scrub, consistent with the hypothesis that undisturbed Florida scrub resists invasion. Results suggest that, in xeric habitats, land managers should give higher priority to restoring disturbed habitats or controlling expansion from disturbed habitat edges rather than to eradicating roadside populations of torpedograss.
Sewanee: The University of the South, located in Franklin County, Tennessee, is a 5,263 ha site that encompasses a variety of plateau and cove habitats on the southern Cumberland Plateau in southeastern Tennessee. The vascular flora of the University of the South was documented from 1948–2015 and comprises 1,118 species and lesser taxa in 553 genera and 150 families. We documented 229 exotic taxa, 20.5% of the flora. This flora contains six state records, 74 Franklin County records, and two potential new species. Eighteen taxa are listed as protected either at the state or federal level, including the federally listed endangered Clematis morefieldii and state listed endangered Diamorpha smallii, Silphium brachiatum, and Symphyotrichum pratense. When compared to the five other published floras for the southern Cumberland Plateau in Tennessee, the University of the South flora is the most diverse, capturing 69% of the total taxa at the species level for the region. The high diversity of plant species in the University of the South flora reflects the broad range of habitats that can be found within the campus and contiguous natural areas. This flora demonstrates that herbaria at small liberal arts colleges can play an important role in the documentation and promotion of plant biodiversity within their region.
Much of western Sainte (Ste.) Genevieve County, Missouri, is underlain by parts of the LaMotte sandstone formation. The geological properties of this bedrock have led to the formation of canyons and cliffs, which harbor “glacial relicts” and other regionally rare, restricted plant species. A partial survey of the flora at Horton Farm Conservation Area (HFCA) in Ste. Genevieve County was performed from June 2012 to July 2014 to provide local conservation officials with relevant data to make informed management decisions. Four specific areas of interest were selected: a cliff complex near Rough Creek, a small acid seep, a glade/woodland complex, and the riparian corridor along Jonca Creek. A total of 214 vascular plant species was collected from HFCA: 23 from the acid seep area, 120 from Jonca Creek, 48 from the glade/woodland, and 77 from the cliff area. Included were 5 species of conservation concern, and 16 county records were documented. A checklist of the collected species is included, and a new combination is published—Aureolaria flava (L.) Farw. var. calycosa (Mack. & Bush) A.P. Braun.