Amy N. Wright

Impact of Insecticide Treatment on Herbivory and Reproductive Success of the Federally Endangered Plant Clematis morefieldii Kral

ABSTRACT  Herbivory is common on the federally endangered Clematis morefieldii (Ranunculaceae), but little is known about its effect on reproductive output. Over 3 yr, we applied the insecticide Sevin (0.26% carbaryl) or water (as a control) to 40 plants (20 per treatment) every 3 wk during the growing season. Herbivores destroyed fewer flower buds on insecticide-treated plants (18.4% fewer in 2010, 45.6% fewer in 2011, 39.7% fewer in 2012), but fruit production increased 3.7-fold on insecticide-treated plants only in 2011. High rainfall during peak flowering/fruiting (April–June) influenced the effectiveness of treatments by boosting achene production in 2011. We compared the amounts of vegetative herbivory (vertebrate browse damage, invertebrate browse damage, piercing-sucking herbivore damage, or leaf miner damage) within each year. Both vertebrate and invertebrate browse damage were significantly greater (1.2- to 2.2-fold) on control plants for all three years. Piercing-sucking herbivory was greater (25–40% more) on control plants during most of the growing season for all three years. Vertebrate damage was more frequent on insecticide-treated plants (25–40% greater) during 2012. During high rainfall years, invertebrate herbivory reduced reproductive output, either directly by attacking flower buds/flowers or indirectly by vegetative herbivory that reduces resources available for reproduction. Insecticide use during years of high insect infestation could be a viable option for managers seeking to increase seed output by this rare plant.

Reproductive Biology of the Federally Endangered Clematis morefieldii Kral (Ranunculaceae)

ABSTRACT  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 Conservancys 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.