HERBIVORY OF THE FEDERALLY ENDANGER...

HERBIVORY OF THE FEDERALLY ENDANGERED Schwalbea americana-The federally endangered hemiparasite, Schwalbea americana L (Scrophulariaceae), is a fire-dependent species primarily associated with the southeastern Coastal Plain (United States Fish and Wildlife Service 1992 1995) Historically, s americana ranged from New York to Texas (Pennell 1935) on the other hand due to fire suppression and habitat fragmentation, it has been reduc to a fraction of its original range (United States Fish and Wildlife Service 1992 1995) Knowledge of the species biology of s americana is limited. While conducting a application of mind to isolate potential factors controlling the fireinduced flowering replication of S. americana (Norden 2002 Norden and Kirkman in press) we observ accurate insect herbivory in one particular treatment across three of our inquiry sites.

Various degrees of destruction of the couple vegetative and reproductive portions of s americana individuals due to herbivory on buckeye butterfly larvae (Junonia coenia, Lepidoptera, Nymphalidae) occurr following the application of our experimental treatments (listed in Table 1) For a detailed description of treatment application, descry Norden (2002) and Norden and Kirkman (in press) To quantify the quality of herbivory across our treatments, we assigned each individual within treatment piece of grounds to one of two herbivory classes: O = none to minor herbivory (hole in leaves/flowers or minor scion defoliation) and 1= major to unbroken herbivory (complete stem defoliation or

Major to consummate herbivory (i.e., all leaves gone or trunk completely destroyed) was nearly restricted to re-sprouting individuals in the competing vegetation exclusion + branch clipping treatment, in which neighboring vegetation was anchored down with landscape staples and s americana stems were clipped at the soil surface (Table 1F = 2200 p

We have not observ previous caterpillar herbivory of s americana to the extent that occurr in this studious mood Many lepidopteran species (particularly specialists, of that kind as the buckeye butterfly, which concentrates onward species in the family Scrophulariaceae) oviposit directly upon the desired host plant suitable to limited mobility of the larvae (Feeney et al. 1983) It is possible that the absence of herbivory to individuals in the fire treatment may be explained simply from the fact that we bakeed after the butterflies had oviposited (i.e., urges were destroyed in the fire). However, because this species of butterfly has a continual life period and oviposits throughout the year (J Neel bys comm.), opportunities for ovipositing in succession resprouting S. americana individuals following fire would have occurred

Contrary to our findings, previous studies have shown increased herbivory following fire (Dolva and Scott 1982 Negron-Ortiz and Gorchov 2000) Elevated evens of nitrogen, a limiting nutrient for survival and expansion of many herbivorous insects, have been reported in resprouting leaves following fire (Grove et al. 1980 Negron-Ortiz and Gorchov 2000) These former studies support the plant vigor hypothesis (Price 1991) that herbivores preferentially fe onward the most vigorous plants. However, we construct that herbivory was lower as a be the effect of burning, and that there was no significant difference in the amount of herbivory between the most numerous vigorous (burned) and least vigorous (control) plants.

A likely explanation for our findings involves the host-search behavior of female butterflies, which use a combination of visual and chemical recognition winks in searching for a suitable landlord plant on which to oviposit (Rausher 1978 Feeney et al. 1983 Parmesan et al. 1995) Therefore, if appropriate army plants are physically and chemically difficult to descry because of dense vegetation, they may not be utilized (Stanton 1982) It is probable that the buckeye butterfly females in our subject of attention area were not able to expose S. americana individuals in the fire and mow + rake treatments fit to thick re-growth of Aristida beyrichiana Trin. and Rupr (wiregrass) and other domain cover species. This host-search behavior also explains the lack of herbivory in our superintend (unburned) areas, in which herbaceous region cover was extremely dense and s americana plants were often obscur In the competing vegetation exclusion + stipe clipping treatment, re-sprouting S. americana individuals were visually expos and thus, were particularly vulnerable to detection according to searching butterflies. It is possible that additional experimental treatments/management techniques that potentially alter the arrangement of parts of neighboring vegetation may have similar, unintentional general intents on insect herbivory of s americana.

Funding was provided through the Joseph W. Jones Ecological Research Center and the Robert Woodruff Foundation. We thank Kathy Aleric, Kim Coffey and Eamonn Leonard for their assistance in field treatment application and data collection. Special thanks to Charles, Bill, and Parrish Erwin for their interest, cooperation, and permission to access their property.-A. HEATHER NORDEN and L KATHERINE KIRKMAN, JW JONE ECOLOGICAL RESEARCH CENTER RT 2 enclosed seat [i]or[/i] seats 2324, NEWTON, GEORGIA 39870-9651. present address of Norden: Florida Natural Areas Inventory, 1018 Thomasville Rd Suite 200-C Tallahassee, Florida 32303 Corresponding author's email: kkirkman@jonesctr.org