Plant herbivore interactions Dr. Steven C. Pennings University of Houston

Department of Biology and Biochemistry University of Houston Houston Texas 77204-5513 USA

scpennin@central.uh.edu https://uh.edu/nsm/biology-biochemistry/people/profiles/steven-pennings/ https://orcid.org/0000-0003-4757-7125 Georgia Coastal Ecosystems LTER Project

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

gcelter@uga.edu https://gce-lter.marsci.uga.edu/ Dr. Steven C. Pennings University of Houston

Department of Biology and Biochemistry University of Houston Houston Texas 77204-5513 USA

scpennin@central.uh.edu https://uh.edu/nsm/biology-biochemistry/people/profiles/steven-pennings/ https://orcid.org/0000-0003-4757-7125 Principal investigator Dr. Chuan-Kai Ho Texas A&M University

5007 Avenue U Texas A&M University Galveston Texas 77551 USA

ckho88@pie.com.tw Graduate research assistant 2026

C. Ho (PhD student, UH) and S. Pennings (UH) tested the hypothesis that an omnivorous crab would have strong top-down control on an arthropod food web on the shrub Iva frutescens. It is generally believed that the diverse and reticulate interactions promoted by omnivory will tend to reduce strong trophic cascades. In both laboratory and field experiments, however, crabs suppressed both predator and herbivore populations, releasing plants from herbivore pressure and promoting plant performance. They also evaluated whether high-latitude plants are better food for herbivores than low-latitude plants. Preliminary results support this hypothesis, but suggest that the results may vary among feeding guilds.

Question 2: How do the spatial and temporal patterns of biogeochemical processes, primary production, community dynamics, decomposition, and disturbance vary across the estuarine landscape, and how do they relate to environmental gradients? (more information)

LTER NSF Georgia GCE Iva frutescens arthropod crab top-down Overall geographic extent of the research project -81.493498 -81.195661 31.552554 31.304063 2002-01-01 2008-12-31

National Science Foundation grant numbers OCE-9982133, OCE-0620959, DEB 0296160, and DEB 0638796

estuary marsh complex Eulonia - Transitional salt marsh/upland forest site at the upper reach of the Sapelo River near Eulonia, Georgia. The main marsh area is to the north of the channel where the upland is controlled by DNR. Several small creeks lie within the study area. Residential development is increasing on the upland areas south of the channel. A hydrographic sonde is deployed within this site attached to a private dock to the south of the main channel near the HW-17 bridge. The sonde is accessed from a dock on a private residence off of highway 17. As of late 2017 the property is owned by Linda Hornby. She asks that we notify her by text about an hour before arriving to service the sondes. There is no reason to go to this property other than for sonde work. -81.428481 -81.410732 31.546750 31.533963 Hunt Camp - Barrier island/marsh site on western Sapelo Island. This site is located at the upper reaches of the Duplin River, and is within the Sapelo Island National Estuarine Research Reserve. Existing well fields border small marsh area to northwest, some wells have been installed to south end of hammock where marsh is more extensive and permanent plots are located. Two existing hydrographic sondes and weather stations within this site are operated by SINERR (Hunt Camp dock) and UGAMI (flume dock). -81.295506 -81.258908 31.497026 31.462320 Four Mile Island - Low salt marsh/estuary site encompassing the southwestern end of Four Mile Island and the Sapelo River near Sapelo Sound. The large island is totally marsh, with no upland, and no development. Nearby areas, like "Sutherland Bluff", are developing with golf courses. A hydrographic sonde is deployed within this site attached to channel marker 4 (under U.S. Coast Guard permit). Salinity regime is similar to seawater. -81.318961 -81.292844 31.552554 31.533604 North Sapelo - High salinity marsh/Sapelo Sound site. Few or no small creeks, but one large creek is easily accessed. Further upstream upland drainage is affected by culvert at Reynolds' duck pond. Upland is heavily forested. Hydrographic sonde is deployed adjacent to this site attached to a channel marker (under U.S. Coast Guard permit). A huge mud flat is present at the northern tip of Sapelo Island. -81.233249 -81.195661 31.546868 31.515188 Meridian - Inland marsh and tidal creek site near Meridian, Georgia. The primary marsh site is to the south of the dock in front of the Sapelo Island Visitor Center. Some small creeks and one large creek (Hudson Creek) are present. Upland is heavily forested. Marsh to the north of the dock can be used for additional studies if larger areas are required. Upland to the North is being developed for residential use, so future access is uncertain. The USGS super station site (weather station plus multiple-sensor sonde) is deployed off the ferry dock. Salinity is similar to seawater because there is little freshwater input from the upland. -81.370752 -81.357256 31.463533 31.448419 Folly River - Salt marsh/tidal creek site at the Folly River near Doboy Sound. No upland areas present. The north side of Doboy Sound immediately opposite is similar, but creeks are not as nice. No existing markers are close enough for sonde deployment, so we will initially use the existing sonde at Marsh Landing operated by UGAMI for surrogate hydrographic data. -81.354413 -81.327201 31.442538 31.417640 Dean Creek - Doboy Sound/salt marsh site at the southern end of Sapelo Island near Dean Creek and the Sapelo lighthouse. A few small creeks are present, but a large creek (Dean Creek) is easily accessed. Upland is composed of small hammocks and some constructed causeways, with sand dune complexes east of Dean Creek and extending to the beach. Upper end of the watershed is affected by a culvert at Beach Road and heavy student use of marsh immediately adjacent to culvert. A hydrographic sonde is deployed in Doboy Sound near Commodore Island approximately 1.5km from this site. GCE6 is also the focus of Sapelo Island Microbial Observatory research on microbial diversity and genomics (http://simo.marsci.uga.edu) -81.299522 -81.264378 31.394072 31.371003 Carrs Island - Freshwater marsh site along the northern bank of Hammersmith Creek at the south end of Carrs Island. Upland area is heavily forested. Northern 3/4 of the island was diked for rice agriculture, but the southern 1/4 is undisturbed. A hydrographic sonde is deployed in the Altamaha River near Hammersmith Creek, adjacent to this site. -81.493498 -81.475900 31.348774 31.334364 Alligator Creek - Mid-estuary/salt marsh site on the west side of Friday Cap Creek along the Altamaha River. This is a brackish marsh with salinities around 14 PSU during drought, less than 5 PSU normally. A hydrographic sonde is deployed adjacent to this site in the Altamaha River near Alligator Creek, attached to the US Coast Guard Daymarker 2 pilings. -81.426272 -81.410634 31.317808 31.304063 Rockdedundy Island - Lower estuary tidal creek and marsh site at Rockdedundy Island west of Wolf Island. A hydrographic sonde is deployed approximately 2km from this site in the Altamaha River near Rockdedundy Island, attached to the US Coast Guard Daymarker 201 pilings. -81.346730 -81.326495 31.358142 31.339173 Ho, C.-K. and Pennings, S.C. 2008. Consequences of omnivory for trophic interactions on a salt-marsh shrub. Ecology. 89(6):1714-1722. (DOI: 10.1890/07-1069.1) https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/07-1069.1 Pennings, S.C., Ho, C.-K., Salgado, C., Wieski, K., Dave, N., Kunza, A.E., Wason, E.L. 2007. Presentation: Latitudinal variation in herbivore pressure in Atlantic Coast salt marshes. Joint Ecological Society of America / Society for Ecological Restoration 2007 Meeting, August 5-10, 2007, San Jose, CA. Ho, C.-K. and Pennings, S.C. 2007. Presentation: Bergmann¡'s Rule and latitudinal variation in herbivore body size. Joint Ecological Society of America / Society for Ecological Restoration 2007 Meeting, August 5-10, 2007, San Jose, California, USA. Pennings, S.C., Zimmer, M., Dias, N., Sprung, M., Davé, N., Ho, C.-K., Kunza, A., McFarlin, C., Mews, M., Pfauder, A. and Salgado, C. 2007. Latitudinal variation in plant-herbivore interactions in European salt marshes. Oikos. 116:543-549. Ho, C.-K. and Pennings, S. C. Presentation: Preference and performance in plant-herbivore interactions across latitude. 91st Annual Meeting of the Ecological Society of America. August 6-11, 2006, Memphis, Tennessee, USA. Ho, C.-K. and Pennings, S.C. 2005. Poster: Consequences of Omnivory for Trophic Interactions: A Case from Salt Marshes. Ecological Society of America 2005 Meeting - Ecology at multiple scales, August 7-12, 2005, Montreal, Canada. Ho, C.-K. and Pennings, S.C. 2005. Presentation: Consequences of ominivory. The 18th Biennial Conference of the Estuarine Research Federation. Oct. 16-20, 2005, Norfolk, Virginia. Goranson, C.E., Ho, C.-K. and Pennings, S.C. 2004. Environmental gradients and herbivore feeding preferences in coastal salt marshes. Oecologia. 140:591-600. Salgado, C., Ho, C.-K., Davé, N. and Pennings, S.C. 2003. Poster: Strength of plant-herbivore interactions varies across latitude in Atlantic coast salt marshes. 2003 Meeting of the International Biogeographic Society. International Biogeographic Society, January 4-8, 2003, Mesquite, NV. Ho, C.-K., Salgado, C.S., Dave, N.B. and Pennings, S.C. 2003. Poster: Latitudinal variation in herbivore densities and damage to plants in coastal salt marshes. Ecological Society of America, August 3-8, 2003, Savannah, GA.