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Authors Pennings, SC; Selig, ER; Houser, LT; Bertness, MD
Author Full Name Pennings, SC; Selig, ER; Houser, LT; Bertness, MD
Title Geographic variation in positive and negative interactions among salt marsh plants
Source ECOLOGY
Language English
Document Type Article
Author Keywords biogeography; competition; facilitation; latitude; positive interactions; salt marsh
Keywords Plus COMMUNITY ORGANIZATION; SPARTINA-ALTERNIFLORA; LATITUDINAL GRADIENT; SPECIES-DIVERSITY; PANICUM-HEMITOMON; DRIVEN VARIATION; COMPETITION; FACILITATION; PATTERNS; PREDATION
Abstract A pressing problem for ecologists is determining whether our understanding of communities, often developed from work at fine scales, can explain processes across broader scales. Here, we explore whether models of positive interactions developed in southern New England can be applied to geographic scales. Salt marsh plants may interact positively by ameliorating harsh physical conditions such as salinity stress. Because marsh porewater salinities are higher in low- vs. high-latitude marshes, we tested the hypothesis that positive interactions are increasingly important at low latitudes. Previous work supported this hypothesis at the regional scale: within New England, positive interactions were rare in Maine but common in Rhode Island. We conducted parallel experiments in Georgia and Alabama to determine whether similar results would be obtained in a geographic comparison. Nine species of salt marsh plants were transplanted into control plots or plots with neighboring vegetation removed, in three marsh zones, at two sites each in Georgia and Alabama. Removing neighbors increased porewater salinities; nevertheless, plants usually performed best in neighbor-removal treatments, indicating that most interactions were competitive rather than facilitative. Several mechanisms might explain these results. For-widely distributed species, southern individuals may be more salt tolerant than northern conspecifics. We tested this hypothesis by comparing the salt tolerance of northern and southern conspecifics of three species in a common garden experiment. In two species, southern plants were more salt tolerant than northern conspecifics. Although this pattern may explain the rarity of facilitation in the south for some species, it cannot explain our overall results because few species were studied in both geographic regions. The most likely explanation for our results is that northern marsh floras are dominated by salt-sensitive species that are likely to be facilitated by neighbors, whereas southern marsh floras are dominated by salt-tolerant species that are unlikely to benefit substantially from neighbor amelioration of soil salinities. These results illustrate the difficulties inherent in extrapolating results from even well understood systems to different geographic locations or scales. Intraspecific adaptations and community composition are often likely to vary geographically, complicating our efforts to construct geographically robust generalities about community structure and processes.
Author Address Univ Georgia, Inst Marine, Sapelo Isl, GA 31327 USA; Brown Univ, Dept Ecol & Evolutionary Biol, Providence, RI 02912 USA
Reprint Address Pennings, SC (corresponding author), Univ Houston, Dept Biol & Biochem, Houston, TX 77204 USA.
ResearcherID Number Pennings, Steven C/A-8326-2013
ORCID Number Pennings, Steven C/0000-0003-4757-7125
Times Cited 132
Total Times Cited Count (WoS, BCI, and CSCD) 140
Publisher ECOLOGICAL SOC AMER
Publisher City WASHINGTON
Publisher Address 1707 H ST NW, STE 400, WASHINGTON, DC 20006-3915 USA
ISSN 0012-9658
29-Character Source Abbreviation ECOLOGY
ISO Source Abbreviation Ecology
Publication Date JUN
Year Published 2003
Volume 84
Issue 6
Beginning Page 1527
Ending Page 1538
Digital Object Identifier (DOI) 10.1890/0012-9658(2003)084[1527:GVIPAN]2.0.CO;2
Page Count 12
Web of Science Category Ecology
Subject Category Environmental Sciences & Ecology
Document Delivery Number 706KB
Unique Article Identifier WOS:000184451900022
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