Epiphytic Species Composition Research Articles

Epiphyte and herbivore interactions impact recruitment in a marine subtidal system

Marine assemblages are influenced by the rate and timing of species settlement and recruitment. Both abiotic factors and biotic interactions can impact recruitment rates of marine species in a variety of systems. However, the impacts of species which recruit at the same time upon each other are less well understood. We investigated the relationship between the recruitment of Lacuna vincta, a small (<6 mm shell diameter) marine snail, and two species of algal epiphytes, the native Ceramium virgatum and the invasive Neosiphonia harveyi, in the shallow subtidal zone of Narragansett Bay, Rhode Island. All three species exhibit peak recruitment densities during two months in the summer. We found that the presence of algal epiphytes facilitates the recruitment rate of L. vincta, regardless of the epiphyte species composition. We also found a positive relationship between the number of L. vincta present and epiphyte recruitment, which is disproportionately driven by higher recruitment of N. harveyi than C. virgatum. Understanding recruitment dynamics and interactions is vital to effectively mitigate the effects of and adaptations to changes due to the establishment of non-native species.

Trilhas podem influenciar a composição florística e a diversidade de epífitas na Floresta Atlântica?

Um tipo de efeito de borda ainda pouco explorado é aquele exercido por trilhas. Testamos a hipótese de que áreas a diferentes distâncias de uma trilha em um fragmento de Mata Atlântica em São Paulo difeririam em relação à composição e diversidade de espécies de epífitas vasculares. Instalamos 20 parcelas de 2 × 50 m para marcar os forófitos nos quais seria feito o levantamento das epífitas. Diferenças na composição florística entre as áreas mais próximas e mais distantes da trilha não foram suficientes para agrupar as parcelas de cada área de forma coesa pela análise de ordenação NMDS. A diversidade (riqueza e equabilidade) de espécies mostrou-se também similar. Parece que o impacto causado pela trilha não seria suficiente para influenciar essa comunidade epifítica, o que pode ser devido a outros fatores ambientais que estariam atuando no trecho investigado ou simplesmente porque as epífitas não responderiam a um efeito de borda como o de trilhas.

Epiphyte Biodiversity in the Coffee Agricultural Matrix: Canopy Stratification and Distance from Forest Fragments

Quality of the agricultural matrix profoundly affects biodiversity and dispersal in agricultural areas. Vegetatively complex coffee agroecosystems maintain species richness at larger distances from the forest. Epiphytes colonize canopy trees and provide resources for birds and insects and thus effects of agricultural production on epiphytes may affect other species. We compared diversity, composition, and vertical stratification of epiphytes in a forest fragment and in two coffee farms differing in management intensity in southern Mexico. We also examined spatial distribution of epiphytes with respect to the forest fragment to examine quality of the two agricultural matrix types for epiphyte conservation. We sampled vascular epiphytes in a forest fragment, a shade polyculture farm, and a shade monoculture farm at 100 m, 200 m, and 400 m from the forest. Epiphyte and orchid richness was greater in the forest than in the monoculture but richness was similar in the forest and polyculture farm. Epiphyte species composition differed with habitat type, but not with distance from the forest. In the forest, epiphytes were distributed throughout tree canopies, but in the farms, epiphytes were primarily found on trunks and larger branches. Epiphyte richness and species similarity to forest species declined with distance from the forest fragment in the monoculture, but richness and similarity to forest species did not decline with distance from forest in the polyculture. This suggests polyculture coffee has greater conservation value. In contrast, monoculture coffee is likely a sink habitat for epiphytes dispersing from forests into coffee. Coffee farms differ from forests in terms of the habitat they provide and species composition, thus protecting forest fragments is essential for epiphyte conservation. Nonetheless, in agricultural landscapes, vegetatively complex coffee farms may contribute to conservation of epiphytes more than other agricultural land uses.

A hierarchical framework for investigating epiphyte assemblages: networks, meta‐communities, and scale

Epiphytes are an important component of many forested ecosystems, yet our understanding of epiphyte communities lags far behind that of terrestrial-based plant communities. This discrepancy is exacerbated by the lack of a theoretical context to assess patterns in epiphyte community structure. We attempt to fill this gap by developing an analytical framework to investigate epiphyte assemblages, which we then apply to a data set on epiphyte distributions in a Panamanian rain forest. On a coarse scale, interactions between epiphyte species and host tree species can be viewed as bipartite networks, similar to pollination and seed dispersal networks. On a finer scale, epiphyte communities on individual host trees can be viewed as meta-communities, or suites of local epiphyte communities connected by dispersal. Similar analytical tools are typically employed to investigate species interaction networks and meta-communities, thus providing a unified analytical framework to investigate coarse-scale (network) and fine-scale (meta-community) patterns in epiphyte distributions. Coarse-scale analysis of the Panamanian data set showed that most epiphyte species interacted with fewer host species than expected by chance. Fine-scale analyses showed that epiphyte species richness on individual trees was lower than null model expectations. Therefore, epiphyte distributions were clumped at both scales, perhaps as a result of dispersal limitations. Scale-dependent patterns in epiphyte species composition were observed. Epiphyte-host networks showed evidence of negative co-occurrence patterns, which could arise from adaptations among epiphyte species to avoid competition for host species, while most epiphyte meta-communities were distributed at random. Application of our "meta-network" analytical framework in other locales may help to identify general patterns in the structure of epiphyte assemblages and their variation in space and time.

Non-indigenous macroalga hosts different epiphytic assemblages to conspecific natives in southeast Australia

Codium fragile ssp. tomentosoides is one of the five most invasive macroalgae worldwide. We compared epiphytic assemblages between native (ssp. tasmanicum and ssp. novae-zelandiae combined) and non-indigenous (ssp. tomentosoides) subspecies of Codium fragile on three rocky intertidal shores in southeast Australia. Twelve species of epiphytes covered up to 20% of the surface of both native and non-indigenous Codium subspecies, but none were unique to either subspecies. For C. fragile subspecies, epiphytic cover declined from the lower (older) parts of the thallus to the branch tips. The abundance and species composition of epiphytes differed significantly between native and non-indigenous C. fragile, but differences varied among rocky shores. Results demonstrate that non-indigenous C. fragile does not play a functionally similar role to closely related native Codium subspecies. Spatial differences in epiphytic assemblages between Codium subspecies among rocky shores demonstrate that effects of non-indigenous species may be strongly location specific. Thus, our study emphasises the need to investigate variation in the effects of invaders across the regional landscape.

Variation in biomass and species composition of epiphytic community on the different aged leaves of Zostera marina (Chlorophyta)

The development of the epiphytic community on the leaves of Zostera marina was followed by comparing variations in epiphytic organic carbon, chlorophyll a, cell abundance, and species composition between the younger and older leaves. Biomass of epiphytic community on Z. marina depended on leaf age; particulate organic carbon and cell abundance on the older leaves were 21 and 192 times higher than those on the youngest leaves, respectively. The abundant taxa of epiphytic community were Leptolyngbia sp. (Cyanobacteria), Cocconeis scutellum, Campylopyxis garkeana, and Gomphonemataceae (Bacillariophyceae), and the change of species composition of epiphytic community was independent on the leaf age. Significant relation between CHLa and POC showed organic matter on the leaves was consisted of algal cells. The amount of epiphytic POC was well correlated with diatom cell abundance (P<0.1), but not with total cell abundance. The prevalence of diatoms instead of Cyanobacteria on the leaves was shown by both chemical and taxonomic analyses. Low POC/DW ratios of epiphytic community on the older leaves indicated that inorganic suspended particles were more likely to adhere.

Conservation of Vascular Epiphyte Diversity in Shade Cacao Plantations in the Chocó Region of Ecuador

ABSTRACTTo assess the contributions of rustic shade cacao plantations to vascular epiphyte conservation, we compared epiphyte species richness, abundance, composition, and vertical distributions on shade trees and in the understories of six plantations and adjacent natural forests. On three phorophytes and three 10 × 10 m understory plots in each of the agroforestry plantations and natural forests, 54 and 77 species were observed, respectively. Individual‐based rarefaction curves revealed that epiphyte species richness was significantly higher on forest phorophytes than on cacao farm shade trees; detailed analyses showed that the differences were confined to the inner and outer crown zones of the phorophytes. No differences in epiphyte species richness were found in understories. Araceae, Piperaceae, and Pteridophyta were less species‐rich in plantations than in forests, while there were no differences in Orchidaceae and Bromeliaceae. Regression analysis revealed that epiphyte species richness on trunks varied with canopy cover, while abundance was more closely related to soil pH, canopy cover, and phorophyte height. For crown epiphytes, phorophyte diameter at breast height (dbh) explained much of the variation in species richness and abundance. There were also pronounced downward shifts in the vertical distributions of epiphyte species in agroforests relative to natural forests. The results confirm that epiphyte diversity, composition, and vertical distributions are useful indicators of human disturbance and showed that while the studied plantations serve to preserve portions of epiphyte diversity in the landscape, their presence does not fully compensate for the loss of forests.

Diversidade de bromélias epífitas na Reserva Particular do Patrimônio Natural Serra do Teimoso - Jussari, BA

A presença de epífitas vasculares em florestas tropicais está freqüentemente associada a ambientes mésicos e de altitude média. Este trabalho objetivou investigar a diversidade e a composição de espécies de bromélias epífitas na Reserva Natural da Serra do Teimoso que é uma área de transição entre as florestas ombrófila e a semidecídua. A amostragem foi adaptada do "Protocolo para Amostragem Rápida e Representativa da Diversidade de Epífitas Vasculares e Não-Vasculares de Florestas Tropicais" utilizando-se oito indivíduos de Cariniana legalis localizados entre 285 m e 573 m de altitude. Foram registradas 19 morfoespécies e 526 grupos de bromélias. Quase um terço das espécies possui distribuição ampla e 27,3% é endêmica do sul da Bahia. O índice de Shannon foi 2,2 nats.indivíduo-1 e o número de espécies estimado foi 25 (SD = ±3,5). A maioria dos indivíduos de Jequitibá possuiu abundância e composição de bromélias semelhantes entre si com predominância de espécies de Aechmea e Hohenbergia. Três novas ocorrências para o sul da Bahia e mais um gênero ainda não coletado na área foram registrados. Os resultados estão de acordo com o padrão de menor diversidade de epífitas em florestas mais secas. Somente com técnicas específicas para acessar as grandes árvores do dossel, foi possível registrar as novas ocorrências, pois tais espécies são exclusivas das copas das grandes árvores. Comparada as outras metodologias para levantamentos florísticos, a metodologia empregada teve um baixo esforço amostral apresentando resultados semelhantes. As grandes árvores possuem especial importância para as epífitas devido à concentração de espécies e de indivíduos sobre elas. Assim, seria aconselhável que outros levantamentos utilizassem metodologias de acesso ao dossel para coletar epífitas mais apropriadamente nas grandes árvores.

Species richness and species composition of vascular epiphytes in the lucidophyllous forests in southern Kyushu

Species richness and species composition of vascular epiphytes in the lucidophyllous forests in southern Kyushu

Long-term changes of epiphytic lichen species composition over landscape gradients: an 18 year time series

Abstract:The study aimed to determine how the response of the epiphytic lichen vegetation to sulphur air pollution is affected by interaction with other factors (distance from pollution sources, habitat, altitude, initial eutrophication of the tree bark). It was based on a series of four successive recordings taken over a period of 18 years with increasing pollution levels and on the same set of 139 solitary trees. Relationships between habitat variables and lichen community composition are assessed using canonical correspondence analysis. The data set comprised 69 lichen species. Ordination of initial species composition on trees revealed two major gradients: eutrophication and acidity.The species composition significantly changed with time, with a general decrease of the total number of lichen species per tree. In general, species sensitive to air pollution decreased, while tolerant species increased in number. Change over time differed depending on the position of the tree within the landscape (relative to one major source of pollution, the town of Tábor, whereas the distance to the other source, Sezimovo Ústí, was not significant) and on the initial species composition found on the tree. Trees under the effect of eutrophication changed their species composition less, indicating that the effect of eutrophication (mainly increased bark pH) may ameliorate the effects of air pollution; a local effect of eutrophication also seems to play an important role. Distance to pollution sources had only a small impact on the rate of change and perhaps other local conditions (sheltered or humid position, altitude) play a role in this interaction. There was a decrease of the overall heterogeneity of the data set over time. This means that the gradients in species composition attributable to these variables became less important over time. Therefore, one of the effects of air pollution is also a general homogenization of the lichen vegetation of the solitary trees.

Species richness and species composition of epiphytes in a lucidophyllous forest in Mt. Omoridake, Aya, Miyazaki Prefecture

Species richness and species composition of epiphytes in a lucidophyllous forest in Mt. Omoridake, Aya, Miyazaki Prefecture

Retrospective analysis of epiphyte assemblages in relation to seagrass loss in a eutrophic coastal embayment

This is a retrospective study of shifts in species composition of epiphytic macroalgae that occurred during a period of seagrass loss in Cockburn Sound, Western Australia. Detailed analysis of data on relative abundances of 108 epiphytic taxa collected over 2 yr from 27 widely dispersed sites around Cockburn Sound showed differences in epiphyte composition between sites with loss of sea- grasses (Loss sites) and those with no loss in the the long-term (No Loss sites). Future seagrass losses, however, were not predicted by shifts in species composition. Most species were rare and varied with season of sampling. Hence, varying assemblages of species contributed to differences on each sam- pling occasion. Only 6 of the 108 species were strong, consistent contributors to differences between Loss and No Loss sites (Sphacelaria sp., Laurencia sp., Enteromorpha intestinalis, E. prolifera, Ulva lactuca, Acrochaetium sp.) and could be considered as 'indicator species'. Only 2 species (Sphacelaria sp. and Laurencia sp.) were present consistently in high abundances at No Loss sites. Foliose green algae (Ulva sp., Enteromorpha spp.), commonly considered to signal eutrophication, were found con- sistently in higher abundances at Loss sites. Shifts in epiphyte species composition correlated with patterns of nutrient loading and seagrass decline, in addition to the increases in biomass reported earlier, but did not predict future seagrass loss.

Species richness and species composition of epiphytes in a lucidophyllous forest on Mt. Kurino-dake, Kagoshima Prefecture

Species richness and species composition of epiphytes in a lucidophyllous forest on Mt. Kurino-dake, Kagoshima Prefecture

Vertical stratification of vascular epiphytes in submontane and montane forest of the Bolivian Andes: the importance of the understory

We studied species richness, composition, and vertical distribution of vascular epiphytes at two sites in the Bolivian Andes. To account for the epiphyte flora on understory trees, epiphytes on shrubs and small trees were sampled in 20 × 20 m2 subplots around each sampled canopy tree; this understory zone U is introduced as an addition to the well-established five vertical Johansson tree zones. More than 20% of about 500 species recorded were found only in the understory subplots, including ca. 40% of aroids, 35%–40% of piperoids, and 25%–30% of ferns. Habitat generalists (occurring in three or more zones) were most common, contributing about 50% of all species, specialists (occurring only in two zones, or in three continuous ones) 34%–42%, and hemiepiphytes 6%–16%. Canopy epiphytes (occurring > 90% in tree zones Z3–5) were mainly represented by orchids and ferns, many with special adaptations to drought stress such as pseudobulbs, succulence, and poikilohydry. Trunk epiphytes ( > 90% in understory and tree zones Z1–2) reached highest relative species numbers among piperoids and ferns. Most hemiepiphytes were also trunk epiphytes, due to their characteristic growth pattern, and included mainly aroids. The vertical distribution of epiphytes within a tree is determined by several microenvironmental gradients, with light intensity, wind speed, and air temperature increasing and air humidity decreasing from the ground level to the canopy.

Contribution of benthic and epiphytic diatoms to clam and oyster production in the Akkeshi-ko estuary

The species composition and dynamics of phytoplankton in the water column and its contribution to clam, Ruditapes philippinarum, and oyster, Crassostrea gigas, production were studied in the Akkeshi-ko estuary, eastern part of Hokkaido, Japan. A total 128 taxa of diatoms were identified, with 103 and 102 species occurring on the surface sediments and in the water column, respectively. Amphora sp., Bacillaria paradoxa var paxilifer, Cocconeis scutellum, Navicula sp., Nitzschia sigma, Paralia sulcata, Rhoicosphenia curvata, Synedra ulna and Thalassiosira sp. were most common and dominant in all stations in both water column and surface sediment. Benthic diatoms were most dominant in both water column and surface sediment. The species composition of epiphytes was, in part, similar to diatom assemblage of the water column and also to that of the surface sediment. The benthic and pelagic ratio in the diatom assemblage of the water column was very high. Benthic diatoms were able to resuspend into water column by turbulence stimulated by wind. Chlorophyll a concentration in the water column increased as wind speed increased. Seventy and 67% of the gut contents oysters consisted of benthic diatoms in 2003 and 2004 and also 78 and 87% of clams in 2003 and 2004, respectively. The availability of benthic and epiphytic diatom assemblages contributes significantly to food resources for clam and oyster mariculture due to resuspension by disturbance in the Akkeshi-ko estuary.

Productivity aspects of three tropical seagrass species in areas of different nutrient levels in Kenya

Previous work conducted in two seagrass areas of different nutrient status, along the Kenyan coast, has shown that the seagrasses were characterised by differences in the species composition and biomass of epiphytic algae. This study was undertaken to evaluate the productivity patterns of the seagrass species growing in these same sites. Studies were made on Thalassodendron ciliatum (Forskål) den Hartog, Thalassia hemprichii (Ehrenberg) Aschers and Cymodocea rotundata Ehrenberg and Hempr. ex Ascherson growing in the lagoons of Nyali and Vipingo, along the Kenyan coast, during the South East (SE) and North East (NE) monsoon periods. The results of this study revealed differences in the levels of nitrate within the water column, with Vipingo having lower levels of around 4 μM during the low tide period of the SE monsoon while nitrate levels in Nyali reached levels of 16 μM during the same period. Of the three seagrass species studied, C. rotundata had the highest shoot densities in both sites. The shoot densities of C. rotundata reached levels of 1300 shoots m −2 compared to an average of 600 shoots m −2 for both T. ciliatum and T. hemprichii. The stems of T. ciliatum were found to be 200 mm long in Nyali whereas those in Vipingo were 80 mm in length. Of the three seagrasses T. ciliatum and T. hemprichii showed significant differences in total leaf growth between the two sites. However, of these two species, only T. hemprichii showed distinct differences in leaf production and biomass when the two sites were compared. Leaves of T. hemprichii showed growth rates of 0.008 g dw shoot −1 day −1 in Nyali while the growth rate in Vipingo was 0.004 g dw shoot −1 day −1. Leaf production rates were approximately 0.005 g dw shoot −1 day −1 for T. ciliatum in both Nyali and Vipingo and that of C. rotundata was approximately 0.0015 g dw shoot −1 day −1 in the two sites. This suggests that of the three species studied, T. hemprichii may have been influenced by the nutrient input in Nyali. The abundance of epiphytes on the stems of T. ciliatum was higher in Nyali during both seasons; therefore we suggest that although the composition of epiphytic species is the main indicator of nutrient enrichment in these areas the enhanced productivity of T. hemprichii may be another indicator of the nutrient status of these study sites.

Effects of selective logging on vascular epiphyte diversity in a moist lowland forest of Eastern Himalaya, India

Effect of selective logging on vascular epiphyte diversity was investigated in a moist lowland forest of Eastern Himalaya. Three epiphytic groups viz. orchids, pteridophytes and non-orchid angiosperm epiphytes were specifically studied in closed, selectively logged and in unlogged forests with treefall gaps. Logging reduced the structural complexity of the forests and altered their microclimate. With logging, there was a general decline in richness and abundance of epiphytes except orchids. The abundance and species composition of pteridophytes and non-orchid angiosperm epiphytes were related to microclimate and substrate features while their richness were correlated only with canopy cover. In contrast, orchid species composition was related to forest structure. A combination of management strategies is required for conservation of all epiphyte groups. A mosaic of logged and unlogged forest patches with undisturbed forests in proximity would maintain the diversity of pteridophytes and other angiosperms. However, for full representation of orchids, it is necessary to maintain the structural diversity of the tree forms.

Seasonal and vertical distribution of marine epiphytic algae in the Evoikos Gulf (Aegean Sea, Greece)

The subtidal epiphytic communities of both macroalgae and microalgae of the Aegean Sea have been inadequately investigated. In this paper epiphytic algal assemblages thriving on different hosts [i.e. the phaeophyte Padina pavonia (L.) LAMOUROUX, the chlorophyte Halimeda tuna (ELLIS et SOLANDER) LAMOUROUX and the seagrass Posidonia oceanica (L.) DELILE], were studied in a typical oligotrophic site of the Aegean Sea (Dikastika, Attica Peninsula) during the course of one year (June 1997-May 1998). A total of 47 taxa of epiphytic macroalgae were identified, with Hypnophyceae and Ephemerophyceae being the dominant life forms. The major algal groups (rhodophytes, phaeophytes, chlorophytes) showed a distinct seasonality, with rhodophytes predominating on all hosts. The majority of epiphytes favoured a certain position on the host thallus or blade. A distinct vertical zonation pattern was found, with epiphytes covering only certain host areas (upper-, middle-, lower parts of the plant), and further differentiated between the frond edge and blade's lamina. A total of 175 taxa of diatoms were identified and the diatom assemblages bear great resemblance to typical epiphytic floras, with dominant genera Mastogloia, Amphora, Nitzschia, Diploneis, Navicula and Cocconeis. Mass development of epiphytic diatoms on certain hosts implies host preference, but no host-specificity could be ascertained. The total epiphytic species composition seems to be affected by the seasonal alteration of abiotic factors. Epiphytic macroalgal species abundance and diversity was the highest during spring, having a possible competitive influence on the epiphytic diatom growth, whereas higher species abundance of diatoms during summer might furthermore be attributed to the surface increase of macroalgae.

Nutrient induced changes in the species composition of epiphytes on Cladophora glomerata Kütz. (Chlorophyta)

Cladophora glomerata is a widely distributed filamentous freshwater alga that hosts a complex microalgal epiphyte assemblage. We manipulated nutrients and epiphyte abundances to access their effects on epiphyte biomass, epiphyte species composition, and C. glomerata growth. C. glomerata did not grow in response to these manipulations. Similarly, nutrient and epiphyte removal treatments did not alter epiphyte biovolume. Epiphyte species composition, however, changed dramatically with nutrient enrichment. The epiphyte assemblage on unenriched C. glomerata was dominated by Epithemia sorex and Epithemia adnata, whereas the assemblage on enriched C. glomerata was dominated by Achnanthidium minutissimum, Nitzschia palea and Synedra spp. These results indicate that nutrients strongly structure epiphyte species composition. Interactions between C. glomerata and its epiphytes were not affected by epiphyte species composition in our experiment but may be when C. glomerata is actively growing.

Species-specific impacts of grazing amphipods in an eelgrass-bed community

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 223:201-211 (2001) - doi:10.3354/meps223201 Species-specific impacts of grazing amphipods in an eelgrass-bed community J. Emmett Duffy*, Annie M. Harvilicz School of Marine Science and Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, Virginia 23062-1346, USA *E-mail: jeduffy@vims.edu ABSTRACT: Small, grazing invertebrates often benefit seagrasses by cropping their epiphytic algal competitors. Yet predictive relations between grazer abundance and seagrass performance are elusive, in significant part because of poorly understood diversity in mesograzer feeding biology. We conducted experiments in eelgrass Zostera marina microcosms to explore how differences in feeding between 2 common grazing amphipod taxa affected accumulation and species composition of epiphytes on eelgrass, as well as amphipod population growth, competition and production, over a 4-week period in summer. Gammarus mucronatus and ampithoids (a mixture of Cymadusa compta and Ampithoe longimana) were stocked, singly and in combination, along with a grazer-free control treatment. Amphipod population growth rates indicated that the 2 taxa competed for a common limiting resource, presumably periphyton, which was essentially eliminated in all grazer treatments. Final abundances of both amphipod taxa were 53 to 68% lower in treatments where the other grazer was present than in single-species grazer treatments. A common carrying capacity was also indicated by the nearly identical final biomass of amphipods across treatments, despite 2-fold variation in initial amphipod densities. These results support the hypothesis that the 2 amphipod taxa are roughly equivalent in terms of resource requirements and production rates. Despite this equivalence, subtle differences in diet breadth between amphipod taxa translated into substantial differences in biomass and composition of the fouling assemblage among treatments. Whereas grazer-free eelgrass became heavily fouled with periphyton and tunicates, eelgrass exposed to G. mucronatus alone was overgrown by the red alga Polysiphonia harveyi, which reached a biomass equal to the total fouling mass of grazer-free controls. P. harveyi was nearly absent from all other treatments. In contrast, eelgrass with ampithoids was virtually devoid of all fouling material. Thus, similar mesograzer species can have markedly different impacts on fouling assemblages, and these occur despite strong similarity in grazer energetics and primary food sources. Our results may help to reconcile evidence of diet overlap and diffuse competition among mesograzer species with the different feeding preferences and community impacts shown for several mesograzers in experimental studies. KEY WORDS: Amphipods · Ampithoe longimana · Community structure · Competition · Cymadusa compta · Gammarus mucronatus · Grazing · Mesograzers · Resource limitation · Zostera marina Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 223. Online publication date: November 28, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.