Grass Matrix Research Articles

Bioremediation of CdII from aquatic systems by Bermuda grass matrix

Bioremediation of CdII from aquatic systems by Bermuda grass matrix

Preparation of spiked grass for use as an environmental radioactivity reference material

Measurement of radionuclides from environmental samples includes a wide variety of matrix compositions and densities. To improve the traceability of environmental monitoring, LNE-LNHB intends to produce mixed γ-ray reference materials with a known mass activity and a composition as representative as possible of real environmental samples. This paper describes the preparation and characterization of a low density treated grass matrix spiked with mixed γ-emitters. This material was used in a proficiency test exercise whose results are presented.

Shrubs versus ‘gullivers’: woody species coping with disturbance in grasslands

Resprouting of trees and shrubs in forest-grassland ecotones is a key process to understand the dynamics of these systems under different disturbance regimes. This study integrates resprouting of grassland shrubs and pioneer forest trees (‘gullivers’), burned in subtropical lowland grassland and cut in temperate highland grassland of Rio Grande do Sul, Brazil. Per grassland site, 20 individuals each of 1–2 grassland shrub species (Asteraceae) and two forest tree species (Myrsinaceae, Myrtaceae) were tagged, and post-disturbance survival and growth monitored for 1 year at 2–4 month intervals. Differences in resprouting vigour (summed-up basal area of resprouted shoots per pre-disturbance summed-up area of basal stems), and in density and allometry of resprouted shoots (allocation mode) were compared between tree and shrub species by linear mixed effects modelling and multiple comparisons, using the Tukey test. All grassland shrub individuals resprouted and regained 73–142 % (species average) of pre-disturbance basal area within one year, as opposed to 14–24 % in trees. All Myrtaceae ‘gullivers’ resprouted, but up to two-thirds of Myrsine individuals did not survive disturbance. Tree species tended to produce either many slender or few stout shoots, while shrub species were intermediate between these extremes. Forest trees regained 22–46 % of pre-disturbance height, independent of allocation mode, and grassland shrubs up to 73 %. This suggests that grassland fires allow grassland shrubs but not forest trees to persist and to grow to reproductive size. Differing sprout allocation modes may reflect allometric constraints rather than strategies to outgrow the fire-prone grass matrix.

Effects of grasses on sapling establishment and the role of transplanted saplings on the light environment of pastures: implications for tropical forest restoration

AbstractQuestionDoes the presence of grasses affect the establishment (survival and growth) of tree saplings in an abandoned tropical pasture, and what is the potential of established saplings to modify pasture microenvironmental conditions, particularly light incidence?LocationAbandoned cattle pasture, in the humid tropics of SE Mexico (18°25′–18°45′ N, 95°00′–95°18′ W).MethodsThe establishment of four native fast‐growing tree species in a tropical abandoned pasture was evaluated. Saplings of Cecropia obtusifolia, Hampea nutricia, Omphalea oleifera and Erythrina folkersii were transplanted using a split‐plot design. Plant survival and growth were evaluated over 12 mo under two experimental treatments: presence and absence of grasses. Light incidence at ground level was used to evaluate microclimate conditions under the grass matrix, compared to light incidence under saplings established in the pasture.ResultsSaplings had high survival (49–88%) regardless of the presence of grasses. In the presence of grasses, growth of surviving saplings either increased or was not impacted, and in only one out of eight comparisons did grasses negatively affect growth. The impact of saplings on light incidence in abandoned pastures depended on sapling species architecture: species with large total leaf area and canopy area ( H. nutricia and E. folkersii) significantly reduced light incidence (12–29% of total incidence), while narrow‐canopy species ( C. obtusifolia and O. oleifera) generated less intense shade (37–89% of total incidence).ConclusionsGrasses did not seem to represent a crucial limiting factor in sapling establishment of fast‐growing native species in the short term. In addition, shading by recruited saplings of some native species could be important to out‐compete grasses in the future, as well as for ‘facilitating’ regeneration of more shade‐tolerant species. Transplantation of fast‐growing native saplings into abandoned pastures, even without manipulation of the grasses, could be a useful practice for landscape‐scale restoration programmes in tropical areas. Evaluation of the longer‐term consequences (beyond the 1‐yr span of this study) warrants further research.

Regional seed mixtures for the re‐creation of species‐rich meadows in theWhiteCarpathianMountains: results of a 10‐yr experiment

AbstractQuestionsHow does sowing a regional seed mix compare with a commercial grass mix and natural regeneration for re‐creating species‐rich hay meadow vegetation? What is the trajectory of vegetation change of these treatments over 10 yr compared with ancient meadow vegetation on a nearby nature reserve? What factors indicate successful restoration on ex‐arable land?LocationWhiteCarpathian (BíléKarpaty)Mountains,CzechRepublic.MethodsIn 1999 an experiment was set up to investigate methods of re‐establishing species‐rich meadow vegetation on ex‐arable land. Large plots sown with a regional seed mixture (RSM) were compared with three other ‘lower cost’ treatments – sowing narrow 2.5‐m wide strips of theRSMinto a matrix of commercial grasses (RCG), sowing strips ofRSMinto a matrix of natural regeneration (RNR) and natural regeneration alone (NR). Results are presented for years 2000, 2004 and 2009.ResultsRegional grass species established and persisted in cover and species number, regional herb species established and persisted in number but declined in cover. Perennial weeds increased in years 2000–2004 but had declined by 2009. The vegetation showed a gradual convergence in the direction of the ancient meadow vegetation and the vegetation was species‐rich but a long way from the ancient meadow composition.ConclusionsThe experiment demonstrated lasting benefits of regional seed mixtures, including rapid establishment of meadow species with no perennial weed stage, producing vegetation suitable for haymaking. However, sowing regional seed mixtures is the most expensive method and colonization of these plots by unsown target species was slow. Satisfactory results were achieved by the cheaper method of sowing strips of regional seed mixture in a matrix of natural regeneration or natural regeneration alone, and colonization by unsown target species was the more successful here, although some of this was due to colonization (cross‐contamination) from adjacent plots. The poorest results were in the commercial grass treatments due to strong competition from sown commercial grasses. Overall, to achieve biodiversity goals in grassland restoration it is essential to use seeds of regional provenance.

Can Carbon and Phosphorous Amendments Increase Native Forbs in a Restoration Process? A Case Study in the Northern Tall‐grass Prairie (U.S.A.)

In the northern Great Plains (United States), sites with less than 20% of native species are difficult to restore. We have experimented with a restoration method that shows some promise. It consists of systematically installing simulated small‐scale patches (8.0 m2 in size) over 25% of an old field and then seeding these patches with native species. The working hypothesis is that these patches will generate a constant source of propagules which in time will lead to increases in native species diversity within the surrounding grass matrix. The objective of this paper was to determine whether soil amendments should be used to facilitate the establishment and persistence of native species (primarily forbs) within these patches. We seeded the patches with a mixture of native grass and forb species and applied four soil treatments: P fertilization, C additions, C + P, and a control (no amendments). Results for the first 5 years were as follows: (1) seeded forb richness was mostly unaffected by soil amendments; (2) seeded and nonseeded forb biomass and density were substantially reduced by C additions, whereas they were unaffected or increased under P additions; (3) both seeded and non‐native grass biomass substantially increased with C additions; and (4) there was an inverse relationship between native seeded forbs and non‐native grass biomass. Our conclusions are that: (1) P amendments are a potential tool for enhancing native seeded forb biomass in simulated small‐scale disturbance patches; and (2) C additions, although enhancing seeded grass biomass do not reduce the biomass of non‐native grasses.

Edge behaviour in a minute parasitic wasp

1. Changes in the density of an organism near a boundary elements (edge effects) are often thought to be generated by changes in movement behaviour, but in most cases the mechanism underlying these effects is unknown. 2. We quantified the movement behaviour of a minute parasitic wasp, Anagrus columbi, in relation to edges in its habitat. This wasp attacks eggs of the planthopper Prokelisia crocea, which inhabits a wet prairie ecosystem composed of patches of its host plant prairie cordgrass (Spartina pectinata) interspersed within a matrix of mudflat, smooth brome (Bromus inermis) and native grasses. Two edge types are common in this system, cordgrass-mudflat and cordgrass-brome. 3. We conducted mark-recapture experiments in which wasps were released at the cordgrass-matrix edge and 50 cm within cordgrass or matrix, for both edge types. The marked wasps were recaptured using a grid of sticky traps. We fitted an advection-diffusion model to these data, yielding estimates of the diffusion rate and advection coefficient for cordgrass and matrix, for each release position and edge type. 4. The spatial distribution of wasps was well-described by the advection-diffusion model. The pattern suggests that marked wasps strongly biased their movements towards the edge when released in matrix, and to a lesser extent when released in cordgrass, while edge releases showed little bias. The advection coefficients were similar for the two edge types, as were the diffusion rates for the three substrates (cordgrass, brome, mudflat). The diffusive and advective components of movement were of comparable magnitude for matrix and cordgrass releases, suggesting equal amounts of directed and random movement. 5. Our results suggest the wasps are attracted to cordgrass patches across short distances, and that bias in their movements may concentrate them at the patch edge. Their edge behaviour is qualitatively different from that of the host insect. 6. The methodology described here could be readily adapted to other systems, where direct observations of movement are difficult but mark-recapture studies are feasible.

Quantitative assessment of shrub–grass mosaic development in grazed shrublands: An example in the Patagonian Monte (Argentina)

Grazing alters the spatial structure of shrubs and perennial grasses in desert shrub communities. The resulting spatial distribution of shrub–grass patches constitutes a sensitive indicator of the integrated result of grazing impacts on them. While several procedures were developed to estimate the size of shrub clumps, metrics of the geometry of the interacting grass matrix received less attention. In this study, we conceptualised the spatial structure of shrub–grass patches as consisting of two components: a grass crown of ill-defined outer borders (the ‘grass component’) encircling a shrub clump (the ‘shrub component’). We fitted exponential functions to autocorrelograms of spatially explicit shrub–grass cover data surveyed at different locations of the Patagonian Monte (Argentina) differing in livestock grazing pressure. After that, we derived two metrics from the function parameters that quantitatively estimate the size of both the shrub and the grass components of shrub–grass patches. The patterns of variation of these metrics are consistent with field measurements and observations previously reported for the studied areas, indicating that they are sensitive indicators of the state of development of the shrub–grass mosaic under different grazing pressures. These results suggest that its applicability to similar semi-arid shrublands deserves further attention.

Phylogenetic Studies in the Paniceae (Poaceae-Panicoideae): Ocellochloa, a New Genus from the New World

Abstract The present contribution continues a critical revision of Panicum, particularly with the delimitation of “incertae sedis” taxa. A phylogenetic analysis of Paniceae based on cpDNA sequence data (ndhF) was performed with special emphasis on section Stolonifera of Panicum. Fourteen sequences of species of sect. Stolonifera and Echinolaena were added to a panicoid grass matrix previously published giving a total of 140 sequences. As a result, Ocellochloa is here described as a new genus including 12 new combinations: O. andreana, O. biglandularis, O. brachystachya, O. chapadensis, O. craterifera, O. irregularis, O. latissima, O. piauiensis, O. pulchella, O. rudis, O. soderstromii , and O. stolonifera. The position of Panicum venezuelae, previously placed in section Stolonifera with the above mentioned species, clearly indicates that this species is not closely related to the Ocellochloa clade. This conclusion is supported by several morphological characters, such as the presence of axillary infloresc...

Precision Prairie Reconstruction (PPR): A Technique for Increasing Native Forb Species Richness in an Established Grass Matrix

Carolyn E. Grygiel, Jack E. Norland and Mario E. Biondini

The ecological value of Eryngium horridum in maintaining biodiversity in subtropical grasslands

AbstractThe role of facilitation in the structuring of plant communities has been often demonstrated in environments under high abiotic stress, especially in semi‐arid and arid ecosystems and high elevations. Few studies, however, analysed facilitation in systems that are highly productive and rich in species, which are thought to be theoretically unlikely to demonstrate strong effects of facilitation. Here, we investigate the importance of Eryngium horridum, a rosette species, on the maintenance of plant diversity in subtropical grasslands in southern Brazil. We evaluated facilitation in areas under two different types of management: abandonment and grazing. Plots were established in areas with and without individuals of E. horridum and all species were identified and had their cover estimated. The Relative Neighbour Effect index was calculated in order to verify the presence of competition or facilitation. Our results indicated facilitation in both abandoned and in grazed grasslands, but apparently through different mechanisms. In the first case, the plant's architecture opens the canopy and allows more light to reach small forbs in the grass matrix. In the second case, E. horridum appears to protect more palatable species from herbivores. Otherwise considered an obnoxious species, E. horridum plays an important ecological role in subtropical grasslands in southern Brazil by facilitating other species and consequently, increasing local richness. Areas with this rosette species are important sources of diaspores, which are able to colonize new open sites and thus, maintain biodiversity.

Small‐scale spatial dynamics of vegetation in a grazed Uruguayan grassland

AbstractWe explored the small‐scale plant species mobility in a subhumid native grassland subjected to grazing by cattle in south‐western Uruguay. We established four permanent plots of 40 × 40 cm, divided in 16 × 16 cells. In each cell, the presence of species was seasonally recorded for 2 years and annually recorded for 4 years. By nesting the cells, we studied the mobility at different scales, from 6.25 cm2 to 400 cm2. At each scale we measured species richness, cumulative richness and the turnover rates of the dominant species. We found that the cumulative species richness was an increasing power function, with higher accumulation rates with smaller spatial scale. Although species richness showed seasonal fluctuations, the mean species richness was constant during the study period. We detected significant spatio‐temporal variability in mobility patterns among species. Certain species showed a high capacity to colonize new sites, whereas other species rotate among sites that they previously occupied. Grazed communities in Uruguayan Campos are structured as a dense matrix of perennials grasses and forbs, where vegetative propagation is the main form of growth of the species. The small‐scale dynamics and the high variability in the mobility characteristics could be linked with the diversity of growth forms and spatial strategies of the species in this community. We believe that a high degree of small‐scale spatial dynamics contribute to explain the species coexistence and the apparent stability of communities at local scales.

The role of environmental context in mapping invasive plants with hyperspectral image data

Lepidium latifolium (perennial pepperweed) is a noxious Eurasian weed invading riparian and wetland areas of the western US. Effective management of Lepidium requires detailed, accurate maps of its distribution, as may be provided by remote sensing, to contain existing infestations and eradicate incipient populations. We mapped Lepidium with 3 m spatial resolution, 128-band HyMap image data in three sites of California's San Francisco Bay/Sacramento–San Joaquin Delta Estuary (Rush Ranch in Suisun Marsh and the Greater Jepson Prairie Ecosystem and the Cosumnes River Preserve in the Delta). These sites are markedly different in terms of hydrology, salinity, species composition, and structural and landscape diversity. Aggregated classification and regression tree models (CART), incorporating the results of mixture tuned matched filter (MTMF) analyses and spectral physiological indexes, were used to map Lepidium at the three sites. This approach was sufficiently flexible and robust to detect Lepidium with similar accuracies (~ 90%) at both Rush Ranch and Jepson Prairie, but was unsuccessful at Cosumnes River Preserve. Comparisons of the behavior of the MTMFs and the CARTs between sites reveal the importance of environmental context in species mapping. Rush Ranch presents the simplest conditions for mapping Lepidium: it is the wettest and least diverse site and Lepidium is spectrally distinct from co-occurring species. At Jepson Prairie, several co-occurring species closely resemble Lepidium spectrally. Nevertheless, hyperspectral data provide sufficient spectral detail to resolve Lepidium even at this challenging site, which is facilitated by phenological separation from the matrix of annual grasses. At Cosumnes River Preserve, however, Lepidium is neither spectrally nor phenologically distinct, and consequently could not be mapped successfully. Evidence suggests that the success of a remote sensing analysis declines as site complexity increases (species, structural, and landscape diversity; spectral variability; etc.), although this relationship is complex, indirect, and may be phenology-dependent.

Stable isotopes analysis to assess the trophic role of ants in a Mediterranean agroecosystem

Abstract1 Stable isotopes signatures (δ13C and δ15N) of the most important tree‐dwelling ants in an olive orchard were examined, together with the signatures of the most common herbivores, predators and sap‐sucking insects. The olive orchard consists of separate subunits (trees) surrounded by a matrix of grasses or bare ground, and the role of ants in such a system is not fully understood.2 None of the selected ant species was exclusive to the olive trees because they were also observed foraging on vegetation (mainly thistle) under the tree crowns. Hence, the relative contributions of these two sources of energy (olive trees versus herbs/grasses) were assessed by comparing the δ13C of ants with the signatures of plants and those of other arthropods collected on the trees and on nearby thistles. Next, the trophic level occupied by the ants and their ecological role within the olive food web were determined by examining the δ15N values and their relationship with indices of ecological performance measuring the potential pressure exerted by each species on the ecosystem.3 The analysis of 13C signatures revealed a different contribution of the two energy sources, olive trees versus herbs and grasses, with the former being more important for ants. The analysis of 15N signatures suggested separate roles for different ant species: some (Crematogaster scutellaris, Lasius lasioides) occupied a higher trophic level, mostly involved in predation, whereas others (Camponotus piceus, Camponotus lateralis) occupied a lower level, probably involved more in homopteran tending. A fifth species (Camponotus aethiops) was in an intermediate position. Finally, the δ15N levels of the species were significantly correlated with indices of ecological performance.

A field experiment to recreate species rich hay meadows using regional seed mixtures

Species rich semi-natural grasslands are an important but threatened habitat throughout Europe and much of the former area has been lost since the 1950s. However, in some countries large areas have been preserved and the demand for meadow recreation by sowing seed mixtures is increasing. In the White Carpathians Protected Landscape Area (Czech Republic) the use of commercial seed mixtures is undesirable and the use of regional mixtures has been investigated. The costs for seeding large areas are high and lower cost techniques are needed. In 1999 a field experiment was set up to investigate the establishment of hay meadow vegetation comparing sowing a regional mixture all over a plot with sowing narrow 2.5 m strips of regional seed mixtures into a matrix of a commercial grass mixture or into natural regeneration. The results after five seasons showed good establishment of the sown species in the meadow treatment. Spread of sown species from the sown strips into the surrounding matrix occurred but the cover of species was lower in the commercial grass matrix compared with the natural regeneration matrix. Colonisation of some plots by unsown desirable grassland species from adjacent grassland habitats also occurred, but more species colonised the natural regeneration matrix than the commercial grasses or the sown meadow matrix itself. Overall, the results indicate that, in appropriate situations, sown strips can provide a lower cost but slower and longer-term alternative to field scale sowing of regional seed mixtures for recreation of hay meadow vegetation.

Simulating the impacts of vegetation structure on the occurrence of a small mammalian carnivore in semi-arid savanna rangelands

In arid and semi-arid savannas, species diversity is strongly influenced by structural diversity, which in these systems is characteristically formed by woody vegetation. Shrub encroachment, associated with overgrazing by domestic livestock, changes the structural diversity and hence affects biodiversity. Many investigations have been carried out with focus on the structure building trees, but little is known about the importance of shrubs. Here, we present a spatially explicit and individual-based population model for analysing the influence of shrub encroachment on the occurrence of yellow mongooses ( Cynictis penicillata) in the Southern Kalahari, South Africa. This analysis is based on field investigations in Southern Africa. The results of the modelling study are in line with the results of a field study, in which the same unimodal relationship between shrub cover and yellow mongoose abundance was found. The model could explain this relationship by the need of shrubs as protective structures on the one hand, and the need of foraging habitat in the grass matrix on the other hand. To evaluate the factors influencing the population dynamics at different levels of shrub encroachment we carried out an extensive sensitivity analysis. Finally, we determined a range of existence of the yellow mongoose for various shrub covers. Model results indicate a lower and an upper limit of critical shrub densities at 1% and 38%, respectively. These limits indicate the range in shrub cover allowing the persistence of the yellow mongoose in the Southern Kalahari.

Resource complementation and the response of an insect herbivore to habitat area and fragmentation

Few studies have disentangled the effects of the area and fragmentation of a focal habitat type on species that use multiple habitat types within a landscape. We experimentally investigated the effects of habitat area, habitat fragmentation, and matrix composition on the movement and distribution of Melanoplus femurrubrum. Adults of this grasshopper feed preferentially on grasses, but oviposit almost exclusively in soil dominated by forbs. We compared population densities among plots that were made to vary in the area and fragmentation of clover habitat and composition of the matrix (grass or bare ground) within which clover habitat was embedded. In addition, a mark-recapture survey was conducted to examine effects of habitat area, fragmentation, and matrix composition on loss of individuals from a plot's clover habitat and movement between clover subplots within plots. Overall densities of adult M. femurrubrum (averaged over clover and matrix) were 2.2x higher in plots where the matrix was composed of grass as compared to bare ground, and 1.8x higher in plots with 64 compared to 16 m(2) of clover habitat. Overall densities of nymphs were also positively influenced by greater clover area, but were unaffected by matrix composition. Within focal clover habitat embedded in grass matrix, adult densities were 2.1x higher in small clover subplots than large clover subplots. We conclude that the grass matrix had a positive effect on adult densities, but not nymph densities, because grass and forb-dominated habitats likely provide complementary resources only for adults. The aggregation of adults on small clover subplots within grass matrix was mainly attributed to a greater rate of emigration loss per unit area. In addition, this study emphasizes that a species' response to changes in the area of a focal habitat type can depend significantly on the availability of complementary resources in the surrounding landscape.

Screening and selection of lactic acid bacteria strains suitable for ensiling grass

Lactic acid bacteria (LAB) strains shown to have broad-spectrum antimicrobial activity were screened for potential as grass silage inoculants. The strains capable of rapidly lowering the pH of the grass matrix and with low proteolytic activity were assessed in laboratory-scale silos in a grass matrix containing natural microbial flora. Screening of nine candidate strains was performed first in a grass extract medium. The four most promising strains were selected on the basis of growth rate in the medium, capacity to reduce pH and ability to limit the formation of ammonia-N. The efficiency of the selected strains was further assessed in a laboratory-scale ensiling experiment. Untreated (no additive) and formic acid served as controls. All tested inoculants improved silage quality compared with untreated. With one exception (Pediococcus parvulus E315) the fermentation losses in the inoculated silages were even lower than in the acid-treated control silage. Pure lactic acid fermentation was obtained in the timothy-meadow fescue silage with all inoculants. The results obtained in the ensiling experiments were consistent with those of the screening procedure, which appeared to predict correctly the potential of LAB as silage inoculants. The strains with a low ammonia production rate in the grass extract medium behaved similarly in the silage. Especially in this respect the strain Lactobacillus plantarum E76 was superior to the other candidates. The screening method using grass extract proved to be useful in strain selection. The rapid screening method developed for the LAB strains provides a useful tool for more systematic product development of commercial inoculant preparations. Time consuming and laborious ensiling experiments can be limited only to the most promising strains.

Microbial communities of a native perennial bunchgrass do not respond consistently across a gradient of land-use intensification

To test if native perennial bunchgrasses cultivate the same microbial community composition across a gradient in land-use intensification, soils were sampled in fall, winter and spring in areas under bunchgrasses (‘plant’) and in bare soils (‘removal’) in which plots were cleared of living plants adjacent to native perennial bunchgrasses ( Nassella pulchra). The gradient in land-use intensification was represented by a relict perennial grassland, a restored perennial grassland, and a perennial grass agriculture site on the same soil type. An exotic annual grassland site was also included because perennial bunchgrasses often exist within a matrix of annual grasses in California. Differences in soil resource pools between ‘plant’ and ‘removal’ soils were observed mainly in the relict perennial grassland and perennial grass agriculture site. Seasonal responses occurred in all sites. Microbial biomass carbon (C) and dissolved organic C were greater under perennial bunchgrasses in the relict perennial grassland and perennial grass agriculture site when comparing treatment means of ‘plant’ vs. ‘removal’ soil. In general, soil moisture, microbial respiration, and nitrate decreased from fall to spring in ‘plant’ and ‘removal’ soils, while soil ammonium and net mineralizable nitrogen (N) increased only in ‘plant’ soils. A canonical correspondence analysis (CCA) of phospholipid fatty acid (PLFA) profiles from all sites showed that land-use history limits the similarity of microbial community composition as do soil C and N dynamics among sites. When PLFA profiles from individual sites were analyzed by CCA, different microbial PLFA markers were associated with N. pulchra in each site, indicating that the same plant species does not retain a unique microbial fingerprint across the gradient of land-use intensification.

Abstracts of Papers, Thirtieth Annual Albert L. Tester Memorial Symposium, 16-18 March 2005

Abstracts of Papers Thirtieth Annual Albert L. Tester Memorial Symposium, 16-18 March 2005 Abstract The Albert L. Tester Memorial Symposium is held in honor of Professor Albert Tester, who, at the time of his death in 1974, was Senior Professor of Zoology at the University of Hawai'i at Mānoa. The faculty and students of the Department of Zoology proposed an annual symposium of student research papers as a means of honoring, in a continuing and active way, Dr. Tester's lively encouragement of student research in a broad range of fields within marine biology. Papers reporting original research on any aspect of science are solicited from students at the university and these papers are presented at the symposium, which takes place during the spring semester. Income from contributions to the Albert L. Tester Memorial Fund of the University of Hawai'i Foundation is used to provide prizes for the three best papers, judged on quality, originality, and importance of research reported, as well as the quality of the public presentation. Judges include Department of Zoology faculty members and the previous year's student award winners. In addition, a distinguished scholar from another university or research institution is invited to participate in the symposium as a judge and to present the major symposium address. In 2005 the distinguished visitor and judge was Dr. Stephen Palumbi, Stanford University, Hopkins Marine Station, Pacific Grove, California. A Proposal to Study Connectance of Pollination Systems in Dry Forests of Hawai'i Patrick Aldrich2 Traditionally, mutualistic plant-animal interactions have been placed in a dichotomy of specialized versus generalized relationships within a community. Recently ecologists have become aware that this split is artificial, and most systems are made up of connections and networks analogous to food webs. Using network theory and connectivity to describe species interactions can help explain the structural organization of the species richness of communities and how introduced pollinator species in the system can affect its stability. Hawaiian dry forests located at Pu'uwa'awa'a on the island of Hawai'i provide a system to study networks of native and introduced pollinators in a fragmented, altered landscape. Because most of the understory of the Hawaiian dry forests is a matrix of grasses, only the overstory trees will be used in this study. Observations will be made at inflorescences of all dominant tree species within the dry forest system. Each day a single species will be selected, based on phenology, and observed from sunrise to sunset. Data will be entered into a binary-coded matrix to examine interactions and connections between pollinators and plants. Analyses, following food web and network theory, will be used to test whether the connectivity is structured or random. [End Page 305] Ecological and Behavioral Factors Influencing Patterns of Interbreeding and Genetic Diversity in the Hawaiian Spinner Dolphin3 Kimberly R. Andrews4 In many cetacean populations, reproductively isolated subgroups exist within populations even when these subgroups live in the same geographic range or are capable of traveling to other subgroups' ranges. The factors that lead to reproductive isolation in these cetacean populations are often complex. For the Hawaiian spinner dolphin (Stenella longirostris), there is variability throughout the Hawaiian Archipelago in factors such as geographic distance between suitable habitat, prey distribution, habitat type and availability, population size, and social structure. To investigate whether these factors have led to reproductive isolation between subgroups and influenced genetic diversity, genetic structure and genetic diversity of the spinner dolphin throughout Hawai'i were investigated. Genetic samples were collected from Kure Atoll (34 samples), Midway Atoll (57), Pearl and Hermes Reef (21), French Frigate Shoals (13), Ni'ihau (39), O'ahu (47), Maui (60), and the Big Island (77). A 429-base pair region of the mitochondrial DNA (mtDNA) control region and 12 microsatellite loci were used to evaluate genetic structure and diversity. Analysis of molecular variance (AMOVA) indicated significant genetic structure for the spinner dolphin within Hawai'i for both mtDNA and microsatellites. The pattern of genetic structure could not be explained only by geographic distance between populations, indicating the presence of additional, more complex factors influencing patterns of interbreeding. An unexpected peak in genetic diversity was found at...