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Andrew Olaf Shelton - One of the best experts on this subject based on the ideXlab platform.
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Appendix E. Female Phyllospadix serrulatus spadix removal experiment.
2016Co-Authors: Andrew Olaf SheltonAbstract: -
Appendix D. Number of Phyllospadix serrulatus and P. scouleri seedlings found recruited to algae and seagrass, years 2006 and 2007 combined; ANOVA table for the percent cover of Phyllospadix spp. found in surveys for seedling recruitment conducted in
2016Co-Authors: Andrew Olaf SheltonAbstract:Number of Phyllospadix serrulatus and P. scouleri seedlings found recruited to algae and seagrass, years 2006 and 2007 combined; ANOVA table for the percent cover of Phyllospadix spp. found in surveys for seedling recruitment conducted in April and May 2006 and 2007, at four sites; and ANOVA table for the percent cover of articulated coralline algae, Neorhodamela larix and Odonthalia spp., found in surveys for seedling recruitment conducted in April and May 2006 and 2007, at four sites
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the origin of female biased sex ratios in intertidal seagrasses Phyllospadix spp
Ecology, 2010Co-Authors: Andrew Olaf SheltonAbstract:Flowering sex ratios of dioecious plants are commonly male-biased but rarely female-biased. While greater costs of reproduction from females have been repeatedly demonstrated and explain male biases, male reproductive costs almost never exceed female costs, making the origins of female biases enigmatic. I investigated the seagrasses Phyllospadix scouleri and P. serrulatus (surfgrasses), which have some of the most extreme female-biased sex ratios documented (>90% female), to identify the mechanisms driving sex ratio bias. I developed sex-linked amplified fragment length polymorphism (AFLP) markers and applied them to three P. scouleri life stages at four sites to determine when during the life cycle sex ratio bias arises. Sex ratios were even among seedlings but became more female-biased at later life stages, indicating that sex ratios were driven by male-biased mortality. To identify when during the life cycle sex ratio bias developed, I examined sex differences in survival among seedlings and three aspects of reproductive costs that could potentially generate biased sex ratios under field conditions. No differences in seedling survival between the sexes were detected, and there was no evidence of substantial sex differences in costs of reproduction. I found no support for a trade-off between current and future reproduction or between reproductive investment and growth. Thus, costs of reproduction appear unlikely to drive sex ratio bias in surfgrass. Instead, small sex differences in growth and survival spread across the life cycle appear to be responsible for female-biased sex ratios and suggest that life history trade-offs other than reproductive costs drive sex ratio bias.
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The origin of female‐biased sex ratios in intertidal seagrasses (Phyllospadix spp.)
Ecology, 2010Co-Authors: Andrew Olaf SheltonAbstract:Flowering sex ratios of dioecious plants are commonly male-biased but rarely female-biased. While greater costs of reproduction from females have been repeatedly demonstrated and explain male biases, male reproductive costs almost never exceed female costs, making the origins of female biases enigmatic. I investigated the seagrasses Phyllospadix scouleri and P. serrulatus (surfgrasses), which have some of the most extreme female-biased sex ratios documented (>90% female), to identify the mechanisms driving sex ratio bias. I developed sex-linked amplified fragment length polymorphism (AFLP) markers and applied them to three P. scouleri life stages at four sites to determine when during the life cycle sex ratio bias arises. Sex ratios were even among seedlings but became more female-biased at later life stages, indicating that sex ratios were driven by male-biased mortality. To identify when during the life cycle sex ratio bias developed, I examined sex differences in survival among seedlings and three aspects of reproductive costs that could potentially generate biased sex ratios under field conditions. No differences in seedling survival between the sexes were detected, and there was no evidence of substantial sex differences in costs of reproduction. I found no support for a trade-off between current and future reproduction or between reproductive investment and growth. Thus, costs of reproduction appear unlikely to drive sex ratio bias in surfgrass. Instead, small sex differences in growth and survival spread across the life cycle appear to be responsible for female-biased sex ratios and suggest that life history trade-offs other than reproductive costs drive sex ratio bias.
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The ecological and evolutionary drivers of female-biased sex ratios: two-sex models of perennial seagrasses.
The American Naturalist, 2010Co-Authors: Andrew Olaf SheltonAbstract:Abstract: Among sexually reproducing species, differences between the sexes within species are ubiquitous. Despite the clear effect of sex differences on sex ratios and population growth rates, demographic models rarely consider both sexes explicitly. Here I explore the causes of extreme female‐biased sex ratios in two marine angiosperms (Phyllospadix spp.). Using demographic data, I develop two‐sex matrix projection models to assess the magnitude of demographic differences necessary to generate observed sex ratios and the consequences of sex differences for population growth rates. I demonstrate that small sex differences in survival can generate biased sex ratios, but the importance of sexual reproduction differs markedly between species. Even in the absence of a direct trade‐off between sexual and asexual reproduction, the presence of two reproductive modes affects both the importance of sex and the sex‐ratio bias. Using sensitivity analyses, I quantify the contribution of shared and sex‐specific vital...
Jung-im Park - One of the best experts on this subject based on the ideXlab platform.
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A New and Effective Transplanting Technique Using Wire Netting for Restoration of the Surfgrass, Phyllospadix japonicus, in Exposed Rocky Shores
Journal of Coastal Research, 2018Co-Authors: Jung-im Park, Jong-hyeob Kim, Jae Hoon Kim, Jeong Hee ShimAbstract:ABSTRACT Park, J.-I.; Kim, j.-H.; Kim, J.H., and Shim, J.H., 2018. A New and Effective Transplanting Technique Using Wire Netting for Restoration of the Surfgrass, Phyllospadix japonicus, in Exposed Rocky Shores. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 326–330. Coconut Creek (Florida), ISSN 0749-0208. The surfgrass Phyllospadix japonicus is an abundant seagrass along the exposed rocky shores of the Korean peninsula. However, many surfgrass meadows on this area have been severely damaged by anthropogenic factors, leading to a growing interest on the restoration of surfgrass habitats. Few attempts have been made to develop transplanting techniques for surfgrass, owing to the low transplant survival in high-energy rocky shores. The present study evaluates the performance of a new transplantation method for P. japonicus based on affixing surfgrass transpla...
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An effective seeding method for restoring the surfgrass Phyllospadix japonicus using an aartificial reef
Ocean Science Journal, 2014Co-Authors: Jung-im Park, Min Ho Son, Jeong Bae Kim, Kun-seop LeeAbstract:Phyllospadix japonicus is an abundant surfgrass that thrives mainly along the exposed rocky shores of Northeastern Asia. On the eastern coast of Korea, surfgrass populations have been adversely affected by increasing human pressures. We developed a seeding method using an artificial reef for the restoration of P. japonicus . In January 2005, we planted P. japonicus seeds on the lower part of coarse hemp-plant brush that was embedded densely on the concave surface on the top of artificial reefs. The reefs were then installed on an exposed rocky shore. To evaluate the feasibility of this seed-based surfgrass restoration technique, we monitored the seedling/shoot density and morphological characteristics of the shoots over a 2-year period. Seedlings began to emerge within the first month after seeding, reaching densities of up to 275.0 shoots m^-2 by April 2005. After an initial decline, shoot density increased through the production of lateral shoots, and densities of up to 997.1 shoots m^-2 were observed by the end of the experiment. Shoot height, the number of leaves, and leaf width rapidly increased during the first year after seeding, whereas the number of rhizome internodes and rhizome length rapidly increased during the second year. The P. japonicus shoots exhibited approximately 63.4 mm of rhizome elongation during the study period. Because seeded P. japonicus on the artificial reefs were successfully established at the study site, this seeding method using an artificial reef may offer an effective approach to restoring surfgrass habitat.
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Germination rate of Phyllospadix japonicus seeds relative to storage methods and periods
Ocean Science Journal, 2014Co-Authors: Jung-im Park, Kun-seop Lee, Min Ho SonAbstract:To determine the optimal storage method and longest possible storage period of Phyllospadix japonicus seeds, we examined post-storage germination rates using different storage methods and periods for P. japonicus seeds harvested in Korean coastal waters. P. japonicus seeds are classified as recalcitrant seeds with an average moisture content of 45.4%. Germination rates of P. japonicus seeds stored in seawater at 4 °C, seawater at room temperature with air supply, and an aquarium with continuous seawater circulation ranged from 35.0% to 43.5%, whereas seeds stored in seawater at 30°C, a refrigerator at −20°C, and a desiccator at room temperature did not germinate. Seeds stored at 4°C maintained germination rates of 72.5∼73.0% until 30 days of storage, but showed rapidly decreasing germination rates after 60 days and no germination after 180 days. Since few studies have investigated seed storage of P. japonicus , these results will serve as useful data for seed-based P. japonicus habitat restoration.
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Development of transplantation method for the restoration of surfgrass, Phyllospadix japonicus, in an exposed rocky shore using an artificial underwater structure
Ecological Engineering, 2010Co-Authors: Jung-im Park, Kun-seop LeeAbstract:Abstract The surfgrass Phyllospadix japonicus is an abundant seagrass on the exposed rocky shores of the Korean peninsula. Many surfgrass meadows on the coasts of Korea have been adversely affected by anthropogenic activities and natural phenomena such as “rock whitening,” which is caused by overgrowths of crustose coralline algae. Few attempts have been made to develop transplanting techniques for surfgrass, owing to the difficulty of transplant survival on exposed rocky shores. We developed a new Phyllospadix Transplant System (PTS), which was an artificial underwater structure constructed of a 4:5:1 ratio of cement, sand, and water. In January 2005, we transplanted P. japonicus shoots using the newly developed PTS. P. japonicus shoots were tied together at the lower part of the sheaths to iron screws, which were placed in a hollow part of the PTS, with latex elastic. To evaluate the feasibility of this transplantation technique, we compared vegetative and reproductive shoot densities, growth, and morphological characteristics in transplants to those of shoots in nearby natural beds over a 2-year period. Transplant density increased gradually without significant initial shoot loss. Approximately 6 months after transplantation, leaf growth of transplants was similar to that of naturally growing shoots. The shoot heights and sheath lengths of transplants were similar to those of naturally growing shoots at 10–15 months post-planting. Approximately 50 mm of rhizome elongation was detected in P. japonicus transplants over the 2-year period. Since P. japonicus transplants attached to the PTS successfully established at the test area, the transplantation of surfgrass using the PTS may be an effective approach to restoring the habitat of P. japonicus .
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Peculiar growth dynamics of the surfgrass Phyllospadix japonicus on the southeastern coast of Korea
Marine Biology, 2009Co-Authors: Jung-im ParkAbstract:The surfgrass Phyllospadix japonicus is endemic to exposed shores of the northeastern Pacific Ocean. Unlike the majority of seagrasses, P. japonicus grows on rocky substrata. The specific physical features of the habitat are likely related to the peculiar ecological characteristics of P. japonicus . However, few studies have been conducted thus far on the growth dynamics of Phyllospadix spp., largely due to the turbulent water conditions in its habitat. P. japonicus is a dominant seagrass species, and it plays critical ecological roles on the eastern coast of Korea. Here, we examined its growth dynamics for the first time on the Korean coast. We measured shoot density, biomass, leaf production, phenology, morphology, tissue nutrient content, as well as environmental factors including underwater photon flux density (PFD), water temperature and water column nutrient concentrations from March 2003 to December 2005. Shoot density, biomass, leaf productivity and morphological characteristics exhibited significant seasonal variations; maximum values of these variables occurred in winter and early spring, and the minima were recorded in late summer and early fall. PFD and water temperature were, respectively, positively and negatively correlated with leaf production. Nutrient availability fluctuated substantially, but there was no evidence of distinct seasonal variation, nor was it correlated with leaf production. Leaf chlorophyll concentrations were correlated strongly with leaf production, whereas tissue nutrient contents were unrelated to leaf production. Maximum potential seed production ranged from 1,200 seeds m^−2 in 2004 to 3,445 seeds m^−2 in 2003; however, seedlings were rarely detected through the observation period. Thus, P. japonicus meadows at the study site appeared to persist through vegetative propagation. Leaf C content varied bimodally, with peaks in spring and fall. Leaf N content was minimal during months in which leaf productivity was lowest. These patterns in tissue nutrient content are clearly different from those of the majority of soft-substratum seagrasses and appear to relate to the reduced physiological tolerance of high temperature in P. japonicus compared to other temperate seagrasses.
Sally J. Holbrook - One of the best experts on this subject based on the ideXlab platform.
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Patterns and sources of variation in flowering, seed supply and seedling recruitment in surfgrass Phyllospadix torreyi
Marine Ecology Progress Series, 2009Co-Authors: Daniel C. Reed, Carol A. Blanchette, Sally J. Holbrook, Suzanne WorcesterAbstract:Knowledge of patterns and sources of variation in adult reproduction and juvenile recruitment is essential for understanding the dynamics of populations and their capacity to recover from disturbances. In-depth knowledge of this kind is lacking for many species of seagrass. Here we examined the degree to which temporal and spatial variation in seedling density in the surfgrass Phyllospadix torreyi was explained by the local production and deposition of seeds. We did this by measuring floral density, seed production, seed supply and seedling recruitment at 5 sites near Santa Barbara, California, USA, over a 4 yr period. We found that the local density of dehisced female spadices explained nearly 41% of the variation in the number of seeds caught in seed traps. Large seed crops were common in the absence of nearby males and noticeable numbers of seeds were peri- odically caught in traps when female flowers were locally rare or absent, suggesting that pollen and seed dispersal occasionally occurred over distances greater than the scale of our study sites (i.e. >50 m). Overall, the summer densities of female spadices at a site explained >60% of the variation in the density of seedlings that recruited to the site the following winter. Deviations from positive asso- ciations among surfgrass flowers, seeds and seedlings appeared to reflect interannual variability in environmental conditions. Most notable was the coincidence of universally low fruit production and seedling recruitment during the 1997-1998 El Nino event. Seedling density varied independently of rates of seed deposition when all years were examined, but was highly dependent on rates of seed supply when the seedling data from the 1998 El Nino winter were omitted from the analysis. Collec- tively, our observations demonstrated significant coupling between adult reproduction and local recruitment in surfgrass that was interrupted by adverse growing conditions associated with the 1997-1998 El Nino.
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An Experimental Evaluation of Different Methods of Restoring Phyllospadix torreyi (Surfgrass)
Restoration Ecology, 2004Co-Authors: J. Scott Bull, Daniel C. Reed, Sally J. HolbrookAbstract:The surfgrass Phyllospadix torreyi is an abundant seagrass found on rocky exposed shores of the Pacific coast of North America. In southern California surfgrass populations are adversely affected by a range of natural events and anthropogenic activities. Few attempts have been made to develop restoration methods for surfgrass, and none have investigated the efficacy of using different life stages. We evaluated several techniques for restoration in intertidal and subtidal habitats using: (1) laboratory-reared seedlings transplanted to the field (2) sprigs (short lengths of rhizome containing a few shoots) transplanted from undisturbed populations, and (3) plugs (a cohesive clump of shoots and rhizomes) transplanted from undisturbed populations. We calculated the net change in the aerial coverage of surfgrass after 6 months, taking into account the recovery or additional losses from the donor population, and amount of effort involved in transplanting. Transplanted seedlings survived poorly and had minimal rhizome growth at both the intertidal and the subtidal sites, yet the individuals that did survive showed a 275% increase in leaf number. Survivorship of transplanted plugs was high in both habitats; however, physical disturbances to the donor populations exacerbated damage sustained at the time of collecting, yielding a substantial net loss in surfgrass. Sprigs transplanted to the subtidal had higher survivorship (71 versus 48%) and a greater increase in the aerial coverage of rhizome (86 versus 42%) than those transplanted to the intertidal. Of the three techniques, transplanted sprigs had the greatest overall increase in aerial coverage per unit effort, suggesting that this method may be the most effective approach for restoring P. torreyi.
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Survival experiments with outplanted seedlings of surfgrass (Phyllospadix torreyi) to enhance establishment on artificial structures
ICES Journal of Marine Science, 2002Co-Authors: Sally J. Holbrook, Daniel C. Reed, J. Scott BullAbstract:Surfgrass (Phyllospadix torreyi) is considered a valuable plant for enhancing biogenic habitat on artificial structures on the west coast of North America. Its populations establish only slowly, prompting efforts to develop techniques to accelerate the process. We present results from outplanting tests of laboratory-reared seedlings in their natural environment using various techniques. Survival rates after 3 months were compared with those of naturally recruited seedlings. Seedlings require a host plant during their early stages, and both natural hosts (algae) and artificial hosts (nylon strings and nets attached to the bottom) were tested. Survival of naturally recruited seedlings was only 30%, and only in the case where seedlings were hooked into braided nylon netting glued to the substrate were comparable survival rates observed. The results suggest that using this technique may be a promising approach to establishing populations of P. torreyi on artificial structures. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.
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Spatial and temporal patterns of predation on seeds of the surfgrass Phyllospadix torreyi
Marine Biology, 2000Co-Authors: Sally J. Holbrook, Daniel C. Reed, K. Hansen, Carol A. BlanchetteAbstract:Spatial and temporal patterns of predation on seeds of the seagrass Phyllospadix torreyi S. Watson were quantified at four sites near Santa Barbara, California, USA. Over a period of four flowering seasons during 1995 to 1998, monthly patterns of seed fall and intensity of seed predation were similar among sites, but were temporally quite variable. Abundance of dispersed seeds varied greatly both among seasons and years. Within any one year, seeds were present in the environment every month, but they peaked in abundance during the fall months following the annual flowering period. Seeds were more abundant during the earlier years of the study. The intensity of predation steadily increased throughout the study period, from a low of ≤10% seeds consumed during 1995 to ∼50% consumption by 1997, and it was not correlated with abundance of seeds in the environment. Pre-dispersal seed loss also was estimated in two flowering seasons by counting the numbers of seeds consumed prior to release from the plant, and was relatively low (
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spatial and temporal patterns of predation on seeds of the surfgrass Phyllospadix torreyi
Marine Biology, 2000Co-Authors: Sally J. Holbrook, Daniel C. Reed, K. Hansen, Carol A. BlanchetteAbstract:Spatial and temporal patterns of predation on seeds of the seagrass Phyllospadix torreyi S. Watson were quantified at four sites near Santa Barbara, California, USA. Over a period of four flowering seasons during 1995 to 1998, monthly patterns of seed fall and intensity of seed predation were similar among sites, but were temporally quite variable. Abundance of dispersed seeds varied greatly both among seasons and years. Within any one year, seeds were present in the environment every month, but they peaked in abundance during the fall months following the annual flowering period. Seeds were more abundant during the earlier years of the study. The intensity of predation steadily increased throughout the study period, from a low of ≤10% seeds consumed during 1995 to ∼50% consumption by 1997, and it was not correlated with abundance of seeds in the environment. Pre-dispersal seed loss also was estimated in two flowering seasons by counting the numbers of seeds consumed prior to release from the plant, and was relatively low (<15%). No differences were detected among the four study sites in patterns of pre-dispersal loss. Field surveys were done at two sites to identify potential seed predators. Three of the most abundant species identified in these surveys were tested in the laboratory to determine size-specific patterns of feeding activity and to assess which early life stages of P. torreyi (fruits within spadices, dehisced fruits, seedlings) were most vulnerable to predation. All three of the early life stages were consumed. The crabs Pugettiaproducta (Randall) and Pachygrapsus crassipes Randall were much more voracious predators than the isopod Idotea resecata Stimpson.
Carol A. Blanchette - One of the best experts on this subject based on the ideXlab platform.
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Where a male is hard to find: consequences of male rarity in the surfgrass Phyllospadix torreyi
Marine Ecology Progress Series, 2012Co-Authors: Christine A. Buckel, Carol A. Blanchette, Robert R. Warner, Steven D. GainesAbstract:Determining whether seed production is limited by pollen availability has been an area of intensive study. Past studies have focused largely on terrestrial species with biotic pollina- tion modes, but precise causes and consequences of pollen limitation remain unknown. Here, sex ratio, seed production, seed recruitment, and viability were examined in intertidal populations of a dioecious, abiotically pollinated marine angiosperm, Phyllospadix torreyi (Torrey's surfgrass). Using field surveys and a common garden experiment, this study was conducted near Santa Bar- bara, California, USA, from 2007 to 2008. Reproduction and recruitment of P. torreyi primarily occur near the parental source (tens of meters) because female reproductive success ratio (RSR, mea- sured as the ratio of fertilized ovules to total ovules) increased with local pollen production (RSR range: 0.02�0.71), and seed recruitment was predicted by local (site) seed production and elevation zone within the intertidal. Low RSR at sites with extreme male rarity (
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Patterns and sources of variation in flowering, seed supply and seedling recruitment in surfgrass Phyllospadix torreyi
Marine Ecology Progress Series, 2009Co-Authors: Daniel C. Reed, Carol A. Blanchette, Sally J. Holbrook, Suzanne WorcesterAbstract:Knowledge of patterns and sources of variation in adult reproduction and juvenile recruitment is essential for understanding the dynamics of populations and their capacity to recover from disturbances. In-depth knowledge of this kind is lacking for many species of seagrass. Here we examined the degree to which temporal and spatial variation in seedling density in the surfgrass Phyllospadix torreyi was explained by the local production and deposition of seeds. We did this by measuring floral density, seed production, seed supply and seedling recruitment at 5 sites near Santa Barbara, California, USA, over a 4 yr period. We found that the local density of dehisced female spadices explained nearly 41% of the variation in the number of seeds caught in seed traps. Large seed crops were common in the absence of nearby males and noticeable numbers of seeds were peri- odically caught in traps when female flowers were locally rare or absent, suggesting that pollen and seed dispersal occasionally occurred over distances greater than the scale of our study sites (i.e. >50 m). Overall, the summer densities of female spadices at a site explained >60% of the variation in the density of seedlings that recruited to the site the following winter. Deviations from positive asso- ciations among surfgrass flowers, seeds and seedlings appeared to reflect interannual variability in environmental conditions. Most notable was the coincidence of universally low fruit production and seedling recruitment during the 1997-1998 El Nino event. Seedling density varied independently of rates of seed deposition when all years were examined, but was highly dependent on rates of seed supply when the seedling data from the 1998 El Nino winter were omitted from the analysis. Collec- tively, our observations demonstrated significant coupling between adult reproduction and local recruitment in surfgrass that was interrupted by adverse growing conditions associated with the 1997-1998 El Nino.
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Stasis or kinesis? Hidden dynamics of a rocky intertidal macrophyte mosaic revealed by a spatially explicit approach
Journal of Experimental Marine Biology and Ecology, 2005Co-Authors: Bruce A. Menge, Gary W. Allison, Carol A. Blanchette, Terry M. Farrell, Annette M. Olson, Teresa A. Turner, Peter G. Van TamelenAbstract:Abstract Macrophyte mosaics, or tile-like assemblages of turfy marine macroalgae and surfgrass ( Phyllospadix scouleri ), are persistent and highly diverse along the central Oregon coast. To test the hypothesis that spatial pattern and species abundances are relatively invariant in this system, we studied community structure, disturbance, and species interactions from 1985 to 1990. Abundances and disturbance in permanently marked plots at each of five sites spanning wave-exposed to wave-protected areas were monitored photographically each year. The analysis was spatially explicit, incorporated position effects, and allowed determination of species displacements. To interpret the potential influence of substratum on disturbance, we quantified rock hardness and sediment depth at each site. Field experiments tested the role of grazers and spatial interactions on maintenance of between-patch boundaries. Mosaic dynamics varied with wave exposure. At wave-exposed and wave-protected sites, average patterns of abundance and assemblage structure were relatively constant through time, but analysis of transition probabilities showed high rates of change among mosaic elements at wave-exposed sites and low rates of change at wave-protected sites. At wave-exposed sites, most changes involved Phyllospadix displacing neighboring macroalgal turfs but rarely the reverse. At all wave-exposures, surfgrass was the most frequently disturbed mosaic element. Disturbed areas were quickly colonized by macroalgae. At wave-exposed sites, disturbances were closed by regrowth of surfgrass. Disturbance rates were similar across wave-exposures, with wave forces causing most loss at wave-exposed sites and a combination of substratum failure and sediment burial causing most loss at wave-protected sites. At wave-exposed sites, disturbances tended to be larger (436.7 vs. 278.6 cm 2 ) but less numerous (228 vs. 484 total disturbances) than at wave-protected sites. At wave-exposed sites, surfgrass overgrew all other species except the kelp Lessoniopsis littoralis , which was competitively equivalent to surfgrass. Grazing had no effect on spatial interactions. Disturbance prevented surfgrass monocultures, and with variable dispersal and patchy recruitment, maintained mosaic structure. At wave-protected sites, standoffs were the usual outcome of interactions, and patchiness resulted primarily from colonization of disturbances and subsequent succession. Like mussels, Phyllospadix are simultaneously dominant competitors, the most disturbance-susceptible species, and poor colonizers. These features are shared by theoretical models exploring the processes underlying spatially structured assemblages, and may characterize spatially structured systems in general.
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Spatial and temporal patterns of predation on seeds of the surfgrass Phyllospadix torreyi
Marine Biology, 2000Co-Authors: Sally J. Holbrook, Daniel C. Reed, K. Hansen, Carol A. BlanchetteAbstract:Spatial and temporal patterns of predation on seeds of the seagrass Phyllospadix torreyi S. Watson were quantified at four sites near Santa Barbara, California, USA. Over a period of four flowering seasons during 1995 to 1998, monthly patterns of seed fall and intensity of seed predation were similar among sites, but were temporally quite variable. Abundance of dispersed seeds varied greatly both among seasons and years. Within any one year, seeds were present in the environment every month, but they peaked in abundance during the fall months following the annual flowering period. Seeds were more abundant during the earlier years of the study. The intensity of predation steadily increased throughout the study period, from a low of ≤10% seeds consumed during 1995 to ∼50% consumption by 1997, and it was not correlated with abundance of seeds in the environment. Pre-dispersal seed loss also was estimated in two flowering seasons by counting the numbers of seeds consumed prior to release from the plant, and was relatively low (
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spatial and temporal patterns of predation on seeds of the surfgrass Phyllospadix torreyi
Marine Biology, 2000Co-Authors: Sally J. Holbrook, Daniel C. Reed, K. Hansen, Carol A. BlanchetteAbstract:Spatial and temporal patterns of predation on seeds of the seagrass Phyllospadix torreyi S. Watson were quantified at four sites near Santa Barbara, California, USA. Over a period of four flowering seasons during 1995 to 1998, monthly patterns of seed fall and intensity of seed predation were similar among sites, but were temporally quite variable. Abundance of dispersed seeds varied greatly both among seasons and years. Within any one year, seeds were present in the environment every month, but they peaked in abundance during the fall months following the annual flowering period. Seeds were more abundant during the earlier years of the study. The intensity of predation steadily increased throughout the study period, from a low of ≤10% seeds consumed during 1995 to ∼50% consumption by 1997, and it was not correlated with abundance of seeds in the environment. Pre-dispersal seed loss also was estimated in two flowering seasons by counting the numbers of seeds consumed prior to release from the plant, and was relatively low (<15%). No differences were detected among the four study sites in patterns of pre-dispersal loss. Field surveys were done at two sites to identify potential seed predators. Three of the most abundant species identified in these surveys were tested in the laboratory to determine size-specific patterns of feeding activity and to assess which early life stages of P. torreyi (fruits within spadices, dehisced fruits, seedlings) were most vulnerable to predation. All three of the early life stages were consumed. The crabs Pugettiaproducta (Randall) and Pachygrapsus crassipes Randall were much more voracious predators than the isopod Idotea resecata Stimpson.
Daniel C. Reed - One of the best experts on this subject based on the ideXlab platform.
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Patterns and sources of variation in flowering, seed supply and seedling recruitment in surfgrass Phyllospadix torreyi
Marine Ecology Progress Series, 2009Co-Authors: Daniel C. Reed, Carol A. Blanchette, Sally J. Holbrook, Suzanne WorcesterAbstract:Knowledge of patterns and sources of variation in adult reproduction and juvenile recruitment is essential for understanding the dynamics of populations and their capacity to recover from disturbances. In-depth knowledge of this kind is lacking for many species of seagrass. Here we examined the degree to which temporal and spatial variation in seedling density in the surfgrass Phyllospadix torreyi was explained by the local production and deposition of seeds. We did this by measuring floral density, seed production, seed supply and seedling recruitment at 5 sites near Santa Barbara, California, USA, over a 4 yr period. We found that the local density of dehisced female spadices explained nearly 41% of the variation in the number of seeds caught in seed traps. Large seed crops were common in the absence of nearby males and noticeable numbers of seeds were peri- odically caught in traps when female flowers were locally rare or absent, suggesting that pollen and seed dispersal occasionally occurred over distances greater than the scale of our study sites (i.e. >50 m). Overall, the summer densities of female spadices at a site explained >60% of the variation in the density of seedlings that recruited to the site the following winter. Deviations from positive asso- ciations among surfgrass flowers, seeds and seedlings appeared to reflect interannual variability in environmental conditions. Most notable was the coincidence of universally low fruit production and seedling recruitment during the 1997-1998 El Nino event. Seedling density varied independently of rates of seed deposition when all years were examined, but was highly dependent on rates of seed supply when the seedling data from the 1998 El Nino winter were omitted from the analysis. Collec- tively, our observations demonstrated significant coupling between adult reproduction and local recruitment in surfgrass that was interrupted by adverse growing conditions associated with the 1997-1998 El Nino.
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An Experimental Evaluation of Different Methods of Restoring Phyllospadix torreyi (Surfgrass)
Restoration Ecology, 2004Co-Authors: J. Scott Bull, Daniel C. Reed, Sally J. HolbrookAbstract:The surfgrass Phyllospadix torreyi is an abundant seagrass found on rocky exposed shores of the Pacific coast of North America. In southern California surfgrass populations are adversely affected by a range of natural events and anthropogenic activities. Few attempts have been made to develop restoration methods for surfgrass, and none have investigated the efficacy of using different life stages. We evaluated several techniques for restoration in intertidal and subtidal habitats using: (1) laboratory-reared seedlings transplanted to the field (2) sprigs (short lengths of rhizome containing a few shoots) transplanted from undisturbed populations, and (3) plugs (a cohesive clump of shoots and rhizomes) transplanted from undisturbed populations. We calculated the net change in the aerial coverage of surfgrass after 6 months, taking into account the recovery or additional losses from the donor population, and amount of effort involved in transplanting. Transplanted seedlings survived poorly and had minimal rhizome growth at both the intertidal and the subtidal sites, yet the individuals that did survive showed a 275% increase in leaf number. Survivorship of transplanted plugs was high in both habitats; however, physical disturbances to the donor populations exacerbated damage sustained at the time of collecting, yielding a substantial net loss in surfgrass. Sprigs transplanted to the subtidal had higher survivorship (71 versus 48%) and a greater increase in the aerial coverage of rhizome (86 versus 42%) than those transplanted to the intertidal. Of the three techniques, transplanted sprigs had the greatest overall increase in aerial coverage per unit effort, suggesting that this method may be the most effective approach for restoring P. torreyi.
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Survival experiments with outplanted seedlings of surfgrass (Phyllospadix torreyi) to enhance establishment on artificial structures
ICES Journal of Marine Science, 2002Co-Authors: Sally J. Holbrook, Daniel C. Reed, J. Scott BullAbstract:Surfgrass (Phyllospadix torreyi) is considered a valuable plant for enhancing biogenic habitat on artificial structures on the west coast of North America. Its populations establish only slowly, prompting efforts to develop techniques to accelerate the process. We present results from outplanting tests of laboratory-reared seedlings in their natural environment using various techniques. Survival rates after 3 months were compared with those of naturally recruited seedlings. Seedlings require a host plant during their early stages, and both natural hosts (algae) and artificial hosts (nylon strings and nets attached to the bottom) were tested. Survival of naturally recruited seedlings was only 30%, and only in the case where seedlings were hooked into braided nylon netting glued to the substrate were comparable survival rates observed. The results suggest that using this technique may be a promising approach to establishing populations of P. torreyi on artificial structures. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.
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Spatial and temporal patterns of predation on seeds of the surfgrass Phyllospadix torreyi
Marine Biology, 2000Co-Authors: Sally J. Holbrook, Daniel C. Reed, K. Hansen, Carol A. BlanchetteAbstract:Spatial and temporal patterns of predation on seeds of the seagrass Phyllospadix torreyi S. Watson were quantified at four sites near Santa Barbara, California, USA. Over a period of four flowering seasons during 1995 to 1998, monthly patterns of seed fall and intensity of seed predation were similar among sites, but were temporally quite variable. Abundance of dispersed seeds varied greatly both among seasons and years. Within any one year, seeds were present in the environment every month, but they peaked in abundance during the fall months following the annual flowering period. Seeds were more abundant during the earlier years of the study. The intensity of predation steadily increased throughout the study period, from a low of ≤10% seeds consumed during 1995 to ∼50% consumption by 1997, and it was not correlated with abundance of seeds in the environment. Pre-dispersal seed loss also was estimated in two flowering seasons by counting the numbers of seeds consumed prior to release from the plant, and was relatively low (
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spatial and temporal patterns of predation on seeds of the surfgrass Phyllospadix torreyi
Marine Biology, 2000Co-Authors: Sally J. Holbrook, Daniel C. Reed, K. Hansen, Carol A. BlanchetteAbstract:Spatial and temporal patterns of predation on seeds of the seagrass Phyllospadix torreyi S. Watson were quantified at four sites near Santa Barbara, California, USA. Over a period of four flowering seasons during 1995 to 1998, monthly patterns of seed fall and intensity of seed predation were similar among sites, but were temporally quite variable. Abundance of dispersed seeds varied greatly both among seasons and years. Within any one year, seeds were present in the environment every month, but they peaked in abundance during the fall months following the annual flowering period. Seeds were more abundant during the earlier years of the study. The intensity of predation steadily increased throughout the study period, from a low of ≤10% seeds consumed during 1995 to ∼50% consumption by 1997, and it was not correlated with abundance of seeds in the environment. Pre-dispersal seed loss also was estimated in two flowering seasons by counting the numbers of seeds consumed prior to release from the plant, and was relatively low (<15%). No differences were detected among the four study sites in patterns of pre-dispersal loss. Field surveys were done at two sites to identify potential seed predators. Three of the most abundant species identified in these surveys were tested in the laboratory to determine size-specific patterns of feeding activity and to assess which early life stages of P. torreyi (fruits within spadices, dehisced fruits, seedlings) were most vulnerable to predation. All three of the early life stages were consumed. The crabs Pugettiaproducta (Randall) and Pachygrapsus crassipes Randall were much more voracious predators than the isopod Idotea resecata Stimpson.