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2020 |
Uno, Hiromi; Pneh, Shelley Ecological Research, 35 (3), pp. 474-481, 2020. Abstract | Links | BibTeX | Tags: diversity, ecological function, predator-prey dynamics, Riparian, STREAM @article{Uno2020b, title = {Effect of source habitat spatial heterogeneity and species diversity on the temporal stability of aquatic‐to‐terrestrial subsidy by emerging aquatic insects}, author = {Hiromi Uno and Shelley Pneh}, doi = {10.1111/1440-1703.12125}, year = {2020}, date = {2020-05-25}, journal = {Ecological Research}, volume = {35}, number = {3}, pages = {474-481}, abstract = {Duration and temporal stability of resource subsidy largely affect the response of recipient communities. Factors that influence the temporal dynamics of resource subsidy from aquatic‐to‐terrestrial habitats by emerging aquatic insects were examined in this study. By measuring the flux of aquatic insect emergence from six habitats in a river over summer, we found that the timing of emergence varied by habitats for each dominant taxa, and that different species emerged at different times of the summer sequentially. We found that spatial variation in the emergence timing caused by the spatial heterogeneity of the water temperature, and so on in the source habitat can temporally stabilize the subsidy of each species from the whole river. Similarly, we found that the variation in emergence timing between species contributed to the temporal stability of subsidies from each habitat. The contribution of spatial heterogeneity to the temporal stability varied by the focal species and the contribution of species diversity varied by habitats. This study demonstrates how the ecological function of spatial heterogeneity and species diversity crosses the boundary of ecosystems by temporally stabilizing resource subsidies.}, keywords = {diversity, ecological function, predator-prey dynamics, Riparian, STREAM}, pubstate = {published}, tppubtype = {article} } Duration and temporal stability of resource subsidy largely affect the response of recipient communities. Factors that influence the temporal dynamics of resource subsidy from aquatic‐to‐terrestrial habitats by emerging aquatic insects were examined in this study. By measuring the flux of aquatic insect emergence from six habitats in a river over summer, we found that the timing of emergence varied by habitats for each dominant taxa, and that different species emerged at different times of the summer sequentially. We found that spatial variation in the emergence timing caused by the spatial heterogeneity of the water temperature, and so on in the source habitat can temporally stabilize the subsidy of each species from the whole river. Similarly, we found that the variation in emergence timing between species contributed to the temporal stability of subsidies from each habitat. The contribution of spatial heterogeneity to the temporal stability varied by the focal species and the contribution of species diversity varied by habitats. This study demonstrates how the ecological function of spatial heterogeneity and species diversity crosses the boundary of ecosystems by temporally stabilizing resource subsidies. |
2003 |
Sabo, John L Hot rocks or no hot rocks: overnight retreat availability and selection by a diurnal lizard Journal Article Oecologia, 136 (3), pp. 329-335, 2003. Abstract | Links | BibTeX | Tags: Habitat selection, Retreat site, Riparian, Sceloporus occidentalis, Thermoregulation @article{Sabo2003, title = {Hot rocks or no hot rocks: overnight retreat availability and selection by a diurnal lizard}, author = {John L. Sabo}, url = {https://angelo.berkeley.edu/wp-content/uploads/Hot-Rocks-or-No-Hot-Rocks-Overnight-Retreat-Availability-and-Selection-by-a-Diurnal-Lizard_Sabo_2003.pdf}, doi = {10. 1007/s00442-003-1292-6 }, year = {2003}, date = {2003-08-00}, journal = {Oecologia}, volume = {136}, number = {3}, pages = {329-335}, abstract = {I used radio telemetry to determine the effects of substrate size and composition on overnight retreat site selection by western fence lizards (Sceloporus occidentalis). In watersheds of northern California (USA), these lizards occupy two habitat types differing in substrate characteristics: rocky cobble bars found in the dry, active channels of rivers and grassy upland meadows. Rocky substrates, found almost exclusively on cobble bars, provided warmer potential retreat sites than all available retreat sites on meadows during the first 5 h of inactivity. Only cobble and sand substrates provided retreats with temperatures within the preferred daily active range (32-36°C) during the inactive period for these lizards (1900-0900 hours). Females on a cobble bar used rocks as retreats on >90% of nights during the breeding season whereas females on a meadow used wood (>70% of nights) and burrows (>25% of nights). In contrast to females, cobble bar males used rocks significantly less frequently (<70%) and slept in the open air significantly more frequently (25% vs. <1%). Cobble bar females further, showed a significant preference for cobbles 15 cm thick, whereas the rocks used by males did not differ significantly in thickness from those measured in randomly placed transects. Rocks 15 cm thick were the warmest retreats commonly available on this habitat type. Thus, thermal microenvironments available to and chosen by gravid female lizards differ considerably between river and non-river habitats.}, keywords = {Habitat selection, Retreat site, Riparian, Sceloporus occidentalis, Thermoregulation}, pubstate = {published}, tppubtype = {article} } I used radio telemetry to determine the effects of substrate size and composition on overnight retreat site selection by western fence lizards (Sceloporus occidentalis). In watersheds of northern California (USA), these lizards occupy two habitat types differing in substrate characteristics: rocky cobble bars found in the dry, active channels of rivers and grassy upland meadows. Rocky substrates, found almost exclusively on cobble bars, provided warmer potential retreat sites than all available retreat sites on meadows during the first 5 h of inactivity. Only cobble and sand substrates provided retreats with temperatures within the preferred daily active range (32-36°C) during the inactive period for these lizards (1900-0900 hours). Females on a cobble bar used rocks as retreats on >90% of nights during the breeding season whereas females on a meadow used wood (>70% of nights) and burrows (>25% of nights). In contrast to females, cobble bar males used rocks significantly less frequently (<70%) and slept in the open air significantly more frequently (25% vs. <1%). Cobble bar females further, showed a significant preference for cobbles 15 cm thick, whereas the rocks used by males did not differ significantly in thickness from those measured in randomly placed transects. Rocks 15 cm thick were the warmest retreats commonly available on this habitat type. Thus, thermal microenvironments available to and chosen by gravid female lizards differ considerably between river and non-river habitats. |
2002 |
Bastow, Justin L; Sabo, John L; Finlay, Jacques C; Power, Mary E A basal aquatic-terrestrial trophic link in rivers: algal subsidies via shore-dwelling grasshoppers Journal Article Oecologia, 131 (2), pp. 261-268, 2002. Abstract | Links | BibTeX | Tags: pygmy grasshopper, Riparian, river-watershed exchange, subsidy, tetrigidae @article{Bastow2002, title = {A basal aquatic-terrestrial trophic link in rivers: algal subsidies via shore-dwelling grasshoppers}, author = { Justin L. Bastow and John L. Sabo and Jacques C. Finlay and Mary E. Power }, url = {https://angelo.berkeley.edu/wp-content/uploads/A-Basal-Aquatic-Terrestrial-Trophic-Link-in-Rivers-Algal-Subsidies-via-Shore-Dwelling-Grasshoppers_Bastow_2002.pdf}, doi = {10.1007/S00442-002-0879-7 }, year = {2002}, date = {2002-03-14}, journal = {Oecologia}, volume = {131}, number = {2}, pages = {261-268}, abstract = {Rivers provide important resources for riparian consumers, especially in arid or seasonally arid biomes. Pygmy grasshoppers (Paratettix aztecus and P. mexicanus; Tetrigidae) graze river algae stranded along shorelines of the South Fork Eel River in northern California (39°44′N, 123°39′W) as the river recedes during the summer drought. Densities of tetrigids during the mid to late summer were highest (1 $text{individual}/text{m}^{2}$ in July) within 1 m of the river margin, and declined to near zero at 4 m from the margin, especially during peak temperatures in the afternoon. These observations suggested that the distribution of tetrigids was determined by the availability of algae, water, or both. We manipulated the presence/absence of water and beached algae (Cladophora glomerata) in a 2×2 factorial design. All treatments were positioned 2 m upslope from the river's edge (about 30 cm above the water table), where the cobble bar was naturally dry and devoid of algae and densities of tetrigids were lower than at the river margin (0.4 individuals/m2 in July). Tetrigids responded only to the wet Cladophora treatment, which had 30× higher densities than other treatments. Stable isotopic signatures (δ 13C) of tetrigids (-19.7‰) collected from the same cobble bars were more similar to those of epilithic algae (-20.4‰) than terrestrial plants (-28.2‰), and higher than those of acridid grasshoppers (-27.9‰) from the same habitats. Mixing models suggest that 88-100% of the C in tetrigid grasshoppers at our study site is derived from riverine algae. A preliminary analysis suggests that tetrigids ingested sufficient quantities of algae to easily meet their energetic demands during the summer. This study supports the idea that algae, produced in stream systems, can determine the distribution and relative abundance of a common terrestrial scavenger and provide an additional pathway for energy exchange between rivers and riparian food webs.}, keywords = {pygmy grasshopper, Riparian, river-watershed exchange, subsidy, tetrigidae}, pubstate = {published}, tppubtype = {article} } Rivers provide important resources for riparian consumers, especially in arid or seasonally arid biomes. Pygmy grasshoppers (Paratettix aztecus and P. mexicanus; Tetrigidae) graze river algae stranded along shorelines of the South Fork Eel River in northern California (39°44′N, 123°39′W) as the river recedes during the summer drought. Densities of tetrigids during the mid to late summer were highest (1 $text{individual}/text{m}^{2}$ in July) within 1 m of the river margin, and declined to near zero at 4 m from the margin, especially during peak temperatures in the afternoon. These observations suggested that the distribution of tetrigids was determined by the availability of algae, water, or both. We manipulated the presence/absence of water and beached algae (Cladophora glomerata) in a 2×2 factorial design. All treatments were positioned 2 m upslope from the river's edge (about 30 cm above the water table), where the cobble bar was naturally dry and devoid of algae and densities of tetrigids were lower than at the river margin (0.4 individuals/m2 in July). Tetrigids responded only to the wet Cladophora treatment, which had 30× higher densities than other treatments. Stable isotopic signatures (δ 13C) of tetrigids (-19.7‰) collected from the same cobble bars were more similar to those of epilithic algae (-20.4‰) than terrestrial plants (-28.2‰), and higher than those of acridid grasshoppers (-27.9‰) from the same habitats. Mixing models suggest that 88-100% of the C in tetrigid grasshoppers at our study site is derived from riverine algae. A preliminary analysis suggests that tetrigids ingested sufficient quantities of algae to easily meet their energetic demands during the summer. This study supports the idea that algae, produced in stream systems, can determine the distribution and relative abundance of a common terrestrial scavenger and provide an additional pathway for energy exchange between rivers and riparian food webs. |
Sabo, John L; Power, Mary E Numerical response of riparian lizards to aquatic insects and the short-term consequences for alternate terrestrial prey Journal Article Ecology, 83 (11), pp. 3023-3036, 2002. Abstract | Links | BibTeX | Tags: Carabidae, food web, indirect effects, insect, lizard, Lycosidae, numerical response, Riparian, river–watershed exchange, Sceloporus occidentalis, subsidy, Western fence lizard @article{Sabo2002, title = {Numerical response of riparian lizards to aquatic insects and the short-term consequences for alternate terrestrial prey}, author = {John L. Sabo and Mary E. Power}, url = {https://angelo.berkeley.edu/wp-content/uploads/Numerical-response-of-riparian-lizards-to-aquatic-insects-and-the-short-term-consequences-for-alternate-terrestrial-prey_Sabo_2002.pdf}, doi = {10.2307/3071839}, year = {2002}, date = {2002-00-00}, journal = {Ecology}, volume = {83}, number = {11}, pages = {3023-3036}, abstract = {Spatial subsidies, or inputs of resources from more productive donor habitats, can cause numerical responses in consumer populations via behavioral and demographic mechanisms. In addition, subsidies may have indirect effects on the in situ prey of these consumers. These indirect effects can be either negative (e.g., apparent competition) or positive (e.g., via diet shifts) depending on the relative strength of the predator’s functional and numerical responses to prey subsidies. Here we report a numerical response by a lizard (Western fence lizard, Sceloporus occidentalis) to experimental reductions in the flux of river-derived insects. Initially, equal densities of lizards declined significantly faster in plots in which aquatic insect abundance was reduced by nearly 50% (season average) relative to controls. Abundance and biomass of terrestrial arthropods declined significantly between the start and end of the experiment across treatments. Despite consistently lower lizard abundance in plots with reduced subsidy levels, however, relative declines in the abundance and biomass of in situ terrestrial arthropods (all taxa combined) were not significantly different between reduced- and ambient-subsidy plots. Relative declines in spider biomass differed significantly between treatments and were higher in reduced-subsidy than ambient-subsidy plots, but only over one of three 3-wk sampling intervals. Thus, over the biologically active summer season, aquatic subsidies exerted brief positive or no significant indirect effects on the in situ prey of riparian lizards. These results suggest that, although aquatic insect prey may determine the spatial distribution and local abundance of riparian predators, the effects of increased predator density on in situ prey may be offset by higher per capita predation by these consumers on in situ prey in subsidy-poor relative to subsidy-rich habitats. Numerical response of lizards to aquatic insects and short-term consequences for terrestrial prey. }, keywords = {Carabidae, food web, indirect effects, insect, lizard, Lycosidae, numerical response, Riparian, river–watershed exchange, Sceloporus occidentalis, subsidy, Western fence lizard}, pubstate = {published}, tppubtype = {article} } Spatial subsidies, or inputs of resources from more productive donor habitats, can cause numerical responses in consumer populations via behavioral and demographic mechanisms. In addition, subsidies may have indirect effects on the in situ prey of these consumers. These indirect effects can be either negative (e.g., apparent competition) or positive (e.g., via diet shifts) depending on the relative strength of the predator’s functional and numerical responses to prey subsidies. Here we report a numerical response by a lizard (Western fence lizard, Sceloporus occidentalis) to experimental reductions in the flux of river-derived insects. Initially, equal densities of lizards declined significantly faster in plots in which aquatic insect abundance was reduced by nearly 50% (season average) relative to controls. Abundance and biomass of terrestrial arthropods declined significantly between the start and end of the experiment across treatments. Despite consistently lower lizard abundance in plots with reduced subsidy levels, however, relative declines in the abundance and biomass of in situ terrestrial arthropods (all taxa combined) were not significantly different between reduced- and ambient-subsidy plots. Relative declines in spider biomass differed significantly between treatments and were higher in reduced-subsidy than ambient-subsidy plots, but only over one of three 3-wk sampling intervals. Thus, over the biologically active summer season, aquatic subsidies exerted brief positive or no significant indirect effects on the in situ prey of riparian lizards. These results suggest that, although aquatic insect prey may determine the spatial distribution and local abundance of riparian predators, the effects of increased predator density on in situ prey may be offset by higher per capita predation by these consumers on in situ prey in subsidy-poor relative to subsidy-rich habitats. Numerical response of lizards to aquatic insects and short-term consequences for terrestrial prey. |
1997 |
Gresens, Susan E Interactive effects of diet and thermal regime on growth of the midge Pseudochironomus richardsoni Malloch Journal Article Freshwater Biology, 38 (2), pp. 365-373, 1997, ISSN: 0046-5070. Abstract | Links | BibTeX | Tags: Blackwater River, diptera, larval chironomidae, rapid growth, Riparian, river food webs, SECONDARY PRODUCTION, size, STREAM, temperature @article{Gresens1997, title = {Interactive effects of diet and thermal regime on growth of the midge Pseudochironomus richardsoni Malloch}, author = {Susan E. Gresens}, url = {https://angelo.berkeley.edu/wp-content/uploads/Gresens_FreshwaterBiology1997.pdf}, doi = {10.1046/j.1365-2427.1997.00248.x}, issn = {0046-5070}, year = {1997}, date = {1997-10-00}, journal = {Freshwater Biology}, volume = {38}, number = {2}, pages = {365-373}, abstract = {1. Larvae of Pseudochironomus richardsoni were reared to pupation in individual enclosures, in one of three thermal habitats in a northern California stream. The average temperature range in cold seeps was 15-21 degrees C, while the main channel ranged from 20 to 27 degrees C, and side pools ranged from 18 to 33 degrees C. Diet consisted of either diatoms or algal detritus. 2. Specific growth rate ranged from 0.057 to 0.267 day(-1). Specific growth and developmental rates were highest on a diatom diet, and increased with temperature. Regressions of growth rate on mean microsite temperature were also significantly altered by diet. Differences in specific growth rate due to diet are magnified at higher temperatures. 3. Pupae reared on diatoms were larger than those reared on detritus. The mass of pupae reared on detritus decreased with increasing temperature. However, there was no significant relationship between pupal mass and temperature for larvae reared on diatoms. 4. The combined effects of food quality and thermal environment on growth of the midge P. richardsoni are significantly different from the independent effects of diet and temperature. Interactive effects of food quality and temperature may influence the contribution of certain aquatic habitats (algal mats) to invertebrate secondary production.}, keywords = {Blackwater River, diptera, larval chironomidae, rapid growth, Riparian, river food webs, SECONDARY PRODUCTION, size, STREAM, temperature}, pubstate = {published}, tppubtype = {article} } 1. Larvae of Pseudochironomus richardsoni were reared to pupation in individual enclosures, in one of three thermal habitats in a northern California stream. The average temperature range in cold seeps was 15-21 degrees C, while the main channel ranged from 20 to 27 degrees C, and side pools ranged from 18 to 33 degrees C. Diet consisted of either diatoms or algal detritus. 2. Specific growth rate ranged from 0.057 to 0.267 day(-1). Specific growth and developmental rates were highest on a diatom diet, and increased with temperature. Regressions of growth rate on mean microsite temperature were also significantly altered by diet. Differences in specific growth rate due to diet are magnified at higher temperatures. 3. Pupae reared on diatoms were larger than those reared on detritus. The mass of pupae reared on detritus decreased with increasing temperature. However, there was no significant relationship between pupal mass and temperature for larvae reared on diatoms. 4. The combined effects of food quality and thermal environment on growth of the midge P. richardsoni are significantly different from the independent effects of diet and temperature. Interactive effects of food quality and temperature may influence the contribution of certain aquatic habitats (algal mats) to invertebrate secondary production. |