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Pamela M Kittelson - One of the best experts on this subject based on the ideXlab platform.
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sources of variation in insect density on Lupinus arboreus sims effects of environment source population and plant genotype
American Midland Naturalist, 2004Co-Authors: Pamela M KittelsonAbstract:Abstract Temporal and spatial variability in herbivory can be influenced by plant genotype, environmental conditions and their interactions. However, few studies correctly control for the relative influence of these factors. Here, I report results from a reciprocal common garden experiment designed to tease apart the effect of local environmental variation and plant genotype on the abundance of four insect species: Dasineura lupini (Felt), D. lupinorum (Gagne), Epinotia infuscana (Walsingham) and Orgyia vetusta (Boisduval). Full-sib/half-sib families of Lupinus arboreus Sims were made within three different natal populations; replicates from each lupine family then were transplanted back into common gardens located in each of the three parental populations. In two separate years I measured how insect density varied between local environments, within a population of related lupine and among the three populations of lupine. For each insect species, local environment influenced density substantially and micr...
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variation in Lupinus arboreus alkaloid profiles and relationships with multiple herbivores
Biochemical Systematics and Ecology, 2004Co-Authors: Lynn S Adler, Pamela M KittelsonAbstract:Abstract Variation in plant defensive profiles can be affected by environmental factors, genetic factors, and their interactions, and different feeding guilds may have different responses to variation in defenses. Here we present results of a factorial breeding design in Lupinus arboreus from three sites of origin to determine how parental effects, population differences, and environmental effects influence alkaloid profiles and resistance to multiple herbivores. Alkaloids were identified and quantified in seeds and adult plants grown at each of the three sites. We also censused five different herbivores on plants over 2 years and determined the relationship between each herbivore density and total alkaloids, alkaloid profiles, plant size and site. We found strong effects of origin, maternal parent, and maternal×paternal interactions on seed alkaloid profiles, and effects of origin, destination site, their interactions, and maternal×paternal interactions on leaf alkaloid profiles. However, there was no correlation between alkaloid concentration or specific compounds in seeds and full-sib adult plants. Density of the leaf galler Dasineura lupinorum and the fungus Colletotrichium spp. was affected by total alkaloid concentration and alkaloid profiles, while density of apical flies and bud gallers was not affected by any alkaloid measure. Red and green forms of the leaf galler had different responses to alkaloids, and green leaf gallers and fungi had opposite responses to measures of alkaloid profiles. These results highlight the complexity of interactions between herbivores and plant defenses, and indicate that measuring selection for defense traits may not be straightforward in natural environments that include multiple herbivore guilds.
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fine scale genetically based differentiation of life history traits in the perennial shrub Lupinus arboreus
Evolution, 2001Co-Authors: Pamela M Kittelson, John L MaronAbstract:Abstract Across large spatial scales, plants often exhibit genetically based differentiation in traits that allow adaptation to local sites. At smaller spatial scales, sharp boundaries between edaphic conditions also can create strong gradients in selection that counteract gene flow and result in local adaptation. Few studies, however, have examined the degree to which continuous populations of perennial plants exhibit genetically based differentiation in life-history traits over small spatial scales. We quantified the degree of genetically based differentiation in adaptive traits among bush lupine (Lupinus arboreus) from nearby dune and grassland sites (sites separated by <0.75 km) that formed part of a larger continuous population of L. arboreus. We also investigated the spatial genetic structure of bush lupine by examining how genetic structure differed between seeds and juvenile plants that were less than two years old. We calculated F-statistics from gel electrophoresis of 10 polymorphic loci. We the...
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outcrossing rate and inbreeding depression in the perennial yellow bush lupine Lupinus arboreus fabaceae
American Journal of Botany, 2000Co-Authors: Pamela M Kittelson, John L MaronAbstract:Little is known about the breeding systems of perennial Lupinus species. We provide information about the breeding system of the perennial yellow bush lupine, Lupinus arboreus, specifically determining self-compatibility, outcrossing rate, and level of inbreeding depression. Flowers are self-compatible, but autonomous self-fertilization rarely occurs; thus selfed seed are a product of facilitated selfing. Based on four isozyme loci from 34 maternal progeny arrays of seeds we estimated an outcrossing rate of 0.78. However, when we accounted for differential maturation of selfed seeds, the outcrossing rate at fertilization was lower, ;0.64. Fitness and inbreeding depression of 11 selfed and outcrossed families were measured at four stages: seed maturation, seedling emergence, seedling survivorship, and growth at 12 wk. Cumulative inbreeding depression across all four life stages averaged 0.59, although variation existed between families for the magnitude of inbreeding depression. Inbreeding depression was not manifest uniformly across all four life stages. Outcrossed flowers produced twice as many seeds as selfed flowers, but the mean performance of selfed and outcrossed progeny was not different for emergence, seedling survivorship, and size at 12 wk. Counter to assumptions about this species, L. arboreus is both self-compatible and outcrosses ;78% of the time.
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effects of genetic structure of Lupinus arboreus and previous herbivory on platyprepia virginalis caterpillars
Oecologia, 1999Co-Authors: Richard Karban, Pamela M KittelsonAbstract:Two leaf-feeding caterpillars, western tussock moth (Orgyia vetusta) and ranchman's tiger moth (Platyprepia virginalis) are abundant on Lupinus arboreus along the California coast. Previous experiments and observations suggested that feeding caused by either of these two folivores could reduce the performance and possibly the abundance and distribution of the other species. Previous common garden experiments also indicated that genetically determined characteristics of the host plants were important for O. vetusta. Here we examined the effects of familial origin of the host plant, and previous damage caused by O. vetusta on the abundance of P. virginalis. Plants with parents from one of three locations had higher numbers of P. virginalis than plants with parents from the other two locations. However, this effect of plant origin depended on the statistical analysis and was not as strong as the effect of prior damage by O. vetusta on numbers of P. virginalis. Counter to our expectation, bushes that supported higher levels of damage by O. vetusta in the previous summer had more P. virginalis caterpillars. This strong effect could result by both moth species selecting bushes with the same traits or as the result of herbivory by O. vetusta enhancing the susceptibility of bushes for P. virginalis.
Dave Goulson - One of the best experts on this subject based on the ideXlab platform.
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population dynamics of the invasive weed Lupinus arboreus in tasmania and interactions with two non native pollinators
Weed Research, 2012Co-Authors: Dave Goulson, Ellen L RotherayAbstract:The factors that determine which plant species become invasive weeds are not well understood and there have been few studies of population dynamics in the early stages of invasion. Here, we examine changes in population size, pollinator visitation and seed set of the tree lupin, Lupinus arboreus, in Tasmania between 1999 and 2010. Lupinus arboreus is a native of California that has become a major environmental weed in New Zealand and Chile, but has not yet become a serious weed in Tasmania. Our data suggest that the main pollinators of L. arboreus are honeybees and the bumblebee, Bombus terrestris, which invaded in 1992. There was no clear evidence for an impact of the arrival of bumblebees. Lupinus arboreus population size increased by 76% between 1999 and 2010, despite weed control programmes. Populations appeared to be unstable; 43% of populations detected in 1999 were extinct by 2010, but this was more than offset by establishment of new populations. Inland populations tended to be smaller and were more likely to go extinct, compared with coastal populations, and some coastal populations had increased fourfold in 11years. Large populations in 2010 tended to have higher seed set than smaller populations. The overall rate of increase suggests that L. arboreus may become a major environmental weed in Tasmania. Control of expanding populations is likely to become more difficult if, as we observed, seed set increases with population size. © 2012 The Authors. Weed Research © 2012 European Weed Research Society.
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pollination of the invasive exotic shrub Lupinus arboreus fabaceae by introduced bees in tasmania
Biological Conservation, 2002Co-Authors: Jane C Stout, Andrea R Kells, Dave GoulsonAbstract:Exotic plant invasions threaten ecological communities world-wide. Some species are limited by a lack of suitable pollinators, but the introduction of exotic pollinators can facilitate rapid spread. In Tasmania, where many non-native plants are naturalised, exotic honeybees (Apis mellifera) and bumblebees (Bombus terrestris) have become established. We determined how these species affect the pollination of Lupinus arboreus, an invasive, nitrogen-fixing shrub, which is rarely visited by native pollinators. The proportion of flowers setting seed and the number of ovules fertilised per flower were positively related to the visitation rates of both exotic bee species. There was no effect of bee visitation rates on the proportion of seeds aborted prior to maturity, possibly due to post-fertilisation environmental constraints. We conclude that the spread of B. terrestris may not alter the fecundity of L. arboreus because of the pollination service provided by A. mellifera, and discuss potential interactions between these two bee species.
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Pollination of the invasive exotic shrub Lupinus arboreus (Fabaceae) by introduced bees in Tasmania." Biological Conservation 106: 425‐434. Exotic plant invasions threaten ecological communities world‐wide. Some species are limited by a lack of suitable p
2002Co-Authors: Jane C Stout, Andrea R Kells, Dave GoulsonAbstract:Exotic plant invasions threaten ecological communities world-wide. Some species are limited by a lack of suitable pollinators, but the introduction of exotic pollinators can facilitate rapid spread. In Tasmania, where many non-native plants are naturalised, exotic honeybees (Apis mellifera) and bumblebees (Bombus terrestris) have become established. We determined how these species affect the pollination of Lupinus arboreus, an invasive, nitrogen-fixing shrub, which is rarely visited by native pollinators. The proportion of flowers setting seed and the number of ovules fertilised per flower were positively related to the visitation rates of both exotic bee species. There was no effect of bee visitation rates on the proportion of seeds aborted prior to maturity, possibly due to postfertilisation environmental constraints. We conclude that the spread of B. terrestris may not alter the fecundity of L. arboreus because of the pollination service provided by A. mellifera, and discuss potential interactions between these two bee species. # 200
John L Maron - One of the best experts on this subject based on the ideXlab platform.
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Consumers limit the abundance and dynamics of a perennial shrub with a seed
2006Co-Authors: Matthew J Kauffman, John L MaronAbstract:abstract: For nearly 30 years, ecologists have argued that predators of seeds and seedlings seldom have population-level effects on plants with persistent seed banks and density-dependent seedling survival. We parameterized stage-based population models that incorporated density dependence and seed dormancy with data from a 5.5-year experiment that quantified how granivorous mice and herbivorous voles influence bush lupine (Lupinus arboreus) demography. We asked how seed dormancy and density-dependent seedling survival mediate the impacts of these consumers in dune and grassland habitats. In dune habitat, mice reduced analytical l (the intrinsic rate of population growth) by 39%, the equilibrium number of aboveground plants by 90%, and the seed bank by 98%; voles had minimal effects. In adjacent grasslands, mice had minimal effects, but seedling herbivory by voles reduced analytical l by 15% and reduced both the equilibrium number of aboveground plants and dormant seeds by 63%. A bootstrap analysis demonstrated that these consumer effects were robust to parameter uncertainty. Our results demonstrate that the quantitative strengths of seed dormancy and densitydependent seedling survival-not their mere existence-critically mediate consumer effects. This study suggests that plant population dynamics and distribution may be more strongly influenced by consumers of seeds and seedlings than is currently recognized
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fine scale genetically based differentiation of life history traits in the perennial shrub Lupinus arboreus
Evolution, 2001Co-Authors: Pamela M Kittelson, John L MaronAbstract:Abstract Across large spatial scales, plants often exhibit genetically based differentiation in traits that allow adaptation to local sites. At smaller spatial scales, sharp boundaries between edaphic conditions also can create strong gradients in selection that counteract gene flow and result in local adaptation. Few studies, however, have examined the degree to which continuous populations of perennial plants exhibit genetically based differentiation in life-history traits over small spatial scales. We quantified the degree of genetically based differentiation in adaptive traits among bush lupine (Lupinus arboreus) from nearby dune and grassland sites (sites separated by <0.75 km) that formed part of a larger continuous population of L. arboreus. We also investigated the spatial genetic structure of bush lupine by examining how genetic structure differed between seeds and juvenile plants that were less than two years old. We calculated F-statistics from gel electrophoresis of 10 polymorphic loci. We the...
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outcrossing rate and inbreeding depression in the perennial yellow bush lupine Lupinus arboreus fabaceae
American Journal of Botany, 2000Co-Authors: Pamela M Kittelson, John L MaronAbstract:Little is known about the breeding systems of perennial Lupinus species. We provide information about the breeding system of the perennial yellow bush lupine, Lupinus arboreus, specifically determining self-compatibility, outcrossing rate, and level of inbreeding depression. Flowers are self-compatible, but autonomous self-fertilization rarely occurs; thus selfed seed are a product of facilitated selfing. Based on four isozyme loci from 34 maternal progeny arrays of seeds we estimated an outcrossing rate of 0.78. However, when we accounted for differential maturation of selfed seeds, the outcrossing rate at fertilization was lower, ;0.64. Fitness and inbreeding depression of 11 selfed and outcrossed families were measured at four stages: seed maturation, seedling emergence, seedling survivorship, and growth at 12 wk. Cumulative inbreeding depression across all four life stages averaged 0.59, although variation existed between families for the magnitude of inbreeding depression. Inbreeding depression was not manifest uniformly across all four life stages. Outcrossed flowers produced twice as many seeds as selfed flowers, but the mean performance of selfed and outcrossed progeny was not different for emergence, seedling survivorship, and size at 12 wk. Counter to assumptions about this species, L. arboreus is both self-compatible and outcrosses ;78% of the time.
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effect of seed predation on seed bank size and seedling recruitment of bush lupine Lupinus arboreus
Oecologia, 1997Co-Authors: John L Maron, Ellen L SimmsAbstract:Whether seed consumers affect plant establishment is an important unresolved question in plant population biology. Seed consumption is ubiquitous; at issue is whether seedling recruitment is limited by safe-sites or seeds. If most seeds inhabit sites unsuitable for germination, post-dispersal seed consumption primarily removes seeds that would otherwise never contribute to the population and granivory has minimal impacts on plant abundance. Alternatively, if most seeds ultimately germinate before they lose viability, there is greater potential for seed consumption to affect plant recruitment. Of the many studies on seed consumption, few ask how seed loss affects seedling recruitment for species with long-lived seed banks. We examined post-dispersal seed predation and seedling emergence in bush lupine (Lupinus arboreus), a woody leguminous shrub of coastal grasslands and dunes in California. We followed the fate of seeds in paired experimental seed plots that were either protected or exposed to rodent granivores in grassland and dune habitats. Significantly more seeds were removed by rodents in dunes than grasslands. In dunes, where rodent granivory was greatest (65% and 86% of seeds removed from plots by rodents in two successive years), there is a sparse seed bank (6.6 seeds m−2), and granivory significantly reduced seedling emergence (in the same two years, 18% and 19.4% fewer seedlings emerged from exposed versus protected plots), suggesting seed rather than safe-site limited seedling recruitment. In contrast, rodents removed an average of 6% and 56% of seeds from grassland plots during the same two years, and the grassland seed bank is 43-fold that of the dunes (288 seeds m−2). Even high seed consumption in the second year of the study only marginally influenced recruitment because seeds that escaped predation remained dormant. Burial of seeds in both habitats significantly reduced the percentage of seeds removed by rodents. Results suggest that granivores exert strong but habitat-dependent effects on lupine seed survival and seedling emergence.
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interspecific competition and insect herbivory reduce bush lupine Lupinus arboreus seedling survival
Oecologia, 1997Co-Authors: John L MaronAbstract:Seedlings suffer high mortality in most plant populations, with both competition and herbivory proposed as being important mechanisms causing seedling death. The relative strength of these factors, however, is often unknown. Here I ask how interspecific competition for light and insect herbivory jointly affect seedling survival of bush lupine (Lupinus arboreus), a native shrub common to coastal California. Bush lupine seedlings germinate in grasslands during winter, and throughout spring potentially compete for light with surrounding fast-growing annual grasses. By early summer, after grasses have died, seedlings can be defoliated by a locally abundant caterpillar, the western tussock moth (Orgyia vetusta). I examined the relative importance of competition and insect herbivory on seedling survival in two separate experiments. First, I compared seedling mortality in plots either exposed to or protected from tussock moth larvae. Plants were protected from herbivory by the judicious use of insecticide; control plants were sprayed with water. Tussock moth herbivory resulted in significantly greater (31%) seedling mortality. To determine the effects of interspecific competition for light on seedling survival, I manipulated the density of grass surrounding lupine seedlings. I removed all vegetation surrounding some individuals, and left intact vegetation surrounding others. Reducing competition resulted in a 32% increase in seedling survival from February to June, as well as changes in seedling growth. To determine whether there are interactive effects of competition and herbivory on seedling survival, I enclosed tussock moth larvae on half of all surviving seedlings within each of the two prior competition treatments, comparing growth and survival of defoliated and undefoliated seedlings. Defoliation in June led to an additional 50% mortality for individuals that had grown with competitors through spring, and a 53% additional mortality for seedlings that grew without competitors through spring. Thus, although competition and herbivory both caused substantial seedling mortality, there was no statistical interaction between these factors. Competition-free plants were not less vulnerable to herbivory than plants that previously grew with competitors. Taken together, these experiments indicate that competition and herbivory are both important sources of mortality for bush lupine seedlings.
Richard Karban - One of the best experts on this subject based on the ideXlab platform.
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effects of genetic structure of Lupinus arboreus and previous herbivory on platyprepia virginalis caterpillars
Oecologia, 1999Co-Authors: Richard Karban, Pamela M KittelsonAbstract:Two leaf-feeding caterpillars, western tussock moth (Orgyia vetusta) and ranchman's tiger moth (Platyprepia virginalis) are abundant on Lupinus arboreus along the California coast. Previous experiments and observations suggested that feeding caused by either of these two folivores could reduce the performance and possibly the abundance and distribution of the other species. Previous common garden experiments also indicated that genetically determined characteristics of the host plants were important for O. vetusta. Here we examined the effects of familial origin of the host plant, and previous damage caused by O. vetusta on the abundance of P. virginalis. Plants with parents from one of three locations had higher numbers of P. virginalis than plants with parents from the other two locations. However, this effect of plant origin depended on the statistical analysis and was not as strong as the effect of prior damage by O. vetusta on numbers of P. virginalis. Counter to our expectation, bushes that supported higher levels of damage by O. vetusta in the previous summer had more P. virginalis caterpillars. This strong effect could result by both moth species selecting bushes with the same traits or as the result of herbivory by O. vetusta enhancing the susceptibility of bushes for P. virginalis.
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Host-plant-mediated interactions between a generalist folivore and its tachinid parasitoid
The Journal of Animal Ecology, 1993Co-Authors: Gregory M. English-loeb, Alison K. Brody, Richard KarbanAbstract:We investigated the consequences of feeding on different species of host-plants on the performance of a generalist lepidopteran larva (Platyprepia virginalis (Bvd.) Arctiidae) and its interactions with a tachinid fly parasitoid (Thelairia bryanti Curran). Growth rate of P. virginalis was not different for larvae reared individually on either poison hemlock, Conium maculatum L., bush lupine, Lupinus arboreus Sims, or fiddle neck, Amsinckia menziesii (Lehm.) under laboratory conditions. 3. Further, larvae caged in the field on either hemlock or lupine did not differ in developmental rates or pupal mass. In 1 of 2 years survivorship was higher for moth larvae caged on hemlock
Ellen L Simms - One of the best experts on this subject based on the ideXlab platform.
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an empirical test of partner choice mechanisms in a wild legume rhizobium interaction
Proceedings of The Royal Society B: Biological Sciences, 2006Co-Authors: Ellen L Simms, Lee D Taylor, Joshua Povich, Richard P Shefferson, Joel L Sachs, M Urbina, Yla R TausczikAbstract:Mutualisms can be viewed as biological markets in which partners of different species exchange goods and services to their mutual benefit. Trade between partners with conflicting interests requires mechanisms to prevent exploitation. Partner choice theory proposes that individuals might foil exploiters by preferentially directing benefits to cooperative partners. Here, we test this theory in a wild legume– rhizobium symbiosis. Rhizobial bacteria inhabit legume root nodules and convert atmospheric dinitrogen (N2) to a plant available form in exchange for photosynthates. Biological market theory suits this interaction because individual plants exchange resources with multiple rhizobia. Several authors have argued that microbial cooperation could be maintained if plants preferentially allocated resources to nodules harbouring cooperative rhizobial strains. It is well known that crop legumes nodulate non-fixing rhizobia, but allocate few resources to those nodules. However, this hypothesis has not been tested in wild legumes which encounter partners exhibiting natural, continuous variation in symbiotic benefit. Our greenhouse experiment with a wild legume, Lupinus arboreus, showed that although plants frequently hosted less cooperative strains, the nodules occupied by these strains were smaller. Our survey of wild-grown plants showed that larger nodules house more Bradyrhizobia, indicating that plants may prevent the spread of exploitation by favouring better cooperators.
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effect of seed predation on seed bank size and seedling recruitment of bush lupine Lupinus arboreus
Oecologia, 1997Co-Authors: John L Maron, Ellen L SimmsAbstract:Whether seed consumers affect plant establishment is an important unresolved question in plant population biology. Seed consumption is ubiquitous; at issue is whether seedling recruitment is limited by safe-sites or seeds. If most seeds inhabit sites unsuitable for germination, post-dispersal seed consumption primarily removes seeds that would otherwise never contribute to the population and granivory has minimal impacts on plant abundance. Alternatively, if most seeds ultimately germinate before they lose viability, there is greater potential for seed consumption to affect plant recruitment. Of the many studies on seed consumption, few ask how seed loss affects seedling recruitment for species with long-lived seed banks. We examined post-dispersal seed predation and seedling emergence in bush lupine (Lupinus arboreus), a woody leguminous shrub of coastal grasslands and dunes in California. We followed the fate of seeds in paired experimental seed plots that were either protected or exposed to rodent granivores in grassland and dune habitats. Significantly more seeds were removed by rodents in dunes than grasslands. In dunes, where rodent granivory was greatest (65% and 86% of seeds removed from plots by rodents in two successive years), there is a sparse seed bank (6.6 seeds m−2), and granivory significantly reduced seedling emergence (in the same two years, 18% and 19.4% fewer seedlings emerged from exposed versus protected plots), suggesting seed rather than safe-site limited seedling recruitment. In contrast, rodents removed an average of 6% and 56% of seeds from grassland plots during the same two years, and the grassland seed bank is 43-fold that of the dunes (288 seeds m−2). Even high seed consumption in the second year of the study only marginally influenced recruitment because seeds that escaped predation remained dormant. Burial of seeds in both habitats significantly reduced the percentage of seeds removed by rodents. Results suggest that granivores exert strong but habitat-dependent effects on lupine seed survival and seedling emergence.
