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A Spatiotemporal Analysis of the Effects of Urbanization’s Socio-Economic Factors on Landscape Patterns Considering Operational Scales. SUSTAINABILITY 2020. [DOI: 10.3390/su12062543] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Landscape patterns are significantly affected during the urbanization process. Identifying the spatiotemporal impacts of urbanization’s socio-economic factors on landscape patterns is very important and can provide scientific evidence to support urban ecological management and guide managers to establish appropriate sustainability policies. This article applies multiscale geographically weighted regression (MGWR) to reveal the relationships between landscape patterns and the socio-economic factors of urbanization in Shenzhen, China, from 2000 to 2015, in five-year intervals. MGWR is a powerful extension of geographically weighted regression (GWR) that can not only reveal spatial heterogeneity patterns but also measure the operational scale of covariates. The empirical results indicate that MGWR is superior to GWR. Furthermore, the changes in operational scale represented by the spatial bandwidth of MGWR in different years reflect temporal changes in the spatial relationships of given factors, which is significant information for urban studies. These multiscale relationships between landscape patterns and the socio-economic factors of urbanization, revealed via MGWR, are useful for strategic planning around urban dynamic development and land resource and ecological landscape management. The results can provide additional insight into landscape and urbanization studies from a multiscale perspective, which is important for local, regional, and global urban planning.
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Waddle E, Piedrahita LR, Hall ES, Kendziorski G, Morris WF, DeMarche ML, Doak DF. Asynchrony in individual and subpopulation fecundity stabilizes reproductive output of an alpine plant population. Ecology 2019; 100:e02639. [DOI: 10.1002/ecy.2639] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 01/07/2019] [Accepted: 01/16/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Ellen Waddle
- Environmental Studies Program University of Colorado Boulder Colorado 80302 USA
| | - Lucas R. Piedrahita
- Biology Department Appalachian State University Boone North Carolina 28608 USA
| | - Elijah S. Hall
- Biology Department Juniata College Huntingdon Pennsylvania 16652 USA
| | - Grace Kendziorski
- Environmental Studies Program University of Colorado Boulder Colorado 80302 USA
| | - William F. Morris
- Department of Biology Duke University Durham North Carolina 27708 USA
| | - Megan L. DeMarche
- Environmental Studies Program University of Colorado Boulder Colorado 80302 USA
| | - Daniel F. Doak
- Environmental Studies Program University of Colorado Boulder Colorado 80302 USA
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3
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Edmunds PJ. Intraspecific variation in growth rate is a poor predictor of fitness for reef corals. Ecology 2017; 98:2191-2200. [PMID: 28555884 DOI: 10.1002/ecy.1912] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 04/23/2017] [Accepted: 05/05/2017] [Indexed: 01/29/2023]
Abstract
Genetic variation underlying differences in organism performance is subject to natural selection, and organisms with high values of genetically determined phenotypic measures of fitness should perform better than those that do not. Using small scleractinian corals (i.e., ≤40-mm diameter), this principle was tested with 20 yr of census data from St. John, US Virgin Islands. Using growth rate (change in diameter) as a measure of fitness, growth in one year was tested for association with growth and survivorship in the following two years, and this process was repeated over 20 yr using a 3-yr sliding window. Virtually all variation in growth was independent of colony size, and growth among pairs of years was highly variable, with corals that grew fast in one year rarely growing fast in the next 2 yr. While growth in some pairs of years was positively correlated, ≤4% of the growth variance was explained by growth in the preceding 2 yr. Survivorship was related positively to growth in the preceding year, but the association was weak, it did not extend over 3 yr, and was inconsistent over the study. These results demonstrate the importance of the environment in translating phenotypic measures of fitness into future performance, and for small Caribbean corals, they suggest that environmental conditions may preempt genotype in determining short-term success.
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Affiliation(s)
- Peter J Edmunds
- Department of Biology, California State University, 18111 Nordhoff Street, Northridge, California, 91330-8303, USA
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4
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Banks SC, Lorin T, Shaw RE, McBurney L, Blair D, Blyton MDJ, Smith AL, Pierson JC, Lindenmayer DB. Fine-scale refuges can buffer demographic and genetic processes against short-term climatic variation and disturbance: a 22-year case study of an arboreal marsupial. Mol Ecol 2015; 24:3831-45. [PMID: 26089175 DOI: 10.1111/mec.13279] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 06/13/2015] [Accepted: 06/16/2015] [Indexed: 11/29/2022]
Abstract
Ecological disturbance and climate are key drivers of temporal dynamics in the demography and genetic diversity of natural populations. Microscale refuges are known to buffer species' persistence against environmental change, but the effects of such refuges on demographic and genetic patterns in response to short-term environmental variation are poorly understood. We quantified demographic and genetic responses of mountain brushtail possums (Trichosurus cunninghami) to rainfall variability (1992-2013) and to a major wildfire. We hypothesized that there would be underlying differences in demographic and genetic processes between an unburnt mesic refuge and a topographically exposed zone that was burnt in 2009. Fire caused a 2-year decrease in survival in the burnt zone, but the population grew after the fire due to immigration, leading to increased expected heterozygosity. We documented a fire-related behavioural shift, where the rate of movement by individuals in the unburnt refuge to the burnt zone decreased after fire. Irrespective of the fire, there were long-term differences in demographic and genetic parameters between the mesic/unburnt refuge and the nonmesic/burnt zone. Survival was high and unaffected by rainfall in the refuge, but lower and rainfall-dependent in the nonmesic zone. Net movement of individuals was directional, from the mesic refuge to the nonmesic zone, suggesting fine-scale source-sink dynamics. There were higher expected heterozygosity (HE ) and temporal genetic stability in the refuge, but lower HE and marked temporal genetic structure in the exposed habitat, consistent with reduced generational overlap caused by elevated mortality and immigration. Thus, fine-scale refuges can mediate the short-term demographic and genetic effects of climate and ecological disturbance.
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Affiliation(s)
- Sam C Banks
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
| | - Thibault Lorin
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
| | - Robyn E Shaw
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
| | - Lachlan McBurney
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
| | - David Blair
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
| | - Michaela D J Blyton
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia.,Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Annabel L Smith
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
| | - Jennifer C Pierson
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
| | - David B Lindenmayer
- The Fenner School of Environment and Society, The Australian National University, Canberra, ACT, 2601, Australia
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5
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Sigourney DB, Munch SB, Letcher BH. Combining a Bayesian nonparametric method with a hierarchical framework to estimate individual and temporal variation in growth. Ecol Modell 2012. [DOI: 10.1016/j.ecolmodel.2012.08.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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6
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Haymes KL, Fox GA. Variation among individuals in cone production in Pinus palustris (Pinaceae). AMERICAN JOURNAL OF BOTANY 2012; 99:640-645. [PMID: 22434774 DOI: 10.3732/ajb.1100339] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
PREMISE OF THE STUDY Reproductive output varies considerably among individuals within plant populations, and this is especially so in cone production of conifers. While this variation can have substantial effects on populations, little is known about its magnitude or causes. METHODS We studied variation in cone production for 2 years within a population of Pinus palustris Mill. (longleaf pine; Pinaceae). Using hurdle models, we evaluated the importance of burn treatments, tree size (dbh), canopy status (open, dominant, subordinate), and number of conspecific neighbors within 4 m (N(4)). KEY RESULTS Cone production of individuals-even after accounting for other variables-was strongly correlated between years. Trees in plots burned every 1, 2, or 5 years produced more cones than those burned every 7 years, or unburned. Larger trees tend to produce more cones, but the large effects of the other factors studied caused substantial scatter in the dbh-cone number relationship. Among trees in the open, dbh had little explanatory power. Subordinate trees with three neighbors produced no cones. CONCLUSIONS Tree size alone was a weak predictor of cone production. Interactions with neighbors play an important role in generating reproductive heterogeneity, and must be accounted for when relating cone production to size. The strong between-year correlation, together with the large variance in cone production among trees without neighbors, suggests that still more of the variance may be explainable, but requires factors outside of our study.
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Affiliation(s)
- Kelly L Haymes
- Department of Integrative Biology, University of South Florida, Tampa, Florida 33620, USA
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Einum S, Forseth T, Finstad AG. Individual variation in response to intraspecific competition: problems with inference from growth variation measures. Methods Ecol Evol 2011. [DOI: 10.1111/j.2041-210x.2011.00167.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Huss M, Van Kooten T, Persson L. Intra-cohort cannibalism and size bimodality: a balance between hatching synchrony and resource feedbacks. OIKOS 2010. [DOI: 10.1111/j.1600-0706.2010.18454.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Foldvik A, Finstad AG, Einum S. Relating juvenile spatial distribution to breeding patterns in anadromous salmonid populations. J Anim Ecol 2010; 79:501-9. [DOI: 10.1111/j.1365-2656.2009.01652.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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10
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11
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Huss M, Byström P, Persson L. Effetcs of ontogenetic scaling on resource exploitation and cohort size distributions. OIKOS 2010. [DOI: 10.1111/j.1600-0706.2009.17897.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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12
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Zuidema PA, Brienen RJW, During HJ, Güneralp B. Do persistently fast-growing juveniles contribute disproportionately to population growth? A new analysis tool for matrix models and its application to rainforest trees. Am Nat 2009; 174:709-19. [PMID: 19778168 DOI: 10.1086/605981] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Plants and animals often exhibit strong and persistent growth variation among individuals within a species. Persistently fast-growing individuals have a higher chance of reaching reproductive size, do so at a younger age, and therefore contribute disproportionately to population growth (lambda). Here we introduce a new approach to quantify this "fast-growth effect." We propose using age-size-structured matrix models in which persistently fast and slow growers are distinguished as they occur in relatively young and old age classes for a given size category. Life-cycle pathways involving fast growth can then be identified, and their contribution to lambda is quantified through loop analysis. We applied this approach to an example species, the tropical rainforest tree Cedrela odorata, that shows persistent growth variation among individuals. Loop analysis showed that juvenile trees reaching the 10-cm diameter class at below-median age contributed twice as much to lambda as slow juvenile growers. Fast growth to larger-diameter categories also contributed disproportionately to lambda. The results were robust to changes in parameter values and life-history trade-offs. These results show that the fast-growth effect can be strong in long-lived species. Persistent growth differences among individuals should therefore be accommodated for in demographic models and life-history studies.
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Affiliation(s)
- Pieter A Zuidema
- Ecology and Biodiversity, Institute of Environmental Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands.
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13
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Huss M, Byström P, Persson L. Resource heterogeneity, diet shifts and intra-cohort competition: effects on size divergence in YOY fish. Oecologia 2008; 158:249-57. [PMID: 18781331 DOI: 10.1007/s00442-008-1140-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Accepted: 08/08/2008] [Indexed: 11/27/2022]
Abstract
Most organisms exhibit a substantial size variation among individuals due to individual differences in experienced biotic and abiotic environmental conditions and because individuals undergo growth and development during most of their life time. One important issue in this context is how size variation within cohorts may develop over time. Here, we tested the hypothesis, in gape-limited animals such as fish, that size divergence among individuals within a cohort depends on the opportunity to undergo size-dependent diet shifts, by allowing initially larger individuals to make an early diet shift when the first resource becomes limiting. We used young-of-the-year perch (Perca fluviatilis) as our study organism. Competitive intensity and the opportunity to undergo a diet shift from zooplankton to macroinvertebrates affected both mean growth rates and the extent to which inter-individual variation in growth was manifested. As predicted, increased competition combined with the presence of both zooplankton and benthic macroinvertebrates increased the degree of size variation. However, size divergence was also observed among individuals when only the initial resource, zooplankton, was available. We argue that only non-exploitative interactions, such as dominance structures and social interactions, could have caused this latter pattern, as exploitative competition is expected to lead to size convergence due to the superior competitive ability of smaller individuals. Our results suggest that diet shifts are not a prerequisite for size divergence in animal cohorts, and that dominance and social interactions may have similar effects on size variation within cohorts. Finally, development of size variation is suggested to have strong implications for overall cohort performance.
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Affiliation(s)
- Magnus Huss
- Department of Ecology and Environmental Science, Umeå University, 901 87, Umeå, Sweden.
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14
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Einum S, Nislow KH, Mckelvey S, Armstrong JD. Nest distribution shaping within-stream variation in Atlantic salmon juvenile abundance and competition over small spatial scales. J Anim Ecol 2007; 77:167-72. [PMID: 18005129 DOI: 10.1111/j.1365-2656.2007.01326.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
1. Spatial heterogeneity in population density is predicted to have important effects on population characteristics, such as competition intensity and carrying capacity. Patchy breeding distributions will tend to increase spatial heterogeneity in population density, whereas dispersal from breeding patches will tend to decrease it. The potential for dispersal to homogenize densities is likely to differ both among organisms (e.g. plants vs. mobile animals) and throughout ontogeny (e.g. larvae vs. adults). However, for mobile organisms, experimental studies of the importance of breeding distributions from the wild are largely lacking. 2. In the present study, experimental manipulations replicated over eight natural streams and 2 years enabled us to test for effects of the distribution of Atlantic salmon eggs over spatial scales which are relevant to local interactions among individuals. Artificial nests were placed along 250 m study reaches at one of two levels of nest dispersion - patchy (two nests per stream) and dispersed (10 nests per stream) - while holding total egg density (eggs m(-2) stream area) constant. 3. Nest dispersion had significant effects on the spatial distribution of the resulting juveniles in their first summer. Patchy nest distributions resulted in a highly right-skewed frequency distribution of local under-yearling densities (among 25 m sampling sections), as sample sections adjacent to the nest sites had relatively high densities. In contrast, dispersed nest distributions yielded approximately normal density distributions. Sections with high relative densities in the patchy nest distribution treatments also had relatively small juvenile body sizes, and patchy egg distribution appeared to produce a higher redistribution of individuals from the first to the second juvenile growth season than the dispersed distribution. 4. Because patchy breeding distribution combined with limited early dispersal can create spatial variation in density over scales directly relevant for individual interactions, this will be one important component in determining mean levels of early juvenile competition and its spatial variation within populations. Assuming random or ideal-free distribution of individuals may therefore underestimate the mean level of density experienced by juveniles over surprisingly small spatial scales (orders of magnitude smaller than total spatial extent of populations), even for mobile organisms.
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Affiliation(s)
- Sigurd Einum
- Norwegian University of Science and Technology, Department of Biology, NO-7491 Trondheim, Norway.
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15
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Pachepsky E, Bown JL, Eberst A, Bausenwein U, Millard P, Squire GR, Crawford JW. Consequences of intraspecific variation for the structure and function of ecological communities Part 2: Linking diversity and function. Ecol Modell 2007. [DOI: 10.1016/j.ecolmodel.2007.05.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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16
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Peacor SD, Schiesari L, Werner EE. Mechanisms of nonlethal predator effect on cohort size variation: ecological and evolutionary implications. Ecology 2007; 88:1536-47. [PMID: 17601145 DOI: 10.1890/06-1066] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Understanding the factors responsible for generating size variation in cohorts of organisms is important for predicting their population and evolutionary dynamics. We group these factors into two broad classes: those due to scaling relationships between growth and size (size-dependent factors), and those due to individual trait differences other than size (size-independent factors; e.g., morphology, behavior, etc.). We develop a framework predicting that the nonlethal presence of predators can have a strong effect on size variation, the magnitude and sign of which depend on the relative influence of both factors. We present experimental results showing that size-independent factors can strongly contribute to size variation in anuran larvae, and that the presence of a larval dragonfly predator reduced expression of these size-independent factors. Further, a review of a number of experiments shows that the effect of this predator on relative size variation of a cohort ranged from negative at low growth rates to positive at high growth rates. At high growth rates, effects of size-dependent factors predominate, and predator presence causes an increase in the scaling of growth rate with size (larger individuals respond less strongly to predator presence than small individuals). Thus predator presence led to an increase in size variation. In contrast, at low growth rates, size-independent factors were relatively more important, and predator presence reduced expression of these size-independent factors. Consequently, predator presence led to a decrease in size variation. Our results therefore indicate a further mechanism whereby nonlethal predator effects can be manifest on prey species performance. These results have strong implications for both ecological and evolutionary processes. Theoretical studies indicate that changes in cohort size variation can have profound effects on population dynamics and stability, and therefore the mere presence of a predator could have important ecological consequences. Further, changes in cohort size variation can have important evolutionary implications through changes in trait heritability.
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Affiliation(s)
- Scott D Peacor
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan 48824, USA.
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17
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Ovadia O, Dohna HZ, Booth G, Schmitz OJ. Consequences of body size variation among herbivores on the strength of plant–herbivore interactions in a seasonal environment. Ecol Modell 2007. [DOI: 10.1016/j.ecolmodel.2007.03.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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18
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Huss M, Persson L, Byström P. The origin and development of individual size variation in early pelagic stages of fish. Oecologia 2007; 153:57-67. [PMID: 17415592 DOI: 10.1007/s00442-007-0719-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Accepted: 03/06/2007] [Indexed: 10/23/2022]
Abstract
Size variation among individuals born at the same time in a common environment (within cohorts) is a common phenomenon in natural populations. Still, the mechanisms behind the development of such variation and its consequences for population processes are far from clear. We experimentally investigated the development of early within-cohort size variation in larval perch (Perca fluviatilis). Specifically we tested the influence of initial variation, resulting from variation in egg strand size, and intraspecific density for the development of size variation. Variation in egg strand size translated into variation in initial larval size and time of hatching, which, in turn, had effects on growth and development. Perch from the smallest egg strands performed on average equally well independent of density, whereas larvae originating from larger egg strands performed less well under high densities. We related this difference in density dependence to size asymmetries in competitive abilities leading to higher growth rates of groups consisting of initially small individuals under high resource limitation. In contrast, within a single group of larvae, smaller individuals grew substantially slower under high densities whereas large individuals performed equally well independent of density. As a result, size variation among individuals within groups (i.e. originating from the same clutch) increased under high densities. This result may be explained by social interactions or differential timing of diet shifts and a depressed resource base for the initially smaller individuals. It is concluded that to fully appreciate the effects of density-dependent processes on individual size variation and size-dependent growth, consumer feedbacks on resources need to be considered.
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Affiliation(s)
- Magnus Huss
- Department of Ecology and Environmental Science, Umeå University, 901 87 Umeå, Sweden.
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19
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Gurney WSC, Veitch AR. The Dynamics of Size-at-Age Variability. Bull Math Biol 2007; 69:861-85. [PMID: 17237914 DOI: 10.1007/s11538-006-9167-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2005] [Accepted: 09/06/2006] [Indexed: 11/25/2022]
Abstract
In this paper, we propose a theoretical framework within which a unified treatment of the key sources of size-at-age variability-size dependence of growth rate, stochastic growth rate variations and individual-to-individual variability in growth performance-is possible. We use this framework to develop a general criterion for growth depensation in cohorts, which we define as the increase of the coefficient of variation of size-at-age, with increasing age. We use this criterion to show that size dependence of growth rate, acting alone, is depensatory only if the growth rate increases faster than linearly with size (that is, if growth is faster than exponential), while stochastic growth rate variation is invariably depensatory. Many species exhibit growth rates that scale less than linearly with size; indeed the commonly used von Bertalanffy model shows growth rates which actually decrease with size. In such a species, the size dependence of growth rate acts compensatorily, while stochastic growth rate variability is depensatory. We show that the tension between these two mechanisms leads to quasi-stationary size-at-age variability, which we can calculate analytically in some special cases and obtain by a simple numerical procedure where analysis is impractical.
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Affiliation(s)
- William S C Gurney
- Department of Statistics and Modelling Science, University of Strathclyde, Glasgow G1 1XH, Scotland.
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20
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Peacor SD, Pfister CA. Experimental and model analyses of the effects of competition on individual size variation in wood frog (Rana sylvatica) tadpoles. J Anim Ecol 2006; 75:990-9. [PMID: 17009762 DOI: 10.1111/j.1365-2656.2006.01119.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Size variation is a ubiquitous feature of animal populations and is predicted to strongly influence species abundance and dynamics; however, the factors that determine size variation are not well understood. 2. In a mesocosm experiment, we found that the relationship between mean and variation in wood frog (Rana sylvatica) tadpole size is qualitatively different at different levels of competition created by manipulating resource supply rates or tadpole density. At low competition, relative size variation (as measured by the coefficient of variation) decreased as a function of mean size, while at high competition, relative size variation increased. Therefore, increased competition magnified differences in individual performance as measured by growth rate. 3. A model was developed to estimate the contribution of size-dependent factors (i.e. based on size alone) and size-independent factors (i.e. resulting from persistent inherent phenotypic differences other than size that affect growth) on the empirical patterns. 4. Model analysis of the low competition treatment indicated that size-dependent factors alone can describe the relationship between mean size and size variation. To fit the data, the size scaling exponent that describes the dependence of growth rate on size was determined. The estimated value, 0-83, is in the range of that derived from physiological studies. 5. At high competition, the model analysis indicated that individual differences in foraging ability, either size-based or due to inherent phenotypic differences (size-independent factors), were much more pronounced than at low competition. The model was used to quantify the changes in size-dependent or size-independent factors that underlie the effect of competition on size-variation. In contrast to results at low competition, parameters derived from physiological studies could not be used to describe the observed relationships. 6. Our experimental and model results elucidate the role of size-dependent and size-independent factors in the development of size variation, and highlight and quantify the context dependence of individual (intrapopulation) differences in competitive abilities.
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Affiliation(s)
- Scott D Peacor
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA.
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21
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Peacor SD, Bence JR, Pfister CA. The effect of size-dependent growth and environmental factors on animal size variability. Theor Popul Biol 2006; 71:80-94. [PMID: 17056078 DOI: 10.1016/j.tpb.2006.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2006] [Revised: 07/23/2006] [Accepted: 08/17/2006] [Indexed: 10/24/2022]
Abstract
The origin of variation in animal growth rate and body size is not well understood but central to ecological and evolutionary processes. We develop a relationship that predicts the change in relative body size variation within a cohort will be approximately equal to the relative change in mean per unit size growth rate, when only size-dependent factors affect growth. When modeling cohort growth, relative size variation decreased, remained unchanged, or increased, as a function of growth rate-size scaling relationships, in a predictable manner. We use the approximation to predict how environmental factors (e.g., resource level) affect body size variation, and verified these predictions numerically for a flexible growth model using a wide range of parameter values. We also explore and discuss the assumptions underlying the approximation. We find that factors that similarly affect mean growth rate may differently affect size variation, and competition may increase body size variation without changing size-independent relationships. We discuss implications of our results to the choice of growth equations used in models where body size variation is an important variable or output.
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Affiliation(s)
- Scott D Peacor
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA.
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22
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Pfister CA, Wang M. BEYOND SIZE: MATRIX PROJECTION MODELS FOR POPULATIONS WHERE SIZE IS AN INCOMPLETE DESCRIPTOR. Ecology 2005. [DOI: 10.1890/04-1952] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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23
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Crone EE, Polansky L, Lesica P. Empirical Models of Pollen Limitation, Resource Acquisition, and Mast Seeding by a Bee‐Pollinated Wildflower. Am Nat 2005; 166:396-408. [PMID: 16224693 DOI: 10.1086/432561] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Accepted: 04/07/2005] [Indexed: 11/03/2022]
Abstract
Synchronous mast seeding is increasingly recognized as common in plant populations. Recent theoretical models show that synchronous mast seeding could be a consequence of resource allocation and storage within individual plants, coupled by pollen limitation in low-flowering years. We used long-term population and weather data to parameterize models of flowering based on stored resources and pollen limitation in Astragalus scaphoides, a bee-pollinated plant that flowers in alternate years. We used these models to test whether internal resource dynamics could explain mast seeding in A. scaphoides and, if so, whether synchrony was caused by pollen limitation and/or fluctuations in precipitation. We compared predictions of models that included all combinations of three factors: constant versus precipitation-dependent resource gain, uniform versus heterogeneous resource gain (among individual plants), and resource-dependent versus resource- and pollen-limited fruit set. Pollen limitation and heterogeneous resource gain were necessary and sufficient to explain alternate-year flowering, but precipitation increased the quantitative match between model predictions and flowering dynamics. Together, our results support the importance of density-dependent pollen limitation as an ultimate and proximate cause of mast seeding in A. scaphoides. Precipitation does not act as a direct cue for synchrony in this species but might affect long-term resource gain and fruiting dynamics.
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Affiliation(s)
- Elizabeth E Crone
- Wildlife Biology Program and Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, Montana 59802,USA.
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Fujiwara M, Kendall BE, Nisbet RM, Bennett WA. ANALYSIS OF SIZE TRAJECTORY DATA USING AN ENERGETIC-BASED GROWTH MODEL. Ecology 2005. [DOI: 10.1890/04-1351] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Wearing HJ, Rohani P, Cameron TC, Sait SM. The dynamical consequences of developmental variability and demographic stochasticity for host-parasitoid interactions. Am Nat 2004; 164:543-58. [PMID: 15459884 DOI: 10.1086/424040] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 06/08/2004] [Indexed: 11/03/2022]
Abstract
Few age-structured models of species dynamics incorporate variability and uncertainty in population processes. Motivated by laboratory data for an insect and its parasitoid, we investigate whether such assumptions are appropriate when considering the population dynamics of a single species and its interaction with a natural enemy. Specifically, we examine the effects of developmental variability and demographic stochasticity on different types of cyclic dynamics predicted by traditional models. We show that predictions based on the deterministic fixed-development approach are differentially sensitive to variability and noise in key life stages. In particular, we find that the demonstration of half-generation cycles in the single-species model and the multigeneration cycles in the host-parasitoid model are sensitive to the introduction of developmental variability and noise, whereas generation cycles are robust to the intrinsic variability and uncertainty that may be found in nature.
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Affiliation(s)
- Helen J Wearing
- Institute of Ecology, University of Georgia, Athens, Georgia 30602. USA.
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