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Rüger N, Condit R. Testing metabolic theory with models of tree growth that include light competition. Funct Ecol 2012. [DOI: 10.1111/j.1365-2435.2012.01981.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Rüger N, Berger U, Hubbell SP, Vieilledent G, Condit R. Growth strategies of tropical tree species: disentangling light and size effects. PLoS One 2011; 6:e25330. [PMID: 21966498 PMCID: PMC3178650 DOI: 10.1371/journal.pone.0025330] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 09/01/2011] [Indexed: 11/26/2022] Open
Abstract
An understanding of the drivers of tree growth at the species level is required to predict likely changes of carbon stocks and biodiversity when environmental conditions change. Especially in species-rich tropical forests, it is largely unknown how species differ in their response of growth to resource availability and individual size. We use a hierarchical Bayesian approach to quantify the impact of light availability and tree diameter on growth of 274 woody species in a 50-ha long-term forest census plot in Barro Colorado Island, Panama. Light reaching each individual tree was estimated from yearly vertical censuses of canopy density. The hierarchical Bayesian approach allowed accounting for different sources of error, such as negative growth observations, and including rare species correctly weighted by their abundance. All species grew faster at higher light. Exponents of a power function relating growth to light were mostly between 0 and 1. This indicates that nearly all species exhibit a decelerating increase of growth with light. In contrast, estimated growth rates at standardized conditions (5 cm dbh, 5% light) varied over a 9-fold range and reflect strong growth-strategy differentiation between the species. As a consequence, growth rankings of the species at low (2%) and high light (20%) were highly correlated. Rare species tended to grow faster and showed a greater sensitivity to light than abundant species. Overall, tree size was less important for growth than light and about half the species were predicted to grow faster in diameter when bigger or smaller, respectively. Together light availability and tree diameter only explained on average 12% of the variation in growth rates. Thus, other factors such as soil characteristics, herbivory, or pathogens may contribute considerably to shaping tree growth in the tropics.
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Rüger N, Huth A, Hubbell SP, Condit R. Determinants of mortality across a tropical lowland rainforest community. OIKOS 2011. [DOI: 10.1111/j.1600-0706.2010.19021.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Wright SJ, Kitajima K, Kraft NJB, Reich PB, Wright IJ, Bunker DE, Condit R, Dalling JW, Davies SJ, Díaz S, Engelbrecht BMJ, Harms KE, Hubbell SP, Marks CO, Ruiz-Jaen MC, Salvador CM, Zanne AE. Functional traits and the growth–mortality trade‐off in tropical trees. Ecology 2010; 91:3664-74. [DOI: 10.1890/09-2335.1] [Citation(s) in RCA: 650] [Impact Index Per Article: 46.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Wolf A, Davies S, Condit R. Ecological Insights from Long-term Research Plots in Tropical and Temperate Forests. ACTA ACUST UNITED AC 2009. [DOI: 10.1890/0012-9623-90.4.519] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Poorter L, Wright SJ, Paz H, Ackerly DD, Condit R, Ibarra-Manríquez G, Harms KE, Licona JC, Martínez-Ramos M, Mazer SJ, Muller-Landau HC, Peña-Claros M, Webb CO, Wright IJ. Are functional traits good predictors of demographic rates? Evidence from five neotropical forests. Ecology 2008; 89:1908-20. [PMID: 18705377 DOI: 10.1890/07-0207.1] [Citation(s) in RCA: 302] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A central goal of comparative plant ecology is to understand how functional traits vary among species and to what extent this variation has adaptive value. Here we evaluate relationships between four functional traits (seed volume, specific leaf area, wood density, and adult stature) and two demographic attributes (diameter growth and tree mortality) for large trees of 240 tree species from five Neotropical forests. We evaluate how these key functional traits are related to survival and growth and whether similar relationships between traits and demography hold across different tropical forests. There was a tendency for a trade-off between growth and survival across rain forest tree species. Wood density, seed volume, and adult stature were significant predictors of growth and/or mortality. Both growth and mortality rates declined with an increase in wood density. This is consistent with greater construction costs and greater resistance to stem damage for denser wood. Growth and mortality rates also declined as seed volume increased. This is consistent with an adaptive syndrome in which species tolerant of low resource availability (in this case shade-tolerant species) have large seeds to establish successfully and low inherent growth and mortality rates. Growth increased and mortality decreased with an increase in adult stature, because taller species have a greater access to light and longer life spans. Specific leaf area was, surprisingly, only modestly informative for the performance of large trees and had ambiguous relationships with growth and survival. Single traits accounted for 9-55% of the interspecific variation in growth and mortality rates at individual sites. Significant correlations with demographic rates tended to be similar across forests and for phylogenetically independent contrasts as well as for cross-species analyses that treated each species as an independent observation. In combination, the morphological traits explained 41% of the variation in growth rate and 54% of the variation in mortality rate, with wood density being the best predictor of growth and mortality. Relationships between functional traits and demographic rates were statistically similar across a wide range of Neotropical forests. The consistency of these results strongly suggests that tropical rain forest species face similar trade-offs in different sites and converge on similar sets of solutions.
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Morlon H, Chuyong G, Condit R, Hubbell S, Kenfack D, Thomas D, Valencia R, Green JL. A general framework for the distance-decay of similarity in ecological communities. Ecol Lett 2008; 11:904-17. [PMID: 18494792 PMCID: PMC2613237 DOI: 10.1111/j.1461-0248.2008.01202.x] [Citation(s) in RCA: 267] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 01/23/2008] [Accepted: 04/04/2008] [Indexed: 11/30/2022]
Abstract
Species spatial turnover, or beta-diversity, induces a decay of community similarity with geographic distance known as the distance-decay relationship. Although this relationship is central to biodiversity and biogeography, its theoretical underpinnings remain poorly understood. Here, we develop a general framework to describe how the distance-decay relationship is influenced by population aggregation and the landscape-scale species-abundance distribution. We utilize this general framework and data from three tropical forests to show that rare species have a weak influence on distance-decay curves, and that overall similarity and rates of decay are primarily influenced by species abundances and population aggregation respectively. We illustrate the utility of the framework by deriving an exact analytical expression of the distance-decay relationship when population aggregation is characterized by the Poisson Cluster Process. Our study provides a foundation for understanding the distance-decay relationship, and for predicting and testing patterns of beta-diversity under competing theories in ecology.
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Hubbell SP, He F, Condit R, Borda-de-Agua L, Kellner J, Ter Steege H. Colloquium paper: how many tree species are there in the Amazon and how many of them will go extinct? Proc Natl Acad Sci U S A 2008; 105 Suppl 1:11498-504. [PMID: 18695228 PMCID: PMC2556410 DOI: 10.1073/pnas.0801915105] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
New roads, agricultural projects, logging, and mining are claiming an ever greater area of once-pristine Amazonian forest. The Millennium Ecosystems Assessment (MA) forecasts the extinction of a large fraction of Amazonian tree species based on projected loss of forest cover over the next several decades. How accurate are these estimates of extinction rates? We use neutral theory to estimate the number, relative abundance, and range size of tree species in the Amazon metacommunity and estimate likely tree-species extinctions under published optimistic and nonoptimistic Amazon scenarios. We estimate that the Brazilian portion of the Amazon Basin has (or had) 11,210 tree species that reach sizes >10 cm DBH (stem diameter at breast height). Of these, 3,248 species have population sizes >1 million individuals, and, ignoring possible climate-change effects, almost all of these common species persist under both optimistic and nonoptimistic scenarios. At the rare end of the abundance spectrum, however, neutral theory predicts the existence of approximately 5,308 species with <10,000 individuals each that are expected to suffer nearly a 50% extinction rate under the nonoptimistic deforestation scenario and an approximately 37% loss rate even under the optimistic scenario. Most of these species have small range sizes and are highly vulnerable to local habitat loss. In ensembles of 100 stochastic simulations, we found mean total extinction rates of 20% and 33% of tree species in the Brazilian Amazon under the optimistic and nonoptimistic scenarios, respectively.
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LaFrankie JV, Ashton PS, Chuyong GB, Co L, Condit R, Davies SJ, Foster R, Hubbell SP, Kenfack D, Lagunzad D, Losos EC, Nor NSM, Tan S, Thomas DW, Valencia R, Villa G. Contrasting structure and composition of the understory in species-rich tropical rain forests. Ecology 2008; 87:2298-305. [PMID: 16995630 DOI: 10.1890/0012-9658(2006)87[2298:csacot]2.0.co;2] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In large samples of trees > or = 1 cm dbh (more than 1 million trees and 3000 species), in six lowland tropical forests on three continents, we assigned species with >30 individuals to one of six classes of stature at maturity (SAM). We then compared the proportional representation of understory trees (1-2 cm dbh) among these classes. The understory of the three Asian sites was predominantly composed of the saplings of large-canopy trees whereas the African and American sites were more richly stocked with trees of the smaller SAM classes. Differences in class representation were related to taxonomic families that were present exclusively in one continent or another. Families found in the Asian plots but not in the American plot (e.g., Dipterocarpaceae, Fagaceae) were predominantly species of the largest SAM classes, whereas families exclusive to the American plots (e.g., Melastomataceae sensu stricto, Piperaceae, and Malvaceae [Bombacacoidea]) were predominantly species of small classes. The African plot was similar to Asia in the absence of those American families rich in understory species, while similar to America in lacking the Asian families rich in canopy species. The numerous understory species of Africa were chiefly derived from families shared with Asia and/or America. The ratio of saplings (1-2 cm dbh) to conspecific canopy trees (>40 cm dbh) was lower in American plots than in the Asian plots. Possible explanations for these differences include phenology, moisture and soil fertility regimes, phyletic constraints, and the role of early successional plants in forest development. These results demonstrate that tropical forests that appear similar in tree number, basal area, and the family taxonomy of canopy trees nonetheless differ in ecological structure in ways that may impact the ecology of pollinators, dispersers, and herbivores and might reflect fundamental differences in canopy tree regeneration.
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Chave J, Condit R, Muller-Landau HC, Thomas SC, Ashton PS, Bunyavejchewin S, Co LL, Dattaraja HS, Davies SJ, Esufali S, Ewango CEN, Feeley KJ, Foster RB, Gunatilleke N, Gunatilleke S, Hall P, Hart TB, Hernández C, Hubbell SP, Itoh A, Kiratiprayoon S, Lafrankie JV, Loo de Lao S, Makana JR, Noor MNS, Kassim AR, Samper C, Sukumar R, Suresh HS, Tan S, Thompson J, Tongco MDC, Valencia R, Vallejo M, Villa G, Yamakura T, Zimmerman JK, Losos EC. Assessing evidence for a pervasive alteration in tropical tree communities. PLoS Biol 2008; 6:e45. [PMID: 18318600 PMCID: PMC2270308 DOI: 10.1371/journal.pbio.0060045] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Accepted: 01/14/2008] [Indexed: 11/18/2022] Open
Abstract
In Amazonian tropical forests, recent studies have reported increases in aboveground biomass and in primary productivity, as well as shifts in plant species composition favouring fast-growing species over slow-growing ones. This pervasive alteration of mature tropical forests was attributed to global environmental change, such as an increase in atmospheric CO2 concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of over 2 million trees in ten large (16-52 ha each) forest plots on three continents to evaluate the generality of these findings across tropical forests. Aboveground biomass increased at seven of our ten plots, significantly so at four plots, and showed a large decrease at a single plot. Carbon accumulation pooled across sites was significant (+0.24 MgC ha(-1) y(-1), 95% confidence intervals [0.07, 0.39] MgC ha(-1) y(-1)), but lower than reported previously for Amazonia. At three sites for which we had data for multiple census intervals, we found no concerted increase in biomass gain, in conflict with the increased productivity hypothesis. Over all ten plots, the fastest-growing quartile of species gained biomass (+0.33 [0.09, 0.55] % y(-1)) compared with the tree community as a whole (+0.15 % y(-1)); however, this significant trend was due to a single plot. Biomass of slow-growing species increased significantly when calculated over all plots (+0.21 [0.02, 0.37] % y(-1)), and in half of our plots when calculated individually. Our results do not support the hypothesis that fast-growing species are consistently increasing in dominance in tropical tree communities. Instead, they suggest that our plots may be simultaneously recovering from past disturbances and affected by changes in resource availability. More long-term studies are necessary to clarify the contribution of global change to the functioning of tropical forests.
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Zillio T, Condit R. The impact of neutrality, niche differentiation and species input on diversity and abundance distributions. OIKOS 2007. [DOI: 10.1111/j.0030-1299.2007.15662.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Engelbrecht BMJ, Comita LS, Condit R, Kursar TA, Tyree MT, Turner BL, Hubbell SP. Drought sensitivity shapes species distribution patterns in tropical forests. Nature 2007; 447:80-2. [PMID: 17476266 DOI: 10.1038/nature05747] [Citation(s) in RCA: 749] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Accepted: 03/14/2007] [Indexed: 11/08/2022]
Abstract
Although patterns of tree species distributions along environmental gradients have been amply documented in tropical forests, mechanisms causing these patterns are seldom known. Efforts to evaluate proposed mechanisms have been hampered by a lack of comparative data on species' reactions to relevant axes of environmental variation. Here we show that differential drought sensitivity shapes plant distributions in tropical forests at both regional and local scales. Our analyses are based on experimental field assessments of drought sensitivity of 48 species of trees and shrubs, and on their local and regional distributions within a network of 122 inventory sites spanning a rainfall gradient across the Isthmus of Panama. Our results suggest that niche differentiation with respect to soil water availability is a direct determinant of both local- and regional-scale distributions of tropical trees. Changes in soil moisture availability caused by global climate change and forest fragmentation are therefore likely to alter tropical species distributions, community composition and diversity.
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Wright SJ, Hernandéz A, Condit R. The Bushmeat Harvest Alters Seedling Banks by Favoring Lianas, Large Seeds, and Seeds Dispersed by Bats, Birds, and Wind. Biotropica 2007. [DOI: 10.1111/j.1744-7429.2007.00289.x] [Citation(s) in RCA: 161] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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66
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Laurance WF, Nascimento HEM, Laurance SG, Andrade A, Ribeiro JELS, Giraldo JP, Lovejoy TE, Condit R, Chave J, Harms KE, D'Angelo S. Rapid decay of tree-community composition in Amazonian forest fragments. Proc Natl Acad Sci U S A 2006; 103:19010-4. [PMID: 17148598 PMCID: PMC1682011 DOI: 10.1073/pnas.0609048103] [Citation(s) in RCA: 313] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Indexed: 11/18/2022] Open
Abstract
Forest fragmentation is considered a greater threat to vertebrates than to tree communities because individual trees are typically long-lived and require only small areas for survival. Here we show that forest fragmentation provokes surprisingly rapid and profound alterations in Amazonian tree-community composition. Results were derived from a 22-year study of exceptionally diverse tree communities in 40 1-ha plots in fragmented and intact forests, which were sampled repeatedly before and after fragment isolation. Within these plots, trajectories of change in abundance were assessed for 267 genera and 1,162 tree species. Abrupt shifts in floristic composition were driven by sharply accelerated tree mortality and recruitment within approximately 100 m of fragment margins, causing rapid species turnover and population declines or local extinctions of many large-seeded, slow-growing, and old-growth taxa; a striking increase in a smaller set of disturbance-adapted and abiotically dispersed species; and significant shifts in tree size distributions. Even among old-growth trees, species composition in fragments is being restructured substantially, with subcanopy species that rely on animal seed-dispersers and have obligate outbreeding being the most strongly disadvantaged. These diverse changes in tree communities are likely to have wide-ranging impacts on forest architecture, canopy-gap dynamics, plant-animal interactions, and forest carbon storage.
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Condit R, Ashton P, Bunyavejchewin S, Dattaraja HS, Davies S, Esufali S, Ewango C, Foster R, Gunatilleke IAUN, Gunatilleke CVS, Hall P, Harms KE, Hart T, Hernandez C, Hubbell S, Itoh A, Kiratiprayoon S, Lafrankie J, de Lao SL, Makana JR, Noor MNS, Kassim AR, Russo S, Sukumar R, Samper C, Suresh HS, Tan S, Thomas S, Valencia R, Vallejo M, Villa G, Zillio T. The Importance of Demographic Niches to Tree Diversity. Science 2006; 313:98-101. [PMID: 16763113 DOI: 10.1126/science.1124712] [Citation(s) in RCA: 194] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Most ecological hypotheses about species coexistence hinge on species differences, but quantifying trait differences across species in diverse communities is often unfeasible. We examined the variation of demographic traits using a global tropical forest data set covering 4500 species in 10 large-scale tree inventories. With a hierarchical Bayesian approach, we quantified the distribution of mortality and growth rates of all tree species at each site. This allowed us to test the prediction that demographic differences facilitate species richness, as suggested by the theory that a tradeoff between high growth and high survival allows species to coexist. Contrary to the prediction, the most diverse forests had the least demographic variation. Although demographic differences may foster coexistence, they do not explain any of the 16-fold variation in tree species richness observed across the tropics.
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Hooper E, Condit R, Legendre P. 2000 Alwyn Gentry Award. Biotropica 2006. [DOI: 10.1111/j.1744-7429.2000.tb00528.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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69
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Wills C, Harms KE, Condit R, King D, Thompson J, He F, Muller-Landau HC, Ashton P, Losos E, Comita L, Hubbell S, Lafrankie J, Bunyavejchewin S, Dattaraja HS, Davies S, Esufali S, Foster R, Gunatilleke N, Gunatilleke S, Hall P, Itoh A, John R, Kiratiprayoon S, de Lao SL, Massa M, Nath C, Noor MNS, Kassim AR, Sukumar R, Suresh HS, Sun IF, Tan S, Yamakura T, Zimmerman J. Nonrandom Processes Maintain Diversity in Tropical Forests. Science 2006; 311:527-31. [PMID: 16439661 DOI: 10.1126/science.1117715] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
An ecological community's species diversity tends to erode through time as a result of stochastic extinction, competitive exclusion, and unstable host-enemy dynamics. This erosion of diversity can be prevented over the short term if recruits are highly diverse as a result of preferential recruitment of rare species or, alternatively, if rare species survive preferentially, which increases diversity as the ages of the individuals increase. Here, we present census data from seven New and Old World tropical forest dynamics plots that all show the latter pattern. Within local areas, the trees that survived were as a group more diverse than those that were recruited or those that died. The larger (and therefore on average older) survivors were more diverse within local areas than the smaller survivors. When species were rare in a local area, they had a higher survival rate than when they were common, resulting in enrichment for rare species and increasing diversity with age and size class in these complex ecosystems.
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Laurance WF, Oliveira AA, Laurance SG, Condit R, Dick CW, Andrade A, Nascimento HEM, Lovejoy TE, Ribeiro JELS. Altered Tree Communities in Undisturbed Amazonian Forests: A Consequence of Global Change?1. Biotropica 2005. [DOI: 10.1111/j.1744-7429.2005.00022.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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71
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Hooper ER, Legendre P, Condit R. FACTORS AFFECTING COMMUNITY COMPOSITION OF FOREST REGENERATION IN DEFORESTED, ABANDONED LAND IN PANAMA. Ecology 2004. [DOI: 10.1890/03-0655] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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72
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Chave J, Condit R, Aguilar S, Hernandez A, Lao S, Perez R. Error propagation and scaling for tropical forest biomass estimates. Philos Trans R Soc Lond B Biol Sci 2004; 359:409-20. [PMID: 15212093 PMCID: PMC1693335 DOI: 10.1098/rstb.2003.1425] [Citation(s) in RCA: 195] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The above-ground biomass (AGB) of tropical forests is a crucial variable for ecologists, biogeochemists, foresters and policymakers. Tree inventories are an efficient way of assessing forest carbon stocks and emissions to the atmosphere during deforestation. To make correct inferences about long-term changes in biomass stocks, it is essential to know the uncertainty associated with AGB estimates, yet this uncertainty is rarely evaluated carefully. Here, we quantify four types of uncertainty that could lead to statistical error in AGB estimates: (i) error due to tree measurement; (ii) error due to the choice of an allometric model relating AGB to other tree dimensions; (iii) sampling uncertainty, related to the size of the study plot; (iv) representativeness of a network of small plots across a vast forest landscape. In previous studies, these sources of error were reported but rarely integrated into a consistent framework. We estimate all four terms in a 50 hectare (ha, where 1 ha = 10(4) m2) plot on Barro Colorado Island, Panama, and in a network of 1 ha plots scattered across central Panama. We find that the most important source of error is currently related to the choice of the allometric model. More work should be devoted to improving the predictive power of allometric models for biomass.
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Laurance WF, Oliveira AA, Laurance SG, Condit R, Nascimento HEM, Sanchez-Thorin AC, Lovejoy TE, Andrade A, D'Angelo S, Ribeiro JE, Dick CW. Pervasive alteration of tree communities in undisturbed Amazonian forests. Nature 2004; 428:171-5. [PMID: 15014498 DOI: 10.1038/nature02383] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2003] [Accepted: 02/02/2004] [Indexed: 11/08/2022]
Abstract
Amazonian rainforests are some of the most species-rich tree communities on earth. Here we show that, over the past two decades, forests in a central Amazonian landscape have experienced highly nonrandom changes in dynamics and composition. Our analyses are based on a network of 18 permanent plots unaffected by any detectable disturbance. Within these plots, rates of tree mortality, recruitment and growth have increased over time. Of 115 relatively abundant tree genera, 27 changed significantly in population density or basal area--a value nearly 14 times greater than that expected by chance. An independent, eight-year study in nearby forests corroborates these shifts in composition. Contrary to recent predictions, we observed no increase in pioneer trees. However, genera of faster-growing trees, including many canopy and emergent species, are increasing in dominance or density, whereas genera of slower-growing trees, including many subcanopy species, are declining. Rising atmospheric CO2 concentrations may explain these changes, although the effects of this and other large-scale environmental alterations remain uncertain. These compositional changes could have important impacts on the carbon storage, dynamics and biota of Amazonian forests.
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Wright SJ, Muller-Landau HC, Condit R, Hubbell SP. GAP-DEPENDENT RECRUITMENT, REALIZED VITAL RATES, AND SIZE DISTRIBUTIONS OF TROPICAL TREES. Ecology 2003. [DOI: 10.1890/02-0038] [Citation(s) in RCA: 268] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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75
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Ibáñez R, Condit R, Angehr G, Aguilar S, García T, Martínez R, Sanjur A, Stallard R, Wright SJ, Rand AS, Heckadon S. An ecosystem report on the Panama Canal: monitoring the status of the forest communities and the watershed. ENVIRONMENTAL MONITORING AND ASSESSMENT 2002; 80:65-95. [PMID: 12437064 DOI: 10.1023/a:1020378926399] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In 1996, the Smithsonian Tropical Research Institute and the Republic of Panama's Environmental Authority, with support from the United States Agency for International Development, undertook a comprehensive program to monitor the ecosystem of the Panama Canal watershed. The goals were to establish baseline indicators for the integrity of forest communities and rivers. Based on satellite image classification and ground surveys, the 2790 km2 watershed had 1570 km2 of forest in 1997, 1080 km2 of which was in national parks and nature monuments. Most of the 490 km2 of forest not currently in protected areas lies along the west bank of the Canal, and its management status after the year 2000 turnover of the Canal from the U.S. to Panama remains uncertain. In forest plots designed to monitor forest diversity and change, a total of 963 woody plant species were identified and mapped. We estimate there are a total of 850-1000 woody species in forests of the Canal corridor. Forests of the wetter upper reaches of the watershed are distinct in species composition from the Canal corridor, and have considerably higher diversity and many unknown species. These remote areas are extensively forested, poorly explored, and harbor an estimated 1400-2200 woody species. Vertebrate monitoring programs were also initiated, focusing on species threatened by hunting and forest fragmentation. Large mammals are heavily hunted in most forests of Canal corridor, and there was clear evidence that mammal density is greatly reduced in hunted areas and that this affects seed predation and dispersal. The human population of the watershed was 113 000 in 1990, and grew by nearly 4% per year from 1980 to 1990. Much of this growth was in a small region of the watershed on the outskirts of Panama City, but even rural areas, including villages near and within national parks, grew by 2% per year. There is no sewage treatment in the watershed, and many towns have no trash collection, thus streams near large towns are heavily polluted. Analyses of sediment loads in rivers throughout the watershed did not indicate that erosion has been increasing as a result of deforestation, rather, erosion seems to be driven largely by total rainfall and heavy rainfall events that cause landslides. Still, models suggest that large-scale deforestation would increase landslide frequency, and failure to detect increases in erosion could be due to the gradual deforestation rate and the short time period over which data are available. A study of runoff showed deforestation increased the amount of water from rainfall that passed directly into streams. As a result, dry season flow was reduced in a deforested catchment relative to a forested one. Currently, the Panama Canal watershed has extensive forest areas and streams relatively unaffected by humans. But impacts of hunting and pollution near towns are clear, and the burgeoning population will exacerbate these impacts in the next few decades. Changes in policies regarding forest protection and pollution control are necessary.
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Hubbell SP, Ahumada JA, Condit R, Foster RB. Local neighborhood effects on long-term survival of individual trees in a neotropical forest. Ecol Res 2002. [DOI: 10.1046/j.1440-1703.2001.00445.x] [Citation(s) in RCA: 237] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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77
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Condit R, Pitman N, Leigh EG, Chave J, Terborgh J, Foster RB, Núñez P, Aguilar S, Valencia R, Villa G, Muller-Landau HC, Losos E, Hubbell SP. Beta-diversity in tropical forest trees. Science 2002; 295:666-9. [PMID: 11809969 DOI: 10.1126/science.1066854] [Citation(s) in RCA: 580] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The high alpha-diversity of tropical forests has been amply documented, but beta-diversity-how species composition changes with distance-has seldom been studied. We present quantitative estimates of beta-diversity for tropical trees by comparing species composition of plots in lowland terra firme forest in Panama, Ecuador, and Peru. We compare observations with predictions derived from a neutral model in which habitat is uniform and only dispersal and speciation influence species turnover. We find that beta-diversity is higher in Panama than in western Amazonia and that patterns in both areas are inconsistent with the neutral model. In Panama, habitat variation appears to increase species turnover relative to Amazonia, where unexpectedly low turnover over great distances suggests that population densities of some species are bounded by as yet unidentified processes. At intermediate scales in both regions, observations can be matched by theory, suggesting that dispersal limitation, with speciation, influences species turnover.
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Abstract
By integrating a wide range of experimental, comparative, and theoretical approaches, ecologists are starting to gain a detailed understanding of the long-term dynamics of vegetation. We explore how patterns of variation in demographic traits among species have provided insight into the processes that structure plant communities. We find a common set of mechanisms, derived from ecological and evolutionary principles, that underlie the main forces shaping systems as diverse as annual plant communities and tropical forests. Trait variation between species maintains diversity and has important implications for ecosystem processes. Hence, greater understanding of how Earth's vegetation functions will likely require integration of ecosystem science with ideas from plant evolutionary, population, and community ecology.
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79
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Plotkin JB, Potts MD, Yu DW, Bunyavejchewin S, Condit R, Foster R, Hubbell S, LaFrankie J, Manokaran N, Seng LH, Sukumar R, Nowak MA, Ashton PS. Predicting species diversity in tropical forests. Proc Natl Acad Sci U S A 2000; 97:10850-4. [PMID: 11005859 PMCID: PMC27112 DOI: 10.1073/pnas.97.20.10850] [Citation(s) in RCA: 162] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2000] [Accepted: 07/26/2000] [Indexed: 11/18/2022] Open
Abstract
A fundamental question in ecology is how many species occur within a given area. Despite the complexity and diversity of different ecosystems, there exists a surprisingly simple, approximate answer: the number of species is proportional to the size of the area raised to some exponent. The exponent often turns out to be roughly 1/4. This power law can be derived from assumptions about the relative abundances of species or from notions of self-similarity. Here we analyze the largest existing data set of location-mapped species: over one million, individually identified trees from five tropical forests on three continents. Although the power law is a reasonable, zeroth-order approximation of our data, we find consistent deviations from it on all spatial scales. Furthermore, tropical forests are not self-similar at areas =50 hectares. We develop an extended model of the species-area relationship, which enables us to predict large-scale species diversity from small-scale data samples more accurately than any other available method.
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80
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Condit R, Ashton PS, Baker P, Bunyavejchewin S, Gunatilleke S, Gunatilleke N, Hubbell SP, Foster RB, Itoh A, LaFrankie JV, Lee HS, Losos E, Manokaran N, Sukumar R, Yamakura T. Spatial patterns in the distribution of tropical tree species. Science 2000; 288:1414-8. [PMID: 10827950 DOI: 10.1126/science.288.5470.1414] [Citation(s) in RCA: 387] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Fully mapped tree census plots of large area, 25 to 52 hectares, have now been completed at six different sites in tropical forests, including dry deciduous to wet evergreen forest on two continents. One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populations. Here the degree of aggregation in the distribution of 1768 tree species is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centimeter in stem diameter were included, nearly every species was more aggregated than a random distribution. Considering only larger trees (>/= 10 centimeters in diameter), the pattern persisted, with most species being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particulars of these results.
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81
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Hooper E, Condit R, Legendre P. 2000 Alwyn Gentry Award. Biotropica 2000. [DOI: 10.1646/0006-3606(2000)032[0769:aga]2.0.co;2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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82
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Condit R, Ashton PS, Manokaran N, LaFrankie JV, Hubbell SP, Foster RB. Dynamics of the forest communities at Pasoh and Barro Colorado: comparing two 50-ha plots. Philos Trans R Soc Lond B Biol Sci 1999; 354:1739-48. [PMID: 11605618 PMCID: PMC1692684 DOI: 10.1098/rstb.1999.0517] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dynamics of the Pasoh forest in Peninsular Malaysia were assessed by drawing a comparison with a forest in Panama, Central America, whose dynamics have been thoroughly described. Census plots of 50 ha were established at both sites using standard methods. Tree mortality at Pasoh over an eight-year interval was 1.46% yr(-1) for all stems > or = 10 mm diameter at breast height (dbh), and 1.48% yr(-1) for stems > or = 100 mm dbh. Comparable figures at the Barro Colorado Island site in Panama (BCI) were 2.55% and 2.03%. Growth and recruitment rates were likewise considerably higher at BCI than at Pasoh. For example, in all trees 500-700 mm in dbh, mean BCI growth over the period 1985-1995 was 6 mm yr(-1), whereas mean Pasoh growth was about 3.5 mm yr(-1). Examining growth and mortality rates for individual species showed that the difference between the forests can be attributed to a few light-demanding pioneer species at BCI, which have very high growth and mortality; Pasoh is essentially lacking this guild. The bulk of the species in the two forests are shade-tolerant and have very similar mortality, growth and recruitment. The Pasoh forest is more stable than BCI's in another way as well: few of its tree populations changed much over the eight-year census interval. In contrast, at BCI, over 10% of the species had populations increasing or decreasing at a rate of >0.05 yr(-1) compared to just 2% of the species at Pasoh). The faster species turnover at BCI can probably be attributed to severe droughts that have plagued the forest periodically over the past 30 years; Pasoh has not suffered such extreme events recently. The dearth of pioneer species at Pasoh is associated with low-nutrient soil and slow litter breakdown, but the exact mechanisms behind this association remain poorly understood.
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83
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Wills C, Condit R. Similar non-random processes maintain diversity in two tropical rainforests. Proc Biol Sci 1999; 266:1445-52. [PMID: 10457617 PMCID: PMC1690088 DOI: 10.1098/rspb.1999.0799] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Quadrat-based analysis of two rainforest plots of area 50 ha, one in Panama (Barro Colorado Island, BCI) and the other in Malaysia (Pasoh), shows that in both plots recruitment is in general negatively correlated with both numbers and biomass of adult trees of the same species in the same quadrat. At BCI, this effect is not significantly influenced by treefall gaps. In both plots, recruitment of individual species is negatively correlated with the numbers of trees of all species in the quadrats, but not with overall biomass. These observations suggest, but do not prove, widespread frequency-dependent effects produced by pathogens and seed-predators that act most effectively in quadrats crowded with trees. Within-species correlations of mortality with numbers or biomass are not found in either plot, indicating that most frequency-dependent mortality takes place before the trees reach 1 cm in diameter. Stochastic effects caused by BCI's more rapid tree turnover may contribute to a larger variance in diversity from quadrat to quadrat at BCI, although they are not sufficient to explain why BCI has fewer than half as many tree species as Pasoh. Finally, in both plots quadrats with low diversity show a significant increase in diversity over time, and this increase is stronger at BCI. This process, like the frequency-dependence, will tend to maintain diversity over time. In general, these non-random forces that should lead to the maintenance of diversity are slightly stronger at BCI, even though the BCI plot is less diverse than the Pasoh plot.
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84
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Hubbell SP, Foster RB, O'Brien ST, Harms KE, Condit R, Wechsler B, Wright SJ. Light-Gap disturbances, recruitment limitation, and tree diversity in a neotropical forest. Science 1999; 283:554-7. [PMID: 9915706 DOI: 10.1126/science.283.5401.554] [Citation(s) in RCA: 577] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Light gap disturbances have been postulated to play a major role in maintaining tree diversity in species-rich tropical forests. This hypothesis was tested in more than 1200 gaps in a tropical forest in Panama over a 13-year period. Gaps increased seedling establishment and sapling densities, but this effect was nonspecific and broad-spectrum, and species richness per stem was identical in gaps and in nongap control sites. Spatial and temporal variation in the gap disturbance regime did not explain variation in species richness. The species composition of gaps was unpredictable even for pioneer tree species. Strong recruitment limitation appears to decouple the gap disturbance regime from control of tree diversity in this tropical forest.
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85
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Condit R, Sukumar R, Hubbell SP, Foster RB. Predicting Population Trends from Size Distributions: A Direct Test in a Tropical Tree Community. Am Nat 1998; 152:495-509. [PMID: 18811360 DOI: 10.1086/286186] [Citation(s) in RCA: 260] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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86
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Wills C, Condit R, Foster RB, Hubbell SP. Strong density- and diversity-related effects help to maintain tree species diversity in a neotropical forest. Proc Natl Acad Sci U S A 1997; 94:1252-7. [PMID: 11038601 PMCID: PMC19777 DOI: 10.1073/pnas.94.4.1252] [Citation(s) in RCA: 225] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Intraspecific density-dependent effects in the Barro Colorado Island (Panama) study area are far stronger, and involve far more species, than previously had been suspected. Significant effects on recruitment, many extremely strong, are seen for 67 out of the 84 most common species in the plot, including the 10 most common. Significant effects on the intrinsic rate of increase are seen in 54 of the 84 species. These effects are far more common than interspecific effects, and are predominantly of the type that should maintain tree diversity. As a result, the more diverse an area in the forest is, the higher is the overall rate of increase of the trees in that area, although sheer crowding has by itself a negative effect. These findings are consistent with, but do not prove, an important role for host-pathogen interactions (defined broadly) in the maintenance of diversity. Ways are suggested by which to test host-pathogen models and competing models.
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87
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Stacy EA, Hamrick JL, Nason JD, Hubbell SP, Foster RB, Condit R. Pollen Dispersal in Low-Density Populations of Three Neotropical Tree Species. Am Nat 1996. [DOI: 10.1086/285925] [Citation(s) in RCA: 162] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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88
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89
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Condit R, Hubbell SP, Foster RB. Mortality Rates of 205 Neotropical Tree and Shrub Species and the Impact of a Severe Drought. ECOL MONOGR 1995. [DOI: 10.2307/2963497] [Citation(s) in RCA: 498] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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90
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O'Brien ST, Hubbell SP, Spiro P, Condit R, Foster RB. Diameter, Height, Crown, and Age Relationship in Eight Neotropical Tree Species. Ecology 1995. [DOI: 10.2307/1940724] [Citation(s) in RCA: 133] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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91
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92
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Condit R, Hubbell SP, Foster RB. Density Dependence in Two Understory Tree Species in a Neotropical Forest. Ecology 1994. [DOI: 10.2307/1941725] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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93
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94
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Condit R, Hubbell SP, Foster RB. Recruitment Near Conspecific Adults and the Maintenance of Tree and Shrub Diversity in a Neotropical Forest. Am Nat 1992; 140:261-86. [DOI: 10.1086/285412] [Citation(s) in RCA: 180] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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95
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Condit R, Hubbell SP. Abundance and DNA sequence of two-base repeat regions in tropical tree genomes. Genome 1991; 34:66-71. [PMID: 1827419 DOI: 10.1139/g91-011] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Tandem DNA repeats of two-base pairs are potentially important tools for population genetic studies because of their abundance and length variation. As part of our research into the ecology of tropical forest plants, we began a study of dinucleotide repeat regions in several genera of tropical trees. Genomic libraries in bacteriophage lambda were screened with the oligonucleotide probes poly(GT) and poly(AG). Both types of repeat regions were abundant in the genomes of all six plant species examined. Using the size of inserts in the phage libraries and number of phage screened, we estimated that there were 5 x 10(3) to 3 x 10(5) poly(AC) sites per genome, with slightly more AG than AC sites. When libraries were made from smaller fragments of genomic DNA, abundance estimates were higher, suggesting that two-base repeat sites were clustered in the genome. Poly(AC) sites were 16-22 bp in length, and four of the five sequenced were adjacent to either poly(AG)or poly(AT) sites. Other repeat region s appeared in DNA flanking the AC sites. This further demonstrated that two-base repeats and other repetitive DNA were clustered in the genome. Two-base repeats are abundant in plant genomes and could provide a large number of polymorphic markers for studies of plant population genetics.
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96
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Condit R. Models for the population dynamics of transposable elements in bacteria. BIOTECHNOLOGY (READING, MASS.) 1991; 15:151-71. [PMID: 1849036 DOI: 10.1016/b978-0-409-90199-3.50014-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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97
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Condit R, Levin BR. The Evolution of Plasmids Carrying Multiple Resistance Genes: The Role of Segregation, Transposition, and Homologous Recombination. Am Nat 1990. [DOI: 10.1086/285063] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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98
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Condit R. The Evolution of Transposable Elements: Conditions for Establishment in Bacterial Populations. Evolution 1990. [DOI: 10.2307/2409413] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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99
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Condit R, Stewart FM, Levin BR. The Population Biology of Bacterial Transposons: A Priori Conditions for Maintenance as Parasitic DNA. Am Nat 1988. [DOI: 10.1086/284841] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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100
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Borgia G, Kaatz IM, Condit R. Flower choice and bower decoration in the satin bowerbird Ptilonorhynchus violaceus: a test of hypotheses for the evolution of male display. Anim Behav 1987. [DOI: 10.1016/s0003-3472(87)80169-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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