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Orivel, J.; Malé, P.-J.; Lauth, J.; Roux, O.; Petitclerc, F.; Dejean, A.; Leroy, C. |
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Trade-offs in an ant–plant–fungus mutualism |
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Journal Article |
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2017 |
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Proceedings of the Royal Society B: Biological Sciences |
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Proc Biol Sci |
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284 |
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1850 |
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20161679 |
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Species engaged in multiple, simultaneous mutualisms are subject to trade-offs in their mutualistic investment if the traits involved in each interaction are overlapping, which can lead to conflicts and affect the longevity of these associations. We investigate this issue via a tripartite mutualism involving an ant plant, two competing ant species and a fungus the ants cultivate to build galleries under the stems of their host plant to capture insect prey. The use of the galleries represents an innovative prey capture strategy compared with the more typical strategy of foraging on leaves. However, because of a limited worker force in their colonies, the prey capture behaviour of the ants results in a trade-off between plant protection (i.e. the ants patrol the foliage and attack intruders including herbivores) and ambushing prey in the galleries, which has a cascading effect on the fitness of all of the partners. The quantification of partners' traits and effects showed that the two ant species differed in their mutualistic investment. Less investment in the galleries (i.e. in fungal cultivation) translated into more benefits for the plant in terms of less herbivory and higher growth rates and vice versa. However, the greater vegetative growth of the plants did not produce a positive fitness effect for the better mutualistic ant species in terms of colony size and production of sexuals nor was the mutualist compensated by the wider dispersal of its queens. As a consequence, although the better ant mutualist is the one that provides more benefits to its host plant, its lower host–plant exploitation does not give this ant species a competitive advantage. The local coexistence of the ant species is thus fleeting and should eventually lead to the exclusion of the less competitive species. |
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745 |
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Liang, J.; Crowther, T.W.; Picard, N.; Wiser, S.; Zhou, M.; Alberti, G.; Schulze, E.-D.; McGuire, A.D.; Bozzato, F.; Pretzsch, H.; de-Miguel, S.; Paquette, A.; Herault, B.; Scherer-Lorenzen, M.; Barrett, C.B.; Glick, H.B.; Hengeveld, G.M.; Nabuurs, G.-J.; Pfautsch, S.; Viana, H.; Vibrans, A.C.; Ammer, C.; Schall, P.; Verbyla, D.; Tchebakova, N.; Fischer, M.; Watson, J.V.; Chen, H.Y.H.; Lei, X.; Schelhaas, M.-J.; Lu, H.; Gianelle, D.; Parfenova, E.I.; Salas, C.; Lee, E.; Lee, B.; Kim, H.S.; Bruelheide, H.; Coomes, D.A.; Piotto, D.; Sunderland, T.; Schmid, B.; Gourlet-Fleury, S.; Sonké, B.; Tavani, R.; Zhu, J.; Brandl, S.; Vayreda, J.; Kitahara, F.; Searle, E.B.; Neldner, V.J.; Ngugi, M.R.; Baraloto, C.; Frizzera, L.; Bałazy, R.; Oleksyn, J.; Zawiła-Niedźwiecki, T.; Bouriaud, O.; Bussotti, F.; Finér, L.; Jaroszewicz, B.; Jucker, T.; Valladares, F.; Jagodzinski, A.M.; Peri, P.L.; Gonmadje, C.; Marthy, W.; O’Brien, T.; Martin, E.H.; Marshall, A.R.; Rovero, F.; Bitariho, R.; Niklaus, P.A.; Alvarez-Loayza, P.; Chamuya, N.; Valencia, R.; Mortier, F.; Wortel, V.; Engone-Obiang, N.L.; Ferreira, L.V.; Odeke, D.E.; Vasquez, R.M.; Lewis, S.L.; Reich, P.B. |
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Title |
Positive biodiversity-productivity relationship predominant in global forests |
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2016 |
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Science |
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354 |
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6309 |
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The relationship between biodiversity and ecosystem productivity has been explored in detail in herbaceous vegetation, but patterns in forests are far less well understood. Liang et al. have amassed a global forest data set from >770,000 sample plots in 44 countries. A positive and consistent relationship can be discerned between tree diversity and ecosystem productivity at landscape, country, and ecoregion scales. On average, a 10% loss in biodiversity leads to a 3% loss in productivity. This means that the economic value of maintaining biodiversity for the sake of global forest productivity is more than fivefold greater than global conservation costs.Science, this issue p. 196INTRODUCTIONThe biodiversity-productivity relationship (BPR; the effect of biodiversity on ecosystem productivity) is foundational to our understanding of the global extinction crisis and its impacts on the functioning of natural ecosystems. The BPR has been a prominent research topic within ecology in recent decades, but it is only recently that we have begun to develop a global perspective.RATIONALEForests are the most important global repositories of terrestrial biodiversity, but deforestation, forest degradation, climate change, and other factors are threatening approximately one half of tree species worldwide. Although there have been substantial efforts to strengthen the preservation and sustainable use of forest biodiversity throughout the globe, the consequences of this diversity loss pose a major uncertainty for ongoing international forest management and conservation efforts. The forest BPR represents a critical missing link for accurate valuation of global biodiversity and successful integration of biological conservation and socioeconomic development. Until now, there have been limited tree-based diversity experiments, and the forest BPR has only been explored within regional-scale observational studies. Thus, the strength and spatial variability of this relationship remains unexplored at a global scale.RESULTSWe explored the effect of tree species richness on tree volume productivity at the global scale using repeated forest inventories from 777,126 permanent sample plots in 44 countries containing more than 30 million trees from 8737 species spanning most of the global terrestrial biomes. Our findings reveal a consistent positive concave-down effect of biodiversity on forest productivity across the world, showing that a continued biodiversity loss would result in an accelerating decline in forest productivity worldwide.The BPR shows considerable geospatial variation across the world. The same percentage of biodiversity loss would lead to a greater relative (that is, percentage) productivity decline in the boreal forests of North America, Northeastern Europe, Central Siberia, East Asia, and scattered regions of South-central Africa and South-central Asia. In the Amazon, West and Southeastern Africa, Southern China, Myanmar, Nepal, and the Malay Archipelago, however, the same percentage of biodiversity loss would lead to greater absolute productivity decline.CONCLUSIONOur findings highlight the negative effect of biodiversity loss on forest productivity and the potential benefits from the transition of monocultures to mixed-species stands in forestry practices. The BPR we discover across forest ecosystems worldwide corresponds well with recent theoretical advances, as well as with experimental and observational studies on forest and nonforest ecosystems. On the basis of this relationship, the ongoing species loss in forest ecosystems worldwide could substantially reduce forest productivity and thereby forest carbon absorption rate to compromise the global forest carbon sink. We further estimate that the economic value of biodiversity in maintaining commercial forest productivity alone is $166 billion to $490 billion per year. Although representing only a small percentage of the total value of biodiversity, this value is two to six times as much as it would cost to effectively implement conservation globally. These results highlight the necessity to reassess biodiversity valuation and the potential benefits of integrating and promoting biological conservation in forest resource management and forestry practices worldwide.Global effect of tree species diversity on forest productivity.Ground-sourced data from 777,126 global forest biodiversity permanent sample plots (dark blue dots, left), which cover a substantial portion of the global forest extent (white), reveal a consistent positive and concave-down biodiversity-productivity relationship across forests worldwide (red line with pink bands representing 95% confidence interval, right).The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone—US$166 billion to 490 billion per year according to our estimation—is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities. |
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EcoFoG @ webmaster @ |
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703 |
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Levis, C.; Costa, F.R.C.; Bongers, F.; Peña-Claros, M.; Clement, C.R.; Junqueira, A.B.; Neves, E.G.; Tamanaha, E.K.; Figueiredo, F.O.G.; Salomão, R.P.; Castilho, C.V.; Magnusson, W.E.; Phillips, O.L.; Guevara, J.E.; Sabatier, D.; Molino, J.-F.; López, D.C.; Mendoza, A.M.; Pitman, N.C.A.; Duque, A.; Vargas, P.N.; Zartman, C.E.; Vasquez, R.; Andrade, A.; Camargo, J.L.; Feldpausch, T.R.; Laurance, S.G.W.; Laurance, W.F.; Killeen, T.J.; Nascimento, H.E.M.; Montero, J.C.; Mostacedo, B.; Amaral, I.L.; Guimarães Vieira, I.C.; Brienen, R.; Castellanos, H.; Terborgh, J.; Carim, M. de J.V.; Guimarães, J.R. da S.; Coelho, L. de S.; Matos, F.D. de A.; Wittmann, F.; Mogollón, H.F.; Damasco, G.; Dávila, N.; García-Villacorta, R.; Coronado, E.N.H.; Emilio, T.; Filho, D. de A.L.; Schietti, J.; Souza, P.; Targhetta, N.; Comiskey, J.A.; Marimon, B.S.; Marimon, B.-H.; Neill, D.; Alonso, A.; Arroyo, L.; Carvalho, F.A.; de Souza, F.C.; Dallmeier, F.; Pansonato, M.P.; Duivenvoorden, J.F.; Fine, P.V.A.; Stevenson, P.R.; Araujo-Murakami, A.; Aymard C., G.A.; Baraloto, C.; do Amaral, D.D.; Engel, J.; Henkel, T.W.; Maas, P.; Petronelli, P.; Revilla, J.D.C.; Stropp, J.; Daly, D.; Gribel, R.; Paredes, M.R.; Silveira, M.; Thomas-Caesar, R.; Baker, T.R.; da Silva, N.F.; Ferreira, L.V.; Peres, C.A.; Silman, M.R.; Cerón, C.; Valverde, F.C.; Di Fiore, A.; Jimenez, E.M.; Mora, M.C.P.; Toledo, M.; Barbosa, E.M.; Bonates, L.C. de M.; Arboleda, N.C.; Farias, E. de S.; Fuentes, A.; Guillaumet, J.-L.; Jørgensen, P.M.; Malhi, Y.; de Andrade Miranda, I.P.; Phillips, J.F.; Prieto, A.; Rudas, A.; Ruschel, A.R.; Silva, N.; von Hildebrand, P.; Vos, V.A.; Zent, E.L.; Zent, S.; Cintra, B.B.L.; Nascimento, M.T.; Oliveira, A.A.; Ramirez-Angulo, H.; Ramos, J.F.; Rivas, G.; Schöngart, J.; Sierra, R.; Tirado, M.; van der Heijden, G.; Torre, E.V.; Wang, O.; Young, K.R.; Baider, C.; Cano, A.; Farfan-Rios, W.; Ferreira, C.; Hoffman, B.; Mendoza, C.; Mesones, I.; Torres-Lezama, A.; Medina, M.N.U.; van Andel, T.R.; Villarroel, D.; Zagt, R.; Alexiades, M.N.; Balslev, H.; Garcia-Cabrera, K.; Gonzales, T.; Hernandez, L.; Huamantupa-Chuquimaco, I.; Manzatto, A.G.; Milliken, W.; Cuenca, W.P.; Pansini, S.; Pauletto, D.; Arevalo, F.R.; Reis, N.F.C.; Sampaio, A.F.; Giraldo, L.E.U.; Sandoval, E.H.V.; Gamarra, L.V.; Vela, C.I.A.; ter Steege, H. |
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Persistent effects of pre-Columbian plant domestication on Amazonian forest composition |
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2017 |
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Science |
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355 |
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6328 |
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925-931 |
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The marks of prehistoric human societies on tropical forests can still be detected today. Levis et al. performed a basin-wide comparison of plant distributions, archaeological sites, and environmental data. Plants domesticated by pre-Columbian peoples are much more likely to be dominant in Amazonian forests than other species. Furthermore, forests close to archaeological sites often have a higher abundance and richness of domesticated species. Thus, modern-day Amazonian tree communities across the basin remain largely structured by historical human use.Science, this issue p. 925The extent to which pre-Columbian societies altered Amazonian landscapes is hotly debated. We performed a basin-wide analysis of pre-Columbian impacts on Amazonian forests by overlaying known archaeological sites in Amazonia with the distributions and abundances of 85 woody species domesticated by pre-Columbian peoples. Domesticated species are five times more likely than nondomesticated species to be hyperdominant. Across the basin, the relative abundance and richness of domesticated species increase in forests on and around archaeological sites. In southwestern and eastern Amazonia, distance to archaeological sites strongly influences the relative abundance and richness of domesticated species. Our analyses indicate that modern tree communities in Amazonia are structured to an important extent by a long history of plant domestication by Amazonian peoples. |
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EcoFoG @ webmaster @ |
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Sullivan, M.J.P.; Lewis, S.L.; Affum-Baffoe, K.; Castilho, C.; Costa, F.; Sanchez, A.C.; Ewango, C.E.N.; Hubau, W.; Marimon, B.; Monteagudo-Mendoza, A.; Qie, L.; Sonké, B.; Martinez, R.V.; Baker, T.R.; Brienen, R.J.W.; Feldpausch, T.R.; Galbraith, D.; Gloor, M.; Malhi, Y.; Aiba, S.-I.; Alexiades, M.N.; Almeida, E.C.; de Oliveira, E.A.; Dávila, E.Á.; Loayza, P.A.; Andrade, A.; Vieira, S.A.; Aragão, L.E.O.C.; Araujo-Murakami, A.; Arets, E.J.M.M.; Arroyo, L.; Ashton, P.; Aymard C., G.; Baccaro, F.B.; Banin, L.F.; Baraloto, C.; Camargo, P.B.; Barlow, J.; Barroso, J.; Bastin, J.-F.; Batterman, S.A.; Beeckman, H.; Begne, S.K.; Bennett, A.C.; Berenguer, E.; Berry, N.; Blanc, L.; Boeckx, P.; Bogaert, J.; Bonal, D.; Bongers, F.; Bradford, M.; Brearley, F.Q.; Brncic, T.; Brown, F.; Burban, B.; Camargo, J.L.; Castro, W.; Céron, C.; Ribeiro, S.C.; Moscoso, V.C.; Chave, J.; Chezeaux, E.; Clark, C.J.; de Souza, F.C.; Collins, M.; Comiskey, J.A.; Valverde, F.C.; Medina, M.C.; da Costa, L.; Dančák, M.; Dargie, G.C.; Davies, S.; Cardozo, N.D.; de Haulleville, T.; de Medeiros, M.B.; del Aguila Pasquel, J.; Derroire, G.; Di Fiore, A.; Doucet, J.-L.; Dourdain, A.; Droissant, V.; Duque, L.F.; Ekoungoulou, R.; Elias, F.; Erwin, T.; Esquivel-Muelbert, A.; Fauset, S.; Ferreira, J.; Llampazo, G.F.; Foli, E.; Ford, A.; Gilpin, M.; Hall, J.S.; Hamer, K.C.; Hamilton, A.C.; Harris, D.J.; Hart, T.B.; Hédl, R.; Herault, B.; Herrera, R.; Higuchi, N.; Hladik, A.; Coronado, E.H.; Huamantupa-Chuquimaco, I.; Huasco, W.H.; Jeffery, K.J.; Jimenez-Rojas, E.; Kalamandeen, M.; Djuikouo, M.N.K.; Kearsley, E.; Umetsu, R.K.; Kho, L.K.; Killeen, T.; Kitayama, K.; Klitgaard, B.; Koch, A.; Labrière, N.; Laurance, W.; Laurance, S.; Leal, M.E.; Levesley, A.; Lima, A.J.N.; Lisingo, J.; Lopes, A.P.; Lopez-Gonzalez, G.; Lovejoy, T.; Lovett, J.C.; Lowe, R.; Magnusson, W.E.; Malumbres-Olarte, J.; Manzatto, Â.G.; Marimon, B.H.; Marshall, A.R.; Marthews, T.; de Almeida Reis, S.M.; Maycock, C.; Melgaço, K.; Mendoza, C.; Metali, F.; Mihindou, V.; Milliken, W.; Mitchard, E.T.A.; Morandi, P.S.; Mossman, H.L.; Nagy, L.; Nascimento, H.; Neill, D.; Nilus, R.; Vargas, P.N.; Palacios, W.; Camacho, N.P.; Peacock, J.; Pendry, C.; Peñuela Mora, M.C.; Pickavance, G.C.; Pipoly, J.; Pitman, N.; Playfair, M.; Poorter, L.; Poulsen, J.R.; Poulsen, A.D.; Preziosi, R.; Prieto, A.; Primack, R.B.; Ramírez-Angulo, H.; Reitsma, J.; Réjou-Méchain, M.; Correa, Z.R.; de Sousa, T.R.; Bayona, L.R.; Roopsind, A.; Rudas, A.; Rutishauser, E.; Abu Salim, K.; Salomão, R.P.; Schietti, J.; Sheil, D.; Silva, R.C.; Espejo, J.S.; Valeria, C.S.; Silveira, M.; Simo-Droissart, M.; Simon, M.F.; Singh, J.; Soto Shareva, Y.C.; Stahl, C.; Stropp, J.; Sukri, R.; Sunderland, T.; Svátek, M.; Swaine, M.D.; Swamy, V.; Taedoumg, H.; Talbot, J.; Taplin, J.; Taylor, D.; ter Steege, H.; Terborgh, J.; Thomas, R.; Thomas, S.C.; Torres-Lezama, A.; Umunay, P.; Gamarra, L.V.; van der Heijden, G.; van der Hout, P.; van der Meer, P.; van Nieuwstadt, M.; Verbeeck, H.; Vernimmen, R.; Vicentini, A.; Vieira, I.C.G.; Torre, E.V.; Vleminckx, J.; Vos, V.; Wang, O.; White, L.J.T.; Willcock, S.; Woods, J.T.; Wortel, V.; Young, K.; Zagt, R.; Zemagho, L.; Zuidema, P.A.; Zwerts, J.A.; Phillips, O.L. |
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Long-term thermal sensitivity of Earth’s tropical forests |
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2020 |
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Science |
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368 |
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6493 |
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869-874 |
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A key uncertainty in climate change models is the thermal sensitivity of tropical forests and how this value might influence carbon fluxes. Sullivan et al. measured carbon stocks and fluxes in permanent forest plots distributed globally. This synthesis of plot networks across climatic and biogeographic gradients shows that forest thermal sensitivity is dominated by high daytime temperatures. This extreme condition depresses growth rates and shortens the time that carbon resides in the ecosystem by killing trees under hot, dry conditions. The effect of temperature is worse above 32°C, and a greater magnitude of climate change thus risks greater loss of tropical forest carbon stocks. Nevertheless, forest carbon stocks are likely to remain higher under moderate climate change if they are protected from direct impacts such as clearance, logging, or fires.Science, this issue p. 869The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (−9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth’s climate. |
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EcoFoG @ webmaster @ |
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Dezecache, Camille; Faure, Emmanuel; Gond, Valéry; Salles, Jean-Michel; Vieilledent, Ghislain; Herault, Bruno |
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Gold-rush in a forested El Dorado: deforestation leakages and the need for regional cooperation |
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2017 |
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Environmental Research Letters |
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034013 |
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Tropical forests of the Guiana Shield are the most affected by gold-mining in South America, experiencing an exponential increase in deforestation since the early 2000’s. Using yearly deforestation data encompassing Guyana, Suriname, French Guiana and the Brazilian State of Amapá, we demonstrated a strong relationship between deforestation due to gold-mining and gold-prices at the regional scale. In order to assess additional drivers of deforestation due to gold-mining, we focused on the national scale and highlighted the heterogeneity of the response to gold-prices under different political contexts. Deforestation due to gold-mining over the Guiana Shield occurs mainly in Guyana and Suriname. On the contrary, past and current repressive policies in Amapá and French Guiana likely contribute to the decorrelation of deforestation and gold prices. In this work, we finally present a case study focusing on French Guiana and Suriname, two neighbouring countries with very different levels of law enforcement against illegal gold-mining. We developed a modelling framework to estimate potential deforestation leakages from French Guiana to Suriname in the border areas. Based on our assumptions, we estimated a decrease in deforestation due to gold-mining of approx. 4300 hectares in French Guiana and an increase of approx. 12 100 hectares in Suriname in response to the active military repression of illegal gold-mining launched in French Guiana. Gold-mining in the Guiana Shield provides challenging questions regarding REDD+ implementation. These questions are discussed at the end of this study and are important to policy makers who need to provide sustainable alternative employment to local populations in order to ensure the effectiveness of environmental policies. |
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EcoFoG @ webmaster @ |
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Salhi, L.; Nait-Rabah, O.; Deyrat, C.; Roos, C. |
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Numerical Modeling of Single Helical Pile Behavior under Compressive Loading in Sand |
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2013 |
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Electronic Journal of Geotechnical Engineering |
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Electron. J. Geotech. Eng. |
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18 |
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Bundle T |
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helical pile; finite element method; failure mechanisms; sand |
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The present research deals with helical piles behavior in cohesionless soil through finite element modeling. An approach of modeling of the screw-pile geometry has been proposed through the Finite Element Analysis (FEA) computer program Plaxis. The numerical results are compared with measurements from large scale test and the bearing capacity has been estimated using both cylindrical and individual bearing model. Moreover, different failure criterions have been applied to estimate the ultimate capacity. The effect of spacing ratio (S/Dh) on the screw-pile behavior has been further studied. It has found that results from the model fit the field results. Through the study of the load transfer mechanism, the transition from cylindrical shear to individual plate behavior occurs at a value of spacing ratio (1.5 to 2). |
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Laboratoire des matériaux et molécules en milieu amazonien, EcoFoG-Université des Antilles-Guyane, 97351 Cayenne, French Guiana |
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EcoFoG @ webmaster @ |
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525 |
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Vedel, V.; Lalague, H. |
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Standardized sampling protocol for spider community assessment in the Neotropical rainforest |
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2013 |
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Journal of Entomology and Zoology Studies |
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J. Entomol. Zool. Stud. |
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2 |
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1 |
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18-34 |
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Araneae; Biodiversity; French Guiana; Guianese Shield; Impact Assessment |
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We described, here, a standardized protocol to collect the maximum number of spiders per unit of effort from the different strata of a tropical forestry habitat. This would allow quantifying the richness of a site and would allow spatial and temporal comparisons between sites. This protocol was tested and applied in a pilot study at four sites representing three different forestry habitats of the natural reserve of La Trinité (French Guiana). Results showed every feeding guild was well represented and most of the 30 families found are represented by several individuals. Indices of species richness, number of singletons, species richness estimators from the accumulation curves and diversity and similarity indices were also calculated and all indicated that La Trinité is a rich and diverse site for spiders. The standardized protocol showed here its efficiency and its wide cover of micro-habitats and is, therefore, recommended for any impact assessment or diversity of spider study in tropical forestry environment. |
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EcoFoG @ webmaster @ |
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487 |
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Baraloto, C.; Ferreira, E.; Rockwell, C.; Walthier, F. |
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Limitations and Applications of Parataxonomy for Community Forest Management in Southwestern Amazonia |
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2007 |
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Ethnobotany Research & Applications |
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5 |
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77-84 |
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We examined the limitations of parataxonomic inventories for developing management plans for woody plant resources in tropical rain forests of southwestern Amazonia. Using compilations of herbarium labels, forest personnel interviews and published species descriptions, we assessed the accuracy of common names as parataxonomic units (PUs). We identified 384 common names for 310 harvested woody plant species in the Brazilian state of Acre, of which only 50% were unique to a single taxonomic species. About 10% of common names referred to more than one species, more than half of which included multiple genera. For the 106 species from the Acre sample common to the MAP region including Madre de Dios, Peru and Pando, Bolivia, we identified 198 common names. Splitting was much more frequent in this sample, with more than 80% of species having more than one common name. When the Acre sample was expanded to 131 species from the Brazilian Amazon region, including the states of Amazonas and Para, we identified 740 common names, with nearly 90% of species being represented by more than one common name. Errors and inaccuracy of parataxonomy may contribute to market instability if product orders can not be homogenized within regional markets, and to unsustainable harvests if species are mistakenly lumped into single parataxonomic units. We discuss several programs currently being implemented by our collaborative team in the region to address this issue, including field guides based on digital photography, field courses, and workshops featuring discussions between regional inventory personnel and botanists. |
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2008; Limitations and Applications of Parataxonomy for Community Forest Management in Southwestern Amazonia |
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EcoFoG @ eric.marcon @ 14 |
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214 |
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Marcon, E.; Traissac, S.; Lang, G. |
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A Statistical Test for Ripley’s Function Rejection of Poisson Null Hypothesis |
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2013 |
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ISRN Ecology |
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ISRN Ecology |
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2013 |
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Article ID 753475 |
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9 |
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Ripley’s K function is the classical tool to characterize the spatial structure of point patterns. It is widely used in vegetation studies. Testing its values against a null hypothesis usually relies on Monte-Carlo simulations since little is known about its distribution.
We introduce a statistical test against complete spatial randomness (CSR). The test returns the p-value to reject the null hypothesis of independence between point locations. It is more rigorous and faster than classical Monte-Carlo simulations. We show how to apply it to a tropical forest plot. The necessary R code is provided. |
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EcoFoG @ webmaster @ 852 |
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479 |
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Barabe, D.; Lacroix, C.; Gibernau, M. |
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Developmental floral morphology of Syngonium in the context of the tribe Caladieae (Araceae) |
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2012 |
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Willdenowia – Annals of the Botanic Garden and Botanical Museum Berlin-Dahlem |
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42 |
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2 |
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297-305 |
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Aroids; Inflorescence; Phylogeny; Oxalate Crystals; Flower |
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The floral development of Syngonium angustatum is analysed in the context of a recently published molecular phylogeny of the Araceae. The initiation of discoid floral primordia occurs acropetally on the surface of the inflorescence. Female flowers, atypical bisexual flowers, sterile male flowers and male flowers are inserted on the same phyllotactic spirals on the spadix. Stamen primordia are initiated simultaneously on the periphery of more or less circular floral primordia. There are four stamens per flower (rarely three). In a synandrium, the fusion of stamens occurs very early during their developmental cycle. In some flowers one or two stamens remain free. The staminodes are also initiated on the periphery of the discoid floral primordium and their number varies from four to six. The growth of the fused staminodes will eventually form a longitudinal cavity in the centre of the mature synandrode. On the synandrodes located near the female zone, one or two staminodes remain free during development. No atypical bisexual flowers were observed on the inflorescence of Syngonium. The presence of a few calcium oxalate crystals was observed on the surface of all types of flowers. All the atypical flowers located at the base of the sterile zone corresponded to sterile male flowers and resulted from a more or less random disorganisation of the typical structure of a synandrode. In the Aroideae, free stamens or staminodes represent a plesiomorphic condition. The association of synandria and synandrodes is present in all early diverging genera of the tribe Caladieae and could represent the ancestral state. It is not clear if free stamens have evolved once or twice in the tribe Caladieae, both scenarios are possible. |
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EcoFoG @ webmaster @ |
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460 |
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