title: Are all species necessary to reveal ecologically important patterns?
abstract: While studying ecological patterns at large scales, ecologists are often unable to identify all collections, forcing them to either omit these unidentified records entirely, without knowing the effect of this, or pursue very costly and time-consuming efforts for identifying them. These "indets" may be of critical importance, but as yet, their impact on the reliability of ecological analyses is poorly known. We investigated the consequence of omitting the unidentified records and provide an explanation for the results. We used three large-scale independent datasets, (Guyana/ Suriname, French Guiana, Ecuador) each consisting of records having been identified to a valid species name (identified morpho-species - IMS) and a number of unidentified records (unidentified morpho-species - UMS). A subset was created for each dataset containing only the IMS, which was compared with the complete dataset containing all morpho-species (AMS: = IMS + UMS) for the following analyses: species diversity (Fisher's alpha), similarity of species composition, Mantel test and ordination (NMDS). In addition, we also simulated an even larger number of unidentified records for all three datasets and analyzed the agreement between similarities again with these simulated datasets. For all analyses, results were extremely similar when using the complete datasets or the truncated subsets. IMS predicted ≥91% of the variation in AMS in all tests/analyses. Even when simulating a larger fraction of UMS, IMS predicted the results for AMS rather well. Using only IMS also out-performed using higher taxon data (genus-level identification) for similarity analyses. Finding a high congruence for all analyses when using IMS rather than AMS suggests that patterns of similarity and composition are very robust. In other words, having a large number of unidentified species in a dataset may not affect our conclusions as much as is often thought.
authors.affiliation: Ecology and Biodiversity Group, Utrecht University Utrecht, the Netherlands ; Section Botany, Naturalis Biodiversity Center Leiden, the Netherlands.
authors.forename: Edwin
authors.initials: E
authors.lastname: Pos
authors.affiliation: Department of Integrative Biology, University of California Berkeley, California, 94720-3140.
authors.forename: Juan Ernesto
authors.initials: JE
authors.lastname: Guevara Andino
authors.affiliation: IRD, UMR AMAP Montpellier, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Sabatier
authors.affiliation: IRD, UMR AMAP Montpellier, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Molino
authors.affiliation: The Field Museum 1400 S. Lake Shore Drive, Chicago, Illinois, 60605-2496 ; Center for Tropical Conservation, Nicholas School of the Environment, Duke University Durham, North Carolina, 27708.
authors.forename: Nigel
authors.initials: N
authors.lastname: Pitman
authors.affiliation: Endangered Species Coalition 8530 Geren Rd., Silver Spring, Maryland, 20901.
authors.forename: Hugo
authors.initials: H
authors.lastname: Mogollón
authors.affiliation: Universidad Estatal Amazónica Puyo, Ecuador.
authors.forename: David
authors.initials: D
authors.lastname: Neill
authors.affiliation: Universidad Central Herbario Alfredo Paredes, Escuela de Biología Herbario Alfredo Paredes Ap. Postal 17.01.2177, Quito, Ecuador.
authors.forename: Carlos
authors.initials: C
authors.lastname: Cerón
authors.affiliation: Wildlife Ecology and Conservation & Quantitative Spatial Ecology, University of Florida 110 Newins-Ziegler Hall, PO Box 110430, Gainesville, Florida.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Rivas
authors.affiliation: Department of Anthropology, University of Texas at Austin SAC 5.150, 2201 Speedway Stop C3200 Austin, Texas, 78712.
authors.forename: Anthony
authors.initials: A
authors.lastname: Di Fiore
authors.affiliation: Iwokrama International Programme for Rainforest Conservation Georgetown, Guyana.
authors.forename: Raquel
authors.initials: R
authors.lastname: Thomas
authors.affiliation: GeoIS El Día 369 y El Telégrafo, 3° Piso, Quito, Ecuador.
authors.forename: Milton
authors.initials: M
authors.lastname: Tirado
authors.affiliation: Geography and the Environment, University of Texas Austin, Texas, 78712.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Young
authors.affiliation: Northern Arizona University Flagstaff, Arizona, 86011.
authors.forename: Ophelia
authors.initials: O
authors.lastname: Wang
authors.affiliation: GeoIS El Día 369 y El Telégrafo, 3° Piso, Quito, Ecuador.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Sierra
authors.affiliation: Institute of Molecular Plant Sciences, University of Edinburgh Mayfield Rd, Edinburgh, EH3 5LR, UK ; Royal Botanic Garden of Edinburgh 20a Inverleith Row, Edinburgh, EH3 5LR, UK.
authors.forename: Roosevelt
authors.initials: R
authors.lastname: García-Villacorta
authors.affiliation: Tropenbos International Lawickse Allee 11, PO Box 232, Wageningen, 6700 AE, the Netherlands.
authors.forename: Roderick
authors.initials: R
authors.lastname: Zagt
authors.affiliation: Universidad Técnica del Norte, Herbario Nacional del Euador Quito, Ecuador.
authors.forename: Walter
authors.initials: W
authors.lastname: Palacios
authors.affiliation: Herbario Nacional del Ecuador Casilla 17-21-1787, Avenida Río Coca E6-115, Quito, Ecuador.
authors.forename: Milton
authors.initials: M
authors.lastname: Aulestia
authors.affiliation: Ecology and Biodiversity Group, Utrecht University Utrecht, the Netherlands ; Section Botany, Naturalis Biodiversity Center Leiden, the Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Ter Steege
keywords: Beta-diversity; Fisher's alpha; Mantel test; indets; large-scale ecological patterns; morpho-species; nonmetric multidimensional scaling; similarity of species composition; spatial turnover