Effect of size and shape of the sampling unit on the estimation of seed-carrying ants’ species richness in the Monte desert, Argentina
Keywords:
sample size, sampling effort, sub-sampling, asymptotic models, biodiversityAbstract
Species richness is one of the fundamental components for the structure and function of a community. The number of species recorded in a richness assessment depends not only on the characteristics of the focal community but on the size of the sampling area and on sampling effort. The goal of the present study was to establish the optimal size and shape of the sampling unit required to obtain a reliable estimation of the species richness of seed-carrying ants in the central Monte desert, using two simple methods. Ants in two different habitats within the Man and the Biosphere Reserve of Ñacuñán, Mendoza, Argentina, were sampled with 5 m-apart seed baits arranged in three 8x10 grids (2000 m2). After an iterative subsampling protocol, ant species richness was calculated for all possible subgrids of different size (1-80 baits) and shape (from square to elongated), keeping the relative spatial position of the baits. The minimum sampling effort required was evaluated in a graph of mean observed richness in each sub-grid type against sub-grid size (sampling effort). Total species richness in the community (asymptote estimation) was assessed graphically and by fitting three asymptotic models of richness increasing with sampling effort. Different minimum sample sizes were necessary to account for 85% of total ant species richness in grazed and ungrazed landscapes in the Monte desert: 25% of the original sample size (the usual size to estimate the richness of granivorous ants in arid-semiarid areas) would be enough in grazed areas, and >75% in the ungrazed “algarrobal”. Therefore, habitat structure appears to influence the relationship between richness estimation and sampling effort. There were no detectable differences among sub-grid shapes: for a given sampling area, thin rectangular grids seem to detect a similar number of ant species than square ones. The complementary use of graphics and asymptotic models showed to be convenient to detect the optimal sampling effort to estimate ant species richness in different habitats of the Monte desert.
References
CHUST, G; JLI PRETUS; D DUCROT & D VENTURA. 2004. Scale dependency of insect assemblages in response to landscape pattern. Landsc. Ecol. 19:41-57.
COELHO, IR & SP RIBEIRO. 2006. Environmental heterogeneity and seasonal effects in ground-dwelling ant (Hymenoptera: Formicidae) assemblages in the Parque Estadual do Rio Doce, MG, Brazil. Neotr. Ent. 35(1):19-29.
COLWELL, RK & A CODDINGTON. 1994. Estimating terrestrial biodiversity through extrapolation. Phil. Trans. R. Soc. Lond. B 345:101-118.
CUETO, VR. 2006. Escalas en ecología: su importancia para el estudio de la selección de hábitat en aves. Hornero 21(1):1-13.
GOTELLI, NJ & RK COLWELL. 2001. Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness. Ecol. Lett. 4:379-391.
HAIRSTON SR, NG. 1989. Ecological experiments. Purpose, design and execution. Cambridge Studies in Ecology. Cambridge University Press, Cambridge. EE.UU.
JIMÉNEZ-VALVERDE, A & J HORTAL. 2003. Las curvas de acumulación de especies y la necesidad de evaluar la calidad de los inventarios biológicos. Rev. Ibérica
Aracnol. 8:151-161.
LOPEZ DE CASENAVE, J; L MARONE; F JAKSIC & P CAMUS. 2007. Escalas. Pp. 193-213 en: Jaksic y Marone (eds.). Ecología de Comunidades. Segunda edición ampliada. Ediciones Universidad Católica de Chile, Santiago. Chile.
MARONE, L; J LOPEZ DE CASENAVE & VR CUETO. 2000. Granivory in southern South American deserts: conceptual issues and current evidence. BioScience 50:123-132.
MEDEL, RG. 1995. Convergence and historical effects in harvester ant assemblages of Australia, North America, and South America. Biol. J. Linn. Soc. 55:29-44.
MEDEL, RG & RA VÁSQUEZ. 1994. Comparative analysis of harvester ant assemblages of Argentinean and Chilean arid zones. J. Arid Environ. 26:363-371.
MELO, AS; RAS PEREIRA; AJ SANTOS; GJ SHEPHERD; G MACHADO; ET AL. 2003. Comparing species richness among assemblages using sample units: why not use extrapolation methods to standardize different simple sizes? Oikos 101:398-410.
MILESI, FA; L MARONE; J LOPEZ DE CASENAVE; VR CUETO & ET MEZQUIDA. 2002. Gremios de manejo como indicadores de las condiciones del ambiente: un estudio de caso con aves y perturbaciones del hábitat en el Monte central, Argentina. Ecología Austral 12:149-161.
MORENO, CE & G HALFFTER. 2001. On the measure of sampling effort used in species accumulation curves. J. Appl. Ecol. 38:487-490.
MORTON, SR & DW DAVIDSON. 1988. Comparative structure of harvester ant communities in arid Australia and North America. Ecol. Monogr. 58:19-38.
PARMENTER, RR; TL YATES; DR ANDERSON; KP BURNHAM, JL DUNNUM; ET AL. 2003. Small-mammal density estimation: a field comparison of grid-based vs. web-based density estimators. Ecol. Monogr. 73(1):1-26.
ROSENZWEIG, ML. 1995. Species diversity in space and time. Cambridge University Press, Cambridge. EE.UU.
ROSENZWEIG, ML; WR TURNER; JG COX & TH RICKETTS. 2003. Estimating diversity in unsampled habitats of a biogeographical province. Cons. Biol. 17(3):864-874.
SANDERS, NJ; NJ GOTELLI; SE WITTMAN; JS RATCHFORD; AM ELLISON; ET AL. 2007. Assembly rules of ground-foraging ant assemblages are contingent on disturbance, habitat and spatial scale. J. Biogeogr. 34:1632-1641.
SOBERÓN, JM & J LLORENTE. 1993. The use of species accumulation functions for the prediction of species richness. Cons. Biol. 7(3):480-488.
SOBERÓN, JM; R JIMÉNEZ; J GOLUBOV & P KOLEFF. 2007. Assessing completeness of biodiversity databases at different spatial scales. Ecography 30:152-160.
THOMPSON, GG; SA THOMPSON; PC WITHERS& J FRASER. 2007. Determining adequate trapping effort and species richness using species accumulation curves for environmental impact assessments. Austr. Ecol. 32:570-580.
VASCONCELOS, HL; MF LEITE; JMS VILHENA; AP LIMA; ET AL. 2008. Ant diversity in an Amazonian savanna: relationship with vegetation structure, disturbance by fire, and dominant ants. Austr. Ecol. 33:221-231.
ZAR, H. 1996. Biostatistical analysis. 3ra edición. Prentice Hall, Upper Saddle River, NJ. EE.UU. Pp. 662.
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Copyright (c) 2011 María del Mar Beaumont Fantozzi, Javier López de Casenave, Fernando Milesi, Silvia Claver, Víctor R. Cueto
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