Biologia 65/6: 1019—1027, 2010 Section Zoology DOI: 10.2478/s11756-010-0123-6
Species co-occurrences based on a presence/absence null model for Copepoda and cladocerans in Patagonia and Tierra del Fuego lakes and ponds
Patricio De los Ríos1, Andrés Mancilla2 & Marcela Vega1
1Laboratorio de Limnología y Recursos Hídricos, Escuela de Ciencias Ambientales, Facultad de Recursos Naturales, Uni- versidad Católica de Temuco, Casilla 15-D, Temuco, Chile; e-mail: [email protected] 2Instituto de la Patagonia, Universidad de Magallanes, Avenida Bulnes 01855,Casilla113-D,PuntaArenas,Chile
Abstract: The zooplankton assemblages in southern Chilean Patagonia are characterized by calanoid dominance and low species number that is observable under oligotrophic status and wide conductivity values, whereas at mesotrophic status the daphnids are dominant with high species number, and finally at hyper-saline environments halophilic species such as Artemia persimilis and/or the calanoid Boeckella poopensis predominate. In the present study data of different lakes and ponds between 45–53◦ S were analyzed, with the aim to determine potential structures at different sites. For this purpose a null model based in guild structure was applied, considering each guild a different kind of water body (lake, small lake, permanent pond, ephemeral pond, and saline lake). The results revealed in two simulations that guild are structured. These results are similar with other descriptions on the basis of null models that revealed a random pattern of species associations for similar ecosystems due to many species repeated in all or practically all studied sites or similarities of ecological features. Ecological and biogeographical topics were discussed. Key words: Calanoid; Daphnia; Artemia; lakes; ponds; null model
Introduction Rodríguez-Fernández et al. 2006; Segurado & Figueredo 2007). These null models are more robust in comparison The zooplankton assemblages in lakes and ponds in cen- with deterministic models (Gotelli 2000, 2001). tral and southern Patagonia (44–53◦ S) have different The aim of the present study is to apply a null patterns (Soto 1990) due the heterogeneity of water model analysis based on presence-absence of species bodies. For example, in large lakes, small lakes and shal- matrix to determine the absence regulator factors for low ponds of Torres del Paine zooplankton species asso- explanation of species associations in zooplankton in ciations are regulated by conductivity and the trophic central and southern Patagonian lakes and ponds. The status (Soto & De los Ríos 2006; De los Ríos et al. aim of this procedure is the use of non-randomness test 2008a; De los Ríos & Soto 2009). This pattern is sim- to understand community ecology in inland water zoo- ilar descriptions for lakes and ponds in Argentinean plankton. Patagonia (Modenutti et al. 1998) and with descrip- tions of New Zealand lakes and ponds (Jeppensen et al. 1997, 2000). The patterns observed for zooplank- Material and methods ton assemblages in southern Chilean lakes are differ- Study area ent to Europe and North America that have high num- The studied region is located between 45–53◦ S(Aysenand ber of species which are directly associated with surface Magallanes region, Chile), and it is characterized by the (Dodson 1992), and with marked dominance of daphnid presence of large diversity of landscapes, glaciers, valleys, cladocerans (Gillooly & Dodson 2000). snowcaps, lakes and ponds (Niemeyer & Cereceda 1984). From this point of view zooplankton assemblages Within the water bodies there are numerous large and deep are not random, regulatory or deterministic factors ex- lakes, small lakes, shallow permanent and ephemeral ponds, ists to explain the community structure. The absence and saline lakes (De los Ríos 2008). The climate is charac- terized by precipitations in the north from 51◦ S, whereas in of regulatory factors and the random distribution in ◦ the south of 51 S (Niemeyer & Cereceda 1984), the climate species co-occurrence are the basis of null models, one is subpolar with less than 700 mm of precipitation a year, of these models used the presence and absence of species and between October and December there is exposition to to determine the absence of deterministic factors as strong winds of approximately 100 km h−1 (Campos et al. regulators of species co-occurrence or guild structure 1994a, b; De los Ríos & Soto 2009). The studied region has (Frutos 1998; Gotelli 2000, 2001; Abelha et al. 2006; difficult access due its marked isolation, that is an advan-