Regionally Nested Patterns of Fish Assemblages In

Regionally nested patterns of fish assemblages in floodplain lakes of the Magdalena river (Colombia) Carlos Granado-Lorencio1, Andres´ Hernandez´ Serna2, Juan David Carvajal2, Luz Fernanda Jimenez-Segura´ 2, Alejandra Gulfo2 & Frank Alvarez2 1Department of Plant Biology and Ecology, Faculty of Biology, University of Sevilla, Box 1095, 41080 Sevilla, Spain 2Ichthyology Group; Sciences Institute, University of Antioquia, Medellin, Colombia Keywords Abstract Conservation priority, fish assemblage, floodplain lakes, ichtyofauna, Magdalena We investigated if fish assemblages in neotropical floodplain lakes (cienagas) ex- river, nested subsets. hibit nestedness, and thus offer support to the managers of natural resources of the area for their decision making. The location was floodplain lakes of the Correspondence middle section of the Magdalena river, Colombia. We applied the nested sub- Carlos Granado-Lorencio, Department of Plant set analysis for the series of 30 cienagas (27 connected to the main river and Biology and Ecology, Faculty of Biology, three isolated). All fish were identified taxonomically in the field and the ma- University of Sevilla, Box 1095, 41080 Sevilla, Spain. Tel: +034 954557067; Fax: +034 trix for presence–absence in all the lakes was used for the study of the pattern of 954626308; E-mail: [email protected] nestedness. The most diverse order was Characiformes (20 species), followed by Siluriformes (19 species). Characidae and Loricaridae were the richest families. Financed by the Spanish Agency for The species found in all the lakes studied were migratory species (17), and seden- International Cooperation in Development (AECID, D/7500/07). tary species (33). Two species (Caquetaia kraussii and Cyphocharax magdalenae) were widespread across the cienagas archipelago (100% of incidence). Nestedness Received: 4 January 2012; Revised: 31 January analysis showed that the distribution of species over the spatial gradient studied 2012; Accepted: 6 February 2012 (840 km) is significantly nested. The cienagas deemed the most hospitable were Simiti, El Llanito, and Canaletal. Roughly, 13 out of the 50 species caught show Ecology and Evolution 2012; 2(6): markedly idiosyncratic distributions. The resulting dataset showed a strong pattern 1296–1303 of nestedness in the distribution of Magdalenese fishes, and differed significantly doi: 10.1002/ece3.238 from random species assemblages. Out of all the measurements taken in the cienagas, only the size (area) and local richness are significantly related to the range of orderofnestedsubsetpatterns(r = –0.59 and –0.90, respectively, at p < 0.01). Dif- ferential species extinction is suggested as the cause of a nested species assemblage, when the reorganized matrix of species occurring in habitat islands is correlated with the island area. Our results are consistent with this hypothesis. strated when the assemblages of species-poor sites are sub- Introduction sets of those in the successively richer assemblages (Atmar Biodiversity varies throughout the range of environ- and Paterson 1993; Baker and Patterson 2011). The concept mental gradients (landscape), with variations in the rich- of nestedness refers more to a description of an observable ness of species; some areas are rich, whereas others are poor situation than an ecological process, which is why it can be (Watts 1996). Even if there has not been much interest in considered as a measurement of the ordered composition of the study of these types of patterns at a regional or local biodiversity, in a determined geographical area. In any case, level, two alternative paradigms have been proposed to ex- there is no consensus concerning the mechanisms which de- plain local community assembly: dispersal-driven assembly termine nestedness in nature (Higgins et al. 2005). (“island paradigm”) and niche assembly (“trait-environment The Magdalena basin supports a richness comprising paradigm”) (Hubbel 2001). 213 fish species (Maldonado-Ocampo et al. 2008) and Numerous studies have revealed that variations in species includes the most productive fishing areas in Colombia. assemblages can reflect nested distribution patterns at the However, at the present time, the floodplain is undergo- landscape level. Nestedness in metacommunities is demon- ing dramatic transformation and deterioration of habitats, 1296 c 2012 The Authors. Published by Blackwell Publishing Ltd. This is an open access article under the terms of the Creative Commons Attribution Non Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. C. Granado-Lorencio et al. Nested Patterns of Fish Assemblages caused by the expansion of agriculture, cattle, gold min- manifests highly predictable timing, permitting the evolution ing, oil extraction, African palm cultivation, and illicit of adaptive life strategies for the species (Restrepo and Jerfve cocaine plantations. The fishing population is estimated 2000). The fish undertake two kinds of migrations: longitudi- at 35,000 people, with an annual catch of less than nal, along the principal water channel of the river and lateral, 17,000 t year–1 (a sixth part of that caught 30 years ago). between the river channel and the floodplain. As a greater part of the fishes are obtained from the flooded Thirty cienagas of various sizes were selected for sam- cienagas,´ these are overexploited owing to the great num- pling along 840 km of the midsection of the Magdalena ber of fishermen who have no other means for survival. river floodplain between the localities of Puerto Boyacaand´ Along the river channel, the fishermen’s catches are con- Barrancabermeja (27 connected to the main river and three centrated during five months, the three months during the isolated; Fig. 1 and Table 1). Samples were taken during the first season of the year (December–February) and lastly, in high water season (November). The sampling program began the second season (July–August), taking advantage of species in 2008 (10 cienagas) up to 2010 (20 cienagas). The sampling migration. Traditionally, the commercial catches include method was the same for all the lakes. Fish were caught using three species: Prochilodus magdalenae Steindachner, 1879 experimental multifilament gillnets (100 × 3m),withmesh (bocachico), Pseudoplatystoma magdaleniatum Buitrago- sizes from two to 10 cm between opposite knots, and the or- Suarez´ and Burr 2007 (pintadillo), and Pimelodus blochii der of the panels was originally random (Kukilahti et al. 2002; Valenciennes 1840 (blanquillo) (Galvis and Mojica 2004), Robertson et al. 2008). Besides, these kinds of nets are easy but the decline in catches has caused fishing pressure to fall to use, low in cost, and appropriate for varying profundities on species of smaller size, with diminished fertility. Out of and depths (Winemiller et al. 2000). the 44 species “in danger” included in the Red Book of Fish Nets remained set for 24 h and were checked every four from Colombia, which are in the endangered category, 19 hours. In all lakes, fishes were collected within structurally are from the Magdalena River Valley. Two of these which different aquatic habitats: littoral with trees, littoral without are important to fisherman are in the category of Critically trees, pelagic,andthe connecting channel between cienaga and Endangered (Prochilodus magdalenae and Pseudoplatystoma canal. In all analyses for a lake, only the taxa present at that magdaleniatum), three are Endangered (Ageneiosus pardalis, lake were used. We refer to the number of species present at Ichthyoelephas longirostris,andSorubim cuspicaudus), eight a lake as the local species richness at that lake. are Vulnerable, and six are Near Threatened (Mojica et al. In each habitat, measurements of depth, pH, and conduc- 2002). tivity (μS) were taken. The measurements for environmental In order that the conservation of an elevated number of variables were analyzed using a one-way ANOVAwith the aim species in a region should be effective, the first stage requires of discovering differences between habitats (Bonferoni cor- a knowledge of the distribution of species, the patterns of rection included). Pearson’s correlation analysis was used to richness, and taxonomic composition, as well as their inter- explore the possible correlations between the environmental relationships through space and time (Margules and Pressey variables measured. For each cienaga, the area was calculated. 2000; Sachs et al. 2009). For this purpose, methodologies We use the length of the channel that links the cienaga to the should be applied which offer the greatest reliability in terms main river as a measurement of connectivity (Tockner et al. of their results and applicability. Among the few possible al- 1999). ternatives which fulfill these requisites is that of measuring The matrix for presence–absence in all the cienagas was biogeographic nestedness (Patterson and Atmar 1986; Patter- used for the study of the pattern of nestedness. Various sys- son 1987; Atmar and Patterson 1993). It is within this frame- tems have been proposed for measuring the adjustment of a work of reference that the present study has been carried out; determined matrix of presence–absence to the nested subset in a geographical area which brings an elevated biodiversity model: N (Patterson and Atmar 1986), T (Atmar and Patter- of fish, with many endemic species in the hydrographic basin, son 1993), U (Cutler 1991), and C (Wright and Reeves 1992). and an

Load more