Aim Understanding large-scale patterns of beta diversity and endemism is essential for ecoregional conservation planning. We present a study of spatial patterns of faunal diversification and biogeographical relationships in the Andean region of Colombia. This region has a great geomorphological complexity, as it is formed by several mountain ranges with different geologic origins. We hypothesize that this complexity results in a high turnover in species composition among subregions.

Beta diversity, or the turnover in species composition among sampling sites in a region, is an important criterion for obtaining adequate representation of regional biodiversity in systems of protected areas. Recently, the additive model for partitioning regional (gamma) diversity (in opposition to the multiplicative model) has been proposed because it allows a direct measure of the contribution of beta diversity to gamma diversity. We determined avian beta diversity along latitudinal (among neighboring river drainages) and elevational axes in a 1347-km2 region on the western slope of the Central Cordillera of the Colombian Andes, where a regional system of protected areas is being designed. We then compared avian beta diversity between sites based on rapid versus long-term (>1 year) inventories and between fragmented sites versus continuous forest. Overall, beta diversity represented 63.1% of gamma diversity among 16 sites. Elevational differences in species composition accounted for 43.3% of regional diversity, whereas differences among drainages accounted for 19.8%. A complementary cluster analysis showed that sites grouped by elevational zones. Rapid inventories overestimated beta diversity because of sampling effects, but the effect was biologically small. Estimators of species richness derived from species accumulation curves provided a useful alternative to compensate for undersampling in short-term surveys. Forest fragmentation increased beta diversity because of differential local extinction of populations. Nevertheless, in our region, forest fragments contributed to gamma diversity because they contained complementary sets of species. More importantly, they contained populations of special-interest species. Although the region is relatively small, our analyses indicate that spatial differentiation of the biota is an important factor for deciding number and location of protected areas in the Andean region.

This paper addresses the conservation status of the spectacled bear Tremarctos ornatus in the northern Andes (Venezuela, Colombia and Ecuador) by analysing the degree of range fragmentation and estimating habitat availability. From satellite images we constructed maps of remnant habitat blocks, consisting of Andean forest and páramo (high elevation shrublands and grassland) ecosystems. This information was overlain with a road map to determine potential isolation of populations, and a human accessibility model was used to estimate the core area of each block. This analysis revealed that the species' range is fragmented by landscape transformation and roads into 113 blocks >100 km2, representing 42% of the original extent of the bear's distribution. Forty percent of the blocks are <500 km2, and only nine are >5,000 km2. However, taking into account only core area, 56% of the blocks are <500 km2 and only six are >5,000 km2. In addition, many blocks have internal patches of colonization, further reducing habitat quality. This effect is more severe in smaller fragments, where internal disturbances constitute a high proportion of the block area. We used a high population density estimate of 0.25, a medium density of 0.11 and a low density of 0.04 bears per km2 to estimate population sizes. Twenty-nine populations are likely to have >500 individuals with the high estimate, but only nine with the medium and one with the low estimate (largest estimated population was 9,048 bears). These estimates are much lower if only the core area of blocks is used. Hunting has been identified as a major threat for many bear populations. Our analyses indicate that a regional conservation strategy for spectacled bear should focus on maintaining or increasing habitat availability in larger blocks, and reducing human-induced mortality across the region.

With the aim of improving our knowledge about the fish fauna of the Lower Paragua River (Iténez or Guaporé basin), fish collections and physic-chemical analyses of water were conducted in three localities in northern Santa Cruz, on the western border of the Noel Kempff Mercado National Park. Sampling periods lasted 5 days on each of three sites (Piso Firme, Florida y El Refugio) and two seasons (high waters: April-May, low waters: September). By using various fishing methods, 4098 fish belonging to 124 species were collected, 35 of them were new geographic records for the National Park. From all the species, 56% belonged to the Characiformes, 22% to Siluriformes (34 spp.), 15% Perciformes (18 spp. of cichlids), 5% Gymnotiformes and 2% Synbranchiformes, Rajiformes and Beloniformes. Species richness was low in the upper course of the river (Piso Firme: 90 species, Florida: 71 species, El Refugio: 23 species) as well as oxygen levels which reached a critical minimum at El Refugio during low waters and increased cover of floating vegetation. The proportion of new geographic records and the uncertainties about fish distribution and abundance indicate the need to conduct monitoring actions associated to the management plans in the area. Resumen: A fin de conocer la riqueza íctica del Río Bajo Paraguá (cuenca del Iténez o Guaporé) se realizaron colectas de peces y análisis físico-químicos del agua en tres localidades del norte de Santa Cruz, sobre el límite oeste del Parque Noel Kempff Mercado. Los muestreos duraron 5 días en cada sitio (Piso Firme, Florida y El Refugio) y en dos épocas del año (aguas altas: Abril-Mayo; aguas bajas: Septiembre). Utilizando diferentes artes de pesca se capturaron 4098 peces pertenecientes a 124 especies, de las cuales 35 fueron nuevos registros para el Parque Noel Kempff Mercado. De las 124 especies, el 56% correspondió al orden Characiformes, 22% a Siluriformes (con 34 spp), 15% a Perciformes (18 cíclidos), 5% a Gymnotiformes y 2% a Synbranchiformes, Rajiformes y Beloniformes. La riqueza de especies fue menor en el curso superior del río (Piso Firme: 90 especies, Florida: 71 especies y El Refugio: 23 especies), al igual que la concentración de oxígeno que en El Refugio alcanzó niveles críticos en la época de escaso caudal por la mayor cobertura de plantas flotantes. La proporción de nuevos registros geográficos y los interrogantes sobre distribución y abundancia de los peces del Rio Paraguá indican la necesidad de implementar monitoreos sistemáticos asociados a los planes de manejo de la zona. Palabras clave : ictiofauna, inventarios, río Iténez o Guaporé, Parque Nacional Noel Kempff Mercado.