Upslope migration of Andean trees

Aim Climate change causes shifts in species distributions, or ‘migrations’. Despite the centrality of species distributions to biodiversity conservation, the demonstrated large migration of tropical plant species in response to climate change in the past, and the expected sensitivity of species distributions to modern climate change, no study has tested for modern species migrations in tropical plants. Here we conduct a first test of the hypothesis that increasing temperatures are causing tropical trees to migrate to cooler areas. Location Tropical Andes biodiversity hotspot, south‐eastern Peru, South America. Methods We use data from repeated (2003/04–2007/08) censuses of 14 1‐ha forest inventory plots spanning an elevational gradient from 950 to 3400 m in Manu National Park in south‐eastern Peru, to characterize changes in the elevational distributions of 38 Andean tree genera. We also analyse changes in the genus‐level composition of the inventory plots through time. Results We show that most tropical Andean tree genera shifted their mean distributions upslope over the study period and that the mean rate of migration is approximately 2.5–3.5 vertical metres upslope per year. Consistent with upward migrations we also find increasing abundances of tree genera previously distributed at lower elevations in the majority of study plots. Main conclusions These findings are in accord with the a priori hypothesis of upward shifts in species ranges due to elevated temperatures, and are potentially the first documented evidence of present‐day climate‐driven migrations in a tropical plant community. The observed mean rate of change is less than predicted from the temperature increases for the region, possibly due to the influence of changes in moisture or non‐climatic factors such as substrate, species interactions, lags in tree community response and/or dispersal limitations. Whatever the cause(s), continued slower‐than‐expected migration of tropical Andean trees would indicate a limited ability to respond to increased temperatures, which may lead to increased extinction risks with further climate change.     

Biological diversification in a complex region: a spatial analysis of faunistic diversity and biogeography of the Andes of Colombia

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. Location The Andean region of Colombia, including the Santa Marta and Macarena mountain ranges. Methods The region was divided into subregions, represented by the eastern and western slopes of each of the three Andean cordilleras, the Cauca and Magdalena valley bottoms, and the peripheral mountain ranges of Perijá, Macarena and Sierra Nevada de Santa Marta. Species lists for five animal taxa (rodents, bats, birds, frogs and butterflies) were compiled for each subregion and similarities in species composition were determined by cluster analysis. To explore biogeographical relationships, species were classified into one of four distributional categories: endemic, tropical Andean, Andean‐Central American and wide continental distribution. Results The highest species richness in the region was found in the Pacific and eastern versants of the Andes, and the lowest in the Cauca and Magdalena valley bottoms. Inter‐Andean slopes were intermediate in species richness. However, when species richness was calculated per unit area, the most diverse regions were the Santa Marta and Macarena ranges, the Cauca Valley watershed and the Pacific slope. Although each taxonomic group had a different branching pattern, dendrograms indicated five common subregional clusterings: (1) Perijá‐Sierra Nevada, (2) the Pacific slope, (3) the eastern Andean slope, (4) the Cauca and Magdalena valley bottoms, and (5) the inter‐Andean slopes. Clustering patterns of inter‐Andean slopes varied among taxa. In birds, bats and rodents, grouping was by opposite slopes of the same valley, whereas frogs were grouped by mountain ranges and butterflies by valleys and their respective slopes. Seventy‐five per cent of species in all taxa were found in less than five subregions. The fauna of the Magdalena and Cauca valley bottoms was composed mostly of lowland species with wide geographical distributions, whereas the cordilleran fauna was mostly restricted to the tropical Andes. Main conclusions The western and eastern versants of the Andes have the highest species richness, but are also the largest subregions. On a per unit area basis, the peripheral ranges (Santa Marta and Macarena) are the richest, followed by the western portion of the Andes (the Cauca Valley watershed and the Pacific versant). Clustering patterns in dendrograms suggest two major patterns of differentiation of the Andean fauna: one elevational (lowlands vs. highlands) and one horizontal (among ranges and/or slopes). Biogeographical affinities of the inter‐Andean valley bottoms are with the lowland faunas of tropical America. In contrast, Andean faunas diversified locally, resulting in the evolution of a large number of endemic species, particularly among the less vagile taxa. Three different main branches of Andean fauna can be recognized, one confined to the Pacific, another to the eastern (Amazonian‐Llanos) versant of the Andes, and the third one composed by the inter‐Andean slopes of the Cauca and Magdalena valleys. The identification of five main biogeographical units in the Andean region of Colombia has important implications for the conservation of the regional biota. Conservation initiatives that seek to preserve representative samples of the regional biodiversity should take into account the patterns of diversification described here, and the evolutionary processes that gave rise to these patterns.     

The Curatorial Voice: U.S. Institutions Exhibit the Ancient Andes

Two new exhibits on ancient Andean civilizations are open in the United States. Machu Picchu: Unveiling the Mystery of the Incas is a large traveling exhibition and Tiwanaku: Ancestors of the Inca is a smaller temporary exhibition that is not traveling. Both introduce North American audiences to objects and information that have never been exhibited in the United States and each includes some extraordinary artifacts. The two exhibits differ in many ways: Machu Picchu emphasizes information, archaeological science, and cultural history, whereas Tiwanaku focuses on art style and objects. The curatorial voice and point of view are strong in each exhibit, as is the institutional perspective of its originiating museum. In this respect these exhibits differ significantly from contemporary ones on ancient North America, which generally include the voices and points of view of descendant communities and others.     

A new species of Drepanocnemis (Diptera,Muscidae) from Andes in Peru,with an updated phylogenetic analysis of species

Drepanocnemis Stein (Diptera, Muscidae) is a small genus of flies that occur in high altitudes in the Colombian Andes, Ecuador, Peru and Bolivia. Herein we describe Drepanocnemis aurifronssp. nov. from Cuzco, Peru, which is found from high (2904 m) to lower altitudes (707 m). An updated phylogeny, key to species and map of species’ distributions are provided, together with images and illustrations of the male and the female terminalia.     

Reproductive biology of Oreocereus fossulatus (Cactaceae), a long‐lived columnar cactus endemic to the tropical Andes

The geographic dichotomy hypothesis suggests that columnar cacti inhabiting the tropics depend on flower visitors (birds and bats) for their pollination, showing highly specialized animal‐pollinated systems. This pattern has been demonstrated for the northern hemisphere; however, our knowledge of the species of columnar cacti growing in the southern tropics is still scarce. In this study, we studied the reproductive biology of Oreocereus fossulatus (Cactaceae, Tribe Trichocereae), an endemic, columnar cactus of the tropical Andes, to determine if its pollination system tends to be more generalized (mixed systems of autogamy and xenogamy) than specialized (xenogamy) as a consequence of the geographic position of where it lives. Observations of the frequency of visits showed that Patagona gigas (Trochillidae) is its main pollinator. It visits the flowers when they are open, coinciding with the periods of greater floral reward (dusk and dawn of the first day of anthesis). The treatments of autogamy, xenogamy and geitonogamy produced fruits, showing that O. fossulatus exhibits a generalized pollination system, in the same way as its congeneric species O. celsianus, which is distributed farther south in the Prepuna biogeographical region. Our results suggest that species partially specializing in pollination by hummingbirds and, besides, capable of autopollination, could be common in the tropical and subtropical Andes, probably as a response to the unpredictable environments present in their ecosystems.     

The growth form composition of plant communities in the ecuadorian páramos

A growth form classification for the plants of the Ecuadorian páramos is proposed, consisting of ten forms: stem rosettes, basal rosettes, tussocks, acaulescent rosettes, cushions and mats, upright shrubs, prostrate shrubs, erect herbs, prostrate herbs, and trailing herbs.The growth form composition of 192 samples of páramo vegetation from twelve different regions in Ecuador was analysed using multivariate techniques to determine physiognomic types. The distribution of growth forms was significantly related to altitude, rock cover, bare ground and to measures of disturbance and exposure.The dominant growth forms in all the samples belonged to one of Hedberg's (1964) five types, but other forms were also significant components of the vegetation. The majority of Ecuadorian páramo vegetation showed a relatively consistent growth form composition, dominated by tussocks. The accompanying growth forms were mostly acaulescent rosettes, cushions, upright shrubs, prostrate shrubs, erect herbs and prostrate herbs, sometimes with stem rosettes, basal rosettes or trailing herbs.At higher altitudes, the dominance of tussocks was reduced. At first, acaulescent rosettes became dominant, but higher still their dominance was shared with cushions. At the highest altitudes of all, where plant cover was thin, no single growth form was dominant. In other locations where plant cover was sparse, once again no single growth form was dominant. In humid páramos, stem rosettes were co-dominant with tussocks or erect herbs. Basal rosettes, erect herbs and prostrate herbs were locally co-dominant at higher altitudes.The growth form composition of the Ecuadorian páramos showed similarities with other tropical alpine regions, though no comparable quantitative data for these regions are available yet. The quantitative determination of growth form composition may also lead to a better understanding of community structure and the mechanisms which govern it.     

Altitudinal variation of dung beetle (Scarabaeidae: Scarabaeinae) assemblages in the Colombian Andes

Aim We describe the changes in species richness, rarity and composition with altitude, and explore whether the differences in Scarabaeinae dung beetle composition along five altitudinal transects of the same mountain range are related to altitude or if there are interregional differences in these altitudinal gradients. Location Field work was carried out on the eastern slope of the eastern Cordillera, Colombian Andes, between Tamá Peak to the north, in the Tamá National Park (07°23′ N, 72°23′ W) and the San Miguel River (00°28′ N, 77°17′ W) to the south. Methods Sampling was carried out between February 1997 and November 1999 in five regions spanning elevation gradients. In each gradient, six sites were chosen at 250 m intervals between 1000 and 2250 m a.s.l. Results We found a curvilinear relationship between altitude and mean species richness, with a peak in richness at middle elevations. However, the diversity of dung beetle assemblages does not seem to be related to the interregional differences in environmental conditions. The number of geographically restricted species is negatively and significantly related to altitude, with geographically restricted species more frequent at low altitude sites. Ordination delimited the two main groups according to altitude: one with all the highest sites (1750–2250 m a.s.l.) and a second group with the remaining sites (< 1750 m a.s.l.). Analysis of species co‐occurrence shows that these dung beetle assemblages seem to be spatially structured when all sites have the same probability of being chosen. In contrast, the spatial structure of species assemblages seems to be random when the probability of choosing any site is proportional to its altitude. Main conclusions The altitude of sites is the main factor that influences the diversity of these dung beetle assemblages. The peak in species richness at middle elevations, the higher number of geographically restricted species at lower altitudinal levels, and the compositional differences along these mountain gradients seem to result from the mixing at these altitudes of dung beetle assemblages that have different environmental adaptations and, probably, different origins. The relevance of altitude in these assemblages is related to the limited role of these Neotropical high altitude environments as centres of refuge and vicariance for a monophyletic group of warm‐adapted species, for which the vertical colonization of these high mountain environments by lineages distributed at lower altitudes would have been very difficult.     

Direct and indirect effects of glaciers on aquatic biodiversity in high Andean peatlands

The rapid melting of glacier cover is one of the most obvious impacts of climate change on alpine ecosystems and biodiversity. Our understanding of the impact of a decrease in glacier runoff on aquatic biodiversity is currently based on the ‘glacier‐heterogeneity‐diversity’ paradigm, according to which there is high α‐diversity at intermediate levels of glacial influence due to the high degree of environmental heterogeneity caused by glacier water. This α‐diversity pattern generates high levels of between‐site aquatic community variation (high β diversity) and increases regional diversity (γ‐diversity). There is a rich conceptual background in favor of this paradigm, but empirical data supporting it are scarce. We investigated this paradigm by analyzing the different diversity patterns (α, β and γ‐diversity) of four aquatic groups (zooplankton, macroinvertebrates, algae and macrophytes) living in high‐elevation peatlands (>4500 m above sea level). We sampled 200 pools from 20 peatlands along a glacier gradient in the Cordillera Real of Bolivia. We performed structural equation modeling (SEM) to analyze the potential mechanisms underlying the observed diversity patterns. Intermediate levels of glacial influence (15–20% cover) resulted in high heterogeneity, but α‐diversity responded to glacial influence only for the zooplankton group (Cladocera). Our SEM analysis did not identify environmental heterogeneity as a significant variable explaining the relationship between glacier and α‐diversity. Peatland area had a strong positive effect on heterogeneity and diversity. β‐diversity was significantly associated with glacier gradient, and 12.9% of the total regional diversity (γ‐diversity) was restricted to peatlands with a high degree of glacial influence. These species might be lost in a context of glacial retreat. These findings provide new insight into the potential effects of glacial retreat on the aquatic environment and biodiversity in the peatlands of the tropical Andes.