South Ecuador Research Articles

Altitudinal Change in LAI and Stand Leaf Biomass in Tropical Montane Forests: a Transect Study in Ecuador and a Pan-Tropical Meta-Analysis

Leaf area index (LAI) is a key parameter controlling plant productivity and biogeochemical fluxes between vegetation and the atmosphere. Tropical forests are thought to have comparably high LAIs; however, precise data are scarce and environmental controls of leaf area in tropical forests are not understood. We studied LAI and stand leaf biomass by optical and leaf mass-related approaches in five tropical montane forests along an elevational transect (1,050–3,060 m a.s.l.) in South Ecuador, and conducted a meta-analysis of LAI and leaf biomass data from tropical montane forests around the globe. Study aims were (1) to assess the applicability of indirect and direct approaches of LAI determination in tropical montane forests, (2) to analyze elevation effects on leaf area, leaf mass, SLA, and leaf lifespan, and (3) to assess the possible consequences of leaf area change with elevation for montane forest productivity. Indirect optical methods of LAI determination appeared to be less reliable in the complex canopies than direct leaf mass-related approaches based on litter trapping and a thorough analysis of leaf lifespan. LAI decreased by 40–60% between 1,000 and 3,000 m in the Ecuador transect and also in the pan-tropical data set. This decrease indicates that canopy carbon gain, that is, carbon source strength, decreases with elevation in tropical montane forests. Average SLA decreased from 88 to 61 cm2 g−1 whereas leaf lifespan increased from 16 to 25 mo between 1,050 and 3,060 m in the Ecuador transect. In contrast, stand leaf biomass was much less influenced by elevation. We conclude that elevation has a large influence not only on the leaf traits of trees but also on the LAI of tropical montane forests with soil N (nitrogen) supply presumably being the main controlling factor.

Guilds of mycorrhizal fungi and their relation to trees, ericads, orchids and liverworts in a neotropical mountain rain forest

Abstract Mycorrhizas of vascular plants and mycorrhiza-like associations of liverworts and hornworts are integral parts of terrestrial ecosystems, but have rarely been studied in tropical mountain rain forests. The tropical mountain rain forest area of the Reserva Biologica San Francisco in South Ecuador situated on the eastern slope of the Cordillera El Consuelo is exceptionally rich in tree species, ericads and orchids, but also in liverworts. Previous light and electron microscopical studies revealed that tree roots are well colonized by structurally diverse Glomeromycota, and that epiphytic, pleurothallid orchids form mycorrhizas with members of the Tulasnellales and the Sebacinales (Basidiomycota). Sebacinales also occurred in mycorrhizas of hemiepiphytic ericads and Tulasnellales were found in liverworts belonging to the Aneuraceae. On the basis of these findings, we hypothesized that symbiotic fungi with a broad host range created shared guilds or even fungal networks between different plant species and plant families. To test this hypothesis, molecular phylogenetic studies of the fungi associated with roots and thalli were carried out using sequences of the nuclear rDNA coding for the small subunit rRNA (nucSSU) of Glomeromycota and the large subunit rRNA (nucLSU) of Basidiomycota. Sequence analyses showed that Sebacinales and Tulasnellales were only shared within but not between ericads and orchids or between liverworts and orchids, respectively. Regarding arbuscular-mycorrhiza-forming trees, however, 18 out of 33 Glomus sequence types were shared by two to four tree species belonging to distinct families. Nearly all investigated trees shared one sequence type with another tree individual. Host range and potential shared guilds appeared to be restricted to the plant family level for Basidiomycota, but were covering diverse plant families in case of Glomeromycota. Given that the sequence types as defined here correspond to fungal species, our findings indicate potential fungal networks between trees.

Thermal regime from bottom simulating reflectors along the north Ecuador–south Colombia margin: Relation to margin segmentation and great subduction earthquakes

The north Ecuador–south Colombia (NESC) margin has three transverse morphotectonic segments (the Manglares, Tumaco, and Patia segments), each with different tectonic and structural patterns. Following the 1906 subduction earthquake, the NESC margin has been the site of three megathrust events in 1942, 1958, and 1979 for which the rupture zones abut one another. We first investigated variations in heat flow derived from bottom simulating reflectors (BSR) observed along multichannel seismic lines sampling the three morphotectonic segments. Strong along‐strike variations of the BSR‐derived heat flow, just landward of the deformation front, suggest that each morphotectonic segment has a specific thermal regime. Finite element thermal models show that these variations are mainly produced by changes in the age and the dip of the oceanic plate and local hydrothermal cooling. We then examined the relationship between seismogenesis and thermal structure along the plate boundary. The updip limits of the 1942 and 1979 seismogenic zones, estimated from the aftershock area and rupture zone, reach the trench, where the temperature at the top of the subducting plate appears to be 50°–60°C. Between these events the seismogenic zone of the 1958 earthquake is restricted to a region landward of a prominent outer basement high where the temperature appears to be 100°–120°C. We propose that on the NESC margin the updip limit of the seismogenic zone is primarily controlled by low‐temperature processes except for the 1958 event for which the seismogenic updip limit appears to be related to a structural feature in the upper plate.

Anatomy and ultrastructure of mycorrhizal associations of neotropical Ericaceae

Ericaceae are obligatory associated with symbiotic fungi forming several, distinctive categories of mycorrhizas. While ericoid, arbutoid, and monotropoid mycorrhizas are known since many years from ericads of the northern hemisphere and the ericoid mycorrhiza also from Australia, a further mycorrhizal category with hyphal sheath, Hartig net, and intracellular colonization was described by us recently and termed cavendishioid mycorrhiza because it was found on Cavendishia nobilis, a species belonging to the Andean clade (Vaccinioideae) of Ericaceae. As the previous findings indicated a correlation between the mycorrhizal category and the systematic position of Ericaceae, we tested the hypothesis that other ericads of the Andean clade might also form cavendishioid mycorrhizas, while ericads occurring in the same area but not belonging to the Andean clade might not. Mycorrhizas of 20 different ericaceous species, 15 belonging to the Andean clade and 5 to other Vaccinioideae or Ericoideae, were sampled in the tropical mountain rain forest area of South Ecuador and investigated by light and electron microscopy. All the 15 members of the Andean clade ericads displayed a hyphal sheath, as well as inter- and intracellular colonization by hyphae as was found on Cavendishia previously. The five species not belonging to the Andean clade ericads displayed only intracellular colonization by hyphae and hence were typical ericoid mycorrhizal. Ultrastructural studies revealed Sebacinales and ascomycetes as mycorrhiza formers in both associations even within one single cell. The results thus support the hypothesis that the Andean clade of Ericaceae forms mycorrhizas distinct from the arbutoid category and most likely presents an independent evolutionary line in the Ericaceae derived from the ericoid mycorrhizas, justifying the new term “cavendishioid mycorrhiza”.

Regional variability of volcanic ash soils in south Ecuador: The relation with parent material, climate and land use

The high Andes region of south Ecuador is characterised by intense land use changes. These changes affect particularly the páramo, which is a collection of high altitudinal grassland ecosystems. In this region, the interaction between airborne volcanic ashes and the cold and wet climate results in very typical soils, with an elevated organic C contents. The physical soil properties are closely related to the high and reliable base flow in rivers descending from the páramo, which makes them important for the socio-economic development of the region. In this study, we analyse the regional variability of the soils in the south Ecuadorian rio Paute basin. In a first part of the study, data from soil profiles along north–south transects are used to determine the soil properties, and to relate the spatial variability of these properties to the major trends in parent material, volcanic ash deposits and climate. The profiles are Histic Andosols and Dystric Histosols devoid of allophane, with very high amounts of organic matter. Significant differences between the western and central mountain range are observed, as well as a general decrease in Andic properties from north to south, coinciding with the decrease in volcanic influence. Finally, the impact of human activities on the soil properties is assessed in a case study in the Machangara valley. Data from 5 profiles, located in an area with natural grass vegetation and a low degree of human impact are compared with 4 profiles in a heavily disturbed, intensively drained cultivated area. Despite the intensity of the land use, very few significant differences are found.

Water budgets of three small catchments under montane forest in Ecuador: experimental and modelling approach

AbstractThe water budget of forested catchments controls the local water supply and influences the regional climate. To assess the anthropogenic impact on the water cycle, we constructed a water budget for three ∼10 ha catchments under lower montane forest on the east‐facing slope of the Andes in south Ecuador at 1900–2150 m elevation. We used field hydrological measurements and modelled surface flows with TOPMODEL, a semi‐distributed catchment model. We measured incident precipitation, throughfall, stemflow, and surface flow between May 1998 and April 2002 in hourly to weekly resolution, and determined all variables needed to parameterise TOPMODEL. On average, of the four monitored years and three catchments, incident precipitation was 2504 ± SD 123 mm, throughfall 1473 ± 197 mm, and stemflow 25 ± 2 mm yr−1. Fog water input was negligible. Mean annual interception loss in the forest was 1006 ± 270 mm, and mean annual surface flow, calculated with TOPMODEL in an hourly resolution was 1039 ± 48 mm. The resulting mean annual evapotranspiration was 1466 ± 161 mm of which 32% ( =471 ± 162 mm) was transpiration if evaporation from the soil was neglected. Our study catchments show a high evapotranspiration attributable to the strong solar insolation near the equator, the small impact of fog, the generally low intensity of incident precipitation and additional wind‐driven advective energy input. Copyright © 2006 John Wiley & Sons, Ltd.

Description and classification of nonallophanic Andosols in south Ecuadorian alpine grasslands (páramo)

The páramo is a neotropical alpine ecosystem that covers more than 75,000 km 2 of the northern Andes of Colombia, Ecuador, Venezuela, and Peru. It provides important environmental services: more than 10 million people in the Andean highlands benefit from the water supply and regulation function, which is attributed to the volcanic soils that underlie the ecosystem. The soils are also major carbon sinks of global significance. Severe land use changes and soil degradation threaten both the hydrology and carbon sink function. Nevertheless, soil genesis and properties in the páramo is rather poorly understood, nor are their ecological functions well documented. The impact of the geomorphology of the páramo on soil genesis was studied in the rio Paute basin, south Ecuador. Two toposequences were described and analysed. In each toposequence, four pedons were selected representing summit, backslope, undrained plain situation, and valley bottom positions in the landscape. The soils are classified as Hydric Andosols in the World Reference Base for Soil Resources and Epiaquands or Hydrudands in Soil Taxonomy. They are very acidic and have a high organic matter content, high P deficiency, and Al toxicity. Their water content ranges from 2.64 g g − 1 at saturation, down to 1.24 g g − 1 at wilting point, resulting in a large water storage capacity. Two major soil forming processes are identified: (1) volcanic ash deposition and (2) accumulation of organic carbon. Volcanic ash deposits may vary in depth as a result of regional geomorphological factors such as parent material, orientation, slope, and altitude. Organic carbon accumulation is an interaction of both waterlogging, which depends on the position in the landscape, and the formation of organometallic complexes with Al and Fe released during volcanic ash breakdown. Despite the high variability in parent material and topography, the soil is characterised by a notable homogeneity in physico-chemical properties. Statistical analysis reveals that only topographic location has a slight but significant influence on soil pH as well as the organic matter content, saturated conductivity and water retention at high pressure. Finally, the exceptional properties of these soils provide useful insights to improve classification of the Andosols reference group of the FAO World reference Base for Soil Resources.

The effect of land‐use changes on the hydrological behaviour of Histic Andosols in south Ecuador

AbstractThe south Ecuadorian Andean mountain belt between 3500 and 4500 m altitude is covered by a highly endemic and fragile ecosystem called páramo. The Histic Andosols covering this region have highly developed hydric properties and exert a key function in the hydrological regulation of the páramo ecosystem. Unlike most Andosols, their extreme water retention capacity is not due to the presence of typical minerals such as allophane or imogolite. Although these minerals are virtually absent, the large organic carbon content, due to organometallic complexation, gives rise to similar properties. The water content at 1500 kPa can exceed 2000 g kg−1, and the high hydraulic conductivity at saturation (about 15 mm h−1) drops sharply when low suction is applied. The three methods applied, i.e. the inverted auger hole, the tension infiltrometer and the constant‐head permeameter method, give very similar results. The páramo is characterized by a slow hydrological response and a good water regulation, caused by the combination of a high water storage capacity and high conductivity. The wide pore size distribution of the organometallic complexes results in a water retention curve that differs significantly from the classic Mualem–Van Genuchten description, but can better be described with a simple linear or semilogarithmic model. The soils investigated are very prone to irreversible structural changes caused by land‐use changes. The conversion of natural land for cultivation has a large impact on the hydrological function of the region. The water storage capacity increases by 5 to 30%, and the hydraulic conductivity is 31% higher in cultivated catchments. These changes are related to a larger peak flow, a smaller base flow and generally a smaller discharge buffering capacity, despite the higher storage capacity. Copyright © 2005 John Wiley & Sons, Ltd.

Biomass Burning in the Amazon-Fertilizer for the Mountaineous Rain Forest in Ecuador (7 pp)

Biomass burning is a source of carbon, sulfur and nitrogen compounds which, along with their photochemically generated reaction products, can be transported over very long distances, even traversing oceans. Chemical analyses of rain and fogwater samples collected in the mountaineous rain forest of south Ecuador show frequent episodes of high sulfate and nitrate concentration, from which annual deposition rates are derived comparable to those found in polluted central Europe. As significant anthropogenic sources are lacking at the research site it is suspected that biomass burning upwind in the Amazon basin is the major source of the enhanced sulfate and nitrate imput. Regular rain and fogwater sampling along an altitude profile between 1800 and 3185 m has been carried out in the Podocarpus National Park close to the Rio SanFrancisco (3 degrees 58'S, 79 degrees 5'W) in southern Ecuador. pH values, electrical conductivity and chemical ion composition were measured at the TUM-WZW using standard methods. Results reported cover over one year from March 2002 until May 2003. Annual deposition rates of sulfate were calculated ranging between 4 and 13 kg S/ha year, almost as high as in polluted central Europe. Nitrogen deposition via ammonia (1.5-4.4 kg N/ha year) and nitrate (0.5-0.8 kg N/ha year) was found to be lower but still much higher than to be expected in such pristine natural forest environment. By means of back trajectory analyses it can be shown that most of the enhanced sulfur and nitrogen deposition is most likely due to forest fires far upwind of the ecuadorian sampling site, showing a seasonal variation, with sources predominantly found in the East/North East during January-March (Colombia, Venezuala, Northern Brazil) and East/SouthEast during July-September (Peru, Brazil). Our results show that biomass burning in the Amazon basin is the predominant source of sulfur and nitrogen compounds that fertilize the mountaineous rain forest in south Ecuador. The mountaineous rain forest in south Ecuador has developed on poor and acid soils, with low nutrient availability. The additional ferilization resulting from anthropogenic biomass burning constitutes a significant disturbance of this ecosystem, its functioning and biodiversity. Thus it is planned to employ isotope analyses for quantifying the pathways. of nitrate and sulfate deposition in these natural forests.

Rainfall interception in a lower montane forest in Ecuador: effects of canopy properties

Rainfall interception in forests is influenced by properties of the canopy that tend to vary over small distances. Our objectives were: (i) to determine the variables needed to model the interception loss of the canopy of a lower montane forest in south Ecuador, i.e. the storage capacity of the leaves S and of the trunks and branches St, and the fractions of direct throughfall p and stemflow pt; (ii) to assess the influence of canopy density and epiphyte coverage of trees on the interception of rainfall and subsequent evaporation losses. The study site was located on the eastern slope of the eastern cordillera in the south Ecuadorian Andes at 1900–2000 m above sea level. We monitored incident rainfall, throughfall, and stemflow between April 1998 and April 2001. In 2001, the leaf area index (LAI), inferred from light transmission, and epiphyte coverage was determined. The mean annual incident rainfall at three gauging stations ranged between 2319 and 2561 mm. The mean annual interception loss at five study transects in the forest varied between 591 and 1321 mm, i.e. between 25 and 52% of the incident rainfall. Mean S was estimated at 1·91 mm for relatively dry weeks with a regression model and at 2·46 mm for all weeks with the analytical Gash model; the respective estimates of mean St were 0·04 mm and 0·09 mm, of mean p were 0·42 and 0·63, and of mean pt were 0·003 and 0·012. The LAI ranged from 5·19 to 9·32. Epiphytes, mostly bryophytes, covered up to 80% of the trunk and branch surfaces. The fraction of direct throughfall p and the LAI correlated significantly with interception loss (Pearson's correlation coefficient r = −0·77 and 0·35 respectively, n = 40). Bryophyte and lichen coverage tended to decrease St and vascular epiphytes tended to increase it, although there was no significant correlation between epiphyte coverage and interception loss. Our results demonstrate that canopy density influences interception loss but only explains part of the total variation in interception loss. Copyright © 2004 John Wiley & Sons, Ltd.

Tracing water paths through small catchments under a tropical montane rain forest in south Ecuador by an oxygen isotope approach

In three steep microcatchments under tropical montane forest, samples of rainfall, throughfall, organic layer solution (lateral flow), mineral soil solution, and stream water were collected between 23 August 2000 and 15 August 2001. Water samples were analysed for O and partly H isotopes to elucidate the preferential directions — vertical versus lateral — of water flow paths in soils and how they are linked to the precipitation and soil water regime. Additional soil moisture measurements were conducted to support the isotope study. The δ 18O of rainfall shows large variations (−12.6 to +2.1‰) related to different air-masses. There is no correlation between δ 18O values in rainfall, temperature, and rainfall amount. Local meteoric water lines for rainfall and throughfall suggested that evaporation was minimal. The δ 18O values of throughfall and lateral flow are similar to those in rainfall. Variations in δ 18O values of the soil solution and the stream water are smaller (−9.1 to −3.0 and −8.7 to −5.8‰) than those of rainfall, throughfall, and lateral flow. The δ 18O values in stream water increased immediately after an intense rainstorm event to isotope values similar to those of rainfall and lateral flow indicating that during elevated rainfall the water flows rapidly in the organic layers to the stream channel paralleling the surface. This finding was confirmed by the higher volume of water in the organic layer than in the upper mineral soil during the rainstorm event. Our findings suggest that water flow paths through the ecosystem are dominated by vertical directions through the soil profile to the stream channels during normal wet conditions, interrupted by short-term flow direction changes to lateral pathways mainly in the organic layers during rainstorm events. Results from an isotope two-component hydrograph separation for the three microcatchments showed that new rain water (‘event water’) contributed 81, 44, and 78% to the total stormflow runoff during peak discharge of a studied rainstorm event, respectively.

Sinopse de Huberia DC. (Melastomataceae: Merianieae)

This paper is a synopsis of the genus Huberia which has been recently reviewed. It is a neotropical genus comprising 16 species that occur in the Brazilian Atlantic coast and in the Andean cordillera, from south Ecuador to northwest Peru. The author provides a description of the genus, a key, and nomenclatural types, synonymy, distribution, brief habitat descriptions, vernacular names, and a list specimens examined referring to each species. Taxonomic affinities of the species and systematic position of the genus are commented.

Genetic profile of the Ecuadorian Black population (Ecuador–South America) by using the Power Plex® 16 system kit

Allele frequency data for the 15 STR systems and Amelogenine were determined in a population sample of healthy Black unrelated individuals. All loci met Hardy–Weinberg expectations and the high discrimination power of combined system showed the forensic efficiency of these genetic markers. There is a lack of information on Ecuadorian population from a genetic point of view and therefore no previous publications on the distribution of STRs on Black population is available. Blackas are descendents of slaves procedentes of Africa.

The use of the linear reservoir concept to quantify the impact of changes in land use on the hydrology of catchments in the Andes

Abstract. The high Andes region of South Ecuador (The Páramo) is characterised by a cold and wet climate. Most soils of the Páramo region are Andosols and Histosols, with a very high water retention capacity that is affected irreversibly by drying. This key property of Páramo soils buffers catchment outflow, resulting in an almost uniform outflow pattern which, notwithstanding the variability in rainfall, can be very variable in space and time. These soils serve as the most important reservoir of drinking and irrigation water for the densely populated inter-Andean depression region. The Páramo has long served only as an extensive grazing area but recent population pressure and land scarcity have increased cultivation. Two small Páramo catchments (about 2 km2) were monitored intensively for precipitation and discharge for over a year to assess the effect of such land-use changes on the hydrological properties. One catchment is in an undisturbed area and grazed intensively while in the other, local farmers started intensive drainage for cultivation of potatoes about five years ago. The linear reservoir concept has been used to assess the overall retention capacity of the catchments in terms of both peak response and base flow. In this model, every catchment is considered as a series of independent parallel reservoirs, each characterised by mean residence times (T). In every catchment, three major mean residence times can be distinguished. In the undisturbed catchment, an immediate response, characterised by a T of 5.4 hours, is followed by a slower response with a T of 44.3 h. The base flow has a mean T value of 360 h. The response of the cultivated catchment is similar with T values of 3.6 h, 27.2 h and 175 h, respectively. As a result, in the disturbed catchment, water release is about 40% faster than in the undisturbed catchment, so that the base flow falls rapidly to lower levels. The linear reservoir model is a simple way of quantifying the impact of land use changes on the water regulation capacity of Páramo catchments. Keywords: linear reservoir, Páramo, mountain hydrology, land use changes, Ecuador

Genetic profile of the Ecuadorian Mestizo population (Ecuador—South America) by using the Power Plex ® 16 System Kit

Allele frequency data for the 15 STR systems and Amelogenine were determined in a population sample of healthy Mestizo unrelated individuals. All loci met Hardy–Weinberg expectations and the high discrimination power of combined system showed the forensic efficiency of these genetic markers. There is a lack of information on Ecuadorian population from a genetic point of view and therefore no previous publications on the distribution of STRs on Mestizos is available. Mestizos are descendents of Spanish and Amerindian people, however, significant differences were found between the former and the populations from Spanish peninsula, that have been analyzed for these genetic markers.

Soil properties on a chronosequence of landslides in montane rain forest, Ecuador

To assess the impact of landslides on soil fertility in south Ecuador, we compared the properties of shallow translational debris slides with those of adjacent undisturbed soils. A chronosequence of four small landslides, ca. 0.5, ca. 2–3, ca. 8–10, and ca. 20 years old, was selected on a 30–50°, forest-covered, east-facing slope of the eastern cordillera at 1900–2300 m above sea level (a.s.l.). All soils were Dystric Cambisols. The mean mass of the soil organic layer (sum of all O horizons) increased in the order landslide head (46 t ha −1)<central part (“track”, 101 t ha −1)<foot (102 t ha −1)<reference soils (291 t ha −1), implying a variation in nutrient storage of the same order. In the head area, only the oldest landslide had an organic layer. All mineral soils were acidic (pH in H 2O of the A horizon: 3.4–5.2), the effective CEC of the A horizon ranged from 22 to 141 mmol c kg −1, and the base saturation from 13% to 54%; none of these properties was consistently different between landslide and reference soils. The A horizons of the soil in the landslide foot area had greater concentrations of most nutrients than those in the landslide head area. However, differences were not significant. The nutrient concentrations in the landslide foot area resembled those in the A horizons of the reference soils. Thus, the most obvious change in soil properties caused by the landsliding was partial or complete removal of the organic layer, which was not restored during the ca. 20 years covered by the chronosequence. This decreased the topsoil fertility of the landslide area.

Impact of land use changes on the hydrological properties of volcanic ash soils in South Ecuador

Abstract. The effect of land use on the water retention capacity of Umbric Andosols in south Ecuador was studied. The objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.

Tales of Two Cities: Race and Economic Culture in Early Republican North and South America, Guayaquil, Ecuador, and Baltimore, Maryland. By Camilla Townsend. Austin: University of Texas Press, 2000. Pp. 320. Illustrations. Notes. Bibliography. Index. $45.00 cloth.

Tales of Two Cities: Race and Economic Culture in Early Republican North and South America, Guayaquil, Ecuador, and Baltimore, Maryland. By Camilla Townsend. Austin: University of Texas Press, 2000. Pp. 320. Illustrations. Notes. Bibliography. Index. $45.00 cloth.

FLOWERING GEOPHYTES FROM CHILE

FLOWERING GEOPHYTES FROM CHILE

Observations on the Biogeography of the Amotape-Huancabamba Zone in Northern Peru

ABSTRACT Some scientists have suggested that the Huancabamba Depression in northern Peru—i.e., the partial interruption of the Andean chain by the Rio Chamaya drainage system—represents a major biogeographical barrier to montane taxa. Others have suggested that the Amotape-Huancabamba Zone in the Andes of northern Peru and the extreme south of Ecuador is an area of particular biological diversity and possibly a phytogeographical zone in its own right. The phytogeography of this area is investigated here with data mainly from the Loasaceae, supplemented by data on other plant and animal groups and by some new data from Passiflora L. (Passifloraceae) and Ribes L. (Grossulariaceae). The Huancabamba Depression itself does not seem to have been a major dispersal barrier for these groups. However, a phytogeographical zone—the Amotape-Huancabamba Zone—between the Rio Jubones system in Ecuador and the Rio Chamaya system in Peru can be recognized from the available data. This zone seems to be home to numerous ende...