Natural and Cultural History of the Golfo Dulce Region, Costa Rica Historia natural y cultural de la región del Golfo Dulce, Costa Rica

Anton WEISSENHOFER , Werner HUBER , Veronika MAYER , Susanne PAMPERL , Anton WEBER , Gerhard AUBRECHT (scientific editors) Impressum

Katalog / Publication: Stapfia 88 , zugleich Kataloge der Oberösterreichischen Landesmuseen N.S. 80 ISSN: 0252-192X ISBN: 978-3-85474-195-4 Erscheinungsdatum / Date of delivery: 9. Oktober 2008 Medieninhaber und Herausgeber / Copyright: Land Oberösterreich, Oberösterreichische Landesmuseen, Museumstr.14, A-4020 Linz Direktion: Mag. Dr. Peter Assmann Leitung Biologiezentrum: Dr. Gerhard Aubrecht Url: http://www.biologiezentrum.at E-Mail: [email protected] In Kooperation mit dem Verein zur Förderung der Tropenstation La Gamba (www.lagamba.at). Wissenschaftliche Redaktion / Scientific editors: Anton Weissenhofer, Werner Huber, Veronika Mayer, Susanne Pamperl, Anton Weber, Gerhard Aubrecht Redaktionsassistent / Assistant editor: Fritz Gusenleitner Layout, Druckorganisation / Layout, printing organisation: Eva Rührnößl Druck / Printing: Plöchl-Druck, Werndlstraße 2, 4240 Freistadt, Austria Bestellung / Ordering: http://www.biologiezentrum.at/biophp/de/stapfia.php oder / or [email protected] Das Werk einschließlich aller seiner Teile ist urheberrechtlich geschützt. Jede Verwertung außerhalb der en - gen Grenzen des Urheberrechtsgesetzes ist ohne Zustimmung des Medieninhabers unzulässig und strafbar. Das gilt insbesondere für Vervielfältigungen, Übersetzungen, Mikroverfilmungen sowie die Einspeicherung und Verarbeitung in elektronischen Systemen. Für den Inhalt der Abhandlungen sind die Verfasser verant - wortlich. Schriftentausch erwünscht! All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any me - ans without prior permission from the publisher. We are interested in an exchange of publications. Umschlagfoto / Cover: Blattschneiderameisen. Photo: Alexander Schneider. Layout: E. Rührnößl. Zitiervorschlag für das Buch / The complete book may be referenced as follows: Weissenhofer, A., Huber W., Mayer V., Pamperl S., Weber A. & G. Aubrecht (Hrsg.; 2008): Natural and cultu - ral history of the Golfo Dulce region, Costa Rica. — Stapfia 88: 768 pp. Zitiervorschlag für Einzelarbeiten / Single contributions may be referenced as follows: Weissenhofer A., Huber W. & M. Klingler (2008): Geography of the Golfo Dulce region. — Stapfia 88: #-#. Ausstellung / Exhibition: Der Pfad des Jaguars. Tropenstation La Gamba, Costa Rica Ort / Address: Biologiezentrum der Oberösterreichischen Landesmuseen, J.-W.-Klein-Straße 73, 4040 Linz, Austria Zeitraum / Period: 10. Oktober 2008 bis 22. März 2009 Konzept, Organisation und Gestaltung / Concept, organization, design: Mag. Stephan Weigl, Mag. Dr. Werner Huber, Mag. Dr. Anton Weissenhofer, Daniel Schaber Ausstellungstechnik, Mitarbeit / Exhibition techniques, collaboration: Jürgen Plass, Roland Rupp, Bruno Tumfart, Erwin Kapl, Josef Schmidt, Roland Zarre, Michaela Minich, Char - lotte Füreder, Georg Proske, Franz Rammerstorfer Museumspädagogik / Museum education: Mag. Claudia Kiesenhofer Leihgeber / Lenders: Naturhistorisches Museum Wien, Mag. Dr. Werner Huber, Mag. Dr. Anton Weissenhofer, Universität Wien; Mag. Felix Holzmann, Bischofshofen Due to the orographic formation of its interior and HOLDRIDGE L.R. (1971): Forest environments in tropical life zones. its humid climate, the Golfo Dulce Region is rich with A pilot study. — Oxford. biodiversity, containing very dense flora and fauna. Af - MALZER O. (2001): Geological History of Central America and the ter HOLDRIDGE (1971), the region was subdivided into Golfo Dulce Region. — Stapfia 78 : 34-46. different zones, including the tropical rainforest, the MORA C.S. (1990): La Geología y sus procesos. — San José. tropical wetland forest, and tropical premontane rain - TOSI J.A. Jr. (1975): The Corcovado Basin on the Osa Península. forest. The biogeographical situation in this area shows — In : T OSI J.A. Jr. (ed.), Potential national parks, nature re - many similarities to the flora and fauna in the Amazon serves, and wildlife sanctuary areas in Costa Rica: a survey and the Colombian Chocó Region and serves as a land of priorities. San José: Centro Científico Tropical. Separate pp. 12. bridge with a valuable genetic base between North and South America. After unregulated seizure of land by agricultural settlers, lumberjacks, and large landowners in the 1940s and 1950s, regulated, state-subsidised set - tlement reform intended to support agricultural exports in the 1960s, and intensification of the livestock indus - try in the 1970s, primary and secondary forest reserves have shrunk to a minimum. The constant expansion of monocultures on new land has far-reaching conse - quences for the local ecosystem. The conservation and sustainable use of tropical forests is established in the Forest Declaration, Conven - tion on Climate Protection, and Convention on the Protection of Species, which demonstrate worldwide concern for these issues. As a regional example, in the 4,304.80 km 2 drainage basin, the ACOSA (Área de Conservación OSA), which covers an area spanning the Cantons Osa, Golfito und Corredores, aims to pro - tect species diversity within the 17 game preserves, which are 44.7% covered by forest, through integration and an alliance with the Parques Nacionales, Vida Sil - vestres y Forestales (Fig. 2). The main sector of the Cor - covado National Park on the Osa Peninsula covers 424 km 2 and the Piedras Blancas National Park covers 148 km 2. The altitude ranges from sea level to 745 m on the Osa Peninsula (Cerro Rincón and Cerro Mueller in the Fila Matajambre) and to 579 m in the Esquinas for - Addresses of authors: est (Cerro Nicuesa). The Golfo Dulce Forest Reserve Anton WEISSENHOFER (592 km 2) was established between the two parks, there - Werner HUBER by forming a natural forest corridor. Department of Palynology and Structural Botany Faculty Center of Botany References University of Vienna Rennweg 14 CHINCHILLA V.E. (1987): Atlas cantonal de Costa Rica. — IFAM. San José. A-1030 Vienna, Austria

HARTSHORN , G.S. (1983): Plants: introduction. — In: JANZEN D.H. E-mail: [email protected] (ed.), Costa Rican natural history. Chicago: Univ. Chicago [email protected] Press: 118-157. Michael KLINGLER HERRERA -M AC BRYDE O., M ALDONADO V. J IMÉNEZ T.R. & K. T HOMSEN (1997): Osa Península and Corcovado National Park, Costa Workgroup Development Studies Rica. — In: DAVIS S.D., H EYWOOD V.H., H ERRERA -M AC BRYDE O., and Sustainability Science VILLA -L OBOS J.& A.C. H AMILTON (eds), Centres of plant diversi - Institute of Geography ty. A guide and strategy for their conservation. Vol. 3. University of Innsbruck WWF, IUCN. Innrain 52 HERWITZ S.R. (1981): Regeneration of selected tropical tree species in Corcovado National Park, Costa Rica. — Univ. A-6020 Innsbruck, Austria Calif. Publ. Geogr. 24 . E-mail: [email protected]

21 The river network of the Piedras Blancas National Park, Costa Rica La red fluvial del Parque Nacional Piedras Blancas, Costa Rica

J ulia T SCHELAUT , C hristian P ICHLER , A nton W EISSENHOFER & F ritz S CHIEMER

Abstract : Research on tropical streams has progressed markedly over the last decade. However, many aspects of biodiversity and functional processes require more detailed attention. The rivers and streams of the Piedras Blancas National Park in south-west - ern Costa Rica provide a unique opportunity to study near-pristine rainforest streams and tropical freshwater ecology. One of the primary objectives of the study was to provide a survey of the river network within the Río Esquinas catchment. Rivers were analysed with regard to abiotic parameters such as morphology, hydrology, hydrochemistry, sedimentology, and to biotic parame - ters such as canopy cover by the riparian vegetation during the dry and rainy season in 2004. Surveys were carried out on nine streams and rivers, ranging from 1 st order to 4 th order, which empty into the Golfo Dulce at the Pacific Ocean. The paper discuss - es differences between sites according to geology and the seasonal hydrological characteristics of running waters within the catch - ment. The hydrochemical stream signatures indicate different geological sources within the Río Esquinas catchment. High water temperatures (> 25°C) are a permanent feature. The streams and rivers exhibit a high annual variation in discharge, turbidity and hydrochemistry as a result of seasonal rainfall. The mean discharge during the rainy season can be 3 times higher than in the dry season. Detailed morphometric-hydrological measurements at the Quebrada Negra, a 1 st order stream, show a clear picture of a highly heterogeneous, dynamic and unregulated stream course with a sequence of pool and riffle sections. Rapid water level fluc - tuations caused by heavy rains are typical. The abundant riparian vegetation is of major significance for the structure and func - tion of the stream ecosystem. The food web structure and trophic interactions of neotropical streams are analysed, taking the re - sults of the Quebrada Negra as an example.

Key words : neotropical streams, seasonality, hydrology, geomorphology, riparian vegetation, nutrient export, food web.

Resumen : La investigación de cursos de agua tropicales ha aumentado en la última década. Sin embargo, muchos aspectos de la biodiversidad y los procesos funcionales requieren una atención mas detallada. Los ríos y arroyos del Parque Nacional Piedras Blancas, al sudeste de Costa Rica, ofrecen una oportunidad única para estudiar la ecología de los cursos de agua dulce tropicales en estado casi inalterado. Uno de los primeros objetivos del estudio fue estudiar la red fluvial de la cuenca del Río Esquinas. Los ríos fueron analizados teniendo en cuenta factores abióticos como morfología, hidrología, hidroquímica, sedimentología y factores bioticas como capa de vegetación ripariana durante las estaciones seca y lluviosa de 2004. Se realizó un estudio sobre nueve cur - sos de agua, del primer al cuarto orden, que desembocan en el área del Golfo Dulce, en el Océano Pacífico. El trabajo trata sobre las diferencias entre diversos sitios de la cuenca según factores geológicos y las características hidrológicas estacionales de cada curso de agua. Las características hidroquímicas de los ríos indican diversas fuentes geológicas dentro de la cuenca del río Esquinas. La alta temperatura del agua (> 25ºC) es una constante de los ríos que se describen aquí. Los cursos de agua muestran una gran variación anual en descarga, turbidez e hidroquímica debido a las lluvias estacionales. La descarga promedio durante la estación lluviosa puede llegar al triple de la estación seca. Además se investigaron con mayor detalle las condiciones morfométricas e hidrológicas del Quebrada Negra, un curso de primer orden. Los resultados muestran que se trata de un curso de agua heterogé - neo, dinámico y poco regulado, con una secuencia natural de remansos y rápidos. Las rápidas fluctuaciones de nivel causadas por las intensas lluvias son típicas. La abundante vegetación riparia mantiene prinicipalmente a las especies típicas de los cursos de agua de Costa Rica. Se analizan la estructura de la red alimenticia y las interacciones tróficas de los cursos de agua neotropicales – tomando los resultados del Quebrada Negra como ejemplo.

Palabras clave : agua tropicales, características estacionales, hidrología, geomorfología, vegetación riparia, exportación de nutri - entes, red alimenticia.

Stapfia 88 , zugleich Kataloge der oberösterreichischen Landesmuseen Neue Serie 80 (2008): 441-455 Introduction predict the way biological communities adapt to such changing geomorphological and hydrological condi - Studies of neotropical streams and rivers have a long tions. This concept was the first unified hypothesis history, beginning with early explorers and naturalists about how streams and their watersheds work and has who visited these regions and collected aquatic speci - been tested in streams around the world. mens, e.g. von Humboldt and Bonpland (1799-1802), von Spix and von Martius (1817-1820), Bates (1848- This protected area of the Piedras Blancas National 1859). Later, more extensive collections were made by Park, Costa Rica, provides a unique opportunity to professional collectors as well as numerous resident and study near-pristine rainforest streams. A continued pro - visiting scientists (see JACKSON & S WEENEY 1995 ). gram of ecological studies of the Río Esquinas catch - ment and its aquatic subsystems is in progress . There is a growing interest in the study of neotropi - cal lotic systems, and the number of papers published The objective of the present study was to provide an each year that address tropical stream research has in - overview of the overall characteristics of the river net - creased markedly over the last two decades. Although work within the Río Esquinas catchment (Fig. 1). the advances are evident, JACKSON & SWEENEY (1995) Rivers were analysed with regard to abiotic parameters pointed to the pressing need for more research into the such as morphology, hydrology, hydrochemistry, sedi - ecology of zoobenthos, algal and microbial communi - mentology and to biotic parameters such as canopy cov - ties. In particular, there is a strong requirement for re - er by the riparian vegetation. Differences between sites search into aquatic system processes and their interac - according to geological factors and the seasonal hydro - tion with the terrestrial environment in a catchment- logical characteristics of running waters within the orientated context. catchment have been assessed. Research was carried out at nine study streams and rivers ranging from 1 st order Tropical streams provide the opportunity to study streams to the largest river, the Río Esquinas, a 4 th order some general ecological questions e.g. factors that deter - river, that empties into the Pacific Ocean at the Golfo mine patterns of species abundance, distribution and Dulce. Furthermore, the morphometric-hydrological co-occurrence ( ARRINGTON et al. 2005). Patterns deter - conditions of the Quebrada Negra, a 1 st order stream, mined from temperate zones do not necessarily hold for were investigated in more detail. Streams display a more tropical systems because of the greater taxonomic and or less regular alternation between shallow areas of ecological diversity in the tropics ( HOENIGHAUS et al. higher current velocity and mixed gravel-cobble sub - 2004) and general system differences e.g. in tempera - strate (riffles) and deeper areas of slower velocity and ture, hydrology and the source of energy for the biota. finer substrate (pools) . The effects of disturbance, predation and environmen - tal complexity (e. g. DUDGEON 1993), the structure of tropical food webs (e. g. JEPSEN & WINEMILLER 2002) The Río Esquinas catchment and the specific role of fish (e. g. FLECKER et al. 2002) A network of rivers, small streams and drainage represent research questions of a wider ecological scope. channels pass through the national park and its sur - A characteristic feature of tropical rainforests is roundings, which all flow into Río Esquinas (Fig. 1). their high diversity and productivity based on a restrict - “Esquinas” means corner and the river is named after its ed nutrient supply. One resolution of this paradox is the meandering course in its downstream section. The river fast nutrient turnover and high retention capacity. In forms the natural border of the Bosque Esquinas to the this respect, rainforest streams can be considered as the north and west of the national park and drains into the export routes of nutrients and thus they can be used to Pacific Ocean. Extensive mangrove swamps occur along indicate the retention capacities of the system with re - the tidal estuaries next to its mouth. The banks of the spect to the nutrient losses that occur. They are there - two main rivers passing through the La Gamba valley, fore good indicators of the retentivity and integrity of the Río Bonito and the Río Esquinas, consist of farm - the whole rainforest system (e. g. LEWIS 1987). land and secondary forest at different stages of regrowth. Due to logging until the late 20 th century, nearly no pri - Tropical streams form aquatic ecosystems which in - mary forest is left in the lowland, except small patches terconnect intimately with the processes in the riparian along the coast and deep inside the park. However, the gallery forests and the hyporheic zones flowing beyond up-slope areas within the study catchment show almost and beside the visible streams. The River Continuum no signs of anthropogenic disturbance. Most of the Concept (RCC), introduced by VANNOTE et al. (1980) smaller streams lie within primary rainforest. is a tool for displaying and understanding lotic ecosys - tem dynamics. It explains changes in the structure and The river network, especially the Río Bonito, is function of communities in low-order rivers and helps characterised by an almost unaffected geomorphology.

442 Fig. 1 : Río Esquinas catchment with nine sampling sites and the indicated subcatchments of Río Bonito and Quebrada Negra within the Piedras Blancas National Park and its vicinity.

In its connection with the Río Esquinas, it represents a terised by a dense riparian vegetation. In contrast, the very interesting, remarkably preserved, undisturbed and canopy cover of high order rivers such as lower mean - fully developed, longitudinal morphological river con - dering parts of Río Esquinas and downstream parts of tinuum. The upstream area of the Río Bonito, embed - Río Bonito is low and the sediments are dominated by ded in primary forest, can serve as a valuable reference mud and sand. Light levels near the bottom zones are re - section for the investigations of anthropogenic influ - duced due to an increasing water depth and turbidity. ences for Costa Rican rivers. Figure 2 depicts the downstream decrease in slope Headwater streams, like the Quebrada Mari and of rivers along their longitudinal course, with steep Quebrada Negra, are rocky, shallow, narrow and charac - headwaters and waterfalls due to the rocky landscape

Table 1 : Co-ordinates and brief description of the sampling sites from the nine studied rivers.

river coordinates description Quebrada Mari - next to San Miguel, Fila Cruces Quebrada Negra N 08° 42,054', W 083° 12,085' next to the Field Station La Gamba Quebrada Chorro N 08° 42,425', W 083° 10,552' at the waterfall Quebrada Gamba N 08° 42,072', W 083° 11,530' bridge with railing Quebrada Bolsa N 08° 42,452', W 083° 11,137' bridge in La Gamba Quebrada Sardinal N 08° 43,407', W 083° 12,773' 500 m before entering into Río Bonito Río Oro N 08° 43,004', W 083° 10,033' bridge on the way from La Gamba to Interamericana (km 37) Río Bonito N 08° 43,868', W 083° 17,723' 2,5 km upstream the conference with Quebrada Sardinal Río Esquinas N 08° 43,868', W 083° 17,723' 4 km upstream of its mouth before entering into Golfo Dulce

443 formation, followed by a decline in lowland sections further downstream. The confluence of various fast- flowing, turbulent mountain streams (e. g. Q. Negra, Q. Gamba, Q. Chorro) results in a fast-flowing river, which corresponds to the piedmont river type with its larger flow, a braided course and high gravel transport (e. g. lower Río Bonito, Fig. 3). The meandering, low - er part of the Río Esquinas, winds as a large, smoothly- flowing river through the lowlands to the sea. It is high - ly influenced by tidal backwaters and the deposition of sand and fine sediments (up to 10 km inland from the Pacific Ocean). The concave longitudinal profile is evident. Whereas Quebrada Negra shows a steep incline, the slope of Río Esquinas is low. Along the longitudinal course, discharge increases in the dry season from 22.5 ls -1 (Q. Negra) to 397 ls -1 (Q. Gamba), 4270 ls -1 (R. Bonito before the con - fluence with R. Oro) and 10.000 ls -1 (R. Esquinas). Almost all the characteristics of a river vary with position along its length. In general, discharge increases with increasing stream order, resulting in changes in width, depth and velocity. Particle sizes of river bed ma - terial usually shift from an abundance of coarser materi - al upstream to mainly finer material in downstream ar - eas. Sediment size is not only correlated with the stream order, it also depends upon different physical parameters (current velocity, incline) of the stream. The Golfo Dulce region is one of the most humid -1 Fig. 2 : River length [km] versus altitude [m] and flow [ls ] during the dry areas in Costa Rica, with more than 6.000 mm of pre - season 2004 of the Quebrada Negra flowing into Quebrada Gamba, Río Bonito and Río Esquinas. Tributaries like Quebrada Bolsa, Quebrada Chorro cipitation per year. On the Pacific side of Costa Rica, and Río Oro are indicated. distinct dry (December – March) and rainy (May – No - vember) seasons exist. The heaviest rainfalls occur in September, October and November. February and March are the driest months, when days can pass with - out rain. As a result of seasonal rainfall, rivers in this re - gion undergo annual changes in water levels. The dry and rainy seasons affect various morphological and hy - drological parameters, especially stream width, water depth and discharge. Strong geomorphological changes of the river bed are visible after periods of seasonal flood flow events. In the rainy season, frequent (almost daily) rains and storms can cause bank-full conditions and in some cases flooding ( FÜREDER 1994). A comparison of cross sections from the dry and rainy season shows the increase in stream width and wa - ter depth during the rainy season. Distinct seasonal dif - ferences are evident in Figure 4. Río Oro, Quebrada Sar - dinal and Río Bonito become strikingly larger and deep - er during the rainy season. Streams in Figure 5 are arranged based on Strahler’s stream order system starting with 1 st order streams (Q. Fig. 3 : Lower Río Bonito. Negra and Q. Mari). Quebrada Chorro, Quebrada Gam -

444 ba, Quebrada Bolsa, Río Oro and Quebrada Sardinal are 2nd order streams at the respective study sites. Río Boni - to was defined as a 3 rd order river and Río Esquinas as a 4th order river. The recorded flow at these nine rivers shows a distinct increase from low order streams to rivers with higher stream order. The smallest is the Quebrada Negra with a base flow of 0.031 m 3s-1 . The flow of the Río Esquinas was about 300 times as high (10 m 3s-1 ). Furthermore, large fluctuations from the dry to the rainy season are a characteristic feature. Data from the Quebrada Mari and the Río Esquinas are not available for the rainy season. Water flow increased in the late rainy season (September, October). Therefore, differences in flow depended on sampling date. Values ranged from 0.094 m 3s-1 (Q. Negra) to 1.776 m 3s-1 (Q. Sardinal). Sediment size of the river bed differed markedly be - tween the study sites. At seven rivers within the Es - quinas catchment, sediment size was estimated visually in the rainy season (Fig. 6). We used five standard par - ticle size ranges (< 2 mm, 2-6.3 mm, 6.3-20 mm, 20-63 mm, > 63 mm) and noted the proportion of each range in the stream bed sediment. The sites for this analysis were chosen at random. The rivers are thus not compa - rable, but sediment size ranges can be given. The Q 25 , the lower quartile, ranged from 1.5 mm to 9.1 mm. This means that 25% of the sediment sizes were less than 1.5 mm at the site with the finest sediment and smaller than 9.1 mm at the site with the coarsest soil. The Q 50 , the median, ranged from 6.5 mm to 28.9 mm. The Q , 75 Fig. 4 : Cross sections of Quebrada Sardinal, Río Oro and Río Bonito with the upper quartile, extends from 28.5 mm to 91.2 mm. stream width [m] and water level [m] during the dry and rainy season in 2004. The Río Oro showed the smallest sediment size, where - Sampling sites are indicated with red stars in Figure 1. as the Quebrada Bolsa had the coarsest sediment.

Geology and chemistry Tropical rivers generally have lower concentrations of chemical constituents than temperate rivers, because tropical rivers are mostly precipitation-dominated. However local geology is also important. The chemical composition of stream water reflects and thus reveals ge - ological features of the catchment. The chemical regime of the water, particularly nutrient dynamics and export from catchments, provides insights into major aspects of ecosystem functions ( NEWBOLD et al. 1995). The relationship between solute concentration and stream flow can help to explain the interplay among physical, chemical and biological processes within the catchment. The observed physical and chemical differ - ences in solute concentrations among the studied rivers within the Río Esquinas catchment seem largely to be a Fig. 5 : Comparison of the flow [m 3s-1 ] from the nine study rivers during the function of area-specific runoff and geological processes. dry and the rainy seasons. Arrangement of rivers according to stream order Chemical data indicate the same source for Río Es - [1 st – 4 th ]

445 sandstones, often very coarse breccias, but also thin- bedded (pelagic to hemipelagic) limestones, mudstones and radiolarites (maximum thickness 1 metre, deeply red coloured and sometimes forming jasper) are visible in the profiles. The La Gamba field station and the Es - quinas Rainforest Lodge are both located on this unit. Light green tuff crops out on the slope north of the sta - tion, whereas fine-grained, medium grey basalt and boulders of basalt breccia are found in the Quebrada Gamba. Layers of grey-green, fine-grained basalt and dykes and sills of dolerite appear in the profiles of Que - brada Bolsa ( MALZER 2001). Quebrada Sardinal originates in the adjoining “Rin - con Block”, formed almost exclusively by basaltic lavas with only very minor inclusions of radiolarite; this stream enters the Golfito Terrane when discharging in - to Río Bonito. Fig. 6 : Comparison of the sediment size [mm] from seven rivers during the rainy season. Arrangement of rivers according to stream order [1 st – 3 th ]. The Fila Costena, lying to the north and across an Position of sampling sites is indicated in Fig. 1. important NW-SE trending fault zone, differs drastical - ly from the Fila Golfito/Fila Gamba area because it be - quinas and Río Oro within Fila Costena (Fila Cruces), longs to a different megatectonic unit, the “Chorotega while all other tributaries originate in Fila Gamba and Block”. It is characterised by shallow marine limestones Golfito (indicated in Fig. 1). from the Eocene and shales, sandstones and microcon - Fila Golfito and Fila Gamba are formed from Late glomerates of Oligocene or Miocene age. There are no Cretaceous and Early Tertiary rocks of a deep marine major volcanic and volcanoclastic rocks within reach of sequence of oceanic basaltic flows at the base, followed the investigated rivers. An important feature of the Fila Costena is its steep, rugged, rocky slopes with numerous by deep sea carbonates and volcaniclastics, including waterfalls. This catchment area is clearly dominated by some lavas and topped by a volcaniclastic sequence carbonate rocks (CaCO ) with possible occurrences of (mainly tuffs) without lava flows. Waterfalls are present 3 gypsum; high concentrations of CaSO are therefore here, but are not as characteristic here as they are of the 4 present here. Fila Costena. Sediments of the highest layer of this se - quence of the “Golfito Terrane” ( DI MARCO et al. Río Oro and Río Esquinas have the highest alkalin - 2- 1995) are exposed in the Quebrada Bolsa, Chorro and ity and concentrations of SO 4 (Fig. 7). The content of the lower parts of Quebrada Sardinal. Tuffs, siltstones, calcium in the Quebrada Negra, Chorro, Gamba, Sardi - nal, Bolsa and the Río Bonito is between 14.2 and 25.3 mg l -1 . Quebrada Mari (34.8 mg l -1 ), Río Oro (44.4 / 52.4 mg l -1 ) and Río Esquinas (44.3 mg l -1 ) show much higher concentrations. Moreover, conductivity of streams originating in the Fila Cruces is also higher (Q. Mari 260 µS cm -1 , Río Oro 372 / 314 µS cm -1 and Río Esquinas 299 µS cm -1 ) than in other studied rivers which have their source in the Golfo Dulce area. The reported concentrations of nitrate, phosphate, total dis - solved nitrogen and total dissolved phosphorus are clearly correlated with land use. Streams like Quebrada Gamba, Quebrada Bolsa, Río Bonito and Río Esquinas drain agricultural land, which has a strong influence on river chemistry. These rivers are next to plantations (ca - cao, oil palms and other land use) and have higher nu - trient concentrations than those draining forested land. Lowlands are more heavily farmed and settled than up -

Fig. 7 : Ion balances based on concentrations of Ca 2+ , Mg 2+ , Na +, alkalinity and land regions. The pH value of all studied rivers is about 2- 8, in both the dry and the rainy season. SO 4 [mval] for the nine study streams during the dry season in 2004.

446 Riparian Vegetation Carapa guianensis (Meliaceae), Castilla tunu (Moraceae) Virola koschnyi , V. guatemalensis (Myristicaceae) and This species-rich vegetation determines habitat Luehea seemannii (Tiliaceae). structures, access to light and temperature, provides the organic matter supply (e.g. leaf litter) to the aquatic en - Prominent species of the mid-canopy layer are vironment, and reduces the transfer of nutrients and Guatteria chiriquiensis (Annonaceae), Welfia regia (Are - pollutants. These factors have a major influence on the caceae), Cecropia insignis , C. obtusifolia (Cecropiaceae), structure and function of fish and macroinvertebrate Tetrathylacium macrophyllum (Flacourtiaceae), Cupania communities. This special forest type is found along livida (Sapindaceae), Apeiba tibourbou and Trichosper - small rivers with adjacent flat terraces. Trees of the mum grewiifolium (Tiliaceae). riverine vegetation are 35-40 m tall and often have mas - The well represented shrub and ground layer con - sive trunks with widely spreading buttresses ( WEISSEN- tains species like Dieffenbachia oerstedii , Homalomena HOFER et al. 2001). The riverine vegetation represents wendlandii , Philodendron spp., Spathiphyllum wendlandii an ecotone — a buffering and intermediate zone be - (Araceae), Asterogyne martiana (Arecaceae), Costus pul - tween the forest and the aquatic site ( SCHIEMER & ZA- verulentus, C. laevis (Costaceae), Carludovica drudei , Cy - LEWSKI 1992). The abundant riparian vegetation at the clanthus bipartitus (Cyclanthaceae), Episcia lilacina (Ges - Quebrada Negra consists mostly of species typical for neriaceae), various species of Heliconiaceae, Calathea headstreams and small rivers in the Golfo Dulce region lutea (Marantaceae), Piper auritum (Piperaceae), Pentag - (see Fig. 8, which represents a vegetation profile at the onia wendlandii , Psychotria elata (Rubiaceae), Myriocarpa Q. Negra). longipes , Urera elata (Urticaceae) and the fern Nephrolepis sp. (Oleandraceae). Trees of the canopy layer include Spondias mombin (Anacardiaceae), Cordia cymosa (Boraginaceae), Epiphytes are common and conspicuous on exposed Sloanea medusula (Elaeocarpaceae), Hyeronima alchor - branches, e.g. Columnea flaccida, C. polyantha (Gesneri - neoides (Euphorbiaceae), Lonchocarpus sp. (Fabaceae), aceae), but lianas are rare.

Fig. 8 : Riparian vegetation at the Quebrada Negra (~ 300 m downstream from the waterfall and next to the Esquinas Rainforest Lodge). 1. Cordia cymosa (Boraginaceae), 2. Carapa guinensis (Meliaceae), 3. Luehea semannii (Tiliaceae), 4. Cecropia obtusifolia (Cecropiaceae), 5. Apeiba tibourbou (Tiliaceae), 6. Tetrathylacium macrophyllum (Flacourtiaceae), 7. Castilla tunu (Moraceae), 8. Welfia regia (Arecaceae), 9. Lonchocarpus sp. (Fabaceae- Faboideae), 10 . Virola guatemalensis (Myristicaceae), 11 . Cecropia insignis (Cecropiaceae), 12 . Acalypha diversifolia (Euphorbiaceae), 13 . Myriocarpa longipes (Urticaceae), 14 . firma (Cyatheaceae)

447 At study sites along the larger rivers, the riparian slower velocity and finer substrate. Natural dynamics of vegetation is often interrupted due to deforestation or streams are expressed by these alternating riffle and pool logging and therefore adjacent areas are mainly domi - sections. Pool-riffle sequences are the result of particle nated by pasture. These sites (Fig. 1), for example, Río sorting and require a range of sediment sizes to develop. Bonito, Río Oro, Quebrada Bolsa and Río Esquinas, are The intervals of pool-riffle sequences are related to less shaded than those of headwater streams. stream width. Mangrove forests accompany the sheltered seashore The stream is characterised by a wide diversity of and estuary of the Río Esquinas, where tidal inundation habitats with different current velocity, depth and sub - of salt water from the sea occurs. This forest type is strate, and represents high heterogeneity. Current ve - floristically poor, thus representing the opposite ex - locity, stream depth, stream bed width and sediment size treme of the species-rich tropical forest. Rhizophora man - fluctuate within short distances (100 m). Whereas cur - gle (Rhizophoraceae) and Pelliciera rhizophorae (Thea- rent velocities decrease at pool sequences, riffle se - ceae) are common and form nearly pure stands. quences are characterised by higher current velocities. Sites where high velocities were recorded have low av - Quebrada Negra erage depths. In contrast, low velocities occurred at deeper sections (Fig. 10). System-orientated studies concentrated on the Que - brada Negra which is in immediate reach of the Field Although water depth and current velocity in - Station La Gamba. The upper course of the Quebrada creased during the rainy season in 2004 due to the high - Negra is an example of a natural, dynamic and unregu - er flow caused by heavy rain, the depth and velocity lated stream course (see Fig. 9), showing both the mean profiles nonetheless resemble those of the dry season. water depth and the mean current velocity during the Heavy rainfall during the rainy season caused riverbank dry season. erosion, but the pool and riffle sequences showed no major shift between the two seasons within the 100 m Streams are highly heterogeneous environments in course of the Quebrada Negra in 2004. which habitat characteristics vary drastically over small distances ( FENOGLIO et al. 2004). In a naturally flowing The hydrograph a continuous record of discharge river, stream reaches display a more or less regular alter - plotted against time ( ALLAN 1995), in Fig. 11 shows the nation between shallow areas of higher current velocity response of the flow of the Quebrada Negra to rainfall and mixed gravel-cobble substrate and deeper areas of from March 2004 to July 2005. With its distinct dry and Fig. 9 : Course of the Quebrada Negra during the dry season within the 100 m section, with bank level [m] and water depth [m]. Position of the cross sections and the tropical field station are indicated.

448 rainy seasons, it is a good example for rainforest streams in Costa Rica. Most Central American rivers do not sus - tain flood conditions for long periods between succes - sive downpours ( BUSSING 1993). The water level on 23 February 2004 was defined as a baseline of zero to pro - vide a measure of range and fluctuation in water levels over the observation period. Water level zero has a base flow of 0.020 m 3s-1 . Within the sampling time, this was the lowest observed water level. Sudden changes in wa - ter level were the rule. High water levels occurred even in the dry season after rain, but water levels were typi - cally higher in the rainy season in months of heavy and continuous rain, when the soil was soaked and runoff was heavy. The seasonal differences in mean flow discharge are presented in Figure 12. Flow at different water levels was assessed by current velocity measurements along depth profiles at the 55 m cross transect within the 100 m sec - Fig. 10 : Mean current velocity [ms -1 ] and mean depth [m] in the dry season (DS) 2004 within the longitudinal 100 m section. tor. To calculate the mean flow within the two seasons, the average water level of three months of each season mostly controlled and often determined by the seasonal - was taken. The average water level in the dry season ity of the precipitation. Peaks in leaf fall have been re - (December, January and February) is 0.4 cm; in the ported during the dry season for Central American forests rainy season (August, September and October) the cor - (DE LA ROSA 1995). Higher leaf fall during the dry season responding value is 5.6 cm. This includes average flows is responsible for the larger litter input into the stream. of about 22 and 60 ls -1 , respectively. High-flow episodes corresponded with a very short time lag to strong rain During the rainy season, most of the leaf litter is trans - events. Figure 13 shows that water level fluctuations fol - ported downstream by flood pulses and higher flow. Rif - low the precipitation. Each peak of heavy rainfall is fol - fles and pools show very different leaf accumulations. The lowed by a rising water level half an hour later. Turbid - former contain more litter because, at shallow sites, ity generally increased during flooding but cleared quite leaves accumulate at obstacles and form debris dams. quickly when rain stopped. The short-term fluctuations of the Quebrada Negra are very typical and play a more important role than the long-term fluctuations. Water levels rise quickly after the beginning of rain. Water tends to discharge above ground, and not much water disappears into the hyporheic interstitial (underground). Impermeable rocks or soils with large amounts of clay are one potential explanation for this. These soils absorb moisture very slowly, especially when the soils are deep. A smooth running stream can turn into a torrent very rapidly. Water levels not only rise quickly, but also drop quickly, which can be explained by the high resilience of the rainforest. Sudden changes in water level are the rule for streams and rivers of this region in Costa Rica. Headwater streams within rainforests, like the Que - brada Negra, receive low irradiance due to the dense ri - parian vegetation and therefore have a low primary pro - duction. Consequently, much of the energy demand by consumers is met from allochthonous sources, especially Fig. 11 : Water level of the Quebrada Negra and precipitation at the tropical litter fall. Leaf litter entry into neotropical streams is Field Station La Gamba from 23 February 2004 to 1 July 2005.

449 Leaf litter in the Quebrada Negra was recorded as an indicator for the input of organic carbon to the water. Figure 14 shows the huge difference between the two seasons. In the rainy season of 2004, only 4.6 gm -2 were recorded versus 81.2 gm -2 in the dry season. The processing of leaf litter in running waters of temperate regions has been the subject of numerous studies, but equivalent tropical ecosystems have re - ceived little attention ( BENSTEAD 1996). In tropical streams, many leaf types vary in their palatability and tannin levels ( DUDGEON & W U 1999). The decomposi - tion and macroinvertebrate colonisation of leaf litter from four different plant species of the riparian vegeta - tion were investigated within the course of the study “Macroinvertebrates and Leaf Litter Decomposition in a Neotropical Lowland Stream, Quebrada Negra, Costa -1 Fig. 12 : Measured flow [ls ] of five different water levels [m] and accounted Rica” ( TSCHELAUT et al. 2008, RIEMERTH et al. 2008). mean flow [ls -1 ] of the Q. Negra during the dry and rainy season (based on mean water level for three-month periods). Some of the most threatened ecosystems on the planet (e.g. rainforests, coral reefs, freshwater lotic sys - tems) are characterised by extremely complex food webs (LAYMAN et al. 2005). Figure 15 provides an overview of the trophic structure of the rainforest streams of the Esquinas forest. It depicts the trophic interactions and the major trophic pathways based on community com - position and the food habits of the major species. Algae, fine particular organic matter (FPOM), coarse particular organic matter (CPOM) and airborne material are the primary resource basis. The second trophic level is composed of herbivorous macrozooben - thos and fish. Predatory , carnivorous and omniv - orous fish represent the third trophic level. Piscivore fish are on the top of the trophic pyramid. Many species utilise food from two or more trophic levels. The abundance of macroinvertebrates provides abundant food for many other predators, including a di - Fig. 13 : Short-term fluctuation and detailed recording of the water level and precipitation from 13:00 to 17:00 on 8 August 2004 at the Quebrada Negra. verse fish assemblage. Food resources of invertebrate consumers include periphyton and other surface layer complexes, macrophytes, detritus and other . We examined the trophic structure of macroinverte - brates using the system of functional feeding groups (FFG) according to MERRITT & C UMMINS (1996). The Fig. 14 : Mean amount [gm -2 ] of classification of the invertebrate consumers of streams in - collected leaf litter on two sampling to feeding guilds has proved to be very useful for descrip - dates (March 5 2004. / August 8 2004) within the 100 m transect during the tive and analytical purposes (CUMMINS 1973). dry and rainy season in 2004. The Quebrada Negra invertebrate fauna is, in terms of species numbers, mostly made up of collector-gather - ers (53.3%), followed by predators (16.5%), filterers (14.5%), shredders (8.5%) and grazer-scrapers (6.5%). The functional and taxonomic macroinvertebrate com - position is quite similar to that reported from other Costa Rican lowland streams ( PRINGLE & RAMIREZ

450 1998 , ROSEMOND et al. 1998, RAMIREZ & PRINGLE ported from leaf litter bags within the study “Macroin - 2001 ). vertebrates and Leaf Litter Decomposition in a Neotropical Lowland Stream, Quebrada Negra, Costa Due to the low periphyton production in the Que - Rica” ( TSCHELAUT et al. 2008). brada Negra, scrapers and grazers were poorly represent - ed and constitute only 6.5% of the macroinvertebrate Fish are conspicuous and important components of community. tropical river food webs. Fish species almost certainly oc - Ephemeroptera was the most significant group of cupy several of the functional feeding groups and proba - collector-gatherers, and within this group the Leptohy - bly exert the greatest impact. Trophic diversification in phidae (20.1%) and Leptophlebiidae (6.9%) were most tropical river fish assemblages is greater than that of in abundant. Predators were the second major feeding similar habitats of temperate regions that contain less group, dominated by Tanypodinae (7.8%, Diptera, Chi - species ( WINEMILLER 1991, WINEMILLER & JEPSEN 1998). ronomidae). Compared to temperate river fish, tropical fish show pro - portionally more herbivorous, detritivorous and omnivo - Net-spinning caddisflies (Philopotamidae and Hy - rous feeding behaviours ( WINEMILLER 1990, 1991; dropsychidae) are passive filter feeders, constructing WOOTTON & OEMKE 1992). Seasonality plays an impor - nets in exposed locations. Larvae of black flies (Simuli - tant role in tropical river food webs. Flooding brings fish idae) are highly specialised suspension feeders. into contact with a greater abundance and diversity of Major invertebrates that feed on decaying leaves allochthonous food resources, especially within forested (shredders) in our study stream include crane fly larvae watersheds ( GOULDING 1980; HENDERSON 1990). In the (Tipulidae) and beetles (esp. Ptilodactylidae). Shred - Quebrada Negra, population sizes and densities of Poe - ders such as Calamoceratidae (caddisflies) were only re - ciliidae decreased from the dry to the rainy season. This

Fig. 15 : Simplified food web and major trophic pathways, Quebrada Negra, Costa Rica. Ellipses are the resource basis. Major sampled species/families with their percentage of total numbers (fish: n = 1373; macroinvertebrates: n = 738) are shown.

451 may reflect seasonal variation in food supply since the References availability of algae and detritus is reduced after floods. ALLAN J.D. (1995): Stream Ecology – Structure and function of Periphyton production most likely decreased in the rainy running waters. — Chapman and Hall. season because of water turbity and decreased light avail - ARRINGTON D.A., W INEMILLER K.C. & C.A. L AMAN (2005): Communi - ability. Detrital sources increase in the dry period due to ty assembly at the patch scale in a species rich tropical riv - seasonal leaf fall ( CHAPMAN & C HAPMAN 1990). er. — Oecologia 144 : 157-167. The survey of rivers lays the basis for further re - BENSTEAD J.P. (1996): Macroinvertebrates and the processing of leaf litter in a tropical stream. — Biotropica 28 : 367-375. search activities on the aquatic habitats within the Piedras Blancas National Park. Promising research av - BUSSING W.A. (1993): Fish communities and environmental char - acteristics of a tropical rainforest river in Costa Rica. — Rev. enues will be a test of the ecotone and the River Con - Biol. Trop. 41 : 791-809. tinuum Concept in tropical lotic systems for their glob - CHAPMAN C.A. & L.J. C HAPMAN (1990): Density and growth rate of al applicability. some tropical dry forest trees: Comparisons between suc - cessional forest types. — Bull. Torr. Bot. Club 117 : 226-231. The seasonal climate (dry and rainy season) pro - CUMMINS W.K. (1973): Trophic relations of aquatic insects. — vides good conditions for testing the food web theory Ann.Rev.Entomol. 18 : 183-206 . and niche partitioning in neotropical lotic systems. Un - DE LA ROSA C. (1995): Middle American streams and rivers. — In: derstanding the ecological energetics will require de - CUSHING C.E., CUMMINS C.W. & G.W. MINSHALL (eds). Ecosys - tailed research on biogeochemical aspects of rainforest tems of the world 22 – River and stream ecosystems. Else - river systems, nutrient retention and nutrient spiralling vier Science B.V. 7: 189-218. and the role of biofilms. DI MARCO G., B AUMGARTNER P.O. & J.E.T. C HANNEL (1995): Late Cre - taceous – Early Tertiary paleomagnetic data and a revised The Piedras Blancas National Park freshwater in - tectonostratigraphic subdivision of Costa Rica and Western vertebrate fauna is largely unsurveyed and undescribed. Panama. — Geol. Soc. Amer. Special Paper 295 : 1-27. This protected area in the south of Costa Rica offers an DUDGEON D. (1993): The effects of spate-induced disturbance, unique opportunity to study the tropical lotic inverte - predation and environmental complexity on macroinverte - brates in a tropical stream. — Freshwat. Biol. 30 : 189-197. brate community and to identify the relative role of sea - sonal changes in physico-chemical factors, and in the DUDGEON D. & Y.K.K. W U (1999): Leaf litter in a tropical stream: food or substrate for macroinvertebrates? — Arch. Hydro - availability and nature of food resources, in explaining biol. 146 : 65-82. temporal patterns in the functional organisation of FENOGLIO S., B O T. & M. C UCCO (2004): Small scale macroinverte - macroinvertebrate communities. brate distribution in a riffle of a neotropical rainforest stream (Río Bartola, Nicaragua). — Carib. J. Science 40 : Results from such studies can be used to predict taxa 253-257. distribution at local small scales and to identify factors FLECKER A.S., T AYLOR B.W., B ERNHARDT E.S., H OOD J.M., C ORNWELL that can influence micro-distribution patterns in the W.K., C ASSATT S.R., V ANNI M.J. & N.S. A LTMAN (2002): Interac - lotic system. tions between herbivorous fishes and limiting nutrients in a tropical stream ecosystem. — Ecology 83 : 1831-1844.

FÜREDER L. (1994): Driftmuster in tropischen Bächen am Beispiel Acknowledgements Costa Rica. — Dissertation, Naturwissenschaftliche Fakultät der Leopold-Franzens-Universität Innsbruck. We thank the staff at the Tropenstation La Gamba for their support during this research. We thank Otto GOULDING M. (1980): The fishes and the forest. Explorations in Amazonian Natural History. — University of California Malzer for advice on the geology of this region in Costa Press, Berkeley. Rica. Mischka Stachowitsch improved the English and HENDERSON P.A. (1990): Fish of the Amazonian Igapo: stability Diego Barletta translated the abstract. Walter Reck - and conservation in a high diversity-low biomass system. — endorfer helped with statistics. We thank Hubert Kraill J. Fish Biol. 37 : 61-66.

for the hydrochemical analysis. HOENIGHAUS D.J., W INEMILLER K.O. & D.C. T APHORN (2004): Compo - sitional change in fish assemblages along the Andean piemont – Llanos floodplain gradient of the Río Portugue - sa. Venezuela. — Neotropical Ichthyology 2: 85-92.

JACKSON K.J. & W.B. S WEENEY (1995): Present status and future di - rections of tropical stream research. — J. N. Am. Benthol. Soc. 14 : 5-11.

JEPSEN D.B. & K.O. W INEMILLER (2002 ): Structure of tropical river food webs revealed by stable isotope ratios. — Oikos 89 : 46-55.

LAYMAN C.A ., WINEMILLER K.O., ARRINGTON D.A. & D.B. J EPSEN (2005): Body size and trophic position in a diverse tropical food web. — Ecology 86 : 2530-2535 .

452 LEWIS W.M. (1987): Tropical limnology. — Ann. Rev. Ecol. Syst. 18 : 158-184.

MALZER O. (2001): Geological history of Central America and the Golfo Dulce Region. — Stapfia 78 : 34-46.

MERRITT R.W. & K.W. C UMMINS (1996): An introduction to the aquatic insects of North America. — Third Edition, Kendall/Hunt Publishing Company.

NEWBOLD D.J., S WEENEY W.E., J ACKSON C.J. & A.L. K APLAN (1995): Concentrations and export of solutes from six mountain streams in northwestern Costa Rica. — J. N. Am Benthol. Soc. 14 : 21-37.

PRINGLE C.M. & A. R AMIREZ (1998): Use of both benthic and drift sampling techniques to assess tropical stream invertebrate communities along an altitudinal gradient, Costa Rica. — Freshwat. Biol. 39 : 359-373.

RAMIREZ A. & C.M. PRINGLE (2001): Spatial and temporal patterns of invertebrate drift in streams draining a neotropical landscape. — Freshwat. Biol. 46 : 47-62.

RIEMERTH A., GUSENLEITNER M. , D RAXLER G., W ANEK W. & F. SCHIEMER (2008): The role of leaf anatomy and tannins in litter decay in a tropical stream. — In this volume.

ROSEMOND A.D., P RINGLE C.M. & A. R AMIREZ (1998): Macrocon - sumer effects on detritivores and detritus processing in a tropical stream. — Freshwat. Biol. 39 : 515-523.

SCHIEMER F. & M. Z ALEWSKI (1992): The importance of riparian eco - tones for diversity and productivity of riverine fish commu - nities. — Netherlands Journal of Zoology 42 : 323-335.

TSCHELAUT J., WEISSENHOFER A. & F. S CHIEMER (2008): Macroinverte - brates and leaf litter decomposition in a neotropical low - land stream, Quebrada Negra, Costa Rica. — In this vol - ume.

VANNOTE R.L., MINSHALL G.W., CUMMINS C.W., SEDELL J.R. & C.E. CUSHING (1980): The River Continuum Concept. — Can. J. Fish. Aquat. Sci. 37 : 130-137.

WEISSENHOFER A., H UBER W., Z AMORA N., W EBER A. & J.G ONZÁLEZ (2001): A brief outline of the flora and vegetation of the Golfo Dulce Region. — Stapfia 78 : 15-24.

WINEMILLER K.O. (1990): Spatial and temporal variation in tropi - cal fish trophic networks. — Ecol. Monographs 60 : 331-367.

WINEMILLER K.O. (1991): Ecomorphological diversification of Addresses of authors: freshwater fish assemblages from five biotic regions. — Julia TSCHELAUT Ecol. Monographs 61 : 343-365. Christian PICHLER WINEMILLER K.O. & D.B. J EPSEN (1998): Effects of seasonality and Fritz SCHIEMER fish movement on tropical river food webs. — J. Fish Biol. Department of Limnology and Hydrobotany 53 : 267-296. University of Vienna WOOTTON J.T. & M.P. O EMKE (1992): Latitudinal differences in fish Althanstr. 14 community trophic structure, and the role of fish herbivory A- 1091 Vienna, Austria in a Costa Rican stream. — Env. Biol. Fish. 35 : 311-319. E-mail : [email protected] [email protected] [email protected]

Anton WEISSENHOFER Department of Palynology and Structural Botany, Faculty Center of Botany University of Vienna, Rennweg 14 A-1030 Vienna, Austria E-mail : [email protected]

453 d b . o t i n o B o i R ) d - c ( ; o r r o h C a d a r b e u Q ) b ( , a r g e N a d a r b e u Q ) a ( : 1 e t a c a l P

454 a b

c d

Plate 2 : ( a-b ) Quebrada Sardinal; ( c-d ) Rio Esquinas. 45 Contents/Indice

Prefaces and introduction — Prólogos y introducción Dr. Pedro LEON Coordinator, President Aria’s Initiative on Peace with Nature 11

O. Univ.-Prof. Dr. Georg WINKLER Rector of the University Vienna 12

Dr. Josef PÜHRINGER Governor of Upper Austria 13

Introduction Introduccíon 14

ABIOTIC ASPECTS — FACTORES ABIÓTICOS

Geography — Geografía Geography of the Golfo Dulce region (survey) Geografía de la región del Golfo Dulce (sinopsis) WEISSENHOFER A., H UBER W. & K LINGLER M. 19

Geology — Geología Outline of the geology of the Golfo Dulce Region (Costa Rica) and its surroundings in Central America (survey) Vista de conjunto de la geología de la Región del Golfo Dulce (Costa Rica) y de sus inmediaciones en América Central (sinopsis) MALZER O. & F IEBIG M. 23

Geological and mineralogical investigations of the lithologies and their weathering products in a study area south-west of the field station “La Gamba“, Golfo Dulce, Costa Rica Investigación geológica y mineralógica de las rocas y sus productos de meteorización, en un área al suroeste de la estación “La Gamba“, Golfo Dulce, Costa Rica SCHEUCHER L.E.A., V ORTISCH W. & L AGUNA -M ORALES J. 31

Anthropogenic and natural radionuclides in soil of a tropical rainforest of Southern Costa Rica Radionúclidos antropogénicos y naturales en el suelo de un bosque lluvioso tropical del sur de Costa Rica BOSSEW P., H UBMER A. & S TREBL F. 47

Climate — Clima The climate of the Esquinas rainforest (survey) El clima del bosque lluvioso Esquinas (sinopsis) WEISSENHOFER A. & H UBER W. 59 PLANT BIOLOGY — BIOLOGÍA DE PLANTAS

Ecosystems and vegetation — Ecosistemas y vegetación Ecosystem diversity in the Piedras Blancas National Park and adjacent areas (Costa Rica), with the first vegetation map of the area Diversidad de ecosistemas en el Parque Nacional Piedras Blancas y áreas adyacentes (Costa Rica), con la primera presentación de una mapa vegetacional WEISSENHOFER A., H UBER W., K OUKAL T., I MMITZER M., S CHEMBERA E., S ONTAG S., Z AMORA N. & W EBER A. 65

Plant diversity — Diversidad de plantas Plant diversity and biogeography of the Golfo Dulce region, Costa Rica (survey) Diversidad vegetal y biogeografía de la región de Golfo Dulce, Costa Rica (sinopsis) HUBER W., W EISSENHOFER A., Z AMORA N. & W EBER A. 97

Alien plants and invasion patterns in different habitats of the Golfo Dulce area, Costa Rica Plantas exóticas y patrones de invasión en diferentes hábitat del área de Golfo Dulce, Costa Rica HUBER W., W EISSENHOFER A. & E SSL F. 105

Survey of Rubiaceae in the Golfo Dulce area, Costa Rica: New species, combinations and name changes since 2001 Investigaciones en Rubiaceae en el área de Golfo Dulce, Costa Rica: nuevas especies, combinaciónes y cambios de nombre desde 2001 WILL S. & K IEHN M. 111

Medicinal plants in La Gamba and in the Esquinas rain forest Plantas medicinales en La Gamba y de la selva tropical Esquinas LÄNGER R. 121

Life forms — Formas de vida vegetal Plant life forms in the Golfo Dulce region and other neotropical rainforests (survey) Formas de vida vegetal en la región de Golfo Dulce y en otros bosques lluviosos neotropicales (sinopsis) HIETZ P. 129

Terrestrial litter trappers in the Golfo Dulce region: diversity, architecture and ecology of a poorly known group of plant specialists Plantas captadoras de hojarasca en la región de Golfo Dulce: diversidad, arquitectura y ecología de un grupo de plantas especialistas poco conocido WEISSENHOFER A., H UBER W., W ANEK W. & W EBER A. 143

Ecophysiology — Ecofisiología Primary production and nutrient cycling in lowland rainforests of the Golfo Dulce region Producción primaria y ciclo de nutrientes en bosques lluviosos de tierras bajas de la región de Golfo Dulce WANEK W., D RAGE S., H INKO N., H OFHANSL F., P ÖLZ E.-M., R ATZER A. & R ICHTER A. 155 Fungi and lichens — Hongos y líquenes Diversity and ecology of fungi in the Golfo Dulce region (survey) Diversidad y ecología de hongos en la región del Golfo Dulce (sinopsis) PIEPENBRING M. & R UIZ -B OYER A. 179

The lichens of the Golfo Dulce region (survey) Líquenes de la región de Golfo Dulce (sinopsis) BREUSS O. 193

ANIMAL BIOLOGY — BIOLOGÍA DE ANIMALES

Spiders — Arañas Cupiennius (Araneae, Ctenidae): Biology and sensory ecology of a model Spider Cupiennius (Araneae, Ctenidae): Biología y ecología sensorica de una araña modelo BARTH F.G. 211

Key to the Cupiennius (Araneae, Ctenidae) Clave de determinación de genus Cupiennius (Araneae, Ctenidae) BARTH F.G. & C ORDES D. 225

Insects — Insectos Diversity, biogeography and ecology of insects in the Pacific lowlands of Costa Rica, with emphasis on La Gamba (survey) Diversidad, biogeografía y ecología de los insectos en las tierras bajas del Pacífico de Costa Rica con énfasis en La Gamba (sinopsis) SCHULZE C.H. 229

Banderillas: Effects of deforestation on dragonflies (Insecta, Odonata) in the Pacific lowland of Costa Rica Banderillas: Efectos de la deforestación sobre libélulas (Insecta, Odonata) en la tierra baja Pacífica en Costa Rica HOFHANSL F.P. & S CHNEEWEIHS S. 237

Longhorn beetles (Coleoptera, Cerambycidae) of the Golfo Dulce region, Costa Rica Cerambícidos (Coleoptera, Cerambycidae) de la región de Golfo Dulce, Costa Rica HUBWEBER L. 249

Diversity of Euglossini (Hymenoptera, Apidae) in primary and secondary lowland rainforests in south-western Costa Rica Diversidad de Euglossini (Hymenoptera, Apidae) en bosques lluviosos de tierras bajas primarios y secundarios en el sudoeste de Costa Rica GRUBER M.H., M ORAWETZ L. & W IEMERS M. 257

Stingless bees of the Golfo Dulce region, Costa Rica (Hymenoptera, Apidae, Apinae, Meliponini) Las abejas sin aguijón de la región de Golfo Dulce, Costa Rica (Hymenoptera, Apidae, Apinae, Meliponini) JARAU S. & B ARTH F.G. 267 Butterfly diversity of the Piedras Blancas National Park and its vicinity – a preliminary assessment (: Papilionidae & Hesperioidea) Diversidad de mariposas del Parque Nacional Piedras Blancas y zonas cercanas – una evaluación preliminar (Lepidoptera: Papilionidae & Hesperioidea) WIEMERS M. & F IEDLER K. 277

Feeding behaviours of neotropical butterflies (Lepidoptera, Papilionoidea) Ingestión de alimentos en mariposas neotropicales (Lepidóptera, Papilionoidea) KRENN H.W. 295

Amphibians and reptiles — Anfibios y reptiles The amphibians and reptiles of the Golfo Dulce region (survey) Los anfibios y reptiles de la región del Golfo Dulce (sinopsis) HÖBEL G. 305

Plasticity and geographic variation in the reproductive ecology of gladiator frogs, particularly Hypsiboas rosenbergi Plasticidad y variación geográfica en la ecología reproductiva de ranas gladiadoras, especialmente Hypsiboas rosenbergi HÖBEL G. 329

Reproductive behaviour of the glass frog Hyalinobatrachium valerioi (Anura: Centrolenidae) at the tropical stream Quebrada Negra (La Gamba, Costa Rica) Comportamiento reproductivo de la rana de cristal Hyalinobatrachium valerioi (Anura: Centrolenidae) en el arroyo tropical Quebrada Negra (La Gamba, Costa Rica) VOCKENHUBER E.A., H ÖDL W. & K ARPFEN U. 335

Birds — Aves Birds of La Gamba – a call for research and scientific collaboration Aves de La Gamba – un llamado para investigación y colaboración científica AUBRECHT G. & S CHULZE C.H. 349

The birds of La Gamba (survey) Los pajaros de La Gamba (sinopsis) TEBB G. 353

Habia atrimaxillaris (Dwight & Griscom) 1924 – the black-cheeked ant-tanager. History of an endemic bird species from SW Costa Rica, from discovery to endangered status Habia atrimaxillaris (Dwight & Griscom) 1924 – tangara hormiguera cabecinegra. Historia de una especie de ave endémica del Sudoeste de Costa Rica – desde su descubrimiento a su estatus de peligro AUBRECHT G. 381

Bird assemblages of forested and human-modified countryside habitats in the Pacific lowlands of southern Costa Rica Grupos de aves de hábitat boscosos y rurales en las tierras bajas del Pacífico del sur de Costa Rica SCHULZE C.H. & R IEDL I. 395 Mammals — Mamíferos Mammals of the Piedras Blancas National Park, Costa Rica: species composition, habitat associations and efficiency of research methods – a preliminary overview (survey) Mamíferos del Parque Nacional Piedras Blancas, Costa Rica: composición de especies, asociaciones de hábitat y eficiencia de métodos de investigación – una panorámica preliminar (sinopsis) LANDMANN A., W ALDER C., V ORAUER A. & E MSER T. 409

Bats of the La Gamba region, Esquinas rain forest, Costa Rica: species diversity, guild structure and niche segregation Murciélagos de la región de La Gamba, bosque lluvioso Esquinas, Costa Rica: diversidad específica, estructura gremial y segregación de nichos LANDMANN A., W ALDER C., V ORAUER A., B OHN S. & W EINBEER M. 423

Limnology — Limnología The river network of the Piedras Blancas National Park, Costa Rica (survey) La red fluvial del Parque Nacional Piedras Blancas, Costa Rica (sinopsis) TSCHELAUT J., P ICHLER C., W EISSENHOFER A. & S CHIEMER F. 441

Macroinvertebrates and leaf litter decomposition in a neotropical lowland stream, Quebrada Negra, Costa Rica Macroinvertebrados y descomposición de residuos de hojas en un curso de agua de tierras bajas neotropical, Quebrada Negra, Costa Rica TSCHELAUT J., W EISSENHOFER A. & S CHIEMER F. 457

The role of leaf anatomy and tannins in litter decay in a tropical stream El rol de la anatomia foliar y de los tanninos en la descomposición de la hojarasca en un arroyo tropical RIEMERTH A. G USENLEITNER M. & S CHIEMER F. 467

Freshwater bryozoans in La Gamba (Costa Rica: Piedras Blancas National Park): a general introduction Briozoos de agua dulce en La Gamba (Costa Rica: Parque Nacional Piedras Blancas): una introducción WÖSS E.R. 485

Ecology of fishes of Quebrada Negra, Costa Rica, a first order neotropical lowland stream Ecología de los peces de Quebrada Negra, Costa Rica, río neotropical de primer orden de tierras bajas PICHLER C. & S CHIEMER F. 495

PLANT- INTERACTIONS — INTERACCIÓNES DE PLANTAS Y ANIMALES

Pollination — Polinización Pollination in the plants of the Golfo Dulce area (survey) Polinización en las plantas del área de Golfo Dulce (sinopsis) WEBER A. 509 Phenology and pollination of Ceiba pentandra (Bombacaceae) in the wet forest of south-eastern Costa Rica Fenología y biología de la polinización de Ceiba pentandra (Bombacaceae) en el bosque húmedo del sudeste de Costa Rica ROJAS -S ANDOVAL J., B UDDE K., F ERNÁNDEZ M., C HACÓN E., Q UESADA M. & L OBO J.A. 539

Phenology of tree species of the Osa Peninsula and Golfo Dulce region, Costa Rica Fenología de especies de árboles de la Península de Osa y la región de Golfo Dulce, Costa Rica LOBO J., A GUILAR R., C HACÓN E. & F UCHS E. 547

Style release experiments in four species of Marantaceae from the Golfo Dulce area, Costa Rica Experimentos acerca de la sensibilidad del estilo en cuatro especies de marantáceas del área del Golfo Dulce, Costa Rica CLASSEN -B OCKHOFF R. & H ELLER A. 557

Notes on the pollination of the perfume flowers of Gloxinia perennis (Gesneriaceae) by euglossine bees Notas sobre la polinización de las flores perfumadas de Gloxinia perennis (Gesneriaceae) por abejas euglossine WITSCHNIG G., H ICKL C. & W EBER A. 573

Scientific work of Austrian students in the “Austrian rainforest” (Piedras Blancas National Park, Costa Rica), with special regard to pollination studies Trabajo científico de los estudiantes en el “Bosque lluvioso de los Austriacos” (Parque Nacional Piedras Blancas, Costa Rica), con especial consideración en los estudios de polinización WEBER A. 579

Ants and plants — Hormigas y plantas A house in the tropics: full pension for ants in Piper plants Una casa en el tropico: pensión completa para hormigas en plantas de Piper FISCHER R. & M AYER V. 589

Does nectar production reduce herbivore pressure on Passiflora species (Passifloraceae) in a tropical rainforest in Costa Rica? Puede la producción de néctar reducir la presión de herbivoría en especies de Passiflora (Passifloraceae) en un bosque tropical de Costa Rica? THURNER M. & M AYER V. 599

HUMAN ASPECTS — ASPECTOS HUMANOS

History and development — Historia y desarrollo Indigenous societies of the south east of Costa Rica, 15th century Sociedades indígenas del sudeste de Costa Rica, siglo XVI BARRANTES CARTÍN C. 609

The stone balls of Palmar Las esferas de piedra de Palmar STEPHENS C. 631

8 Impacts of the United Fruit Company in Southwest Costa Rica Impacto de la United Fruit Company en el Suroeste de Costa Rica STEPHENS C. 635

Corcovado National Park – almost a banana plantation El Parque Nacional Corcovado – casi una plantación bananera STEPHENS C. 645

Case study: economic and structural settlement changes and their consequences in the community of La Gamba, Golfo Dulce region Estudio de caso: Cambios estructurales y económicos de la población y sus consecuencias en la comunidad La Gamba, región del Golfo Dulce KLINGLER M. 649

History of nature exploration — Historia de exploracíon de la naturaleza Un ejemplo de intercambio científico entre Europa y América Latina: las investigaciónes de la expedición científica Austríaca en Costa Rica (1930) An example of scientific interchange between Europe and Latin America: The investigations of the Austrian scientific expedition to Costa Rica (1930) DÍAZ BOLAÑOS R.E. 657

Otto Porsch and the scientific goals and results of the Austrian Costa Rica expedition 1930 Otto Porsch y los objetivos y resultados científicos de la expedición Austriaco-Costarricense de 1930 WEBER A. 667

History of nature conservation — Historia de protección de la naturaleza Before Corcovado: Early conservation initiatives on the Osa Peninsula (survey) Antes del Corcovado: Primeras iniciativas pro-conservación en la Peninsula de Osa (sinopsis) CHRISTEN C.A. 675

Looking back to the foundation of the Corcovado National Park, a crown jewel of nature in Costa Rica Una mirada retrospectiva a la fundación del Parque Nacional Corcovado, una corona de joyas de la naturaleza en Costa Rica UGALDE A. 683

In defence of local livelihoods, the forest and the Golfo Dulce: the campaign against ”Ston Forestal” in the 1990s and its historical roots En defens de los medios de vida locales, el bosque y el Golfo Dulce: la campaña contra Ston Forestal en los 1990 y sus raíces históricas VAN DEN HOMBERGH H. 693

Current conservation projects — Projectos actuales de protección de la naturaleza The Osa biological corridor in the context of the mesoamerican biological corridor El corredor biológico Osa en el contexto del corredor biológico mesoamericano GARCÍA R. 701

9 Conectividad entre el Parque Nacional Piedras Blancas y la Fila de Cal The link between the Piedras Blancas National Park and the Fila de Cal MORERA C. & R OMERO M. 707

The Biological Corridor Project in the Piedras Blancas National Park, Costa Rica. A project to preserve the biodiversity by reforestation and alternative culture, with support of the community La Gamba by new marketing strategies El proyecto de corredor biológico en el Parque Nacional Piedras Blancas, Costa Rica. Un proyecto para preservar la biodiversidad mediante la reforestación y cultivos alternativos, con el apoyo de la comunidad de la Gamba de nuevas estrategias de comercialización WEISSENHOFER A., B ARQUERO M., H UBER W., M AYER V. & N ÁJERA UMAÑA J. 715

Reintroducción de la Lapa Roja ( Ara macao ) en Playa San Josecito, Golfito Reintroduction of the scarlet macaw ( Ara macao ) to Playa San Josecito, Golfito VARELA BENAVIDES I. & J ANIK D. 725

The project “Rainforest of the Austrians” El proyecto “Bosque de los Austriacos” SCHNITZLER M. 733

The “Tropical Research Station La Gamba” – science, education and nature conservation in Costa Rica La “Estación Tropical La Gamba” – sciencia, educación y conservación en Costa Rica ALBERT R. & W EBER A. 739

Ecotourism and local development — Ecoturismo y desarrollo local Ecotourism in La Gamba. An economical and ecological alternative for the residents of La Gamba? Ecoturismo en La Gamba. Una alternativa económica y ecológica para los residentes de La Gamba? FAHRNBERGER M. 743

Sinergias entre ecoturismo y desarrollo local en la península de Osa, Costa Rica Synergistic effects of ecotourism and local development on the Osa Peninsula, Costa Rica MORERA C. 755

APPENDIX — APÉNDICE Authors’ addresses Direcciónes de los autores 763 Vegetation map of the Piedras Blancas Nationalpark, Golfito Forest Reserve and adjacent areas Mapa de vegetación del Parque Nacional Piedras Blancas, Reserva Forestal Golfito y áreas adyacentes

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