Many long-term projects continue at La Selva. A selection of these projects is described in the following section.
Ants. PI: Dr. Cameron Currie (U. Wisconsin-Madison). Funding: NSF and DOE. Dr. Cameron Currie’s laboratory at the University of Wisconsin-Madison, Department of Bacteriology currently has two research projects tied to La Selva Biological Station. Zoology PhD candidate Erica Caldera is studying how population structure influences the evolution of local adaptation between microbial symbionts and their hosts, using the fungus-growing ant Apterostigma sp. as a model organism. Microbiology PhD candidate Adrián Pinto is studying the symbiotic interactions between leaf-cutting ants (Atta cephalotes) and nitrogen-fixing bacteria.
Automated Bird And Amphibian Identification. Automated remote data acquisition, analysis, and dissemination of biodiversity indicators in the context of global climate change. PIs: T. Mitchell Aide and Carlos Corrada (U. Puerto Rico). Funding: DOD Legacy, NSF – Division of Biological Infrastructure. The PIs are developing a generic system for remote automated acoustic data collection, analysis, and dissemination. To accomplish this goal, a team of students and professors in computer science and biology has been assembled to establish the Automated Remote Biodiversity Monitoring Network (ARBIMON). ARBIMON will continuously and remotely census bird and amphibian species based on sound, it will automatically identify species using machine-learning algorithms, and it will disseminate data and results in real time in a dynamic web page. The major products will include open source software (automated sound acquisition and analysis, automated data transfer, update and creation of dynamic web content, database architecture), and a publicly accessible database with all the original recordings. All products will be made available in a project web site.
Bats. Feeding ecology of Neotropical bats. PI: Christian C. Voigt (Leibniz-Institute for Zoo and Wildlife Studies), co-PI: Detlev Kelm (Leibniz-Institute for Zoo and Wildlife Studies). Funding: DFG. This multi-dimensional project focuses on two aspects of bat biology: (1) Mechanisms structuring bat assemblages and (2) physiological adaptations of phytophagous bats. Various field techniques such as radio-telemetry and fecal analysis are used in combination with lab-based stable isotope analyses. The study showed that phyllostomid bats partition the resources of the “La Selva” forest by using different forest strata, different food items and species-specific daytime roosts. The PIs also showed that nectar-feeding bats have one of the highest mass-specific field metabolic rates among mammals and that this high metabolism is fueled almost exclusively with exogenous sugars.
Bosques. Dynamics of regeneration in wet tropical secondary forests. PI: Robin Chazdon (U. Connecticut). Funding: NSF/Ecology. Since 1997, the BOSQUES project has been monitoring vegetation dynamics and ecosystem processes in six secondary forests (12-25 yr old at the start) and two old-growth stands within La Selva and the surrounding region. Although many aspects of forest structure recover rapidly within the first few decades of succession, initial site differences in species richness and composition persist despite successional changes in abundance, size distributions, growth forms, and functional groups.
Cacao. Effects of cacao removal on plant regeneration at La Selva: PI: Carol Horwitz (U. of Miami Coral Gables). Funding: various. This project has been monitoring the effects of cacao removal (from Leslie Holdridge’s original plantations) since the 1990s. The hypothesis that a cacao overstory inhibits recruitment of native trees is being tested over the past ten years of forest regeneration on plots where cacao was removed and on control plots.
The CARBONO Project: Long-term landscape-scale monitoring of tropical rain forest productivity and dynamics. P.I.s David B. Clark (University of Missouri-St. Louis) and Deborah A. Clark (UM-SL) The CARBONO Project is a long-term effort to study the effects of climate on tropical rain forest productivity and dyanmics. The project is based on a network of 18 0.5 ha annually-censused forest inventory plots in three different edaphic conditions. In addition to measuring annual growth, mortality and recruitment of all woody stems >=10 cm diameter and subplots for smaller individuals, project staff also measure bi-weekly litterfall and soil moisture and annual canopy gap formation and coarse woody debris inputs. The project began in 1997 and is on-going with support from the National Science Foundation's LTREB Program and from NASA.
Cichlid Fishes. Reproductive ecology of cichlid fishes. PI: Ronald M. Coleman (California State University, Sacramento). Funding: various, mostly self-financed. This is the field component of a larger research program examining the reproductive ecology of cichlid fishes. The goal is to understand the life history decisions cichlid fishes make when allocating resources to reproduction in general and parental care in particular. All cichlid fishes exhibit some form of post-spawning parental care. Lab and field experiments have shown a clear tradeoff between egg size and egg number (a parent can lay a few large or many small eggs); egg size directly determines hatchling size; hatchling size determines fry size; fry size determines swimming ability and swimming ability determines the locations in the river which can serve as possible nest sites. Most recently, the project has focused on how the periodicity of storms at the La Selva Biological Station (which cause water levels to rise, effectively eliminating backwaters and killing the small fry of small-egged species) set limits on when during the year the small-egged species can spawn. In other words, such species can only spawn when the probability of a large storm is low, allowing their fry enough time to grow large enough to survive the next storm. To understand these storms, temperature (5+ years) and depth (2 years) loggers have been installed to provide long-term monitoring of the Rio Puerto Viejo throughout the year. There is increased interest in the complex interactions of water sources (rain, runoff, creeks, rivers) that determine the water conditions at La Selva.
Ciclos. Study of the interrelationships among carbon, water, and nutrient cycles. PIs: Steve Oberbauer (FIU), Deborah Clark (UMSL), Deborah Lawrence (UVa), Ann Russell (ISU), David Genereux (NCSU), T. McGlynn (USD), M. L. Smith (USDA Forest Service), Nora Bynum (AMNH), Luitgard Schwendenmann (Göttingen Univ). Funding: NSF/Biocomplexity. Using ecosystem modeling, this project is testing the linkages between ecosystem carbon fluxes, watershed hydrological balances, and nutrient availability across the landscape under varying climate, including the ENSO cycle.
Dry Season. Causes and implications of dry season control of tropical wet forest tree growth at very high water levels: direct vs. indirect limitations. Steven Oberbauer (PI), Joseph O’Brien (Co-PI), Florida International University. Funding 2009-2013, NSF/Ecosystems. This project adds an additional dimension to the CARBONO project, a multi-investigator umbrella project that aims to evaluate the stocks and flows of carbon and their controls at La Selva. In this project, the PIs investigate the basis for a recent finding that the growth of tropical moist forest trees is strongly related to the strength of the dry season across a range of rainfall that by all standard measures would be considered more than sufficient for growth. Dry-season controls on tree growth could result from both direct water limitation or via other indirect mechanisms. Direct limitation via dry soil and dry air seems unlikely given the high rainfall, soil moisture, and humidity that occur during the dry season. Potential indirect mechanisms include excessive leaf temperatures lowering photosynthesis, premature leaf loss in response to dry air, low light-use efficiency and canopy photosynthesis during periods of direct sun, and changes in allocation of resources to root biomass or reproduction instead of aboveground growth. This project tests hypotheses of direct water limitation and indirect mechanisms to determine the basis for the dry season rainfall correlation with growth. Understanding the basis for this finding is crucial because tropical moist forests play important roles in the global carbon and water cycles and therefore regional and global climate. Predicted future warming and drying of tropical moist forests could have strong feedback effects on global climate.
Ecos. Effects of species on forest carbon balances. PIs: Ann Russell, Jim Raich, Bill Parton, Mike Ryan, Elizabeth Losos. Funding: NSF. Moist tropical forests have huge amounts of carbon in their biomass and soils, and high rates of productivity: tropical forest growth, disturbance, and land use therefore have potentially large impacts on atmospheric CO2 levels. Accurate modeling of carbon uptake and release by forests is essential for global-change analyses. This project makes use of replicated plantations containing four native tree species, all established in abandoned pasture in 1988, to evaluate species-level controls over whole-forest carbon cycling. By 2005, the species differed in biomass, production, and soil carbon stocks. Three key plant traits that could explain these results, and that influence ecosystem-level carbon balance, are being evaluated: 1) carbon use efficiency (CUE = production / (respiration + production); 2) partitioning among plant parts that have different CUEs (e.g., leaves, wood); and 3) tissue biochemistry, which influences carbon cycling rates.
El Mundo. Tropical plant diversity and species distributions: PI: Phil Rundel (UCLA). Funding: various. This project tests hypotheses regarding neotropical plant diversity, including a test of the mid-domain effect on species richness on an altitudinal transect in the Braulio Carrillo National Park and an investigation of the growth forms of aeroids at La Selva Biological Station.
Emballonurid Project. Vocal ontogeny and complexity in Emballonurid bats. PIs: Mirjam Knörnschild and Otto von Helversen (University Erlangen-Nuremberg). Co-PIs: Martina Nagy (University Erlangen-Nuremberg), Karla Barquero (Tirimbina Rainforest Center). Funding: German Merit Foundation, National Geographic Society. In La Selva, the sac-winged bat Saccopteryx bilineata has been the subject of detailed investigations for over 10 years, revealing a complex vocal repertoire and mating system uncommon in mammals. Since 2005, the vocal repertoire and social mating systems of four other bat species belonging to the same family (Emballonuridae: Saccopteryx leptura, Rhynchonycteris naso, Cormura brevirostris, and Peropteryx kappleri) were studied, all of which have mating systems that differ from the harem-based polygyny found in S. bilineata. Using a comparative approach, acoustic analyses are combined with behavioral observations to test two hypotheses: (1) that vocal repertoire size is dependent on the respective mating system type, with polygyny requiring a bigger vocal repertoire than monogamy due to increased male-male competition; and (2) that the occurrence of infant babbling behavior depends on the size of the species-specific vocal repertoire, with babbling being essential to acquire complex vocal repertoires.
Flora. Digitizing and development of the La Selva flora database: PI: Donald E. Stone (Duke), co-PIs: Charlotte Taylor (Missouri Botanical Garden), Nelson Zamora (INBio). Funding: NSF/BRC. This project is a floristic treatment of the 2,000+ vascular plant species of La Selva that involves digitizing images and georeferencing 22,000 specimens. It is being continually updated on its web site.
Frutos. Relations among growth, fruit and flower production, and annual weather patterns of Dipteryx panamensi, Virola sebifera and V. koschnyi trees: PI: Deedra McClearn (OTS). Funding: various. This is a long-term study of the patterns of growth and reproductive output in three species of trees with large vertebrate-dispersed fruits. Of particular interest is the trade-off between somatic growth and reproduction and how this relation may be affected by climate.
Herbivores. Diet expansions by generalist and specialist herbivores and its consequences for the structure and evolution of a plant-herbivore network. PIs: Carlos García-Robledo and Carol C. Horvitz (University of Miami). Funding: University of Miami, OTS. The interaction between plants and their insect herbivores is considered to be one of the main processes generating biodiversity. It is assumed that plant-herbivore interactions generate insect diversifications through the process of diet specialization. However, specialization alone cannot generate diversity. Recent studies suggest that insect herbivore diversification is the product of cycles of specialization at an evolutionary time scale coupled with the process of colonization of novel host plants in ecological time. Using as study model generalist and specialist rolled-leaf beetles, herbivores of neotropical Zingiberales that are expanding their diets to exotic gingers, the main objectives of this project are (1) to test whether generalist or specialist rolled-leaf beetles are more likely to expand their diets to novel host plants; (2) to determine how diet expansions affect interactions in a plant-herbivore network; and (3) determine if generalist and specialist herbivores differ in their potentials to adapt to novel host plants.
Native Tree Mixtures. Restoration of Degraded Pasturelands Using Pure and Mixed Native Tree Plantations at La Selva Biological Station, Costa Rica. PI: Florencia Montagnini (Yale University). Funding: AW Mellon Foundation, FINNIDA, Finnish Development Agency, CIFOR, Yale University. The objective of this research is to develop guidelines to design and manage tree plantations as a tool for restoration of abandoned pasturelands in the tropics. Growth, productivity, rotation times of 12 native tree species planted in pure and mixed plantation have been measured, and several publications have been written, reporting the best performing species; management guidelines (planting densities, thinning, other), and incidence of pests and diseases. Also studied were economic aspects, nutrient cycling: leaf litter, litter decomposition, superficial roots; nutrient content, and soil chemical properties from annual measurements of soils under plantations and in pasture controls. Most recent studies involve measurements of woody understory growth: abundance and richness of woody understory regeneration at 3, 7 and 15-16 years of age. Results indicated that species richness and abundance was greatest in mixed plantation plots, followed by the pure species plantations, and lowest in the control plots (no trees planted). Upcoming research at the site involves thinning/harvesting the more mature trees to release the natural regeneration developing in their understories.
Ocellated Antbirds. Benefits of cooperation in the maintenance of sociality in obligate army-ant-following birds: The case of the Ocellated Antbird. PI: Johel Chaves (Purdue University). Funding: NSF, Purdue University, OTS, American Ornithologists' Union, Cooper Ornithological Society, Sigma Xi, Idea Wild. Understanding the mechanisms that maintain sociality is a core problem in evolutionary biology. It is hypothesized that direct benefits of cooperation largely explain social living in the ocellated antbird Phaenostictus mcleannani. Ocellated antbirds congregates into groups of dozens of individuals at swarms of predatory nomadic army ants to eat the arthropods that flee from the ants. The birds are not nomadic but nomadism in the ants forces the birds to interact with members of the same species as the ants move. The project utilizes radio telemetry, field experiments and molecular markers to determine the factors that allow these birds to live in social groups. Results show that reciprocal tolerance between unrelated stable neighbors and cooperative food searching are the main factors promoting sociality in these birds.
Orugas. Caterpillars and parasitoids of a Costa Rican tropical wet forest. PI: Lee Dyer (Tulane University). Funding: NSF, National Geographic, Earthwatch Institute, personal funds. This is an ongoing project dedicated to the inventory and dissemination of information on lepidopteran larvae, their host plants, and their parasitoids. Live caterpillar specimens are collected and reared at La Selva Biological Station. The host plant, pupation and emergence dates, size and weight are recorded, along with information about parasitoids that the caterpillars may have hosted. The project goals are: (1) collect new species of Lepidoptera, and associated parasitoid Hymenoptera, Diptera, and Nemata; (2) document diversity and ecology of host plant-herbivore-parasitoid interactions; and (3) disseminate this information via Caterpillars.Org, Proyecto Orugas, and ecological publications.
Plagasus II. Survival and regeneration of natural forest in old timber tree plantations at La Selva: PIs: Elizabeth Braker and Victor Carmona (Occidental College). Funding: various. This project is extending an earlier study on herbivory of young plantation timber trees established in the early 90s at La Selva.
Plantulas. Survival and recruitment of seedlings in the primary forest: PI: Richard Kobe (Michigan State University). Funding: NSF LTREB. This project seeks to determine the patterns of recruitment and spatial distribution of seedlings of forest trees at La Selva. An additional component of the project is the development of a complete key to the seedlings of La Selva trees.
Radar. Toward Regional 3-Dimensional Tropical-Forest Structure and Biomass from Interferometric SAR: PIs: Robert Treuhaft (JPL), João Roberto dos Santos and Luciano Dutra (INPE). Funding: NASA/Terrestrial Ecology Program. This airborne radar experiment at La Selva estimated tropical forest structure in 2004, with a field campaign to measure the vertical structure of the La Selva forest vegetation in 2006. It was performed in part by Jet Propulsion Laboratory (JPL) and the California Institute of Technology. Brazil’s Instituto Nacional de Pesquisas Epsaciais (INPE) and Instituto Nacional de Pesquisas da Amazônia (INPA) are also collaborating on the project.
Roosts. Roosting ecology and seed dispersal of Neotropical bats. PI: Detlev Kelm (Leibniz-Institute for Zoo and Wildlife Studies). Funding: University of Erlangen, Bat Conservation International. Since 2000, natural and artificial diurnal bat roosts are regularly monitored for their use by bats. The focus of the project is on bat behavior and forest restoration and, thus, two aspects of bat biology are of primary interest (1) the importance of roosts in structuring bat communities; (2) the importance of roosts for bat seed dispersal. Data is being collected on species-specific roosting behavior and seed dispersal in the natural forest habitat and in disturbed, agriculturally used habitats. It is shown that artificial bat roosts can be important tools in forest restoration, because such roosts can attract bats, principal seed dispersers, to deforested areas and thus increase seed rain around roosts.
Seeds. Differential handling of palm seeds by Central American agoutis (Dasyprocta punctata; Rodentia) and collared peccaries (Tayassu tajacu; Artiodactyla) has contrasting effects on seed fates. PI: Erin K. Kuprewicz (University of Miami). Funding: OTS, University of Miami. Central American agoutis (Dasyprocta punctata) disperse seeds via scatter-hoarding whereas collared peccaries (Tayassu tajacu) consume and kill most of the seeds they find. The main goal of this study was to determine the effects that agoutis and peccaries each have on the survival of seeds and seedlings at Estación Biológica La Selva, Costa Rica. The PI tracked individual thread-marked seeds of Astrocaryum alatum, Dipteryx panamensis, Iriatrea deltoidea, and Socratea exorrhiza over 36-day periods to determine their fates. Seeds were either exposed to only agoutis and small mammals (excluding peccaries) or to all terrestrial mammals. Agouti hoards were simulated and seeds exposed to invertebrate or vertebrate seed predators for 36 days. Recently-germinated seedlings were placed in the field and their status monitored for six months.
Sensorsoft. Requirements Analysis and Prototyping of Sensor Network Software and Services: PIs: James Beach (U. Kansas), Julio Ibarra (Florida International U.). Funding: NSF/CISE. SENSORSOFT was funded in 2006 as a one-year $200K SGER award to undertake a collaborative task and requirements analysis for sensor system researchers and students at La Selva. The project will publish an analysis and deliver prototype browser applications and web services to address the research requirements and training needs of La Selva scientists and course students.
Sociality. Social behavior of Neotropical bats. PI: Christian C. Voigt (Leibniz-Institute for Zoo and Wildlife Studies), co-PI: Frieder Mayer (Natural History Museum Berlin). Funding: DFG. This project investigates the social behavior of Neotropical bats, mainly of emballonurid species such as the greater sac-winged bat (Saccopteryx bilineata). This species, which has been studied for almost 15 years at La Selva Biological Station, has a harem-polygynous mating system in which a single male defends a group of females. So-called extra-harem paternities are common in colonies of S. bilineata and female mate choice seems to have a strong influence on males' reproductive success. The most recent study shows that males form patrilines within colonies, which causes intense local mate competition.
Spatial Memory. Spatial memory and orientation in bats. PI: York Winter (Erlangen University). Funding: Volkswagen Foundation to the Zoological Institute of Munich University. Ecological neurobiology and the ecology of cognitive functions address a central theme of evolution. Evolutionary changes in organisms result from the constant interaction between the individual and its biotic and abiotic environment. The central nervous system resides at the basis of this interaction, not only for the perception of the outside world but also for the generation of biologically adequate responses. This poses the question how ecological factors influence the development of neural systems and how neural constraints influence the interaction between individual and environment. The goal of this research will be to analyze the mechanisms used by different species of nectar-feeding bats to orient between floral foods locations. This will be achieved by manipulating patterns of resource availability and simultaneously tracking the foraging movements of individual bats employing an automatic radio-telemetric technique. Additional experiments designed to elucidate the sensory cues employed will be performed in flight cages. Complementary behavioral and neurophysiological research will be carried out at Munich University, Germany, with captive individuals.
Streams. Emergent landscape patterns in stream ecosystem processes resulting from groundwater/surface water interactions: PI: Catherine Pringle, (U. Georgia), co-PIs: Frank Triska, (USGS), Alonso Ramírez (U. Puerto Rico). Funding: NSF/LTREB. This project examines how landscape patterns in stream chemistry (resulting from variation in solute-rich groundwater inputs) reflect ecosystem processes such as decomposition rates of organic material and growth rates of freshwater biota. The project has resulted in a 20+ yr dataset on stream solute chemistry which are being evaluated with respect to large-scale climatic phenomena.
Stream Wood. Wood loading in headwater neotropical forest streams. PI: Ellen Wohl, (Colorado State). Funding: NSF Hydrologic Sciences. The aim of this project is to (1) document the spatial distribution of large wood in streams of La Selva and the adjacent national park in order to examine potential controls on wood loading and distribution, and (2) monitor a subset of these sites on a regular basis in order to evaluate the relative importance of transport and decay in removing wood from streams.
TEAM. Long-term biodiversity/ecosystem process monitoring. (www.teamnetwork.org)
Funding: Conservation International – Gordon and Betty Moore Foundation.
The Volcán Barva Transect TEAM Project (VBTTP) was started in December 2003 with PIs: David B. Clark (UMSL), Robert Colwell (U. Connecticut), Jack Longino (Evergreen State College), Elizabeth Losos (OTS) and Alexandra Aparicio as site manager in the two first years. Johanna Hurtado joined the project in 2005 as site manager, and in 2009 she took over running the entire project. From the beginning the VBTTP was designed to function with local parabiologists as the main field technicians.
The TEAM project currently conducts ecological monitoring of three taxa: terrestrial vertebrates (camera trapping), vegetation measurements (within 9 1 ha plots) and Climate monitoring, covering La Selva and up the adjacent 2800m elevational gradient in Braulio Carrillo National Park. This project is part of the team network and one of the current 17 standardized TEAM sites world-wide focusing on intensive tropical ecosystem monitoring
Towers. Landscape-scale three-dimensional distribution of leaf area, photosynthesis, and respiration. PIs: Steve Oberbauer (FIU), co-PIs: David B. Clark (UMSL), Deborah A. Clark (UMSL), Mike Ryan (USFS-Ft. Collins). Funding: NSF Integrated Carbon Cycle Research Program. The TOWERS project is sampling ground to above-canopy vertical transects using a random plot design stratified by soil nutrients and slope. The objective of the TOWERS project is to determine the structure and function of forest canopy across the La Selva landscape in order to obtain estimates of nighttime respiration of tropical forest independent of eddy covariance data.
Trees. Ecology of tropical rainforest trees. PIs: Deborah Clark and David Clark (UMSL). Funding: NSF/LTREB. The TREES Project has censused annual growth and survivorship of ca. 3000 individuals of nine tree species for 23 years, generating the longest-running record of annual performance of tropical trees in the world. The first 17 years of data have been published online for public access (Clark and Clark 2000, 2006). This research has found a highly significant negative correlation between canopy tree growth and night-time temperatures, suggesting that global warming speeds up the rate of atmospheric CO2 accumulation through negative effects on tropical tree carbon balance.
Watersheds. Multi-tracer investigation of interbasin groundwater flow in the lowland rainforest. PI: David Genereux (NCSU), co-PIs: Kip Solomon (U. Utah), Neil Plummer (USGS). Funding: NSF Hydrologic Sciences. Past work at La Selva suggests that interbasin groundwater flow (IGF) beneath surface topographic divides is responsible for large inputs of water and solutes to some lowland rainforest watersheds. In this work age-dating tracers and trace gases are being used together with stable isotopes and major ions to test a conceptual hydrologic model for mixing of old regional groundwater (IGF) and much younger local groundwater in the watersheds.