Guanacaste Conservation Area Research Articles

Effects of the aquarium fish industry in Costa Rica on populations of the Cortez rainbow wrasse Thalassoma lucasanum

Costa Rica hosts an active industry for the collection of marine ornamental reef fish that are supplied to the international aquarium fish trade. Little is known about the effects that collection activities may be having upon target species in Costa Rica, although research elsewhere gives reason for concern. Thalassoma lucasanum (Cortez rainbow wrasse) is an important species in this fishery. Costa Rican collectors prize the vibrantly colored terminal phase T. lucasanum individuals, but also collect the less dramatic initial phase T. lucasanum. We measured the density of T. lucasanum and the length of terminal phase individuals on highly collected reefs close to a fishing village and on nearby less-collected reefs located within the Guanacaste Conservation Area. Our findings show that densities of T. lucasanum were significantly lower and that terminal phase individuals were significantly smaller on the reefs near the fishing village where collection pressure was high. These findings indicate that even moderate amounts of relatively non-destructive aquarium fish extraction can negatively affect targeted populations. We present some suggestions for the reform of the aquarium reef fish industry in Costa Rica, which we believe would improve the long-term sustainability of this fishery.

Rhinoclemmysnema n. g. and three new species of nematodes of the family Atractidae (Cosmocercoidea), with notes on the helminth fauna of Rhinoclemmys pulcherrima (Testudines: Bataguridae) in Costa Rica

Rhinoclemmysnema n. g. and three new species of atractid nematodes, namely, Atractis costaricaensis n. sp., Orientatractis asymmetrica n. sp. and Rhinoclemmysnema multilabiatum were recovered from the small and large intestine of Rhinoclemmys pulcherrima, the painted wood turtle in the Guanacaste Conservation Area, Costa Rica. The genera and three species are characterized by the features of the cephalic region and male tail. Neopolystoma fentoni (conjuctival sac) and Heronimus mollis (lungs) were also collected.

Secondary Forest Detection in a Neotropical Dry Forest Landscape Using Landsat 7 ETM+ and IKONOS Imagery1

ABSTRACTWe integrate forest structure and remotely sensed data for four successional stages (pasture, early, intermediate, and late) of a tropical dry forest area located in the Sector Santa Rosa of the Guanacaste Conservation Area in northwestern Costa Rica. We used a combination of spectral vegetation indices derived from Landsat 7 ETM+ medium resolution and IKONOS high‐resolution imagery. The indices (using the red and near‐infrared bands) simple ratio and normalized difference vegetation index separated the successional stages well. Two other indices using mid‐infrared bands did not separate successional stages as well. In a comparison of the successional stages with chronological age, there was no separability in the spectral reflectance among different age classes. Successional stages, in contrast, showed distinct groups with minimal overlap. We also applied a simple validation in another dry forest located in the Palo Verde National Park in the province of Guanacaste, Costa Rica, with reasonably good results.

First record of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) in Costa Rica

A survey of entomopathogenic nematodes was conducted in the north Pacific (Guanacaste Conservation Area) and southeast Caribbean (Gandoca-Manzanillo Natural Refuge) regions of Costa Rica. Out of a total of 41 soil samples, 5 were positive for entomopathogenic nematodes (20.5%), with 3 (12.3%) containing Steinernema and 2 (8.2%) Heterorhabditis isolates. Morphological and molecular studies were undertaken to characterize these isolates. The Heterorhabditis isolates were identified as Heterorhabditis indica and the three Steinernema isolates were identified as two new undescribed species. H. indica was recovered from a coastal dry forest. Steinernema n. sp. 1 was isolated from a rainforest valley, between volcanoes. Steinernema sp. n. 2 was isolated from sand dunes in the Caribbean Coast (Punta Uva) near the rainforest strip along the coast. Although limited to two geographic regions, this study suggests entomopathogenic nematodes may be diverse and perhaps widely distributed in Costa Rica. A more intensive survey, covering all geographic regions is currently undergoing.

Effects of Forest Fragmentation and Flowering Phenology on the Reproductive Success and Mating Patterns of the Tropical Dry Forest Tree Pachira quinata

Abstract: The results of several studies suggest that forest fragmentation affects the mating patterns and reproductive success of tropical tree species by reducing pollinator activity, pollen deposition, and outcrossing levels. The flowering synchrony of trees has also been proposed as an additional factor in controlling fruit set and regulating levels of outcrossing, particularly in disturbed habitats. We examined the effects of forest fragmentation and flowering phenology on the reproductive success and genetic structure of the progeny produced by the tropical tree Pachira quinata. We conducted our study in the dry forest of Costa Rica and compared trees in two density and environmental conditions: ( 1 ) isolated trees separated by 500 m from other adult conspecifics and located in disturbed sites and ( 2 ) trees from continuous populations of groups of 20 or more reproductive individuals per hectare surrounded by undisturbed mature forest. Our study was conducted in the Guanacaste Conservation Area, Costa Rica, and surrounding areas. To evaluate flowering phenology, trees were classified as having synchronous or asynchronous flowering. The phenological stage of individuals was classified according to the proximity of the peak flowering date of each tree with respect to the mean peak flowering of the rest of the population. Six percent of the flowers produced a fruit in trees from continuous populations, whereas in isolated trees only 3% of the flowers did so. Fruit set was not affected by the flowering phenology of trees but was influenced mainly by factors associated with forest fragmentation. Seed production per fruit was not affected by forest fragmentation or flowering phenology. Overall, total fruit production per tree was not affected by forest fragmentation, because isolated trees tended to produce more flowers than trees from continuous populations. Genetic analysis revealed that the progeny of trees from continuous populations experienced lower levels of relatedness, a tendency for higher levels of outcrossing, and/or more sires than isolated trees. Our results suggest that forest fragmentation can have an effect on the mating patterns of P. quinata, reducing the number of outcross sires represented in the progeny of isolated trees.

The blood parasites of anurans from Costa Rica with reflections on the taxonomy of their trypanosomes.

During May 1997, specimens of 7 species of anurans, that included 5 Phrynohyas venulosa Laurenti, 5 Rana forreri Boulenger, 7 Rana vaillanti Brucchi, 6 Eleutherodactylus fitzingeri Schimdt, 4 Smilisca baudinii Duméril and Bibron, 1 Leptodactylus melanonotus, and 3 Bufo marinus Linneaus, from the Guanacaste Conservation Area, Costa Rica were examined for blood parasites. Their hematozoan fauna included intraerythrocytic and intraleukocytic icosahedral viruses, a rickettsia (Aegyptianella sp.), 2 species of Hepatozoon, Lankesterella minima, 2 unknown species of apicomplexans, 9 morphologically distinct types of trypanosomes, and 2 species of microfilariae. Rana vaillanti, the most aquatic species of frog, harbored the most species of parasites. Recent evidence indicates that morphological changes in the highly pleomorphic trypanosomes of anurans from different geographical regions have not kept pace with biochemical (isozyme) and molecular (DNA sequence) changes. Describing new species based solely on bloodstream trypomastigotes is discouraged. Additional criteria described herein should be applied when naming new species of anuran trypanosomes.

Neopolystoma fentoni n. sp. (Monogenea: Polystomatidae) a parasite of the conjunctival sac of freshwater turtles in Costa Rica.

Neopolystoma fentoni n. sp. is described from the conjunctival sac of Kinosternon leucostomum (Duméril, Bibron, and Duméril 1851) and Rhinoclemmys pulcherrima (Gray 1855) from the Guanacaste Conservation Area in Costa Rica. The new species differs from all other species of Neopolystoma, except N. elizabethae Platt 2000 in possessing a circle of eight genital spines that are recurved and possess a crescent-shaped base. N. fentoni n. sp. differs from N. elizabethae in lacking cecal diverticula and in a number of morphometric criteria.

The Cytosporones, New Octaketide Antibiotics Isolated from an Endophytic Fungus

[structure] Organic extracts from cultures of endophytic fungi collected in the Guanacaste Conservation Area of Costa Rica were screened for antibiotic activity. Two endophytes CR200 (Cytospora sp.) and CR146 (Diaporthe sp.) were found to have potent antibiotic activity. Bioassay-guided fractionation of the extracts from these fungi led to the identification of cytosporones D and E, antibacterial active trihydroxybenzene lactones, and three related but inactive metabolites. The five new octaketides were characterized using X-ray crystallography and NMR.

CR377, a new pentaketide antifungal agent isolated from an endophytic fungus.

Cultures of endophytic fungi collected in the Guanacaste Conservation Area of Costa Rica were screened for antifungal activity. CR377, a new pentaketide antifungal agent, was isolated from the culture broth of a fungus, CR377 (Fusarium sp.), that showed potent activity against Candida albicans in this assay. The structure of CR377 was established using 1- and 2-D NMR and HRFABMS.

Stand Characteristics and Leaf Litter Composition of a Dry Forest Hectare in Santa Rosa National Park, Costa Rica

ABSTRACTOne hectare of tropical dry forest in Guanacaste Conservation Area, Costa Rica was mapped and all trees larger than 10 cm diameter at breast height (DBH) identified. The same hectare was sampled for leaf litter and the two data sets, forest and litter, were compared. Dominant and subdominant species of the forest are represented in the leaf litter, whereas rare tree species are highly variable in their representation in the leaf litter. Relative abundance of dominant and subdominant tree species is represented well by the litter although absolute rank‐order is nor identical between source forest basal area and leaf litter mass. The litter adds a significant component to the source forest data owing to the presence of vines and lianas, and more rarely small trees or shrubs. This indicates that litter studies may be able to add depth to forest diversity surveys. The source forest also was used to test foliar physiognomic reconstructions of climate that have been proposed recently by paleobotanists as an alternative to taxonomic affinities methods. The observed climate of the area does not conform to the climatic values that were predicted by application of these new methods.RESUMENUna hectárea de bosque seco tropical en el Area de Conservación de Guanacaste, Costa Rica fue mapeada, y todos los árboles mayores de 10 cm de dap fueron identificados. En la misma hectárea, se tomaron muestras de hojarasca y los dos colecciones de datos. bosque y hojarasca, fueron comparadas. Se encontró que las especies dominantes y subdominantes del bosque estaban representadas en las muestras de hojarasca, mientras que la presencia de especias arbóreas raras en las muestras de mojarasca fue muy variable. La abundancia relativa de especies arbóreas dominantesestá bien representada en la hojarasca aunque el área basal del bosque de origen y la masa de hojarasca no heron idénticos en rangos absolutos. La hojarasca añade un componente significativo a los datos del bosque de origen debido a la presencia de bejucos y lianas en la hojarasca, y más raramente árboles pequeños y arbustos. Estos datos indican que los estudios de hojarasca pueden incrementar la precisión de las estimaciones de la diversidad de los bosques. El bosque de origen fue usado tarnbien para examinar reconstrucciones del clima basados en la fisiognomia foliar recientemenre propuesras por paleobotánicas como una alternativa a métodos de afinidad raxonómicas. El clima observado en el área no corresponde con los valores climáticos que fueron predecidos por la aplicación de estos nuevos métodos.

Blood Parasites of the Iguanid Lizard, Ctenosaura similis from Costa Rica, with a Description of Hepatozoon gamezi N. Sp.

ABSTRACT. Five species of four genera of hematozoa were observed in the blood of 15 Ctenosaura similis from the Guanacaste Conservation Area in northwestern Costa Rica. The most prevalent parasite, which occurred in all the lizards, was designated a new species, Hepatozoon gamezi, on the basis of light and electron microscopic data on its gamonts and hepatic meronts. In addition, a second species of Hepatozoon, one of Schellackia and one of Trypanosoma are described and illustrated, but not named. Microfilariae which conform with the description of Oswaldofilaria brevicaudata were recorded in 40% of the lizards. Problems in distinguishing and naming new species of certain hemoparasites solely on the basis of peripheral blood films are discussed.

Effects of root competition and canopy openness on survival and growth of tree seedlings in a tropical seasonal dry forest

The effects of seasonality, canopy openness and root competition were studied on seedling development of four canopy tree species. The study was undertaken in secondary dry forest in the Guanacaste Conservation Area, Costa Rica, with an annual rainfall of 1500 mm concentrated into a 6 month period. Four-month-old nursery-grown seedlings of Cedrela odorata, Hymenaea courbaril, Manilkara chicle and Swietenia macrophylla were planted and monitored at one deciduous and one semi-evergreen secondary forest site. Four treatments were established in a 2 × 2 factorial design, combining thinning to increase light levels at the forest floor, and trenching to reduce root competition around the planted seedlings. Seedling growth occurred only in the rainy period and mortality was low during this period. Seedling mortality was high during the dry season, particularly in the first year. Seedling survival was generally lower in the deciduous than in the semi-evergreen forest site. Root trenching increased survival in the deciduous site but had less effect in the semi-evergreen site. Seedling survival was positively related to initial seedling size. Growth was positively affected by root trenching at both sites. High light levels improved seedling growth during the wet season, but had a rather negative impact on survival during the dry season causing exacerbated desiccation for C. odorata and M. chicle, which both had higher survival in the unthinned than in the thinned treatments. Survival after 3 years was less than 3% for the former and about 10% for the latter species. Survival of H. courbaril and S. macrophylla was favoured by both thinning and trenching. H. courbaril had the highest survival of all studied species after 3 years (55%), followed by S. macrophylla (35%).

Germination and development of sown mahogany (Swietenia macrophyllaKing) in secondary tropical dry forest habitats in Costa Rica

ABSTRACTEffects of irradiance, root competition and water availability on germination and seedling establishment ofSwietenia macrophyllaKing were investigated in tropical secondary dry forests in the Guanacaste Conservation Area, Costa Rica. The fate of seeds sown in the beginning and the middle of the rainy season was studied in abandoned pasture, and in deciduous and semi-evergreen secondary forest. In the pasture, experimental treatments were mown and unmown grass. In the forest sites, thinning to increase light and trenching to reduce root competition were combined in a factorial design. Effects of moisture availability on germination were tested by supplementing natural rainfall in the initial rainy month. Germination at the beginning of the rainy season was not influenced by the supplementary water and was higher in the semi-evergreen forest than in the deciduous forest and pasture. In the forests, germination was little affected by irradiance or root competition. More seeds germinated in unmown than in mown pasture during the initial rains, but were not influenced by mowing when sown in the peak of the rainy season. Seedling mortality was low (>10%) during the initial months, but increased greatly in the dry season. Seedlings germinating early in the rainy season had a higher survival than those germinating later. The relatively slight effects of the different treatments and habitats on seedling establishment suggest that this species is rather insensitive to the large microsite variation in secondary vegetation.

Biomass Allocation by Broad-Leaf Mahogany Seedlings, Swietenia macrophylla (King), in Abandoned Pasture and Secondary Dry Forest in Guanacaste, Costa Rica

Root system development of planted and sown seedlings of Swietenia macrophylla King (broad-leaf mahogany) was studied in abandoned pasture and secondary forest in former tropical dry forest in Guanacaste Conservation Area, Costa Rica. Differences between and within secondary dry forest habitats were assumed to cause differences in biomass allocation. Biomass allocation, root/shoot (R/S) ratio, root surface area/leaf area, rooting depth and the root specialization (tap root/total root system), were measured on 5, 13, 29 and 32 month-old seedlings. The youngest seedling groups harvested had been sown directly in the field, while the two oldest age groups had been grown in a nursery and transplanted to the field at three to four months of age. The field conditions were abandoned (Hyparrhenia rufa Stapf) pasture with mown and unmown grass and semi-evergreen secondary forest with normal and with reduced root competition under both thinned and unthinned forest canopy. Seedling biomass was lower in the secondary forest than in the pasture. Biomass was higher in mown than in unmown pasture. In the secondary forest, light availability rather than reduced root competition promoted biomass investment. R/S ratio did not increase by increasing light levels in the forest. A tendency of an increase in R/S ratio and root specialization was found with increasing seedling age, suggesting the importance of uptake and storage organs.