Revista de Biología Tropical

Flora of high mountain tropical peatlands: threats and management measures. Talamanca Range, Costa Rica

Frank González — 2025-02-06

Introduction: Tropical peatlands are highly fragile vegetal formations, especially vulnerable to anthropogenic impacts and changes in climatic conditions. Objective: To characterize the flora of the Talamanca peatlands, as well as identify their dynamics, threats, and impacts. Methods: The flora was analyzed in five peat bogs located in the Buenavista Massif, along the Inter-American Highway, at altitudes of 2 400 - 3 100 m, through field sampling. Subsequently, a Floristic Value Index (IVF) was designed to assess the state of conservation. Results: The floristic richness was determined in the peat bogs studied. A lower biological diversity was found in the three peatlands outside the state-protected natural spaces, suggesting the influence of the edge effect and agro-productive activities or their proximity to the Highway. In contrast, the Salsipuedes and Cerro Paramillo peatlands exhibited greater diversity, highlighting genera such as Blechnum, Puya, Chusquea, Myrsine and Vaccinium, in association with the bryophyte genus Sphagnum. A different floral composition was observed along the strip near the Inter-American Highway, characterized by species with lower water demand, especially genera such as Rubus and Pteridium, among others. Conclusion: From the identified floristic composition, the importance of peatlands as part of the mesoamerican hotspot ecosystems was determined, not only as repositories of biodiversity but also as sensitive indicators of human influence and environmental threats in the region associated with anthropic impact and climate change.

Growth, recruitment and life history parameters of fish in Andean reservoirs

Jorge Luis Escobar Cardona — 2025-01-28

Introduction: The formation of new anthromes such as reservoirs and dams to generate energy for human consumption, provides new environmental scenarios that condition the survival of the pre-existing fish species in the modified system.

Objective: To estimate some of the main population attributes in relation to growth and recruitment discussed in the context of the life histories of the species analyzed for a high-Andean river system.

Methods: Based on the historical sequence (2005-2017) for the seven species with the highest numerical record and frequency distributions, a typical population parameter estimation analysis was employed following the Growth Model proposed by von Bertalanffy (MCvB) and empirical equations to the respective complementary parameters.

Results: A total of 28 651 frequency lengths were analyzed, finding that those species with rapid growth and lower longevity prefer artificial lacustrine environments, species with opportunistic life history strategies (Astyanax microlepis and Roeboides dayi) and with a bimodal recruitment pattern, while species with intermediate growth were seasonal (Brycon henni y Hemibrycon caucanus), registered in tributaries to the reservoir, and in equilibrium (Andinoacara latifrons, Chaetostoma thomsoni and Coptodon rendalli) mainly associated with rivers, reservoirs, and streams or transitional environments to reservoirs.

Conclusion: The analysis of information on the population dynamics and live history of fish coexisting in a reservoir and its surrounding environments suggests a spatial segregation of fish species in response to a possible selection of their biological traits and other bioecological characteristics that sustain their local populations.

Taxonomic richness, diversity, temporal variation, and ecological aspects of fish larvae in the Gulf of Tribugá, Colombia

Mariana Rondon — 2025-01-22

Introduction: The larval phase is critical in the fish life cycle, yet knowledge of its taxonomic identification, abundance, and temporal variation remains limited in tropical coastal environments. Objective: To identify fish larvae in the Gulf of Tribugá, Northern Pacific Colombia, and assess their temporal variability considering regional oceanographic variations. Methods: We studied fish larval assemblages during the cold and warm water periods of 2022.We collected larvae through daytime and oblique tows from 20 m depth to the surface using a 70 cm mouth cylindrical-conical net with 500 µm mesh. Results: We captured a total of 602 larvae of 89 species from 29 families, with Scombridae, Engraulidae, Nomeidae, Gerreidae, Carangidae, and Engraulidae being dominant. Key species included Auxis rochei (36.32 %), Anchoa spp. (11.77 %) and Cubiceps pauciradiatus (8.10 %) during the cold period, and Eugerres lineatus (27.04 %), Eucinostomus gracilis (5.43 %), and Sphoeroides sp.1 (4.12 %) during the warm period. Differences were found in larval assemblage structure and composition between the two periods, with a species turnover rate of 66 %. Conclusions: This study reports the presence of 89 fish species’ larval stages in the Gulf of Tribugá, with each oceanographic period presenting a distinct larval assemblage.

Structure of fish communities in relation to habitat in Matusagaratí Lagoon, Darién, Panama

Samuel Valdés-Díaz — 2025-01-21

Introduction: Matusagaratí lagoon is an ecosystem with diverse habitats and environmental conditions that determine the diversity and distribution of aquatic life. Despite hydraulic connectivity, aquatic habitats generated by this diversity of environmental conditions could determine the composition and structure of fish assemblages. Objective: To understand the structure of fish community in three of these habitats. Methods: Multi-habitat sampling was conducted between March 2022 and September 2023, covering periods of drought and flooding, at 29 sites using different fishing techniques. Results: 1 913 fish from 50 species and 27 families were collected in approximately 320 km². Three fish assemblages were identified, each associated with a specific habitat. The river corridor of the Tuira River had the greatest diversity, followed by the tidal streams and lagoons. Conclusions: The analysis revealed notable differences between these habitats, with the river corridor dominated by peripheral species, while lagoons showed low diversity with generalized or hypoxia-adapted species. The presence of species such as Hoplosternum punctatum, Ageneiosus pardalis and Pimelodus punctatus in the wetland evidences the influence of the Choco region on Panama´s ichthyofauna. These findings could have important implications for the formulation of wetland conservation strategies.

Demographic variations of the spotted snapper Lutjanus guttatus (Perciformes: Lutjanidae) along the Pacific coast of Costa Rica suggest the existence of two population units

Beatriz Farías-Tafolla — 2025-02-12

Introduction: The spotted rose snapper Lutjanus guttatus is one of the commercially most important fish species in tropical and subtropical areas of the Eastern Tropical Pacific. In Costa Rica, L. guttatus is one of the main target species of the artisanal fishery; traditionally, its management has considered a single population that extends along the entire coastal zone. However, there is no evidence that there is only one population unit, which could affect the effective management of this valuable resource. Objective: Determine the population structure of L. guttatus caught on the Pacific coast of Costa Rica through demographic parameters. Methods: A total of 428 specimens, collected in different zones along the Pacific coast of Costa Rica were analyzed, including 190 males and 238 females. The size structure, total length-weight relationship, maturity stages, mean size at sexual maturity, age and growth were estimated, differentiating between the Northern, central, and Southern Pacific of Costa Rica. Results: Demographic variations were observed in size structure, total length-weight relationship, the average size of sexual maturity, and growth rates among the organisms caught in the three sampling regions. Conclusion: The demographic variations of L. guttatus in the different capture areas suggest the probable existence of two separate population units; the first corresponds to the Northern Pacific, and the second includes the central and Southern Pacific areas. The above has important implications for the management of the resource.

Protozoos and metazoos present in two wastewater treatment systems and their relationship with the Sludge Biotic Index

Margarita Loría-Naranjo — 2025-02-04

Introduction: Sludge Biotic Index (SBI) is one of the most used indices for the characterization of the community of microorganisms present in the activated sludge of wastewater treatment systems. However, this index takes into consideration only the density of the predominant functional groups of protozoa that inhabit this sludge. Objective: To evaluate whether the SBI value can be directly related to the number of protozoos and metazoos species found in the activated sludge of two wastewater treatment systems. Methods: This study was carried out on the wastewater generated by the San Vicente de Paul Hospital in Heredia Province, Costa Rica, during the months of February, March, and April 2022. Physicochemical, environmental, operational, and biological parameters were analyzed in a total of 36 samples from a Conventional activated sludge wastewater treatment system and from a Membrane Bioreactor (MBR) (n = 18 for each treatment system). Results: All the parameters evaluated are related to the abundance of microorganisms in the samples analyzed. The SBI value had an important effect on the number of organisms and can be related to the performance of the treatment system in terms of the percentage of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) removal, especially for the MBR system. Conclusions: The SBI can be improved so its calculation not only considers functional groups but also includes genus and species of protozoos and metazoos present in the activated sludge. Which in turn would refine its bioindication potential by being more specific in terms of abundance, behavior and specific requirements of each species.

Motile macroinvertebrates and fishes sheltering in burrows with and without the Indo-Pacific Rock-boring Urchin Echinometra mathaei (Camarodonta: Echinometridae), at Mana Island, Fiji

Floyd Hayes — 2025-02-13

Introduction: Sea urchins of the genus Echinometra are ecosystem engineers that burrow into lower intertidal and subtidal rocks, creating shelter for themselves and a variety of marine animals. Objective: To test the hypothesis that motile macroinvertebrates and fishes shelter proportionately more frequently in burrows with Echinometra mathaei, whose spines potentially offer additional protection, than in burrows without E. mathaei. Methods: We studied the motile macroinvertebrates and fishes sheltering in the burrows of the Indo-Pacific Rock-boring Urchin E. mathaei (Type C) at Mana Island, Fiji. Results: Burrows with E. mathaei averaged shorter in length than burrows without E. mathaei. We observed 42 motile macroinvertebrates of at least eight species and 49 fishes of at least eight species in burrows with E. mathaei (n = 1 127), and four motile macroinvertebrates of three species and one fish of one species in burrows lacking E. mathaei (n = 243). Motile macroinvertebrates occurred with statistically equal frequencies in burrows with E. mathaei (3.6 %) and in burrows without E. mathaei (2.5 %). Fishes occurred significantly more frequently in burrows with E. mathaei (4.3 %) than in burrows without E. mathaei (0.4 %). Conclusion: Fishes, but not motile macroinvertebrates, gain more protection from predators by sheltering in burrows with sea urchins, whose spines offer additional protection, than in burrows without sea urchins.

Two decades of jaguar and puma (Carnivora: Felidae) activity in lowland forest of eastern Ecuador

John Blake — 2025-02-14

Introduction: Jaguars (Panthera onca) and pumas (Puma concolor) are the two largest terrestrial predators in lowland Neotropical forests and as such, are important contributors to the ecosystem. Yet, long-term studies on their temporal and spatial patterns of occurrence are not common. Objectives: To update a previous eight year (2005-2012) camera-trap study on jaguars at Tiputini Biodiversity Station, Yasuní Biosphere Reserve, with data from 2014 through 2023; and to add complementary information on pumas. Methods: We used camera traps set along trails or at mineral licks to document the occurrence of jaguars and pumas. Individual jaguars were identified by their distinctive coat patterns. Results: Capture rates from 2014 to 2023 varied from 0 to 2.94 images/100 trap days for jaguars and from 0.46 to 4.88 for pumas. These rates were similar or increased across all years for both species. We identified 28 individual jaguars during the second sample period, including 18 males and seven females. Periods between captures ranged from 1 to 84 months, with eight individuals recorded over at least 36 months. Including images from the first period (2005-2012), when 21 individuals were identified, it is likely that ~50 individual jaguars have occurred in or close to the research station over 19 years. Jaguars were primarily active during daylight hours, while pumas were more active at night. Conclusions: TBS is embedded within a large biosphere reserve but is too small (~670 ha) to cover the home range of either species. Nonetheless, given the number of records and the fact that capture rates have not declined in the past two decades, this region is important for the conservation of these two species and the many prey they depend on.

Forest covers of the Sinú River basin (Córdoba, Colombia): evidence of tropical dry-humid transitional forests

Merly Yenedith CarrillO-Fajardo — 2025-02-13

Introduction: Dry and humid forests are among the most threatened on the planet in Colombia, they are in Critical Danger, but the status of the transitions is unknown. Objective: To establish the distribution, level of fragmentation, and floristic affinities of the transitional areas between the Tropical Dry Forest (TDF) and Tropical Wet Forest (TWF) in the climatic gradient of the Sinú River basin as a contribution to its conservation management. Methods: The Forest/Non-Forest (B/NB) layer of the study area was at a scale of 1 : 25 000 with Sentinel images (2021-2022) from Planet Scope and other sources, we identified the climatic regions, using climatic data from WorldClim 2.0 (1970-2000) and Giovanni 4.38 (2001-2021), we estimated the level of fragmentation, and we identified floristic affinities from liana sampling and a clustering analysis. Results: The basin has 462 972 ha of forests, 5 % are dry-humid transitional forests, 87 % are humid forests, 6 % are dry forests, and 2 % are mangrove forests. There are more than 1 000 ha of transitional forests in high-extreme fragmentation. The TWF has the lowest fragmentation (little-minimal) and the TDF is the most fragmented. The forested transitions of the basin are more floristically related to TDF. Conclusions: This study contributes to closing the gap in knowledge for determining the distribution patterns of transitional dry-humid tropical forests in the Sinú River basin by applying a replicable integrative methodology. These dry-humid transitional forests should be recognized as another important type of cover for the study of ecological processes under climate change scenarios. It is proposed that dry-humid forests should be included in conservation priorities in the planning and management processes of the territory at different geographic scales and management levels.

Density, size and composition of howler monkeys, Alouatta palliata (Atelidae) and white-faced monkeys, Cebus imitator (Cebidae) in dry forest and reduced canopy areas, Costa Rica

VICTORIA ANTONELLA MARTINEZ DE ZORZI — 2025-01-28

Introduction: The size, density, and composition of primate social groups are essential for understanding group dynamics and determining population management plans for primate conservation. Objective: To determine the size, density, and composition of howler monkeys (Alouatta palliata) and white-faced monkey (Cebus imitator) groups in dry forest environments and areas of reduced canopy in Palo Verde National Park, Costa Rica. Understanding how these species respond to different environments has important implications for conservation and reforestation efforts. Methods: Field sampling was carried out during February 2023 during the peak hours of primate activity (6:00-12:00 and 14:00-18:00). The individuals of both primate species were counted, recognizing the groups found in both types of environments (dry forest and reduced canopy areas). Results: Howler monkey group sizes were significantly larger in dry forests and at a higher percent of canopy cover. As for white-faced monkeys, a higher density was recorded in dry forests compared to the last census in 1987. Conclusion: Greater availability of resources (abundance of food and shelter sites) in closed environments favors the presence of a greater number of howler monkeys. Our analyses show that group size in this primate species depends on the type of environment. This study highlights the importance of long-term monitoring and studies of these parameters in wild primate groups.

Bird composition of a Neotropical city of Chiapas, México: has a metacommunity structure?

Esteban Pineda Diez de Bonilla — 2025-02-05

Introduction: The birds in tropical cities are subject to changes in community composition and structure based on landscape properties and habitat heterogeneity. Urban landscapes offer a set of fragmented habitats restricting dispersion and promoting the metacommunity structure of birds. Objective: To analyze the structure of an urban bird community with a meta-community perspective. Methods: With a spatial array of 60 bird sampling points between May 2015 and February 2016, and estimations of landscape metrics with a satellite image classification, we measured the coherence, turnover, and boundary clumping of three subsets of birds to fit a metacommunity structure pattern and correlate with landscape properties of Tuxtla Gutierrez, a neotropical city with potential for bird conservation. Results: The bird species composition comprises a dominant subset of exotic and synurbic species, another of resident abundant species, and one of rare native species. The dominant species seem to be determined by a Clementsian structure, associated with a bird community with a similar response to the environmental gradient. Both dominant and rare species showed a nested structure associated with environmental filtering processes, such as the amount of available habitat. The occurrence and distribution of abundant to rare species composition were associated with the amount of natural vegetation cover, whereas the dominant species abundance with the extension of urban coverage. Conclusions: The bird species composition in urban landscapes of tropical dry forest regions can be structured as a metacommunity in response to a gradient of vegetation fragmentation due to anthropogenic changes. Synurbic and native species do not show a homogenization of diversity composition. To ensure the conditions for bird diversity conservation in tropical urban landscapes, knowledge of the correlation of landscape elements with community structure and habitat conditions in fragmented environments is needed.

Sporogenesis and ultrastructure of spores in the fern Anemia hirsuta (Anemiaceae)

Edgar Javier Rincón-Barón — 2025-02-06

Introduction: Research into the ontogeny of sporangia and sporogenesis of leptosporangiate ferns is scarce in the scientific literature. Objectives: To describe and analyze the ontogeny of sporangia, sporogenesis, micromorphology, and ultrastructure of mature spores of the fern Anemia hirsuta. Methods: Fertile fronds of A. hirsuta were processed according to standard protocols for sectioning and embedding samples in paraffin and resin. Sections in paraffin were stained with safranin-alcian blue, Toluidine Blue, and PAS/amidoblack. Sections in resin were stained with Toluidine Blue. The samples were prepared for observation under scanning electron microscopy (SEM) to yield detailed descriptions. Mature spores were analyzed by X-ray energy dispersion (XEDS). Ultrathin sections were obtained for transmission electron microscopy (TEM) observation. Results: The entire leptosporangium is formed from a basal and an apical cell derived from a single epidermal cell of the fertile pinna. The mature leptosporangia are globose, with a subapical ring and a short pedicel. During development, the tapetum is initially cellular, and then becomes plasmodial. The sporocytes undergo simultaneous meiotic division to form tetrads of spores in a tetrahedral arrangement. The exospore is formed first, with two layers, a very thin internal layer and a thick outer layer, followed by the endospore, and finally the perispore. The spores are trilete and muriform, with simple or branched siliceous microspines. The perispore associated with the muri and grooves appears to be highly organized with evident ultrastructural differences. Conclusions: The ontogeny of the sporangia and sporogenesis of A. hirsuta is similar to that previously described for leptosporangiate ferns and recorded in some related fossil species. The highly structured and organized perispore is observed. A high silica content in the microspines of the sporodermis is herein reported for the first time in this group.

Epiphytic macrolichen as indicators of environmental changes in a montane forest of Panama

Ana Vissuetti — 2025-01-22

Introduction: Corticolous lichens are organisms that respond to habitat modifications, which is why they are considered model organisms to evaluate environmental changes in different ecosystems. Objectives: To determine the species richness and community composition of corticolous macro lichens in montane forests and forest remnants. In addition, the effect of microclimatic factors in three areas with different degrees of light intensity and density of arboreous vegetation on the species distribution of recorded diversity was evaluated. Methods: The study was conducted in the Volcan Baru National Park, Panama. Three areas with different forest densities and host tree species, Comarostaphylis arbutoides and Quercus spp., were chosen, considering a total of 60 trees, 10 of each species in each area. The canopy's opening close to the host trees and its diameter at breast height were recorded. Linear models and multivariate analysis was used to determine changes in species richness and composition of epiphytic macro lichens. Results: The characteristics of the host trees (e.g. host species and area) conditioned the species richness, while the communities were limited by microclimatic changes (e.g. light) in different areas. Conclusion: The macro lichens communities analyzed responded to changes related to the host tree species and the microclimate, so they can be considered indicators of ecological continuity in tropical montane forests.

High richness and spatio-temporal turnover of insects in urban environments: A case in a Latin American capital

Héctor Aponte — 2025-01-28

Introduction: Urban ecosystems are spaces in the city that provide ecosystem services and house a wide diversity of species. One of the key components that maintain different types of processes is insects. Objective: To characterize insect communities in four parks in a district of Lima by analyzing their composition and structure in two seasons of the year. Methods: For this evaluation, two samplings (winter and summer) were carried out using four traps (pitfall, canopy malaise, ground-level malaise, and night trap). Results: The results show a) a high richness with 191 registered morphospecies, grouped into 12 orders and 8 functional groups; b) a low similarity between parks (less than 40 % for the Jaccard index), which reveals a high spatial turnover; c) differences in community composition between winter and summer (temporal turnover), with greater richness and abundance of individuals in the warm season (139 morphospecies and 1 214 individuals, versus 105 morphospecies and 731 individuals for summer and winter respectively) and d) the variation of functional groups at both times of the year. Conclusion: The results show a high diversity and invite us to continue the study of insect diversity in urban ecosystems on a broader scale. Information Decision-makers must be considered this to implement measures that allow maintaining this richness of species in a framework where citizens can value and get benefits by the important role of these organisms in the city.

Comparative osteology of the caudal skeleton and vertebral column of the freshwater fish Tlaloc (Cyprinodontiformes: Profundulidae)

Sara E. Domínguez-Cisneros — 2025-01-22

Introduction: The family Profundulidae is a lineage of freshwater fish, with a limited geographical distribution extending from Southern Mexico to Central America, composed of two genera Profundulus and Tlaloc; the latter comprised only four species; however, studies based on the analysis of osteological characters are scarce for this family of fish. Objective: To describe the anatomy of the caudal bones and backbone of all species of the genera Tlaloc. Methods: A comparative analysis was performed on 44 cleared and stained specimens to identify the differences and similarities of backbone elements and the organization of the caudal skeleton among the species. Results: The comparison of the caudal skeleton in the species of the genus Tlaloc, revealed a very similar pattern in the morphology of the species; however, some characteristics were detected that may be useful for discrimination of species of the genus; the triangular shaped hipural plate is a characteristic that has only appeared in T. labialis, while in the rest of the species (T. candalarius, T. portillorum and T. hildebrandi), the hypural plate is fan-shaped. The total number of vertebrae, including the vertebral centrum, in the four species of the genus Tlaloc ranged from 33 to 38, of which 15-17 were abdominal vertebrae and 17-21 caudal vertebrae; T. portillorum had the lowest number of total vertebrae (33); while T. labialis had the highest number of total vertebrae (37-38) Conclusions: The consistent relationship to these skeletal elements suggests that the vertebrae and caudal fin ray count is a character of fundamental nature for the profundulid fishes, giving it particular taxonomic significance in that group.