The study used an updated database of Colombian Amazonian fish occurrences compiled from museum collections and recently published records. Locality information was validated and used to assign each record to one of eight physical ecosystem categories: Andean rivers, Andean streams, foothill alluviums, major lowland rivers, floodplains, rapids, small lowland rivers and streams, and shield streams. The analysis used presence-absence data rather than abundance estimates or replicated sampling of individual geological units.

Researchers applied Jaccard dissimilarity and additive partitioning to distinguish species turnover from nestedness, then used hierarchical clustering on principal components analysis and PERMANOVA to assess compositional differences among ecosystems. They also partitioned variation among ecosystem type, spatialized ecosystems and space alone. A weighted bipartite network analysis tested whether the fish communities were more modular than expected under two randomized null models, each run 1,000 times.

Lowland major rivers and floodplains each contained 680 recorded species, the highest totals in the dataset, and lowland major rivers contained 136 unique species. Small lowland rivers and streams supported 396 species, including 84 unique species. Andean streams had the fewest total species, with 47, while shield streams had 16 and no species unique to that category in the database.

Neighbouring ecosystems had significantly less species turnover than nonadjacent ecosystems, a relationship accounting for 57% of the variation in the regression, with a p-value of 0.01. Adjacent systems also had significantly greater nestedness, for which the model reported an R-squared of 0.16 and a p-value of 0.02. A positive relationship between turnover and the number of intervening network nodes was not significant because the network provided few comparisons.

The multivariate analyses also showed substantial ecosystem-level differences. The first principal dimension in the hierarchical clustering represented 33% of the variation and principally separated Andean from lowland ecosystems, while a second dimension accounted for 17% and distinguished communities within the lowlands. PERMANOVA corroborated these differences, with a pseudo-F value of 7.99, an R value of 0.86 and a p-value below 0.01. The broad ecosystem pattern was retained when the analysis was restricted separately to Characiformes and Siluriformes, the two most diverse orders in the region.

Variation partitioning attributed 14.2% of community variation to geomorphologically defined ecosystems, 56.9% to spatialized ecosystems and 28.9% to space alone. The network was significantly modular, with a Q score of 0.31 that exceeded the 97.5% confidence limits of both null models. This analysis identified four modules: 463 species associated with major lowland rivers and floodplains; 323 associated with small lowland rivers, streams and shield streams; 71 associated with Andean rivers, Andean streams and foothill alluviums; and 48 primarily associated with rapids.

The authors interpret the results as evidence that local fish assemblages are not randomly drawn from the regional species pool. Instead, species sorting associated with geomorphology appears to act as an environmental filter, although physical and chemical conditions such as conductivity, hardness and pH may also contribute. Some species occurred across several ecosystem types, including Moenkhausia oligolepis, Astyanax maximus and Hypostomus plecostomoides. The observed structure was also consistent with the metacommunity concept, in which species from a regional pool colonize and sort among habitats.

The findings do not establish the causal mechanism behind these associations, and the analysis was not designed to estimate habitat suitability or abundance-based distribution models. The records came from varied sources rather than a standardized sampling programme, individual geological subunits were not sampled equally, and additional records or finer spatial resolution could refine the results. Shield streams were also sparsely represented, while many Amazonian areas remain unexplored and some species remain undescribed. Even with these limitations, the study identifies geomorphologically defined ecosystems as potential units for conservation and fisheries planning in a region threatened by habitat loss, overfishing, hydroelectric dams and climate change.

Subject of Research: Geomorphological structuring of fish species composition in the Colombian Western Amazon

Article Title: Fish species composition reflects geomorphology in the Western Amazon, the Earth's vertebrate biodiversity hotspot

Article References: Bogotá-Gregory, J. D., DoNascimiento, C., Lima, F. C. T., Correa, S. B., Ohyama, L., Acosta-Santos, A., Agudelo Córdoba, E., Jenkins, D. G., & Albert, J. S. (2026). Fish species composition reflects geomorphology in the Western Amazon, the Earth's vertebrate biodiversity hotspot. Frontiers of Biogeography, 19, Article e173249. https://doi.org/10.21425/fob.19.173249

Image Credits: AI Generated

DOI: 10.21425/fob.19.173249

Keywords: Western Amazon, freshwater fish, geomorphology, species composition, beta diversity, network modularity, Colombian Amazon, community assembly, environmental filtering, Fish, species, composition

The research team, working across the departments of Amazonas, Vaupés, Guainía, and Guaviare, sampled termites and ants between 2002 and 2004 using a modified transect protocol adapted for termite diversity research. At each site, collectors searched eight plots along a 250-meter transect, spending 25 minutes per plot actively excavating nests and probing feeding galleries. The cohabitation criterion was deliberately strict: ants were only recorded as cohabitants when they were observed inside galleries, chambers, or tunnels actively occupied by termites, not merely loitering on the surface. In total, 413 specimens were collected, representing 197 interacting species—110 ant species across 36 genera and 10 subfamilies, and 87 termite species across 50 genera, four families, and seven subfamilies.

When the researchers assembled these encounters into a bipartite network, with termite species on one side and ant species on the other, a distinctive architecture emerged. The network showed moderate connectance (C = 0.279), meaning only a fraction of the possible pairwise interactions actually occurred, and this value did not differ significantly from what a random null model would predict. But modularity—the degree to which species cluster into distinct subgroups that interact more among themselves than with outsiders—was significantly higher than expected by chance (Q = 0.602, p < 0.001). In other words, while any given ant-termit pairing was rare, the ones that did occur were organized into meaningful clusters rather than scattered randomly across the network.

Nestedness, by contrast, was low (NODF = 4.91) and statistically indistinguishable from random expectations, suggesting that the network lacks the hierarchical structure seen in many other mutualistic systems. At the species level, the picture was even more striking: 88.7 percent of the 283 recorded interactions occurred exclusively between a single ant species and a single termite species, with only 11.3 percent repeated more than once. This predominance of unique, species-specific encounters suggests that cohabitation in Amazonian forests is not a generalized free-for-all but a collection of highly particular associations, each shaped by the nesting habits, abundance, and behavioral ecology of the partners involved.

Certain species emerged as structural linchpins. Among ants, the predatory species Pseudoponera stigma stood out dramatically, cohabiting with 21 different termite species and acting as the network’s only hub—a role that combines high within-module connectivity (z = 2.76) with high among-module connectivity (c = 0.815). Other important ants included Pheidole cf. longiscapa, Pheidole biconstricta, Mayaponera arhuaca, and Camponotus cf. orthocephalus, along with Acropyga tricuspis and Ectatomma tuberculatum. On the termite side, Heterotermes tenuis and Nasutitermes ephratae each hosted 11 ant species, while Termes fatalis hosted 10. Termite genera such as Nasutitermes, Heterotermes, and Araujotermes emerged as key nodes, likely because their nesting habits—large aerial nests for Nasutitermes, abundant wood-dwelling chambers for Heterotermes—create stable refuges that ants can exploit.

The researchers also classified species by their topological roles using the framework of Olesen and colleagues, distinguishing peripherals, connectors, module hubs, and network hubs based on within-module degree (z) and among-module connectivity (c). Among termites, 10 species acted as connectors, including Neocapritermes braziliensis, Termes fatalis, Heterotermes tenuis, and Araujotermes parvellus, which bridged otherwise compartmentalized interaction groups. Among ants, Mayaponera arhuaca and Camponotus cf. orthocephalus served as module hubs, while Pseudoponera stigma was the sole network hub. Notably, 31 termite species and 54 ant species were recorded interacting with only a single partner, underscoring how much of the network consists of peripheral, one-off associations rather than broad, generalized relationships.

When the networks were stratified by forest type and conservation status, clear differences appeared. Primary forests—those never subjected to anthropogenic disturbance—supported more complex networks with a greater number of connector species. In primary forest networks, Pseudoponera stigma acted as a connector and Acropyga tricuspis as a network hub, while eight ant species showed high cross-module connectivity. In secondary forests, by contrast, no species functioned as a network hub, all termite species were peripheral, and only two ant species—Pseudoponera stigma and Hypoponera sp. 3—acted as connectors. Modularity was significantly higher than expected in both primary (Q = 0.66, p < 0.001) and secondary forests (Q = 0.79, p < 0.001), but the structural richness differed markedly, with primary forests hosting more intricate cohabitation arrangements.

The comparison between terra-firme and seasonally flooded forests revealed another layer of complexity. Terra-firme forests showed significantly higher modularity than expected (Q = 0.667, p < 0.001), while seasonally flooded forests showed a slightly elevated but statistically non-significant modularity (Q = 0.729, p = 0.10). Interestingly, despite the fact that periodic flooding restricts termite nest establishment in lowland várzea forests, seasonally flooded primary forests exhibited the highest median number of cohabitation events per site. The researchers suggest this paradox may reflect the dynamics described by Pringle and colleagues: while flooding reduces ground-level ant diversity, arboreal ants such as Azteca, Crematogaster, Camponotus, and Pseudomyrmex thrive above the waterline and increasingly exploit available termite nests as refuges when ground-level nesting is limited.

Substrate type also shaped the cohabitation landscape. Wood-based nests—dry, minimally decomposed pieces—supported the highest diversity of cohabiting ant genera, accounting for 47 percent of associations, surpassing the more conspicuous epigeal and arboreal mounds that have traditionally dominated cohabitation studies. Ant genera such as Pheidole, Crematogaster, Camponotus, and Pseudoponera were associated with multiple substrate types, suggesting generalist nesting behavior, while soil-associated genera like Octostruma, Acanthostichus, and Pachycondyla showed more specialized preferences. The hyperdiverse genus Pheidole was recorded across all substrate types, demonstrating the broadest ecological amplitude. A PERMANOVA confirmed that ant assemblages differed significantly across nesting substrates (F = 6.869, R² = 0.47, p = 0.001), with aerial and epigeal substrates supporting more distinct associations than soil or wood.

Trophic guild composition added yet another dimension. Out of 50 termite genera, 60 percent were primarily associated with omnivorous ants, 34 percent with predatory ants, and only 6 percent with herbivorous ants. A PERMANOVA confirmed that termite genera differed significantly in their interaction profiles across dominant ant guilds (F = 12.776, R² = 0.35, p < 0.001), with the first two principal components explaining 91.8 percent of the variation. Genera such as Acorhinotermes, Nasutitermes, Aparatermes, and Neocapritermes showed broad interaction profiles across guilds, while most others displayed more specific affinities. These patterns suggest that the trophic identity of ants plays a structuring role in cohabitation networks beyond termite taxonomy alone, hinting at ecological mechanisms—predation pressure, nutrient exchange, or defensive mutualism—that may underlie these associations.

The study’s authors frame their work as addressing what ecologists call the Eltonian shortfall: the persistent lack of information on species interactions and their functional roles within ecosystems. While taxonomic and distributional gaps have historically dominated biodiversity research, understanding biotic interactions remains a critical and often neglected frontier, particularly in hyperdiverse regions like the Neotropics. By documenting termite-ant cohabitation across multiple forest coverages and nesting substrates, this study provides a rare quantitative window into a cryptic ecological system that has been largely overlooked, revealing that even the most inconspicuous nest-sharing arrangements carry measurable structural signatures.

The implications for conservation are direct. Primary forests, with their greater structural complexity and diversity of nesting substrates, consistently supported more intricate cohabitation networks than secondary forests undergoing succession after logging, agricultural expansion, or cattle ranching. As deforestation pressures intensify across the Amazon frontier, the loss of structurally complex habitats may erode not only species diversity but also the interaction networks that bind communities together. The researchers acknowledge that standardized sampling protocols, constrained by excavation depth and search time, may underestimate the full frequency of rare or transient cohabitation events, and that the high proportion of one-to-one interactions may have inflated modularity estimates in sparse networks. Even so, the consistent patterns across forest types, substrates, and trophic guilds point to a system shaped by real ecological processes rather than mere spatial coincidence—processes that depend on preserving the structural richness of primary forests if these hidden partnerships are to persist.

Subject of Research: Termite-ant cohabitation networks in Amazonian forests

Article Title: Cohabitation networks: exploring how termites and ants share nests in Amazonian forests

Article References: Castro, D., & Fernández, F. (2025). Cohabitation networks: exploring how termites and ants share nests in Amazonian forests. Neotropical Biology and Conservation, 20(3), 221-246. https://doi.org/10.3897/neotropical.20.e154485

Image Credits: AI Generated

DOI: 10.3897/neotropical.20.e154485

Keywords: termites, ants, cohabitation networks, Colombian Amazon, forest conservation, ecological interactions, Cohabitation, networks, exploring, share, nests, Amazonian

The research team, led by Yesika Natali Fernández-Ortiz of the Institute of Public Health at Pontificia Universidad Javeriana in Bogotá, used a concurrent mixed-methods design that combined a structured household survey with ethnographic fieldwork. In 2022, six surveyors recruited from within the community, selected by traditional authorities and trained by the researchers, administered questionnaires to 819 individuals across 161 households, a participation rate of 78.1 percent of the total population of 1,049. Because internet connectivity in the region is limited, the surveyors used mobile devices equipped with offline software and GPS devices to record household locations. Interviews were conducted in Spanish and, where necessary, in Tikuna, the community’s own language. The team also carried out two field stays during 2022, one in the rainy season and one in the dry season, conducting fourteen semi-structured interviews with healers, midwives, community leaders, teachers, and health professionals, alongside participant observation and a social cartography workshop.

The technical findings reveal a health system that exists mostly on paper for the Arara. Although 97.9 percent of respondents were formally affiliated with Colombia’s General System of Social Security in Health, actual use of Western services was low. The nearest hospital with primary care capacity lies in Leticia, roughly 20 kilometers away by boat, and 97.3 percent of respondents who did receive institutional care had to travel there to get it. Departmental data show that Amazonas has 12 service sites, 137 beds, and just two mobile units for a vast, river-dispersed territory, with no public ambulances recorded in the dataset and a workforce skewed toward generalists rather than specialists. Sixteen percent of respondents said they would not seek Western care even for serious health problems, and only 10.6 percent attended routine medical appointments or check-ups.

What the numbers describe, the qualitative accounts explain. Traditional healers in Arara do far more than treat symptoms; they maintain what the community understands as balance between territory, spirits, and people. Their treatments include medicinal plant infusions and baths, prayers, smoke rituals, dietary restrictions, spiritual dances, and cleansing of the surrounding environment. Illness itself is categorized differently than in biomedicine. Alongside headaches, which 35.3 percent of respondents reported, and respiratory infections at 19.8 percent, the community recognizes conditions with spiritual origins, including spiritual harm or bewitchment, a condition called pecho abierto or open chest, and pérdida del cigarrillo, the loss of a baby’s spiritual protection after a fall or shock. A former Curaca, a traditional Magüta authority, told the researchers that the elders’ remedy was always found within the community, not in the city.

The survey also mapped the social architecture of traditional medicine, and it turned out to be gendered in unexpected ways. Among respondents aged 14 and older, 94 percent attributed importance to traditional healers and midwives, with no statistically significant difference between women and men. But participation in the traditional system followed distinct gendered patterns: 12.1 percent of women identified as midwives compared with 2.1 percent of men, and women were also more likely to be apprentice midwives, while men predominated as prayer healers and showed a non-significant tendency toward bonesetting. Education mattered too. Individuals with higher educational attainment were more likely to resort to pharmacies or self-care, whereas use of both health institutions and traditional healers was more frequent among those with lower educational levels, a counterintuitive pattern that suggests Western schooling does not simply displace traditional health beliefs.

Then came COVID-19, and the community’s response became a natural experiment in medical pluralism. Traditional healers interpreted the virus’s arrival through dreams, receiving a vision that the virus was destined mainly for whites or settlers and would not seriously affect Indigenous peoples, a reading that shaped early perceptions of the threat. Yet the community did not reject biomedical prevention outright. Among residents aged 12 and over, 76.9 percent wore face masks in public, 63.5 percent practiced regular hand washing, and 47.8 percent followed quarantine measures. These were layered with traditional practices: 23.5 percent used herbal remedies, 19.7 percent used vapor treatments with medicinal plants, and 14.9 percent observed community diets, collective restrictions that suspended dances and football matches and closed the community to outsiders. One traditional medical leader described the settlement filled with incense smoke that protected those inside it.

Treatment patterns during the pandemic confirmed where trust lay. Of the 223 people who reported having contracted COVID-19, 80.3 percent identified the illness through symptoms alone, without laboratory testing, and about 80 percent refused diagnostic tests when health workers went house to house, with some believing the tests themselves could transmit the virus. Among the infected, 40.8 percent relied exclusively on traditional healers, 36.8 percent combined traditional medicine with support from family and friends, and only 5.4 percent used treatments based solely on Western medicine. Hospitals were perceived as places of death rather than healing, with one community leader stating bluntly that intubation was what killed patients. Vaccination revealed a more negotiated picture: 87.2 percent of the population received at least one vaccine dose, but only 70.8 percent completed the full schedule, as fears circulated on WhatsApp that the vaccine contained a chip or could transform people into animals, and traditional authorities recommended limiting the number of doses.

The researchers are careful about what these findings do and do not show. They document meanings, preferences, and constraints rather than a fully developed service-level integration between the two systems. High formal affiliation with the Colombian health system, they conclude, does not translate into trust or routine use of biomedical services. The authors trace this mistrust to a longer colonial and postcolonial history in which official systems privileged biomedicine as modern and scientific while Indigenous knowledge was stigmatized as backward. Colombian law, including Law 21 of 1991 ratifying ILO Convention 169, formally recognizes Indigenous medical practices, and initiatives such as the Indigenous and Intercultural Health System, SISPI, aim to articulate them with the national system, but structural barriers, institutional racism, and mutual distrust have kept these efforts largely normative rather than operational.

What emerges instead is what medical anthropologists call intermedicality: a selective, negotiated, community-mediated relationship between therapeutic systems rather than a binary choice. The Arara did not treat biomedical care, home remedies, and ritual practice as mutually exclusive; they combined them according to the meaning of the illness, the perceived appropriate response, and the practical conditions of access and trust. Crucially, Indigenous authorities acted as gatekeepers and mediators, determining when public health measures became acceptable and when vaccination teams could enter the community. This suggests that vaccine hesitancy in Indigenous settings cannot be reduced to misinformation alone; it is also bound up with cultural autonomy, historical grievances, and the legitimacy of outside intervention.

The study’s implications are direct. The authors argue that intercultural health must be understood not as an abstract principle but as a lived practice grounded in respect, negotiation, and genuine recognition of Indigenous knowledge. That would mean health services that are not only geographically accessible but capable of engaging with local understandings of illness and community authority, stronger local primary care capacity, better communication between traditional leaders and health institutions, and training that prepares health professionals to work respectfully within Indigenous realities. The researchers also acknowledge limitations: the survey instrument was adapted from tools designed for a mestizo-Western population, the qualitative component relied on a small number of interviews, and the study captured community perspectives far more deeply than those of health providers. Even so, the Arara case delivers a clear message to global public health: in Indigenous territories, formal coverage on paper means little without trust, and trust is built through the community’s own authorities, not around them.

Subject of Research: The interaction and coexistence of traditional and Western medicine in an Indigenous Tikuna community in the Colombian Amazon, including health-seeking behavior and responses to COVID-19.

Article Title: Integration of traditional and Western medicine in the Arara community, Colombian Amazon

Article References: Fernández-Ortiz, Y. N., Amaya-Lara, J. L., Ariza-Ruiz, L. K., Barrera-Aguilera, D. C., Vivas-Sánchez, P., & Mejía-Rocha, M. M. (2026). Integration of traditional and Western medicine in the Arara community, Colombian Amazon. Discover Social Science and Health, 6(1), Article 96. https://doi.org/10.1007/s44155-026-00428-0

Image Credits: AI Generated

DOI: 10.1007/s44155-026-00428-0

Keywords: traditional medicine, Western medicine, Indigenous health, Colombian Amazon, Tikuna, COVID-19, vaccination, intercultural health, medical pluralism, health-seeking behavior, medical anthropology, public health policy