Jordan Karubian

Less than five years remain until 2030 deadlines for the Paris Agreement, the Sustainable Development Goals, and the Global Biodiversity Framework. Yet, the gulf between lofty commitments and actual progress grows wider each year. Field stations have tremendous, largely untapped potential to turn these targets into on-the-ground achievements. This is particularly true in the tropics, where biodiversity and carbon mitigation opportunities are highest. Strengthening tropical field stations creates powerful opportunities to partner with locals, support sustainable livelihoods at the interface of wildlands and protected areas, and integrate Indigenous and traditional knowledge with scientific inquiry to develop informed conservation strategies grounded in context-specific evidence. If we invest in them now, tropical field stations can become the connective tissue between global ambition and local action, translating policy into practice. We summarize the benefits and potential of tropical field stations and recommend ways to maximize their capacity to promote inclusive, effective environmental initiatives.

Drying river networks (DRNs) are globally expanding ecosystems where hydrological intermittence, including surface-flow cessation and habitat fragmentation, profoundly shapes biodiversity, ecological functions, and biogeochemical processes. Despite growing knowledge, the role of microbial communities inhabiting periphyton in tropical DRNs remains poorly understood. Here, we conducted the first spatiotemporal metabarcoding assessment (16S & 18S V4 amplicon sequencing) of bacteria, phototrophs, and fungi in stream periphyton across the Cube Drying River Network, located in Ecuador’s Chocó–Darién biodiversity hotspot. We sampled 20 reaches spanning perennial and intermittent sites during six campaigns across an intermittence gradient. Microbial α-diversity increased with drying, peaking at the highest intermittence (45%), with phototrophs and fungi exhibiting significant gains compared to wetter phases. Community β-diversity declined as intermittence intensified, indicating homogenization of assemblages under sustained hydric stress and restricted dispersal due to disconnection of surface flow. Variation partitioning showed that major dissolved constituents (e.g., Ca²⁺, Mg²⁺, NO₃⁻, TOC) explained ~6% of compositional shifts, while environmental variables and trace elements accounted for smaller fractions. Co-occurrence network analyses revealed that interactions among microbial groups intensified with drying, culminating in highly connected yet low-modularity networks, which suggests reduced resilience under prolonged intermittence. Our results contrast with patterns reported in temperate and arid systems, where drying typically reduces microbial diversity, underscoring the particular dynamics of tropical DRNs, which are dominated by isolated pools and incomplete drying. These findings underscore the role of periphyton as critical microbial hubs that regulate ecosystem functioning under fluctuating flow regimes and emphasize the urgent need to integrate microbial dynamics into global assessments of river network resilience in the face of climate change.

Aims: Forest fragmentation induces edge effects that alter the abiotic environment and plant–enemy interactions, with potential consequences for the regeneration of shade‐tolerant species. Importantly, plant–enemy interactions are context‐dependent, suggesting that fragmentation can differentially modify natural enemy pressure along edge‐interior gradients, weakening some interactions while intensifying others. However, experiments quantifying how multiple natural enemies differentially affect seed germination and seedling establishment at forest edges versus interiors remain scarce. To provide a biotic mechanistic understanding of edge effects in plant regeneration, we experimentally evaluated how natural enemies (vertebrates, insects, and fungi) influence seed germination and seedling establishment of two shade‐tolerant palm species, Prestoea decurrens and Synechanthus warscewiczianus , in forest edges and interiors within a highly fragmented landscape. Location: Choco Forest in northwestern Ecuador. Methods: In an enemy‐exclusion experiment, we manipulated access by natural enemies using wire cages and pesticides and established control plots at 13 paired edge (0–10 m) and interior forest (90–100 m) sites. We monitored seed germination (radicle emergence) and seedling establishment (development of epicotyl and roots) weekly over 5 months. Results: Germination and establishment were consistently higher in the forest interior for both species, highlighting strong negative edge effects on early recruitment. Insects emerged as the primary natural enemies; they negatively impacted the regeneration of P. decurrens in both edge and interior habitats, whereas for S. warscewiczianus , the impact was restricted to the forest interior. Conversely, fungi and vertebrates had no detectable effects. Conclusions: Our findings demonstrate that forest edges and biotic filtering through insect predation limited the regeneration of the two understory palm species evaluated, reducing their regeneration potential in forest remnants within fragmented landscapes. Conservation strategies should prioritize maintaining interior forest conditions, minimizing edges when possible, and preventing seed and seedling damage by insects in restoration programs.

Introduction: Restoring interactions between frugivorous animals and fruiting plant species is pivotal for reestablishing community structure and ecosystem functions in recovering tropical forests. However, the reassembly of seed dispersal interactions within regenerating tropical forests remains poorly understood. Objectives: In this study, we examined changes in the structure and complexity of seed dispersal interactions and network‐level measures across varying stages of tropical forest regeneration in the Chocó Rainforest of northwestern Ecuador. Methods: Using a combination of mist‐netting and camera trap surveys, we sampled seed dispersal interactions across four regenerating forest habitats. We then used an ecological network framework to assess how network‐level metrics and interaction patterns shift across stages of forest recovery. Results: Early successional vegetation fostered high frequency and diversity of seed dispersal interactions, which decreased in more mature forests. As forests transitioned into mid‐successional stages (secondary forests), seed dispersal networks underwent major restructuring, driven by species turnover across habitats. Due to this restructuring, networks shifted from loosely connected, generalist‐dominated systems in early stages of forest succession to more specialized and modular interactions in mature forests. Conclusions: Our results demonstrate that interaction loss and replacement across regenerating forests led to the emergence of more complex and structured seed dispersal networks as forests aged, highlighting how the complexity of mutualistic interactions increases during forest regeneration.

Sexually-selected ornaments typically confer reproductive benefits, but ornamented and unornamented male phenotypes often co-occur in the same population. Reduced social costs are one potential compensatory benefit of unornamented male phenotypes, but few studies have tested this hypothesis in a natural context. Here we present a field-based experiment testing whether ornamented plumage carries social costs in the red-backed fairywren (Malurus melanocephalus), a small Australian songbird that exhibits delayed but flexible plumage maturation. Only one-quarter of one-year-old male red-backed fairywrens acquire ornamented plumage, but young ornamented males obtain greater reproductive success than males that retain brown, female-like plumage. We experimentally tested whether ornamented plumage is associated with social costs by implanting brown one-year-old males with testosterone to induce molt into ornamented plumage, then recorded the resulting social interactions. Testosterone-implanted males developed ornamentation and were chased and attacked more often by conspecific males than were control-implanted males without ornamentation, supporting the hypothesis that molt into ornamented plumage is socially costly. However, despite these apparent costs, some one-year-old males naturally acquired ornamented plumage after pairing with a female. Paired one-year-olds who naturally acquired ornamented plumage exhibited smaller home ranges than the unpaired, implanted males in their natal groups. Post-hoc simulations suggested that smaller home ranges could result in fewer interactions with neighbors, meaning smaller home ranges may reduce the social costs associated with acquiring ornamentation. We discuss the aspects of manipulating ornamentation with testosterone and suggest that our results add to growing evidence that social costs can enforce the honesty of sexually-selected ornaments.

Understanding the genetic architecture of sexually-selected traits is a fundamental goal in evolutionary biology because it can explain the constraints and processes that shape the production of these traits and emergent evolutionary processes, such as introgression. To address these topics, we leverage populations of hybridizing red-backed fairywrens (Malurus melanocephalus) that differ by plumage color (orange vs. red) across a well-classified hybrid zone with a priori evidence of strong female preference for males with redder plumage. We sequenced whole genomes of 36 individuals that vary in plumage hue and found that divergence between even the most phenotypically different individuals was very low, yet we identified several regions with high FST estimates relative to the background divergence. To determine whether loci in these elevated regions were linked to plumage variation across the species range, we sequenced top candidate genetic variants for color differentiation in 285 individuals from 16 populations and traced their frequencies across the range of the species. We found that 15% of these variants were concordant with the plumage cline, with some linked to putative carotenoid processing genes and exhibiting evidence of selection. Considered together, these findings suggest that geographic variation in the sexually-selected plumage color of male red-backed fairywrens is in part explained by adaptive introgression of genes involved in carotenoid coloration. This study highlights how genetic mechanisms underlying color variation can shape patterns of adaptive introgression via sexual selection and phenotypic differentiation in hybridizing taxa.

Habitat selection plays a fundamental role in determining community structure and species coexistence, although the role played by sexual selection in shaping settlement patterns is less well understood. Manakins (Pipridae) are a Neotropical family of lekking birds that exhibit similar behavioral ecology across species, both in terms of resource use and dependence on elaborate visual signaling for mate attraction, yet they differ in the form of their sexually selected displays and ornaments. We characterized and compared the spatial dispersion and habitat attributes of lek sites for four species of sympatric manakins in the Chocó region of northwestern Ecuador to test several hypotheses for habitat selection and lek dispersion. First, the interspecific hotspot hypothesis predicts that if males establish leks in locations where females are likely to be encountered (e.g., resource‐rich patches, topographic channels), then leks of ecologically similar species should cluster in geographic space due to shared patterns of resource use among species. Alternatively, the habitat partitioning hypothesis predicts leks of ecologically similar species to exhibit uniform spatial distributions to minimize competition for shared resources. Finally, the signal enhancement hypothesis proposes that males should establish leks in habitats with ambient light or structural properties optimal for the transmission or production of species‐specific mating signals, and thus leks of different species should segregate in environmental space. We found that leks of sympatric manakin species were randomly distributed in geographic space, inconsistent with the interspecific hotspot and habitat partitioning hypotheses. In addition, manakin species segregated in environmental space based on forest structure characteristics related to visual signaling. These findings suggest that landscape‐level lek site dispersion by sympatric manakins may be primarily influenced by sexual display optimization rather than mechanisms related to their shared ecology. Moreover, this study flags the local population of Masius chrysopterus as a potential conservation concern due to its distinct and limited elevational preferences.

Los bosques húmedos neotropicales han sufrido una intensa deforestación en las últimas décadas. Esto deriva en altas tasas de pérdida y fragmentación de hábitats que provocan disminución de poblaciones de aves y extinciones locales. La cobertura de bosques en la región sur del Chocó de Ecuador es muy baja, por lo que la recuperación y protección de bosques es una prioridad. En la actualidad existen varias iniciativas de restauración de hábitats mediante regeneración asistida, natural y productiva. La reserva de la Fundación para la Conservación de los Andes Tropicales (FCAT), establecida en 2019 en fragmentos de bosque al sureste de la Reserva Ecológica Mache Chindul, protege 670 ha de bosque primario, secundario y zonas degradadas. Desde enero de 2022 iniciamos un proyecto de regeneración en parcelas experimentales de 125 x 125 m en las cuales usamos la técnica de nucleación, con distintos diseños de siembra según las especies de árboles, distancia entre árboles, entre otras variables. En noviembre de 2022 iniciamos un monitoreo de las aves que ocupan estas parcelas. Utilizamos 12 puntos de conteo, de 10 min de duración, en los que contabilizamos todas las aves observadas y calculamos la distancia al punto de muestreo. Hemos registrado 161 especies hasta abril de 2024, la mayoría de ellas típicas de hábitats de transición entre zonas degradadas y bosques secundarios. Los objetivos actuales del muestreo son conocer la composición de la comunidad de aves en las parcelas de estudio y capacitar a dos monitores locales en la identificación y estudio de aves. Desarrollamos todos los puntos de conteo entre un investigador principal y los dos monitores con el objetivo de conseguir, en el mediano plazo, que sean ellos quienes desarrollen el estudio. Esto permitirá asegurar un monitoreo continuo y un empoderamiento local en la generación de conocimiento científico y la conservación.

Anthropogenic pressures such as hunting are increasingly driving the localised functional extinctions of large‐ and medium‐sized wildlife in tropical forests, a phenomenon broadly termed ‘defaunation’. Concurrently in these areas, smaller‐bodied species benefit from factors such as competitive release and increase in numbers. This transformation of the wildlife community can impact species interactions and ecosystem services such as seed dispersal and seed‐mediated geneflow with far‐reaching consequences. Evidence for negative genetic effects following defaunation is well‐documented in large‐seeded plants that require large frugivores for long‐distance seed dispersal. However, how defaunation affects plants with small or medium‐small seeds (< 1.5 cm), which tend to be consumed and dispersed by frugivorous mutualists of a range of body sizes and responses to anthropogenic threats, is not well understood. To better understand defaunation's impacts on tropical plant communities, we investigated spatial and genetic patterns in a hyperabundant medium‐to‐small‐seeded palm, Euterpe precatoria in three sites with different defaunation levels. Results indicate that defaunation is associated with higher fine‐scale spatial genetic structure among seedlings and increased spatial clustering within seedling cohorts and between seedlings and conspecific adults, as well as a reduction in nearest‐neighbour distances between seedlings and conspecific adults. There were no clear effects on inbreeding or genetic diversity. However, we caution these trends may indicate that defaunation reduces seed dispersal services for species previously presumed to be robust to deleterious effects of losing large frugivores by virtue of having smaller seeds and broad suites of dispersal agents, and negative downstream effects on genetic diversity could occur.

The degree to which within-population variation in sexual trait expression relates to resource heterogeneity remains poorly explored. This is particularly true in lek-mating species, where genetic explanations for male phenotypic variance and mating success are dominant. Here, we demonstrate a link between fine-scale fruit resource availability and indices of male mating success in the white-bearded manakin ( Manacus manacus ), a lek-mating frugivorous bird that produces energetically costly courtship displays. We used motion-activated camera traps to monitor male display behaviour and female visitation at male courts while concurrently conducting twice-monthly fruit surveys around courts. We observed significant variability in ripe fruit biomass among display courts and leks, and mean fruit biomass at courts significantly predicted male display rates. In turn, male display rate was the strongest predictor of female visitation to courts. Causal modelling supported the hypothesis that hyper-local fruit availability indirectly affects female visitation via its direct effects on male display rate. The demonstration that resource availability at fine spatial scales predicts display rate in a lekking organism—for which resource-related variables are typically not considered to play important roles in shaping male reproductive variance—has implications for the expression, honesty and maintenance of sexually selected traits under fluctuating ecological conditions.