Assessing the recovery of tropical forest communities requires metrics that capture both species composition and functional roles. While functional diversity indices are often proposed as more informative than taxonomic measures, it remains unclear which indices reliably track patterns consistent with community change during forest succession. To this end, we evaluated understory bird communities in the Chocó rainforest of northwest Ecuador, combining LiDAR‐derived forest structure measurements with species‐level functional traits, to better understand relationships between traits and diversity indices across successional habitats. We observed contrasting patterns in taxonomic and functional diversity across successional habitats. Species richness and Shannon diversity were highest in early successional habitats dominated by open canopies, and in contrast, functional dispersion and Rao's quadratic entropy were greater in secondary and old‐growth forests and associated with increases in canopy height and canopy. Functional divergence, evenness, and redundancy were also strongly associated with changes in morphological traits, such as increases in hand‐wing ratios, beak dimensions, and tarsus length, whereas functional richness was not. These patterns indicate that successional changes in bird communities were characterized less by expansion of the overall functional trait space and more by shifts in the abundance and distribution of functional traits within communities. Functional dispersion and Rao's quadratic entropy provided stronger evidence of successional changes in functional structure than richness‐based metrics, highlighting the importance of incorporating species abundances and trait distributions when assessing community reassembly. Overall, our results demonstrate that taxonomic and functional diversity can follow divergent trajectories during tropical forest succession and that selecting functional diversity metrics that capture abundance‐weighted trait structure can provide more ecologically informative assessments of community recovery in regenerating tropical forests.
Triggered by global warming there is increasing interest in understanding why conspecific populations differentiate along latitudinal gradients. Although microbiomes may shape host traits and vary geographically, how hosts differentially assemble microbiomes across latitudes and how this shapes latitudinal patterns in host trait values has been understudied. This is especially true for organisms with complex life cycles, where metamorphosis may reset the microbiome. We examined microbiome composition along a latitudinal gradient and assessed the relative influence of host and environment in shaping the microbiome of the damselfly Ischnura elegans . We sampled bacterioplankton from high‐latitude (southern Sweden) and low‐latitude (southern France) ponds, along with larval gut and adult abdominal microbiomes from I. elegans inhabiting these ponds. Additionally, we conducted a reciprocal translocation experiment in which larvae with a strongly depleted gut microbiome were transferred between three high‐ and three low‐latitude ponds, allowing microbiome reassembly from the local bacterioplankton, and quantified the growth rate of the larvae. We found latitudinal differences in bacterioplankton and host‐associated microbiomes in adults and to a lesser extent in larvae, highlighting differences in microbiome composition across the latitudinal gradient and suggesting strong environmental effects on microbiome reassembly. Moreover, despite these differences, larvae and adults shared a small proportion of their microbiome (ca 15.83%). The reciprocal translocation experiment revealed that microbiome reassembly in microbiome‐depleted larvae was primarily shaped by the local environment, rather than the host source population or latitude, underscoring the strong influence of environmental filtering in shaping microbiome composition. Moreover, phenotypic differences in larval growth rate between high‐ and low‐latitude populations disappeared after the seven‐day translocation, suggesting that local environmental conditions overruled any underlying genetic differentiation. By combining microbiome sampling across latitudes with a novel reciprocal translocation approach using microbiome‐depleted larvae, our study provides key insights into how the environment shapes host–microbiome associations along geographic gradients.
Understanding how local species richness shapes ecological interactions is key to predicting the resilience of ecological communities. However, it remains unclear whether and how increasing species richness systematically alters niche breadth and the structure of interaction networks, independent of environmental, methodological, and phylogenetic confounding effects. To address this gap, we examined how variation in frugivore species richness influences dietary niche breadth and plant–avian frugivore network organisation across six undisturbed lowland wet tropical forest sites spanning four biodiversity hotspots in south and south‐east Asia. These sites encompassed a seven‐fold gradient in frugivore richness while maintaining broadly comparable forest type and phylogenetic composition. We conducted a total of 4267 h of focal watches on 551 fruiting individuals belonging to 133 bird‐dispersed fleshy‐fruited woody plant species to record over 34 000 feeding visits by 138 avian frugivore species. Joint species distribution models, fit using the hierarchical modelling of species communities (HMSC) framework, showed that frugivore visitation was primarily structured by fruit and seed morphology, with seed size contributing to the greatest proportion of explained variation (42%), followed by fruit width (23.4%), fruit crop size (19.7%), and pulp lipid content (14.9%). Across sites, frugivores in species‐rich communities exhibited narrower dietary breadth. Correspondingly, plant–frugivore networks showed reduced connectance and nestedness and increased modularity with increasing frugivore richness. These results highlight the role of fruit and seed morphology in shaping plant–frugivore interactions and indicate that higher frugivore diversity may reduce dietary niche breadth, likely through increased interspecific competition, potentially leading to the reorganisation of mutualistic network structure. Our findings are consistent with the hypothesis that niche differentiation contributes to the organisation of ecological networks and suggest that local variation in species richness is associated with changes in the architecture of tropical plant–frugivore assemblages.
Ectoparasites temporarily or permanently feed on their hosts and, hence, they are expected to exert a direct or indirect negative impact on host condition and fitness. Here, we conducted a meta‐analysis to examine the effects of ectoparasites on fitness‐related traits of avian hosts. We compiled ~850 effect sizes from available literature reflecting interactions of diverse ectoparasite taxa with a broad spectrum of avian hosts distributed worldwide. We found evidence for complex and multifaceted negative effects of ectoparasites on bird fitness. Host condition‐related traits (e.g. haematology) were more strongly affected by ectoparasites compared to key fitness components, likely reflecting direct impact of ectoparasites on avian condition and health. In contrast, the effects of ectoparasites on avian survival and reproduction showed much greater heterogeneity, supporting strong stochasticity of associations between ectoparasitic pressure and fitness components. Finally, we found conspicuous variation in the impact of different ectoparasite groups on avian fitness, where mites, hemipteran bugs, and blowfly larvae yielded the strongest negative effects, whereas ticks, fleas, and chewing lice showed the weakest effects. We suggest that this variation may likely be driven by key life history traits and life cycles of ectoparasites. Our study builds a comprehensive framework for further ecological research on host–ectoparasite interactions, and it lays the foundation for a broader understanding of evolutionary responses of hosts to ectoparasite‐mediated selection. We also identify major gaps in our knowledge and recommend that future scientific effort focus on enhancing (the still limited) diversity of the host–ectoparasite systems under study.
