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Abstract Although studies of insect decline have recently dominated headlines worldwide, their interpretation requires caution since for most species, we lack long‐term population baselines. In the tropics, where most insect species thrive, our knowledge is even more limited and so reliable insect assessments must originate from well‐established long‐term monitoring efforts. Combining the extensive monitoring data from the Arthropod Program of the Smithsonian Tropical Research Institute (STRI) on Barro Colorado Island (BCI), Panama, we compare whether known arthropod diversity can be detected through metabarcoding of bulk insect samples obtained through automatic light‐trapping. Our study detected 4402 species based on Barcode Index Numbers (BIN) and detected fine‐scale differences between wet and dry seasons and sampling localities. We further refined our analysis to indicate which families and genera explained seasonal turnover. Using samples collected in parallel, but sorted manually as part of the ongoing arthropod monitoring program, we compared these methods. Out of 538 BINs recovered through manual sorting, there was a 70% overlap with the metabarcoding data; however, it represented 30% of the total BINs detected through metabarcoding. Expecting higher detection through metabarcoding, we also compare the results with the 14 years of sampling in BCI to better understand how well the monitoring program has captured the diversity of focal groups. Our results revealed a ~50% overlap between both methods and similar total catch. Barcode Index Numbers manually detected but not recovered by metabarcoding highlight some of the limitations of molecular detection methods such as primer bias. Contrastingly, BINs detected with metabarcoding, but not recovered by the traditional monitoring scheme, highlight the importance of local and regional barcode reference libraries.

Abstract For community ecologists, “neutral or not?” is a fundamental question, and thus, rejecting neutrality is an important first step before investigating the deterministic processes underlying community dynamics. Hubbell's neutral model is an important contribution to the exploration of community dynamics, both technically and philosophically. However, the neutrality tests for this model are limited by a lack of statistical power, partly because the zero‐sum assumption of the model is unrealistic. In this study, we developed a neutrality test for local communities that implements non‐zero‐sum community dynamics and determines the number of new species (Nsp) between observations. For the non‐zero‐sum neutrality test, the model distributed the expected Nsp, as calculated by extensive simulations, which allowed us to investigate the neutrality of the observed community by comparing the observed Nsp with distributions of the expected Nsp derived from the simulations. For this comparison, we developed a new “non‐zero‐sum Nsp test,” which we validated by running multiple neutral simulations using different parameter settings. We found that the non‐zero‐sum Nsp test rejected neutrality at a near‐significance level, which justified the validity of our approach. For an empirical test, the non‐zero‐sum Nsp test was applied to real tropical tree communities in Panama and Malaysia. The non‐zero‐sum Nsp test rejected neutrality in both communities when the observation interval was long and Nsp was large. Hence, the non‐zero‐sum Nsp test is an effective way to examine neutrality and has reasonable statistical power to reject the neutral model, especially when the observed Nsp is large. This unique and simple approach is statistically powerful, even though it only employs two temporal sequences of community data. Thus, this test can be easily applied to existing datasets. In addition, application of the test will provide significant benefits for detecting changing biodiversity under climate change and anthropogenic disturbance.

Abstract Plants and pollinators are linked but their dynamics are scarcely known. Chemical monitoring of male “orchid bees” at two sites revealed 75% of species were stable or increasing. Forest bees of 33 species, with live sighting at Pipeline Road (PR), and trapping on Barro Colorado Island (BCI), included 132,000 individuals. No species or community changes occurred in strong El Niño‐Southern Oscillation (ENSO) climate events, which lasted 145 total months during more than 70 bee generations. Parasite and host bees fluctuated in unison. A few very common species, adapted to relatively disturbed habitat, diminished over time at PR, while sightings and traps revealed stable abundance ranks in Euglossa 40 years on BCI. Bee abundance and biomass were stable but 50% of species had few records. Orchid bees appear more stable in older forest, they were evidently insulated from ENSO disturbance, and probably benefit from the increasing abundance of flowering lianas and vines.

Premise: Soil microbes can influence patterns of diversity in plant communities via plant-soil feedbacks. Intraspecific plant-soil feedbacks occur when plant genotype leads to variations in soil microbial composition, resulting in differences in the performance of seedlings growing near their maternal plants versus seedlings growing near nonmaternal conspecific plants. How consistently such intraspecific plant-soil feedbacks occur in natural plant communities is unclear, especially in variable field conditions., Methods: In an in situ experiment with four native tree species on Barro Colorado Island (BCI), Panama, seedlings of each species were transplanted beneath their maternal tree or another conspecific tree in the BCI forest. Mortality and growth were assessed at the end of the wet season (~4 months post-transplant) and at the end of the experiment (~7 months post-transplant)., Results: Differences in seedling performance among field treatments were inconsistent among species and eroded over time. Effects of field environment were detected at the end of the wet season in two of the four species: Virola surinamensis seedlings had higher survival beneath their maternal tree than other conspecific trees, while seedling survival of Ormosia macrocalyx was higher under other conspecific trees. However, these differences were gone by the end of the experiment., Conclusions: Our results suggest that intraspecific plant-soil feedbacks may not be consistent in the field for tropical tree species and may have a limited role in determining seedling performance in tropical tree communities. Future studies are needed to elucidate the environmental and genetic factors that determine the incidence and direction of intraspecific plant-soil feedbacks in plant communities., (© 2024 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America.)

Premise: The specialized metabolites of plants are recognized as key chemical traits in mediating the ecology and evolution of sundry plant-biotic interactions, from pollination to seed predation. Intra- and interspecific patterns of specialized metabolite diversity have been studied extensively in leaves, but the diverse biotic interactions that contribute to specialized metabolite diversity encompass all plant organs. Focusing on two species of Psychotria shrubs, we investigated and compared patterns of specialized metabolite diversity in leaves and fruit with respect to each organ's diversity of biotic interactions., Methods: To evaluate associations between biotic interaction diversity and specialized metabolite diversity, we combined UPLC-MS metabolomic analysis of foliar and fruit specialized metabolites with existing surveys of leaf- and fruit-centered biotic interactions. We compared patterns of specialized metabolite richness and variance among vegetative and reproductive tissues, among plants, and between species., Results: In our study system, leaves interact with a far larger number of consumer species than do fruit, while fruit-centric interactions are more ecologically diverse in that they involve antagonistic and mutualistic consumers. This aspect of fruit-centric interactions was reflected in specialized metabolite richness-leaves contained more than fruit, while each organ contained over 200 organ-specific specialized metabolites. Within each species, leaf- and fruit-specialized metabolite composition varied independently of one another across individual plants. Contrasts in specialized metabolite composition were stronger between organs than between species., Conclusions: As ecologically disparate plant organs with organ-specific specialized metabolite traits, leaves and fruit can each contribute to the tremendous overall diversity of plant specialized metabolites., (© 2023 Botanical Society of America.)