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Studies of forest dynamics plots (FDPs) have revealed a variety of negative density-dependent (NDD) demographic interactions, especially among conspecific trees. These interactions can affect growth rate, recruitment and mortality, and they play a central role in the maintenance of species diversity in these complex ecosystems. Here we use an equal area annulus (EAA) point-pattern method to comprehensively analyze data from two tropical FDPs, Barro Colorado Island in Panama and Sinharaja in Sri Lanka. We show that these NDD interactions also influence the continued evolutionary diversification of even distantly related tree species in these FDPs. We examine the details of a wide range of these interactions between individual trees and the trees that surround them. All these interactions, and their cumulative effects, are strongest among conspecific focal and surrounding tree species in both FDPs. They diminish in magnitude with increasing phylogenetic distance between heterospecific focal and surrounding trees, but do not disappear or change the pattern of their dependence on size, density, frequency or physical distance even among the most distantly related trees. The phylogenetic persistence of all these effects provides evidence that interactions between tree species that share an ecosystem may continue to promote adaptive divergence even after the species' gene pools have become separated. Adaptive divergence among taxa would operate in stark contrast to an alternative possibility that has previously been suggested, that distantly related species with dispersal-limited distributions and confronted with unpredictable neighbors will tend to converge on common strategies of resource use. In addition, we have also uncovered a positive density-dependent effect: growth rates of large trees are boosted in the presence of a smaller basal area of surrounding trees. We also show that many of the NDD interactions switch sign rapidly as focal trees grow in size, and that their cumulative effect can strongly influence the distributions and species composition of the trees that surround the focal trees during the focal trees' lifetimes.

1. Nutrients are a critical resource for plant growth, but the elements limiting growth in tropical forests have rarely been determined. 2. We investigated the influence of nitrogen (N), phosphorus (P), potassium (K) and micronutrients on seedling biomass and nutrient allocation in a factorial nutrient fertilization experiment in lowland tropical forest at the Barro Colorado Nature Monument, Panama. We also measured 8 years of herbivory and growth for 1800 seedlings. We sought to determine the identity of limiting elements and possible nutrient interactions. 3. The five study species were Alseis blackiana, Desmopsis panamensis, Heisteria concinna, Sorocea affinis and Tetragastris panamensis. Plants grew in deeply shaded understorey with a mean canopy openness of 4.9% (±0.7%; 1 SE). 4. Tissue N concentration increased by 11% with N addition. Tissue P concentration increased by 16% with P addition. Tissue K increased by 4% with K addition. K addition reduced root‐to‐shoot biomass ratio. There was no significant effect of fertilization on specific leaf area or leaf area ratio. 5. The proportion of leaves damaged and the mean level of damage by herbivory increased with P and K addition and showed a significant P × K interaction. 6.7ensp;Across all species and years, relative growth rate of height increased with K addition and with N and P in combination. Relative growth rate of leaf count trended 8.5% higher with K addition (P = 0.076). 7. We also added micronutrients in a parallel experiment. There was no effect of micronutrient addition on any seedling parameter. 8. Synthesis. K addition affected seedlings by enhancing tissue nutrient concentration, increasing herbivory, reducing root‐to‐shoot biomass ratio and increasing height growth. Additional effects of N or P on tissue chemistry, herbivory and growth offer support for the multiple limiting resources hypothesis. Our results suggest that seedling growth is limited by nutrients, especially K, even under highly shaded conditions in this lowland tropical forest.

We maintained a factorial nitrogen (N), phosphorus (P), and potassium (K) addition experiment for 11 years in a humid lowland forest growing on a relatively fertile soil in Panama to evaluate potential nutrient limitation of tree growth rates, fine-litter production, and fine-root biomass. We replicated the eight factorial treatments four times using 32 plots of 40 x 40 m each. The addition of K was associated with significant decreases in stand-level fine-root biomass and, in a companion study of seedlings, decreases in allocation to roots and increases in height growth rates. The addition of K and N together was associated with significant increases in growth rates of saplings and poles (1-10 cm in diameter at breast height) and a further marginally significant decrease in stand-level fine-root biomass. The addition of P was associated with a marginally significant (P = 0.058) increase in fine-litter production that was consistent across all litter fractions. Our experiment provides evidence that N, P, and K all limit forest plants growing on a relatively fertile soil in the lowland tropics, with the strongest evidence for limitation by K among seedlings, saplings, and poles.

We conducted a literature review and added some novel observations of the natural history of the bordered patch butterfly, Chlosyne lacinia (Nymphalidae). Regarding color and patterning, C. lacinia is considered one of the most variable butterflies in the Western Hemisphere, with phenotypic variation occurring in larvae, pupae, and adults. Several studies have been conducted on C. lacinia, partly due to its notable phenotypic variation and status as a pest species of domestic sunflowers (Helianthus annuus). Even so, the origins, development, and maintenance of phenotypic variation remain poorly known. Having the most extensive geographic range of any species in its genus, C. lacinia ranges from Argentina to the mid-latitude midwestern United States. Moreover, C. lacinia displays six distinct adult morphs across its geographic range. Morphologically continuous, relatively geographically narrow gradients between adjacent morphs have given rise to alternative interpretations about subspecies. By providing the first comprehensive maps of adult morphs, including data collected via citizen science in iNaturalist, we provide directions for further research into the species' biology. Realizamos una revisión bibliográfica sobre la historia natural de la mariposa del parche bordeado, Chlosyne lacinia (Nymphalidae) que complementamos con observaciones nuevas. En cuanto al color y el patrón, C. lacinia se considera una de las mariposas más variables del hemisferio occidental, con variación fenotípica en larvas, pupas y adultos. Se han realizado numerosos estudios sobre C. lacinia, principalmente debido a su notable variación fenotípica y a su condición de especie plaga del girasol doméstico (Helianthus annuus). Aun así, el origen, desarrollo y mantenimiento de esta variación fenotípica siguen siendo poco estudiados. Teniendo la distribución geográfica más extensa de todas las especies de su género, C. lacinia se encuentra desde Argentina hasta latitudes medias del medio oeste de Estados Unidos. Además, C. lacinia presenta seis distintos morfos adultos a través de su distribución geográfica. Debido a que morfos geográficamente adyacentes presentan una morfología continua entre ellos, el reconocimiento de las subespecies es controversial. A través de mapas de distribución de cada morfo adulto con datos de iNaturalist, planteamos hipótesis y preguntas para futuras investigaciones sobre la biología de esta especie. [ABSTRACT FROM AUTHOR]