Connectivity Explains Local Ant Community Structure in A Neotropical Forest Canopy: A Large‐Scale Experimental Approach

Understanding how habitat structure and resource availability affect local species distributions is a key goal of community ecology. Where habitats occur as a mosaic, variation in connectivity among patches influences both local species richness and composition, and connectivity is a key conservation concern in fragmented landscapes. Similarly, availability of limiting resources frequently determines species coexistence or exclusion. For primarily cursorial arthropods like ants, gaps between neighboring trees are a significant barrier to movement through the forest canopy. Competition for limited resources such as nest sites also promotes antagonistic interactions. Lianas (woody vines) connect normally isolated neighboring tree crowns and often have hollow stems inhabited by ants. We used two large‐scale liana‐removal experiments to determine how connectivity and nest site availability provided by lianas affect arboreal ant species richness, species composition, and β‐diversity in a lowland tropical forest in Panama. Removing lianas from a tree crown reduced ant species richness up to 35%, and disproportionately affected species that require large foraging areas. Adding artificial connectivity to trees mitigated the effects of liana removal. Ant colonization of artificial nests was higher (73% occupied) in trees without lianas vs. trees with lianas (28% occupied). However, artificial nests typically were colonized by existing polydomous, resident ant species. As a result, nest addition did not affect ant community structure. Collectively, these results indicate that lianas are important to the maintenance of arboreal ant diversity specifically by providing connectivity among neighboring tree crowns. Anticipated increases in liana abundance in this forest could increase the local (tree‐level) species richness of arboreal ants, with a compositional bias toward elevating the density of broad‐ranging specialist predators

Effects of Lightning on Trees: A Predictive Model Based on in situ Electrical Resistivity

The effects of lightning on trees range from catastrophic death to the absence of observable damage. Such differences may be predictable among tree species, and more generally among plant life history strategies and growth forms. We used field‐collected electrical resistivity data in temperate and tropical forests to model how the distribution of power from a lightning discharge varies with tree size and identity, and with the presence of lianas. Estimated heating density (heat generated per volume of tree tissue) and maximum power (maximum rate of heating) from a standardized lightning discharge differed 300% among tree species. Tree size and morphology also were important; the heating density of a hypothetical 10 m tall Alseis blackiana was 49 times greater than for a 30 m tall conspecific, and 127 times greater than for a 30 m tall Dipteryx panamensis. Lianas may protect trees from lightning by conducting electric current; estimated heating and maximum power were reduced by 60% (±7.1%) for trees with one liana and by 87% (±4.0%) for trees with three lianas. This study provides the first quantitative mechanism describing how differences among trees can influence lightning–tree interactions, and how lianas can serve as natural lightning rods for trees

Do Lianas Shape Ant Communities in An Early Successional Tropical Forest?

Almost half of lowland tropical forests are at various stages of regeneration following deforestation or fragmentation. Changes in tree communities along successional gradients have predictable bottom‐up effects on consumers. Liana (woody vine) assemblages also change with succession, but their effects on animal succession remain unexplored. Here we used a large‐scale liana removal experiment across a forest successional chronosequence (7–31 years) to determine the importance of lianas to ant community structure. We conducted 1,088 surveys of ants foraging on and living in trees using tree trunk baiting and hand‐collecting techniques at 34 paired forest plots, half of which had all lianas removed. Ant species composition, β‐diversity, and species richness were not affected by liana removal; however, ant species co‐occurrence (the coexistence of two or more species in a single tree) was more frequent in control plots, where lianas were present, versus removal plots. Forest stand age had a larger effect on ant community structure than the presence of lianas. Mean ant species richness in a forest plot increased by ca. 10% with increasing forest age across the 31‐year chronosequence. Ant surveys from forest \u3e20 years old included more canopy specialists and fewer ground‐nesting ant species versus those from forestsConsequently, lianas had a minimal effect on arboreal ant communities in this early successional forest, where rapidly changing tree community structure was more important to ant species richness and composition

Microsatellite data suggest significant population structure and differentiation within the malaria vector Anopheles darlingi in Central and South America

Background: Anopheles darlingi is the most important malaria vector in the Neotropics. An understanding of A. darlingi's population structure and contemporary gene flow patterns is necessary if vector populations are to be successfully controlled. We assessed population genetic structure and levels of differentiation based on 1,376 samples from 31 localities throughout the Peruvian and Brazilian Amazon and Central America using 5-8 microsatellite loci.Results: We found high levels of polymorphism for all of the Amazonian populations (mean R-S = 7.62, mean H-O = 0.742), and low levels for the Belize and Guatemalan populations (mean R-S = 4.3, mean H-O = 0.457). The Bayesian clustering analysis revealed five population clusters: northeastern Amazonian Brazil, southeastern and central Amazonian Brazil, western and central Amazonian Brazil, Peruvian Amazon, and the Central American populations. Within Central America there was low nonsignificant differentiation, except for between the populations separated by the Maya Mountains. Within Amazonia there was a moderate level of significant differentiation attributed to isolation by distance. Within Peru there was no significant population structure and low differentiation, and some evidence of a population expansion. The pairwise estimates of genetic differentiation between Central America and Amazonian populations were all very high and highly significant (F-ST = 0.1859-0.3901, P < 0.05). Both the D-A and F-ST distance-based trees illustrated the main division to be between Central America and Amazonia.Conclusion: We detected a large amount of population structure in Amazonia, with three population clusters within Brazil and one including the Peru populations. The considerable differences in N-e among the populations may have contributed to the observed genetic differentiation. All of the data suggest that the primary division within A. darlingi corresponds to two white gene genotypes between Amazonia (genotype 1) and Central America, parts of Colombia and Venezuela (genotype 2), and are in agreement with previously published mitochondrial COI gene sequences interpreted as incipient species. Overall, it appears that two main factors have contributed to the genetic differentiation between the population clusters: physical distance between the populations and the differences in effective population sizes among the subpopulations

The Geographic Distribution of Parasite-Induced Fruit Mimicry in Cephalotes atratus (Formicidae: Myrmicinae)

Parasite distributions fundamentally depend on the distributions of their hosts but may be more restricted than their hosts. Host-parasite symbioses tend to be spatially aggregated, and widely distributed host-parasite relationships are rare. Here, we combine field observations with published collection data to document the current known distribution of the nematode, Myrmeconema neotropicum, which infects the Neotropical canopy ant Cephalotes atratus. We report 6 new records from different Brazilian ecosystems, bringing the total number of independent observations of this interaction to 11. The broad distribution of these data points suggests that M. neotropicum infects C. atratus throughout its geographic range, although possible disturbance effects and specific habitat associations of the interaction remain unknown.Keywords: Host, Hymenoptera, Ants, Myrmeconema neotropicum, Rang

Endemic Venezuelan Equine Encephalitis in Northern Peru

Since Venezuelan equine encephalitis virus (VEEV) was isolated in Peru in 1942, >70 isolates have been obtained from mosquitoes, humans, and sylvatic mammals primarily in the Amazon region. To investigate genetic relationships among the Peru VEEV isolates and between the Peru isolates and other VEEV strains, a fragment of the PE2 gene was amplified and analyzed by single-stranded conformation polymorphism. Representatives of seven genotypes underwent sequencing and phylogenetic analysis. The results identified four VEE complex lineages that cocirculate in the Amazon region: subtypes ID (Panama and Colombia/Venezuela genotypes), IIIC, and a new, proposed subtype IIID, which was isolated from a febrile human, mosquitoes, and spiny rats. Both ID lineages and the IIID subtype are associated with febrile human illness. Most of the subtype ID isolates belonged to the Panama genotype, but the Colombia/Venezuela genotype, which is phylogenetically related to epizootic strains, also continues to circulate in the Amazon basin

Spider Field Data

Spider glide index, mass, and wing are

Community ecology of water-filled tree holes in Panama.

Water-filled tree holes are phytotelmata formed when rain collects in branch crotches and other wood-lined cavities. Repeated surveys of natural and artificial water-filled tree holes on Barro Colorado Island (BCI), Panama, (1994--1998) revealed 59 species of macroorganisms associated with this habitat. A typical hole contained 5 or 6 macroorganism species, but up to 14 taxa occurred in some holes. Total macroorganism abundance and species richness increased with hole volume. Species richness in both natural and artificial holes declined with increasing height above the ground. Macroorganism abundance and species richness were not correlated with pH, conductivity or dissolved oxygen content of tree hole water. Microvelia cavicol, a new species discovered in BCI tree holes generally occurred in the same holes throughout the wet season and in successive years. Hole size and shape were the best predictors of its abundance. Leaves from different tree species decomposed at different rates and degraded faster when grazers were present. Pupation success was highest for mosquito larvae reared on Platypodium litter in the tab. Similar results were obtained in the field, where macroorganism species richness and persistence times were greatest in artificial holes containing Platypodium litter. Litter decomposition rates were faster in the presence of mosquitoes, and odonates reduced mosquito survival. Predators had no indirect effect on litter decomposition. Small mosquito larvae apparently escaped predation and maintained a significant grazer effect on litter decay rates in the presence of odonates. Fewer species existed in holes containing large odonates vs. holes from which odonates were excluded. Selective predation is probably responsible for this pattern. Standardized litter addition increased mean species richness in tree holes, whereas litter removal reduced mean richness. Effects of litter manipulations disappeared five weeks after treatments were terminated. In artificial tree holes, litter quantities affected macroorganism abundance and species richness, but only during the first three weeks. Addition of an odonate larva on Week 3 had no effect on abundance, but reduced species richness during the subsequent four weeks