- Award ID(s):
- Publication Date:
- NSF-PAR ID:
- Journal Name:
- Annals of the Missouri Botanical Garden
- Page Range or eLocation-ID:
- 377 to 392
- Sponsoring Org:
- National Science Foundation
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A test of the Geographic Mosaic Theory of Coevolution: investigating widespread species of Amazonian Protium (Burseraceae) trees, their chemical defenses, and their associated herbivore faunasIntroduction Plants and their insect herbivores represent a large fraction of the species in Amazonian forests and are often directly implicated in the origin and maintenance of biodiversity at local and regional scales. How these interactions may change over geographic distance is unknown because very few studies have investigated the herbivore fauna and defense chemicals of any host plant species at multiple sites in tropical forests. One hypothesis, the Geographic Mosaic Theory of Coevolution, predicts that if herbivore assemblages turn over in different parts of a plant’s range, then plant defense chemicals should also change, reflecting local selection pressures. Methods We tested this theory by studying 12 species of Protium (Burseraceae) trees that occur in both Iquitos, Peru, and Manaus, Brazil, in rainforests separated by 1500 km. We surveyed all insects observed directly feeding on the plants in both locations for 48 weeks in Manaus and 64 weeks in Iquitos. We analyzed the secondary metabolites in the leaves of all species in both locations using GC/MS and HPLC. Results and Discussion Although in both locations we found that Protium herbivores were dominated by insects from the orders Hemiptera, Coleoptera and Lepidoptera, we found almost complete turnover in the herbivore species compositionmore »
An aggressive nonconsumptive effect mediates pest control and multipredator interactions in a coffee agroecosystem
Natural pest control is an alternative to pesticide use in agriculture, and may help to curb insect declines and promote crop production. Nonconsumptive interactions in natural pest control that historically have received far less attention than consumptive interactions, may have distinct impacts on pest damage suppression and may also mediate positive multipredator interactions. Additionally, when nonconsumptive effects are driven by natural enemy aggression, variation in alternative resources for enemies may impact the strength of pest control. Here we study control of the coffee berry borer (CBB),
Hypothenemus hampei, by a keystone arboreal ant species, Azteca sericeasur, which exhibits a nonconsumptive effect on CBB by throwing them off coffee plants. We conducted two experiments to investigate: (1) if the strength of this behavior is driven by spatial or temporal variability in scale insect density (an alternative resource that Aztecatends for honeydew), (2) if this behavior mediates positive interactions between Aztecaand other ground‐foraging ants, and (3) the effect this behavior has on the overall suppression of CBB damage in multipredator scenarios. Our behavioral experiment showed that nearly all interactions between Aztecaand CBB are nonconsumptive and that this behavior occurs more frequently in the dry season and with higher densities of scale insects on coffee branches. Ourmore »
The enemy release hypothesis (ERH) posits that introduced species often leave their enemies behind when introduced to a new range. This release from enemies may allow introduced species to achieve higher growth and reproduction and may explain why some invaders flourish in new locations. Red mangroves (
Rhizophora mangle) were introduced to Hawaiʻi from Florida over a century ago. Because Hawaiʻi has no native mangroves, the arrival of R. manglefundamentally changed the structure and function of estuarine shorelines. While numerous enemies affect red mangroves in their native range (tropical America), in Hawaiʻi, mangroves apparently experience little herbivory, which may explain why introduced mangroves are so productive, fecund, and continue to spread. In this study, we compared the effects of enemies in native and introduced populations of brackish red mangroves ( R. mangle) in 8–10 sites in the native range (Florida, Belize, and Panama) and introduced range of mangroves (Hawaiʻi). At each site, we measured the (1) occurrence of enemies using timed visual surveys, (2) occurrence of damage to different mangrove structures (leaves, apical buds, dead twigs, roots, propagules, and seedlings), and (3) rate of propagule herbivory using tethering experiments. Consistent with the ERH, we found an order of magnitude less damage andmore »
Closely related tree species support distinct communities of seed‐associated fungi in a lowland tropical forest
Previous theoretical work has highlighted the potential for natural enemies to mediate the coexistence of species with similar life histories via density‐dependent effects on survivorship. For plant pathogens to play this role, they must differ in their ability to infect or induce disease in different host plant species. In tropical forests characterized by high diversity, these effects must extend to phylogenetically closely related species pairs. Mortality at the seed and seedling stage strongly influences the abundance and distribution of tropical tree species, but the host preferences and spatial distributions of fungi are rarely determined.
We examined how host species identity, relatedness and seed viability influence the composition of fungal communities associated with seeds of four co‐occurring pioneer trees (
Cecropia insignis, C. longipes, C. peltataand Jacaranda copaia). Seeds were buried in mesh bags in five common gardens in the understorey of a lowland tropical forest in Panama and retrieved at intervals from 1 to 30 months. A subset of the seeds in each bag was used to determine germination success. One half of each remaining seed was tested for viability; and the other half was used to culture and identify seed‐infecting fungi.
Seeds were infected by fungi after burial. Although fungal communities differed in viable versusmore »
Although the proportion of germinable seeds decreased gradually over time for all species, intraspecific variation in survival was high at the same location (e.g. ranging from 0% to 100% for
C. peltata) suggesting variable exposure or susceptibility to seed pathogens. Synthesis. Our study provides evidence under field conditions that congeneric tree species with similar life history traits differ markedly in seed‐associated fungal communities when exposed to the same soil‐borne fungi. This is a critical first step supporting pathogen‐mediated coexistence of closely related tree species.
Tritrophic interactions reinforce a negative preference–performance relationship in the tobacco hornworm ( Manduca sexta )
Host plants that promote development of insect herbivores are sometimes less preferred to more toxic plants, which are co‐opted for protection from natural enemies, resulting in higher fitness in communities with strong top‐down control. However, the degree to which variation in growth rate and risk of natural enemy attack drive insect plant preferences is an open question, with little field data available across diverse plant families.
The present study investigated the preference–performance relationship and tritrophic interactions involving the hornworm
Manduca sexta, its natural enemies, and plants in the nightshade family (Solanaceae) using a 2‐year common garden containing 18 wild and domesticated species. The degree to which natural enemy pressure explained field patterns in the laboratory was then tested using targeted assays involving parasitism by the wasp Cotesia congregata.
In the field, the most preferred plants for female oviposition tended to be inversely correlated with the species providing optimal larval growth. Hawkmoths preferred plants in the subgenus
Potatoe, Nicotiana, and Daturacompared with Capsicum, Physalis, and the other Solanumsubgenera. However, larval parasitism by was only significant for hornworms on C. congregata Potatoe/ Daturaand not Nicotiana(i.e. 33% vs. 12% vs. 4% parasitism on Potatoe, Datura, and Nicotiana, respectively). Experimental laboratory rearing confirmed that wasp survival is lower on Nicotianasp. than , which could be driven by nicotine. Solanum lycopersicum
The data obtained inmore »