Plants often modify microsite conditions important for seedling establishment. In tropical moist forest, advance regeneration in the form of shade-suppressed seedlings is a major component of regrowth in new gaps. Tree seedlings may be filtered by the composition and structure of the forest understorey. In a lowland forest in Central Panama, we examined light availability, Utter accumulation and the seedling community (abundance, diversity and composition) under and away from the canopies of a common subcanopy, clonal palm, Oenocarpus mapora, and tested whether seedling abundance varies as a function of changes in understorey light conditions and leaf litter depth. We found evidence that leaf litter was five times deeper and light availability 2 7% lower under O. mapora canopy than where it was absent. The probability of finding a seedling in plots under O. mapora canopies was 33% lower than in plots without the palm. Plots under O. mapora canopies also had 49% fewer species of seedlings and those seedlings came from significantly larger seeds than seedlings in plots not under the palm. Overall, seedling density was positively correlated with light availability and negatively correlated with leaf litter depth. A transplant experiment confirmed that for at least one large-seeded species of dicot, seedlings are negatively affected by the reduction in light availability and increase in leaf litter. Under O. mapora, seedlings of Gustavia superba (Lecythidaceae) had lower survivorship and biomass accumulation than away from the palm. Thus, site conditions produced by large, clonal, multi-layered palms such as O. mapora may reduce establishment of small-seeded and shade-intolerant species, potentially affecting species composition in the understorey seedling pool.

Fragmentation that alters mutualistic relationships between plants and frugivorous animals may reduce the seed dispersal of trees. We examined the effects of forest fragmentation on the distributions of seeds and seedlings of a Central Amazon endemic tree, Duckeodendron cestroides. In the dry seasons of 2002-2004, seeds and first-year seedlings were counted within wedge-shaped transects centered around Duckeodendron adults in fragments and nearby continuous forests at the Biological Dynamics of Forest Fragmentation Project. Analyses showed that fragmentation reduced seed dispersal quantity and quality. The percent and distance of dispersed seeds were both twice as great in continuous forest as in fragments. The distances of each tree's five furthest dispersed seeds were three times greater in continuous forest than fragments. Over the 3-yr study, 20 times more seeds were dispersed more than 10 m from parent crowns in continuous forest than fragments. A regression analysis showed more dispersed seeds at all distances in continuous forest than fragments. Dispersal differences were strong in 2002 and 2004, years of large fruit crops, but weak or absent in 2003, when fruit production was low. As distance from parent crowns increased, the number of seedlings declined more rapidly in fragments than continuous forest. Distance-dependent mortality between the seed and seedling stages appeared to be more important in continuous forest than fragments. This research provides ample, indirect evidence demonstrating that forest fragmentation can result in the breakdown of a seed dispersal mutualism, potentially jeopardizing the reproduction of a rare, tropical tree.Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp.

Exclusion of ants, particularly red imported fire ant, Solenopsis invicta (Buren), from homes, nursing facilities, hospitals, and electrical housings is an important strategy in urban and rural pest control. We conducted a laboratory bioassay to determine the repellency of granular bifenthrin (Talstar: rate 2.087 kg of formulated product/92.88 m2 or 4.6 lb formulated product/1000 feet2 or 4.2 g active ingredient/92.88 m2) to S. invicta foragers. In the field, we compared the efficacy of three widths (0.3, 2.0, and 3.0 m) of granular bifenthrin-treated zones at the rate 2.087 kg of formulated product/92.88 m2 and investigated the survival of individual ants successfully crossing the respective zones. Granular bifenthrin was nonrepellent to fire ant foragers in the laboratory. The 2.0- and 3.0-m treatment zones provided 100% protection for 7 wk after treatment and provided a reduction in the number of ants breaching the treated zone compared with the control for the remaining 9 wk of the study. This level of control may be tolerable for homeowners and is, therefore, considered an effective treatment for 15 wk after treatment. Hospitals, nursing homes, and electrical boxes would have to be treated on a monthly or bimonthly to remain ant free.

Exclusion of ants, particularly red imported fire ant, Solenopsis invicta (Buren), from homes, nursing facilities, hospitals, and electrical housings is an important strategy in urban and rural pest control. We conducted a laboratory bioassay to determine the repellency of granular bifenthrin (Talstar: rate 2.087 kg of formulated product/92.88 m2 or 4.6 lb formulated product/1000 feet2 or 4.2 g active ingredient/92.88 m2) to S. invicta foragers. In the field, we compared the efficacy of three widths (0.3, 2.0, and 3.0 m) of granular bifenthrin-treated zones at the rate 2.087 kg of formulated product/92.88 m2 and investigated the survival of individual ants successfully crossing the respective zones. Granular bifenthrin was nonrepellent to fire ant foragers in the laboratory. The 2.0- and 3.0-m treatment zones provided 100% protection for 7 wk after treatment and provided a reduction in the number of ants breaching the treated zone compared with the control for the remaining 9 wk of the study. This level of control may be tolerable for homeowners and is, therefore, considered an effective treatment for 15 wk after treatment. Hospitals, nursing homes, and electrical boxes would have to be treated on a monthly or bimonthly to remain ant free.

No abstract