Senna multijuga (November shower).

S. multijuga, a tree native to the neotropics, ranges in size at maturity from 6-40 m, although more commonly it takes the form of a medium, slender tree ranging from 6-15 m with a wide-spreading crown (Irwin and Barneby, 1982; Killeen et al., 1993; Parrotta et al., 1995). Many flaky lenticels cover the thin bark. Bark cuts produce an unpleasant smell. The dark green leaves are compound and alternate and grow up to 30 cm, with 25 pairs of opposed or sub-opposed leaflets varying in size and number. Yellow flowers are produced which also vary in size. Seeds are produced in flat, red to purple pods. The narrow, oblong seeds are compressed, range from 1.5-2.1 mm in size, and have a pale, brownish-grey testa (Irwin and Barneby, 1982). Within its natural distribution, a profuse bloom of bright yellow flowers usually occurs during the middle to late rainy season. Seed dormancy is common, although the time that seeds remain viable in the soil is not known. Research has shown that mechanical scarification of the seeds greatly increases germination rate (Lemos Filho et al., 1997). Although the species is relatively disease-free, there are a number of bruchid beetles that predate upon the seeds (Ribeiro and Reynaud, 1998).

Density-dependent seed predation in Attalea geraensis Barb. Rodr. (Arecaceae) caused by bruchid beetles in the Brazilian Cerrado

Palms are an important component of Neotropical communities as they are often diverse and abundant. In some areas, palms occur in high density and act as limiting factor in tree recruitment by limiting tree seedling and sapling abundance. In this study, I evaluated the intensity of seed mortality caused by insects in Attalea geraensis, in a large area of preserved Cerrado (Serra do Cabral, MG, Brazil) during wet season when both A. geraensis fruits and bruchid beetles were abundant. I collected a total of 63 infructescences which had from 3 fruits and 7 seeds to 82 fruits and 251 seeds. Endocarps had from 1 to 6 seeds. Seed mortality per infructescence due to beetles (Pachymerus cardo) was intense, and increases positively and disproportionally according to seed number per infructescence. Besides that, average proportions of seeds preyed upon by insects were consistently high (> 0.83), irrespective of seed number per endocarp. Positive density-dependent seed mortality caused by specialized natural enemies has been assumed to promote species rarity, an important feature of species coexistence in Neotropical forests. Then, the intense seed mortality documented in this study suggests that seed predators may contribute to the richness and diversity of plant species in the Cerrado, the richest and most endangered savanna in the world.

Species of Horismenus Walker (Hymenoptera: Eulophidae) associated with bruchid beetles (Coleoptera: Chrysomelidae: Bruchinae), including five new species

Species of Horismenus Walker associated with bruchid beetles are investigated and five new species are described. Some of the new species are very similar to already described species and have previously been misidentified. The new species include H. depressoides sp. nov. similar to H. depressus Gahan , H. stator sp. nov. similar to H. missouriensis (Ashmead), and H. dennoi & H. multistriatus spp. nov., both similar to H. butcheri Hansson & Aebi and one species, H. gabrielae sp. nov., that is morphologically distinct from the other species but also associated with this host group. All 14 Horismenus species associated with bruchid beetles are included in a key. New host and distributional records are included for H. depressus.

Harnessing ant defence at fruits reduces bruchid seed predation in a symbiotic ant–plant mutualism

In horizontally transmitted mutualisms, mutualists disperse separately and reassemble in each generation with partners genetically unrelated to those in the previous generation. Because of this, there should be no selection on either partner to enhance the other's reproductive output directly. In symbiotic ant–plant mutualisms, myrmecophytic plants host defensive ant colonies, and ants defend the plants from herbivores. Plants and ants disperse separately, and, although ant defence can indirectly increase plant reproduction by reducing folivory, it is unclear whether ants can also directly increase plant reproduction by defending seeds. The neotropical tree Cordia alliodora hosts colonies of Azteca pittieri ants. The trees produce domatia where ants nest at stem nodes and also at the node between the peduncle and the rachides of the infloresence. Unlike the stem domatia, these reproductive domatia senesce after the tree fruits each year. In this study, I show that the tree's resident ant colony moves into these ephemeral reproductive domatia, where they tend honeydew-producing scale insects and patrol the nearby developing fruits. The presence of ants significantly reduced pre-dispersal seed predation by Amblycerus bruchid beetles, thereby directly increasing plant reproductive output.