Recognition of competitive asymmetries reduces the severity of fighting in male Idarnes fig wasps

Occurrence of internally ovipositing non-agaonid wasps and pollination mode of the associated agaonid wasps

Figs (Ficus, Moraceae) and their pollinating fig wasps (Hymenoptera, Agaonidae, Chalcidoidea) are a striking example of obligate mutualism and coevolution. Agaonid females enter the figs to lay their eggs, but also actively or passively transport pollen into the figs at the same time. We examined eight related fig tree species pollinated by host specific Eupristina agaonids to determine the relationships between pollination mode, host pollen, ovule ratios and the ability of the figs to recruit additional non-agaonid pollinators. Uniquely amongst the eight Eupristina species, the pollinator of Ficus curtipes has non-functional pollen pockets and no coxal combs, showing that it pollinates passively. Reflecting this, the anther-to-ovule ratio of F. curtipes is unusually high. In addition to the agaonids, figs support many species of 'non-pollinating fig wasps' (NPFW) that are typically ovule gallers or parasitoids. These mainly oviposit from outside the figs but there are a few species of NPFW that are like agaonids and enter the figs to oviposit. Two of the eight Eupristina pollinated fig trees support host specific internally-ovipositing fig wasps belonging to the chalcidoid genera Diaziella (Sycoecinae) and Lipothymus (Otitesellinae). Reflecting the trees' pollination modes, these fig wasps act as supplementary pollinators of F. curtipes, but not of Ficus glaberrima, where agaonid pollination is active.

Asymmetric competition drives lake use of coexisting salmonids

To what degree are population differences in resource use caused by competition and the occupation of adjacent positions along environmental gradients evidence of competition? Habitat use may be the result of a competitive lottery, or restricted by competition. We tested to what extent population differences in habitat use of two salmonids, cutthroat trout (Oncorhynchus clarki) and Dolly Varden charr (Salvelinus malma) were influenced by interspecific competition. We hypothesized that the depth distribution of Dolly Varden charr would be affected by competition from the more littoral and surface-oriented cutthroat trout, and that the depth distribution of cutthroat trout would be little affected by competition from Dolly Varden charr. Sympatric populations of cutthroat trout and Dolly Varden charr were created by reciprocal transfers of previously allopatric populations in two experimental lakes. We found evidence of asymmetric competition, as Dolly Varden charr were displaced from littoral habitats when sympatric with cutthroat trout, whereas cutthroat trout remained unaffected by the presence of Dolly Varden charr. Evolved differences between the species, and differences between experimental lakes, also contributed to population differences in habitat use, but asymmetric competition remained as the main driver of different depth distributions in sympatry.

Fauna de Hymenoptera em Ficus spp. (Moraceae) na Amazônia Central, Brasil

A interação Ficus (Moraceae) - vespas de figo é considerada um dos exemplos mais extremos de mutualismo entre planta e inseto. Neste trabalho, descreve-se a fauna de vespas de figo associada a cinco espécies de Ficus na Amazônia Central, considerando alguns aspectos do modo de polinização nas espécies Ficus (Urostigma) cremersii, Ficus (Urostigma) greiffiana, Ficus (Urostigma) mathewsii, Ficus (Urostigma) pertusa e Ficus (Pharmacosycea) maxima. O estudo foi desenvolvido durante o período de abril a julho de 2004 em Manaus e Presidente Figueiredo, Estado do Amazonas. O número de espécies de vespas de figo por hospedeiro variou de uma a 13. Vespas do gênero Pegoscapus Cameron, 1906, polinizadoras de Ficus (Urostigma) spp., apresentam pentes coxais e bolsos torácicos adaptados à coleta e ao transporte de pólen, indicando modo ativo de polinização. No subgênero Pharmacosycea, a polinizadora do gênero Tetrapus Mayr, 1885, não apresenta estrutura morfológica adaptada ao transporte de pólen, condizente com o modo passivo de polinização. Além das vespas de figo, F. (Pharmacosyceae) maxima e F. (Urostigma) pertusa apresentaram associação com ácaros, formigas (Solenopsis sp., Formicidae), besouros (Staphylinidae) e larvas de Diptera e Lepidoptera.