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Surveys of leucocoprinaceous fungi (Lepiotaceae, Agaricales, Basidiomycota) in the rainforests of Panama and Brazil revealed several freeliving counterparts of fungi cultivated by primitive attine ants (the lower Attini, Formicidae, Hymenoptera), adding to two such collections identified in a survey by Mueller et al (1998). The accumulated evidence supports the hypothesis that perhaps all fungi of lower attine ants have close free-living relatives. Free-living counterparts of ant-cultivated fungi are collected most readily during the early rainy season; in particular these are free-living mushrooms of fungal counterparts that are cultivated as yeasts in gardens of ants in the. Cyphomyrmex rimosus group. Free-living and symbiotic fungi of these yeast-cultivating ant species might represent a promising study system to compare the biology of sympatric, conspecific fungi existing outside versus inside the attine symbiosis. [ABSTRACT FROM AUTHOR]

Island populations are convenient models of large-scale evolutionary processes and provide natural replicates of evolution. Recently founded island populations also provide an opportunity to study populations derived from few individuals, and these populations, in particular, often show rapid diversification. Here we report morphological and molecular data for the túngara frog, Physalaemus pustulosus, from three different islands of Panama: Coiba, a large island with a rather old túngara frog population; Isla Grande, a small island with a fairly recent population of túngara frogs, and Barro Colorado Island (BCI), a large island artificially created by flooding to form the Panama Canal about 100 yr ago. Frogs from the two natural islands, but not those from BCI, were significantly larger than frogs from the mainland, which is consistent with the "island rule" stating that small species on islands tend to be larger while large species tend to be smaller than their mainland relatives. Genetic diversity, estimated from allelic richness at seven microsatellite loci, was drastically reduced in the Isla Grande population, whereas heterozygosity was not reduced. This result suggests that this island population of frogs went through a severe and recent bottleneck. [ABSTRACT FROM AUTHOR]

Cleaning symbioses represent classic models of mutualism, and some bee mites are thought to perform cleaning services for their hosts in exchange for suitable environments for reproduction and dispersal. These mutual benefits, however, have not been rigorously demonstrated. We tested the sanitary role of bee mites by correlating mite loads with fungal contamination in natural nests of Megalopta genalis and Megalopta ecuadoria and by experimentally manipulating mite loads in artificial cells with developing brood. Field observations revealed significant correlations between the presence of mites and the absence of fungi inside the brood cells, as well as between the absence of mites and increased bee mortality. Likewise, experimental brood cells with mites have fewer fungal colonies than do cells without mites. Field observations and experimental manipulations, therefore, provide clear evidence of the sanitary effect of mites in nests of Megalopta bees. This bee-mite association constitutes one of the few examples of terrestrial cleaning mutualisms.

Background: The fungus-growing ant-microbe symbiosis consists of coevolving microbial mutualists and pathogens. The diverse fungal lineages that these ants cultivate are attacked by parasitic microfungi of the genus Escovopsis. Previous molecular analyses have demonstrated strong phylogenetic congruence between the ants, the ants-cultivated fungi and the garden pathogen Escovopsis at ancient phylogenetic levels, suggesting coevolution of these symbionts. However, few studies have explored cophylogenetic patterns between these symbionts at the recent phylogenetic levels necessary to address whether these parasites are occasionally switching to novel hosts or whether they are diversifying with their hosts as a consequence of long-term host fidelity., Results: Here, a more extensive phylogenetic analysis of Escovopsis lineages infecting the gardens of Apterostigma ants demonstrates that these pathogens display patterns of phylogenetic congruence with their fungal hosts. Particular clades of Escovopsis track particular clades of cultivated fungi, and closely-related Escovopsis generally infect closely-related hosts. Discordance between host and parasite phylogenies, however, provides the first evidence for occasional host-switches or acquisitions of novel infections from the environment., Conclusion: The fungus-growing ant-microbe association has a complex coevolutionary history. Though there is clear evidence of host-specificity on the part of diverse Escovopsis lineages, these pathogens have switched occasionally to novel host fungi. Such switching is likely to have profound effects on how these host and parasites adapt to one another over evolutionary time scales and may impact how disease spreads over ecological time scales.

Túngara frogs (Physalaemus pustulosus) are a model system for sexual selection and communication. Population dynamics and gene flow are of major interest in this species because they influence speciation processes and microevolution, and could consequently provide a deeper understanding of the evolutionary processes involved in mate recognition. Although earlier studies have documented genetic variation across the species' range, attempts to investigate dispersal on a local level have been limited to mark-recapture studies. These behavioural studies indicated high mobility at a scale of several hundred metres. In this study we used seven highly polymorphic microsatellite loci to investigate fine-scaled genetic variation in the túngara frog. We analysed the influence of geographical distance on observed genetic patterns, examined the influence of a river on gene flow, and tested for sex-biased dispersal. Data for 668 individuals from 17 populations ranging in distance from 0.26 to 11.8 km revealed significant levels of genetic differentiation among populations. Genetic differentiation was significantly correlated with geographic distance. A river acted as an efficient barrier to gene flow. Several tests of sex-biased dispersal were conducted. Most of them showed no difference between the sexes, but variance of Assignment Indices exhibited a statistically significant male bias in dispersal.