Edaphic heterogeneity and the evolutionary trajectory of Amazonian plant communities

We investigated how the phylogenetic structure of Amazonian plant communities varies along an edaphic gradient within the non‐inundated forests. Forty localities were sampled on three terrain types representing two kinds of soil: clayey soils of a high base cation concentration derived from the Solimões formation, and loamy soils with lower base cation concentration derived from the Içá formation and alluvial terraces. Phylogenetic community metrics were calculated for each locality for ferns and palms both with ferns as one group and for each of three fern clades with a crown group age comparable to that of palms. Palm and fern communities showed significant and contrasting phylogenetic signals along the soil gradient. Fern species richness increased but standard effect size of mean pairwise distance (SES.MPD) and variation of pairwise distances (VPD) decreased with increasing soil base cation concentration. In contrast, palm communities were more species rich on less cation‐rich soils and their SES.MPD increased with soil base cation concentration. Species turnover between the communities reflected the soil gradient slightly better when based on species occurrences than when phylogenetic distances between the species were considered. Each of the three fern subclades behaved differently from each other and from the entire fern clade. The fern clade whose phylogenetic patterns were most similar to those of palms also resembled palms in being most species‐rich on cation‐poor soils. The phylogenetic structuring of local plant communities varies along a soil base cation concentration gradient within non‐inundated Amazonian rain forests. Lineages can show either similar or different phylogenetic community structure patterns and evolutionary trajectories, and we suggest this to be linked to their environmental adaptations. Consequently, geological heterogeneity can be expected to translate into a potentially highly diverse set of evolutionarily distinct community assembly pathways in Amazonia and elsewhere.     

Are all seeds equal? Spatially explicit comparisons of seed fall and sapling recruitment in a tropical forest

Understanding demographic transitions may provide the key to explain the high diversity of tropical tree communities. In a faunally intact Amazonian forest, we compared the spatial distribution of saplings of 15 common tree species with patterns of conspecific seed fall, and examined the seed-to-sapling transition in relation to locations of conspecific trees. In all species, the spatial pattern of sapling recruitment bore no resemblance to predicted distributions based on the density of seed fall. Seed efficiency (the probability of a seed producing a sapling) is strongly correlated with distance from large conspecific trees, with a >30-fold multiplicative increase between recruitment zones that are most distant vs. proximal to conspecific adults. The striking decoupling of sapling recruitment and conspecific seed density patterns indicates near-complete recruitment failure in areas of high seed density located around reproductive adults. Our results provide strong support for the spatially explicit predictions of the Janzen-Connell hypothesis.     

Spatial Scale or Amplitude of Predictors as Determinants of the Relative Importance of Environmental Factors to Plant Community Structure

The literature on tropical rain forest plant‐community relationships with environmental factors usually does not recognize that the relative importance of environmental factors recorded in each study might be due to their amplitude of variation within sites. Geographic scale, however, is recognized as an important modulator of this relative importance. To disentangle the effects of scale and environmental amplitude, ferns and trees in two landscapes of the same size (each 25 km²) with different soil‐fertility amplitudes but similar soil‐texture range were sampled in central Amazonia. We found that major determinants of community structure were the same for ferns and trees. Texture was the main predictor of community structure in the site with homogeneous soil fertility, while availability of exchangeable cations was the main predictor in the site with a wider fertility range. When both sites were analyzed together, soil fertility was the main predictor of community structure and soil texture segregated floristic subgroups within certain ranges of the soil‐fertility gradient. We conclude that: (1) floristic patterns for trees and ferns are congruent; (2) floristic variation depends on the amplitude of the studied gradients, more than on geographical scale; (3) limiting factors are not necessarily the most important predictors of compositional patterns; and (4) communities are structured hierarchically. Therefore, landscape structure (meaning which combinations of environmental factors, their amplitude of variation and which part of the gradient is found within the landscape) affect our perception of the relative importance that environmental factors will have as predictors of species composition.     

Effect of Tree‐Fall Gaps on Fruit‐Feeding Nymphalid Butterfly Assemblages in a Peruvian Rain Forest

One of the main natural disturbances that affects the structure of rain forests is treefalls, frequently resulting in gaps. Tree‐fall gaps can bring drastic changes in environmental conditions compared with the undisturbed understory. We investigated the effect of tree‐fall gaps on fruit‐feeding butterfly (Nymphalidae) species assemblages in an undisturbed lowland rain forest in southeastern Peru. We used fruit‐baited traps suspended 2 m above ground in 15 tree‐fall gaps ranging in area from 100 to 1000 m² and in adjacent undisturbed understory. Our data support the hypothesis that tree‐fall gap and understory habitats are utilized by different butterfly species assemblages. There were morphological differences between gap and understory species, where the understory species had a larger wing area to thoracic volume. Vegetation structure and composition were important factors affecting the butterfly assemblages. Most of the butterfly species showed an avoidance of vines and a strong association with the presence of trees and shrubs in gaps. There were also differences among gap assemblages that increased with gap size. Some of the species that were associated with gaps have been considered as canopy species. Other gap species in the present study, however, are known to feed on fruits and/or use host plants mainly, or only, occurring in gaps, implicating that the gap assemblage is a mix of canopy species and those unique to gaps. This indicates that, in an undisturbed Amazon forest, tree‐fall gaps may contribute to maintain species diversity by creating a mosaic of specific habitats and resources that favors different butterfly assemblages.     

In praise of the everyday: Trust and the art of social living in an Amazonian community

The article states the high evaluation that an Amazonian people, the Piaroa, place upon the artful skills of everyday existence. It is argued that their emphasis upon the creativity of daily practice is forthcoming from a powerful and egalitarian social philosophy. The difficulties of translating such a philosophy, where the human self is contextualised within a wider cosmic setting, are raised. The aim of translation would be to enable us to engage in dialogue with the Piaroa about common concerns (upon the relation of the individual to the collectivity, for instance, or upon the idea of freedom, or the question of the relation of customs to rational decision making). These are a people who overtly shun the idea of a social rule, yet strongly value sociality, their own customs, and the mutuality of the ties of community. At the same time they demonstrate even more forcefully an ‘obstinate individualism’. A major puzzle to be discussed is the notion that personal autonomy is understood as a social capacity, and a cultural one as well: the volitional I, the social relation, and the cultural artifice are an associated set of values. The centrality of the notions of reflective reason and personal trust to this particular egalitarian ethics will be discussed.     

Le genre Anomalocornis Carvalho & Wygodzinsky 1945 (Heteroptera: Miridae: Phylinae), revision taxonomique,description d’une espèce nouvelle et affinités avec les palmiers néotropicaux

Le genre néotropical Anomalocornis Carvalho & Wygodzinsky 1945, est révisé. Les espèces A. geijskesi Carvalho & Wygodzinsky 1945, A. ariasi Carvalho 1982, A. tucuruiensis Carvalho 1984, A. rondoniensis Carvalho 1984, A. couturieri Carvalho & Costa 1993 and A. peyreti Couturier & Costa 2002 sont redécrites, leurs femelles, ainsi qu’une nouvelle espèce de Colombie, A. gentyi n. sp. sont décrites. Les espèces se différencient entre elles par leur taille, la coloration du corps, la morphologie et la coloration des articles I et II de l’antenne du mâle et par la structure des génitalia. Les différentes espèces sont originaires du Brésil, de Colombie, de l’Equateur, du Pérou et du Surinam. Toutes les espèces, excepté A. ariasi, dont la plante-hôte n’est pas connue, vivent sur les inflorescences de palmiers.