Gianfranco Curletti

Arthropod diversity in a tropical forest

Assessing Creepy Crawlies Arthropods are the most diverse group of terrestrial animal species, yet estimates of the total number of arthropod species have varied widely, especially for tropical forests. Basset et al. (p. 1481, see the cover) now provide more reliable estimates of total arthropod species richness in a tropical rainforest in Panama. Intensive sampling of a half hectare of forest yielded just over 6000 arthropod species. Scaling up this result to the whole forest suggests that the total species diversity lies between 17,000 and 40,000 species. Total arthropod species richness in a tropical rainforest can be best predicted by plant diversity. Most eukaryotic organisms are arthropods. Yet, their diversity in rich terrestrial ecosystems is still unknown. Here we produce tangible estimates of the total species richness of arthropods in a tropical rainforest. Using a comprehensive range of structured protocols, we sampled the phylogenetic breadth of arthropod taxa from the soil to the forest canopy in the San Lorenzo forest, Panama. We collected 6144 arthropod species from 0.48 hectare and extrapolated total species richness to larger areas on the basis of competing models. The whole 6000-hectare forest reserve most likely sustains 25,000 arthropod species. Notably, just 1 hectare of rainforest yields >60% of the arthropod biodiversity held in the wider landscape. Models based on plant diversity fitted the accumulated species richness of both herbivore and nonherbivore taxa exceptionally well. This lends credence to global estimates of arthropod biodiversity developed from plant models.

Choice of metrics for studying arthropod responses to habitat disturbance: one example from Gabon

Abstract.  1 The choice of metrics comparing pristine and disturbed habitats may not be straightforward. We examined the results of a study in Gabon including 21 arthropod focal taxa representing 16 855 individuals separated into 1534 morphospecies. Replication included the understorey of 12 sites representing four stages of land use after logging (old and young forests, savanna and gardens), surveyed for 1 year using three sampling methods. 2 For all focal taxa, we calculated a suite of 13 metrics accounting for the intensity of faunal changes between habitats, namely: abundance; observed, rarefied and estimated species richness; proportion of rare species; additive diversity partitioning; evenness of assemblages; higher taxonomic composition; species turnover; ordination scores of multivariate analyses; nestedness; proportion of site‐specific species and ratios of functional guilds. 3 Most metrics showed large differences between forests and non‐forest habitats, but were not equally discriminating for particular taxa. Despite higher taxonomic groups being present in most habitats, many insect species were site or habitat specific. There was little evidence that the disturbance gradient represented a series of impoverished habitats derived from older forests. Rather, entire suites of species were being replaced as habitats were modified. 4 Metrics based on species identity had a high sensitivity to disturbance, whereas measurements describing community structure were less discriminating in this regard. We recommend using metrics based on abundance, estimated species richness, species turnover estimated by multivariate analyses and guild structure, to avoid misleading interpretations that may result from comparisons of species richness alone.

Arthropod Distribution in a Tropical Rainforest: Tackling a Four Dimensional Puzzle

Quantifying the spatio-temporal distribution of arthropods in tropical rainforests represents a first step towards scrutinizing the global distribution of biodiversity on Earth. To date most studies have focused on narrow taxonomic groups or lack a design that allows partitioning of the components of diversity. Here, we consider an exceptionally large dataset (113,952 individuals representing 5,858 species), obtained from the San Lorenzo forest in Panama, where the phylogenetic breadth of arthropod taxa was surveyed using 14 protocols targeting the soil, litter, understory, lower and upper canopy habitats, replicated across seasons in 2003 and 2004. This dataset is used to explore the relative influence of horizontal, vertical and seasonal drivers of arthropod distribution in this forest. We considered arthropod abundance, observed and estimated species richness, additive decomposition of species richness, multiplicative partitioning of species diversity, variation in species composition, species turnover and guild structure as components of diversity. At the scale of our study (2km of distance, 40m in height and 400 days), the effects related to the vertical and seasonal dimensions were most important. Most adult arthropods were collected from the soil/litter or the upper canopy and species richness was highest in the canopy. We compared the distribution of arthropods and trees within our study system. Effects related to the seasonal dimension were stronger for arthropods than for trees. We conclude that: (1) models of beta diversity developed for tropical trees are unlikely to be applicable to tropical arthropods; (2) it is imperative that estimates of global biodiversity derived from mass collecting of arthropods in tropical rainforests embrace the strong vertical and seasonal partitioning observed here; and (3) given the high species turnover observed between seasons, global climate change may have severe consequences for rainforest arthropods.

Faunal turnover of arthropod assemblages along a wide gradient of disturbance in Gabon

We examined the results of a study in Gamba, Gabon, focusing on the impacts of disturbance on arthropods, including more than 400 000 individuals, from which 21 focal taxa were separated into 1534 morphospecies by parataxonomists. Replication included the understorey of three sites in each of four different stages of forest succession and land use (= ‘habitats’) after logging (old and young forests, savanna and gardens), surveyed over a whole year with three sampling methods. Generally, there was a good correspondence between the number of species sorted by taxonomists and the number of morphospecies sorted by parataxonomists. Despite higher taxonomic groups being present in most habitats, a large proportion of insect species was site- or habitat-specific. Anthropogenic modification of habitats did not result in a monotonic decline of abundance and diversity, as many herbivore pests and their associated predators and parasitoids invaded gardens, where plant productivity was kept artificially high year-round through watering and crop rotation. Because gardens were colonized mostly by invasive crop pests with little relation with the forest fauna, these results emphasize the concept of maintenance of ‘quality biodiversity’ and the value of considering other variables than species richness alone in conservation studies. Further, several lines of evidence indicated that savanna habitats at Gamba supported a species-poor arthropod fauna distinct from that in nearby habitats. It is therefore questionable whether in Africa insect assemblages of savanna represent a smaller subset of their neighboring forest fauna.

O gênero Agrilus Curtis, 1829 nas coleções do Museu de Zoologia da Universidade de São Paulo (Coleoptera: Buprestidae)

E apresentado a lista de especies do genero Agrilus, preservadas no Museu de Zoologia da Universidade de Sao Paulo. Foram identificadas 84 especies, das quais 15 novas para a ciencia, aqui descritas: A. aegrotus sp. nov., A. anceps sp. nov., A. vanini sp. nov., A. casarii sp. nov., A. crux sp. nov., A. dubiosus sp. nov., A. femina sp. nov., A. fusicauda sp. nov., A. geminus sp. nov., A. giannii sp. nov., A. globulus sp. nov., A. ribeiroi sp. nov., A. timorosus sp. nov., A. martinsi sp. nov., A. yeti sp. nov. A. comizon Obenberger, 1935 foi classificado como subespecie de A. chrysostictus Klug, 1825 e vem proposto o novo status de Agriloides agoretus (Obenberger, 1935) e Autarcontes posticalis (Gory & Laporte, 1835) ambos descritos como Agrilus. Sao propostos 9 sinonimos novos: A. fasciatellus Thomson, 1878 (= A. fucatus Obenberger, 1935 syn. nov. = A. laelius Obenberger, 1935 syn. nov. = A. subfasciatellus Obenberger, 1936 syn. nov.); A. lucens Kerremans, 1897 (= A. auriceps Kerremans, 1889 syn. nov. = A. barrandei Obenberger, 1897 syn. nov.); A. violacellus Thomson, 1879 (= A. bathyllus Obenberger, 1933 syn. nov.); A. chrysostictus Klug, 1825 (= A. lucullus Obenberger, 1935 syn. nov. = A. korsakovi Obenberger, 1935 syn. nov.); A. piscis Gory, 1841 (= Agriloides bipunctatus Cobos, 1967 syn. nov.). Alem da lista de Agrilus, foram assinaladas tambem duas especies de Agriloides Kerremans, 1903 e um do Autarcontes Waterhouse, 1887.