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 moststudies 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

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 arthropods1012CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQSolVin-Solvay SA; Smithsonian Institution; Smithsonian Tropical Research Institute; United Nations Environment Programme; Smithsonian Institution; Smithsonian National Museum of Natural History; European Science Foundation (ESF); Global Canopy Programme; Czech Science foundation GACR grant; European Social Fund (ESF); Ministry of Education, Youth & Sports - Czech Republic; French National Research Agency (ANR); Research Council of Norway; Grant Agency of the Czech Republi

IBISCA-Panama, a large-scale study of arthropod beta-diversity and vertical stratification in a lowland rainforest : rationale, study sites and field protocols.

IBISCA-Panama (?Investigating the BIodiversity of Soil and Canopy Arthropods?, Panama module) represents a large-scale research initiative to quantify the spatial distribution of arthropod biodiversity in a Neotropical forest, using a combination of (1) international collaboration, (2) a set of common research questions, and (3) an integrated experimental design. Here, we present the rationale of the programme, describe the study sites, and outline field protocols. In the San Lorenzo Protected Area of Panama, twelve 20 x 20 m sites, all less than 2 km apart, were surveyed for plants and arthropods, from the ground to the upper canopy. Access to the canopy and its fauna was facilitated by fogging, single-rope techniques and a variety of devices such as a canopy crane, the ?SolVin-Bretzel? canopy raft, the canopy bubble and Ikos. IBISCA-Panama represented the first attempt to combine these complementary techniques of canopy access in a large-scale investigation. Such techniques provided spatial replication during initial field work performed in September-October 2003. Temporal replication across seasons consisted of subsequent field work of varying intensity during dry, early wet and late wet periods in 2004. Arthropods were surveyed using 14 different protocols targeting the soil, litter, understorey, mid-canopy and upper canopy habitats. These protocols included: WINKLER sifting; BERLESE-TULLGREN; hand-collecting of galls and social insects; fogging; beating; woodrearing; baits; and various types of traps such as pitfall, small and large flight-interception, sticky, light, and Malaise traps. Currently, analyses of arthropod distribution in this forest concentrate on a set of 63 focal taxa representing different phylogenies and lifehistories. IBISCA-Panama may be considered as a model for largescale research programmes targeting invertebrate biodiversity. Its collaborative modus operandi can be applied to answer a variety of pressing ecological questions related to forest biodiversity, as evidenced by the recent development of further IBISCA programmes in other parts of the world