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.
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The phyletic link of living tarsiers to fossil primates has been a difficult bridge to cross. Although Tarsiidae has been linked to fossil tarsiiforms such as omomyids and microchoerids, as well as to anthropoids, no consensus of opinion has been reached. Here we add several new postcranial elements for one of the most primitive of all tarsiiforms, Teilhardina belgica from Dormaal, Belgium. We compare this new material to that of living and fossil tarsiers as well as to other Eocene fossil primates. Besides the previously known tarsals for Teilhardina, we have been able to add a distal humerus, a proximal ulna, a second metacarpal, a proximal and a distal femur, tibiae, additional tarsals, first metatarsals, and several proximal and middle phalanges. Although most of these postcranial elements compare best with other omomyids, and therefore do not resolve the phyletic relationship of omomyids relative to tarsiers, the fingers and toes of Teilhardina are quite elongated, a similarity to living tarsiers. Middle phalangeal lengths of the diminuitive Teilhardina are comparable in length to much larger species of Tarsius suggesting relatively even longer digits. The digit features of Teilhardina and Tarsius are unusual for primates in general and may in fact represent an ancestral state although hands and feet of other fossil tarsiiforms are needed to test this hypothesis.
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