The neotropical canopy tree Hymenaea courbaril L. (Caesalpiniaceae) has long been hypothesized to depend on mammals for the dispersal of its seeds. Hallwachs (1986) suggested that agouti (Dasyprocta spp., Rodentia) inherited the role of disperser of H. courbaril seeds from large Pleistocene mammals (Janzen & Martin 1982). She further postulated that agouti are currently the only effective dispe...

An (N;M;T )-OR-disperser is a bipartite multigraph G = (V;W;E) with jV j = N , and jW j = M , having the following expansion property: any subset of V having at least T vertices has a neighbor set of size at least M=2. For any pair of constants ; ; 1 > 0, any su ciently large N , and for any T 2(logN) , M 2(logN) , we give an explicit elementary construction of an (N;M;T )-OR-disperser such tha...

Individuals of both dispersal and non-dispersal types (disperser and non-disperser) are found in a population, suggesting that each type has both costs and benefits for fitness. However, few studies have examined the trade-off between the costs and benefits for the types. Here, we artificially selected for walking distance, i.e., an indicator of dispersal ability, in the red flour beetle Tribol...

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-flame ionization detection (GC-FID) was applied for the determination of two tricyclic antidepressant drugs (TCAs), amitriptyline and nortriptyline, from water samples. This method is a very simple and rapid method for the extraction and preconcentration of these drugs from environmental sample solutions. In this m...

Seed dispersal fundamentally influences plant population and community dynamics but is difficult to quantify directly. Consequently, models are frequently used to describe the seed shadow (the seed deposition pattern of a plant population). For vertebrate-dispersed plants, animal behavior is known to influence seed shadows but is poorly integrated in seed dispersal models. Here, we illustrate a...

We study the complexity of approximating the VC dimension of a collection of sets, when the sets are encoded succinctly by a small circuit. We show that this problem is • Σp3-hard to approximate to within a factor 2− for any > 0, • approximable in AM to within a factor 2, and • AM-hard to approximate to within a factor N for some constant > 0. To obtain the Σp3-hardness result we solve a random...