Speciation and phylogeography of Hawaiian terrestrial arthropods.

The Hawaiian archipelago is arguably the world's finest natural laboratory for the study of evolution and patterns of speciation. Arthropods comprise over 75% of the endemic biota of the Hawaiian Islands and a large proportion belongs to species radiations. We classify patterns of speciation within Hawaiian arthropod lineages into three categories: (i) single representatives of a lineage throughout the islands; (ii) species radiations with either (a) single endemic species on different volcanoes or islands, or (b) multiple species on each volcano or island; and (iii) single widespread species within a radiation of species that exhibits local endemism. A common pattern of phylogeography is that of repeated colonization of new island groups, such that lineages progress down the island chain, with the most ancestral groups (populations or species) on the oldest islands. While great dispersal ability and its subsequent loss are features of many of these taxa, there are a number of mechanisms that underlie diversification. These mechanisms may be genetic, including repeated founder events, hybridization, and sexual selection, or ecological, including shifts in habitat and/or host affiliation. The majority of studies reviewed suggest that natural selection is a primary force of change during the initial diversification of taxa.

Evolution and ecology of spider coloration.

Genetic color variation provides a tangible link between the external phenotype of an organism and its underlying genetic determination and thus furnishes a tractable system with which to explore fundamental evolutionary phenomena. Here we examine the basis of color variation in spiders and its evolutionary and ecological implications. Reversible color changes, resulting from several mechanisms, are surprisingly widespread in the group and must be distinguished from true genetic variation for color to be used as an evolutionary tool. Genetic polymorphism occurs in a large number of families and is frequently sex limited: Sex linkage has not yet been demonstrated, nor have the forces promoting sex limitation been elucidated. It is argued that the production of color is metabolically costly and is principally maintained by the action of sight-hunting predators. Key avenues for future research are suggested.

Pseudorabies in captive coyotes.

Pseudorabies (Aujeszky's disease) was diagnosed in three adult captive coyotes (Canis latrans) from southern Indiana (USA). The coyotes died in their outdoor enclosure within a 48 hr period. Histopathology revealed multifocal, nonsuppurative meningioencephalitis and eosinophilic intranuclear inclusion bodies within neurons. Samples of brain were positive for pseudorabies virus by fluorescent antibody testing and virus isolation. Source of infection was the probable consumption of pseudorabies virus-infected pig carcasses.

Multiple origins of a spider radiation in Hawaii.

The Hawaiian Islands are renowned for some of the most spectacular species radiations in the world. Most of these radiations have been attributed to single colonization events, although the evidence supporting monophyletic origins is often poorly resolved and/or ambiguous. Without a concrete understanding of the origins of species radiations, it is impossible to understand the phylogenetic pattern of species proliferation or the spectrum of morphological, ecological, and behavioral modifications attributable to a single colonist. In this study we examined the species radiation of the spider genus Tetragnatha in Hawaii. Unlike their mainland congeners, the Hawaiian Tetragnatha are extremely diverse in morphology, ecology, and behavior. We tested whether this diversity arose from a single or multiple colonization events. We coupled morphological (37 characters) and molecular (sequence from the 12S ribosomal subunit of mitochondrial DNA) approaches to assess the phylogenetic position of the Hawaiian Tetragnatha relative to continental congeners and to examine evidence for monophyly. We provide evidence that the Hawaiian Tetragnatha emanate from multiple origins. At least two independent species radiations, the "spiny-leg" clade and the web-building species Tetragnatha stelarobusta and Tetragnatha acuta, have arisen from one or more founder events. Two additional natural colonizations have resulted in the establishment of non-speciose lineages, as represented by Tetragnatha hawaiensis and Doryonychus raptor.