The biogeography and age of salticid spider radiations (Araneae: Salticidae).

Globally distributed, jumping spiders (Salticidae) are species-rich and morphologically diverse. Recent molecular phylogenetic work has revealed that major clades are largely isolated to particular continental regions, suggesting their radiations postdated Mesozoic continental break up, but corroboration from a multi-gene time-calibrated phylogeny has been lacking, and an important tropical forest region, Central and West Africa, has been largely unsampled. Newly sampled species, many from Gabon, were included among taxa sequenced for the genes 28s, Actin 5C, 16sND1, and CO1. Likelihood and Bayesian analyses show that most of the Gabonese species from forest habitats fall into a single large clade, which we name the Thiratoscirtinae (new subfamily), within the broader Aelurilloida. The aelurilloids, together with the plexippoids, euophryines, heliophanines and smaller groups (e.g. Leptorchestae, Hasarieae, Philaeus group, Salticus), form a large clade that we name the Saltafresia. Most saltafresian diversification appears to have occured in Afro-Eurasia, with the exception of the euophryines (largely Neotropical, Australasian and Southeast Asian) and two radiations in the New World (Habronattus, freyines). Using Bayesian relaxed molecular-clock methods, calibrated by amber fossil data and a geological constraint, we estimate that most recent common ancestor of the family occurred 47-57 million years ago, when the continents would have already separated substantially. The Salticoida is dated to 41-50 million years, and its four major subclades Amycoida, Astioida, Marpissoida, and Saltafresia are each dated to 29-44 million years. By these inferred dates, salticids were radiating while the earth was warmer than today, with expanded megathermal forests and, most likely, diverse insect herbivores. Our phylogeny indicates mixing of radiating faunas from isolated regions has been limited, yet some long-range dispersal events, such as the arrival of the genus Habronattus to the New World, have occurred. Four African species formerly in Viciria are moved to Telamonia, establishing the new combinations Telamonia besanconi (Berland and Millot), Telamonia fuscimana (Simon), Telamonia longiuscula (Thorell), Telamonia thoracica (Thorell). The Marpissoida is expanded to include the Ballinae.

Molecular evolution, functional variation, and proposed nomenclature of the gene family that includes sphingomyelinase D in sicariid spider venoms.

The venom enzyme sphingomyelinase D (SMase D) in the spider family Sicariidae (brown or fiddleback spiders [Loxosceles] and six-eyed sand spiders [Sicarius]) causes dermonecrosis in mammals. SMase D is in a gene family with multiple venom-expressed members that vary in functional specificity. We analyze molecular evolution of this family and variation in SMase D activity among crude venoms using a data set that represents the phylogenetic breadth of Loxosceles and Sicarius. We isolated a total of 190 nonredundant nucleotide sequences encoding 168 nonredundant amino acid sequences of SMase D homologs from 21 species. Bayesian phylogenies support two major clades that we name alpha and beta, within which we define seven and three subclades, respectively. Sequences in the alpha clade are exclusively from New World Loxosceles and Loxosceles rufescens and include published genes for which expression products have SMase D and dermonecrotic activity. The beta clade includes paralogs from New World Loxosceles that have no, or reduced, SMase D and no dermonecrotic activity and also paralogs from Sicarius and African Loxosceles of unknown activity. Gene duplications are frequent, consistent with a birth-and-death model, and there is evidence of purifying selection with episodic positive directional selection. Despite having venom-expressed SMase D homologs, venoms from New World Sicarius have reduced, or no, detectable SMase D activity, and Loxosceles in the Southern African spinulosa group have low SMase D activity. Sequence conservation mapping shows >98% conservation of proposed catalytic residues of the active site and around a plug motif at the opposite end of the TIM barrel, but alpha and beta clades differ in conservation of key residues surrounding the apparent substrate binding pocket. Based on these combined results, we propose an inclusive nomenclature for the gene family, renaming it SicTox, and discuss emerging patterns of functional diversification.

Phylogenetic relationships of Loxosceles and Sicarius spiders are consistent with Western Gondwanan vicariance.

The modern geographic distribution of the spider family Sicariidae is consistent with an evolutionary origin on Western Gondwana. Both sicariid genera, Loxosceles and Sicarius are diverse in Africa and South/Central America. Loxosceles are also diverse in North America and the West Indies, and have species described from Mediterranean Europe and China. We tested vicariance hypotheses using molecular phylogenetics and molecular dating analyses of 28S, COI, 16S, and NADHI sequences. We recover reciprocal monophyly of African and South American Sicarius, paraphyletic Southern African Loxosceles and monophyletic New World Loxosceles within which an Old World species group that includes L. rufescens is derived. These patterns are consistent with a sicariid common ancestor on Western Gondwana. North American Loxosceles are monophyletic, sister to Caribbean taxa, and resolved in a larger clade with South American Loxosceles. With fossil data this pattern is consistent with colonization of North America via a land bridge predating the modern Isthmus of Panama.

Comparative analyses of venoms from American and African Sicarius spiders that differ in sphingomyelinase D activity.

Spider venoms are cocktails of toxic proteins and peptides, whose composition varies at many levels. Understanding patterns of variation in chemistry and bioactivity is fundamental for understanding factors influencing variation. The venom toxin sphingomyelinase D (SMase D) in sicariid spider venom (Loxosceles and Sicarius) causes dermonecrotic lesions in mammals. Multiple forms of venom-expressed genes with homology to SMase D are expressed in venoms of both genera. SMase D activity levels differ among major clades with American Sicarius vastly reduced relative to all Loxosceles and African Sicarius despite expression of SMase D homologs in venoms of American Sicarius. Here we report comparative analyses of protein composition and insecticidal activity of crude venoms from three Sicarius species, two from South Africa and one from Central America. Comparative 2-dimensional electrophoresis shows dense regions of proteins in the size range of SMase D in all three species, but there are differences in sizes and isoelectric points (pIs). Few proteins strictly co-migrate and there are clusters of proteins with similar pIs and molecular weights whose patterns of similarity do not necessarily reflect phylogenetic relatedness. In addition, PD(50) estimates on crickets indicate a small though significant decrease in potency of South American Sicarius venoms relative to African species.