Phylogeny of Neotropical Sicarius sand spiders suggests frequent transitions from deserts to dry forests despite antique, broad-scale niche conservatism.

Phylogenetic niche conservatism (PNC) shapes the distribution of organisms by constraining lineages to particular climatic conditions. Conversely, if areas with similar climates are geographically isolated, diversification may also be limited by dispersal. Neotropical xeric habitats provide an ideal system to test the relative roles of climate and geography on diversification, as they occur in disjunct areas with similar biotas. Sicariinae sand spiders are intimately associated with these xeric environments, particularly seasonally dry tropical forests (SDTFs) and subtropical deserts/scrublands in Africa (Hexophthalma) and the Neotropics (Sicarius). We explore the role of PNC, geography and biome shifts in their evolution and timing of diversification. We estimated a time-calibrated, total-evidence phylogeny of Sicariinae, and used published distribution records to estimate climatic niche and biome occupancy. Topologies were used for estimating ancestral niches and biome shifts. We used variation partitioning methods to test the relative importance of climate and spatially autocorrelated factors in explaining the spatial variation in phylogenetic structure of Sicarius across the Neotropics. Neotropical Sicarius are ancient and split from their African sister-group around 90 (57-131) million years ago. Most speciation events took place in the Miocene. Sicariinae records can be separated in two groups corresponding to temperate/dry and tropical/seasonally dry climates. The ancestral climatic niche of Sicariinae are temperate/dry areas, with 2-3 shifts to tropical/seasonally dry areas in Sicarius. Similarly, ancestral biomes occupied by the group are temperate and dry (deserts, Mediterranean scrub, temperate grasslands), with 2-3 shifts to tropical, seasonally dry forests and grasslands. Most of the variation in phylogenetic structure is explained by long-distance dispersal limitation that is independent of the measured climatic conditions. Sicariinae have an ancient association to arid lands, suggesting that PNC prevented them from colonizing mesic habitats. However, niches are labile at a smaller scale, with several shifts from deserts to SDTFs. This suggests that PNC and long-distance dispersal limitation played major roles in confining lineages to isolated areas of SDTF/desert over evolutionary history, although shifts between xeric biomes occurred whenever geographical opportunities were presented.

Phylogeny of Neotropical Sicarius sand spiders suggests frequent transitions from deserts to dry forests despite antique, broad-scale niche conservatism

Phylogenetic niche conservatism (PNC) shapes the distribution of organisms by constraining lineages to parti-cular climatic conditions. Conversely, if areas with similar climates are geographically isolated, diversificationmay also be limited by dispersal. Neotropical xeric habitats provide an ideal system to test the relative roles ofclimate and geography on diversification, as they occur in disjunct areas with similar biotas. Sicariinae sandspiders are intimately associated with these xeric environments, particularly seasonally dry tropical forests(SDTFs) and subtropical deserts/scrublands in Africa (Hexophthalma) and the Neotropics (Sicarius). We explorethe role of PNC, geography and biome shifts in their evolution and timing of diversification. We estimated atime-calibrated, total-evidence phylogeny of Sicariinae, and used published distribution records to estimateclimatic niche and biome occupancy. Topologies were used for estimating ancestral niches and biome shifts. Weused variation partitioning methods to test the relative importance of climate and spatially autocorrelatedfactors in explaining the spatial variation in phylogenetic structure ofSicariusacross the Neotropics. NeotropicalSicariusare ancient and split from their African sister-group around 90 (57–131) million years ago. Most spe-ciation events took place in the Miocene. Sicariinae records can be separated in two groups corresponding totemperate/dry and tropical/seasonally dry climates. The ancestral climatic niche of Sicariinae are temperate/dryareas, with 2–3 shifts to tropical/seasonally dry areas inSicarius. Similarly, ancestral biomes occupied by thegroup are temperate and dry (deserts, Mediterranean scrub, temperate grasslands), with 2–3 shifts to tropical,seasonally dry forests and grasslands. Most of the variation in phylogenetic structure is explained by long-distance dispersal limitation that is independent of the measured climatic conditions. Sicariinae have an ancientassociation to arid lands, suggesting that PNC prevented them from colonizing mesic habitats. However, nichesare labile at a smaller scale, with several shifts from deserts to SDTFs. This suggests that PNC and long-distancedispersal limitation played major roles in confining lineages to isolated areas of SDTF/desert over evolutionaryhistory, although shifts between xeric biomes occurred whenever geographical opportunities were presented

Strong spatial structure, Pliocene diversification and cryptic diversity in the Neotropical dry forest spider Sicarius cariri.

The Brazilian Caatinga is part of the seasonally dry tropical forests, a vegetation type disjunctly distributed throughout the Neotropics. It has been suggested that during Pleistocene glacial periods, these dry forests had a continuous distribution, so that these climatic shifts may have acted as important driving forces of the Caatinga biota diversification. To address how these events affected the distribution of a dry forest species, we chose Sicarius cariri, a spider endemic to the Caatinga, as a model. We studied the phylogeography of one mitochondrial and one nuclear gene and reconstructed the paleodistribution of the species using modelling algorithms. We found two allopatric and deeply divergent clades within S. cariri, suggesting that this species as currently recognized might consist of more than one independently evolving lineage. Sicarius cariri populations are highly structured, with low haplotype sharing among localities, high fixation index and isolation by distance. Models of paleodistribution, Bayesian reconstructions and coalescent simulations suggest that this species experienced a reduction in its population size during glacial periods, rather than the expansion expected by previous hypotheses on the paleodistribution of dry forest taxa. In addition to that, major splits of intraspecific lineages of S. cariri took place in the Pliocene. Taken together, these results indicate S. cariri has a complex diversification history dating back to the Tertiary, suggesting the history of dry forest taxa may be significantly older than previously thought.

Loxosceles niedeguidonae (Araneae, Sicariidae) a new species of brown spider from Brazilian semi-arid region.

A new species of recluse spider, Loxosceles niedeguidonaesp. n., is described from the Parque Nacional Serra da Capivara, State of Piauí, Brazil. This is the first endemic species described from Brazilian semi-arid environment. The species is included in gaucho group of Gertsch (1967) due to its spermathecal shape and is considered close to Loxosceles chapadensis Bertani, Fukushima & Nagahama, 2010 by the unusual long male palpal tibia, a character not common for species of this group. An updated key for Loxosceles species of gaucho group is presented.