A revision of the textricellin spider genus Raveniella (Araneae:Araneoidea:Micropholcommatidae): exploring patterns of phylogeny and biogeography in an Australian biodiversity hotspot

Abstract

South-western Western Australia is a biodiversity hotspot, with high levels of local endemism and a rich but largely undescribed terrestrial invertebrate fauna. Very few phylogeographic studies have been undertaken on south-western Australian invertebrate taxa, and almost nothing is known about historical biogeographic or cladogenic processes, particularly on the relatively young, speciose Quaternary sand dune habitats of the Swan Coastal Plain. Phylogeographic and taxonomic patterns were studied in textricellin micropholcommatid spiders belonging to the genus Raveniella Rix & Harvey. The Micropholcommatidae is a family of small spiders with a widespread distribution in southern Western Australia, and most species are spatially restricted to refugial microhabitats. In total, 340 specimens of Raveniella were collected from 36 surveyed localities on the Swan Coastal Plain and 17 non-Swan Coastal Plain reference localities in south-western Western Australia. Fragments from three nuclear rRNA genes (5.8S, 18S and ITS2), and one mitochondrial protein-coding gene (COI) were used to infer the phylogeny of the genus Raveniella, and to examine phylogeographic patterns on the Swan Coastal Plain. Five new species of Raveniella are described from Western Australia (R. arenacea, sp. nov., R. cirrata, sp. nov., R. janineae, sp. nov., R. mucronata, sp. nov. and R. subcirrata, sp. nov.), along with a single new species from south-eastern Australia (R. apopsis, sp. nov.). Four species of Raveniella were found on the Swan Coastal Plain: two with broader distributions in the High Rainfall and Transitional Rainfall Zones (R. peckorum Rix & Harvey, R. cirrata); and two endemic to the Swan Coastal Plain, found only on the western-most Quindalup dunes (R. arenacea, R. subcirrata). Two coastally restricted species (R. subcirrata, R. janineae) were found to be morphologically cryptic but genetically highly distinct, with female specimens morphologically indistinguishable from their respective sister-taxa (R. cirrata and R. peckorum). The greater Perth region is an important biogeographic overlap zone for all four Swan Coastal Plain species, where the ranges of two endemic coastal species join the northern and south-western limits of the ranges of R. peckorum and R. cirrata, respectively. Most species of Raveniella were found to occupy long, highly autapomorphic molecular branches exhibiting little intraspecific variation, and an analysis of ITS2 rRNA secondary structures among different species of Raveniella revealed the presence of an extraordinary hypervariable helix, ranging from 31 to over 400 nucleotides in length.

Biogeography and speciation of terrestrial fauna in the south‐western Australian biodiversity hotspot

“…Arenophryne , Aprasia , Ctenophorus , Lerista ) (Figs and ). Additional quantitative (undated) studies on both reptiles (Rabosky et al , ; Melville, Shoo & Doughty, ; Edwards, Keogh & Knowles, ; Kay & Keogh, ) and spiders (Rix et al , ) hint at very similar patterns, especially within the coastal and sub‐coastal sandplain bioregions south of Shark Bay and west of Israelite Bay. In those regions, extremely diverse faunistic assemblages have clearly experienced a complex mix of climatic (e.g.…”

“…A), lizards within the Ctenotus labillardieri species complex (Kay & Keogh, ) and spiders of the genus Raveniella (e.g. R. cirrata ; Rix et al , ).…”

“…Finally, several other animal taxa for which molecular data are available show little evidence of significant phylogeographic subdivision throughout their ranges in SWWA, including the mammals Cercartetus concinnus (Pestell et al , ), Setonix brachyurus (Sinclair, ), Smithopsis crassicaudata (Cooper, Adams & Labrindis, ) and Tarsipes rostratus (Clancy, ); the birds Barnardius zonarius (Joseph & Wilke, ), Biziura lobata (Guay et al , ), Gavicalis virescens (Joseph & Wilke, ) and Malurus splendens (Kearns et al , ); and the spiders Raveniella cirrata and R. peckorum (Rix et al , ). These taxa are significant in that they provide a useful point of comparison against those species with more pronounced phylogeographic structuring, and further highlight key characteristics (e.g.…”

“…More recently, phylogenetic, population genetic and biogeographic studies have also begun to provide quantitative datasets for a number of key animal lineages (see Sections III and IV, below), including for less vagile invertebrate, fish and frog taxa with high levels of endemicity in the region. Thus, while SWWA can still be described as something of a ‘phylogeographic open‐book’ (Rix, Harvey & Roberts, , p. 210) for numerous terrestrial metazoan lineages, three decades of accumulating systematic research on the fauna is beginning to complement and test hotspot concepts born out of botanical research.…”

Out of the twilight zone: phylogeny and evolutionary morphology of the orb-weaving spider family Mysmenidae, with a focus on spinneret spigot morphology in symphytognathoids (Araneae, Araneoidea)

“…The monophyly of symphytognathoids has not been supported by analyses based exclusively on DNA sequence data using a sufficiently dense taxon sample (reviewed in Hormiga & Griswold, ). The recent work on the phylogenetics of symphytognathoids has been driven by studies on micropholcommatine anapids (Rix et al ., , ; Rix & Harvey, ) and on mysmenids (Lopardo et al ., ). These studies have used both morphological and molecular data.…”