Molecular phylogeny of the tropical wandering spiders (Araneae, Ctenidae) and the evolution of eye conformation in the RTA clade

Tropical wandering spiders (Ctenidae) are a diverse group of cursorial predators with its greatest species richness in the tropics. Traditionally, Ctenidae are diagnosed based on the presence of eight eyes arranged in three rows (a 2-4-2 pattern). We present a molecular phylogeny of Ctenidae, including for the first time representatives of all of its subfamilies. The molecular phylogeny was inferred using five nuclear (histone H3, 28S, 18S, Actin and ITS-2) and four mitochondrial (NADH, COI, 12S and 16S) markers. The final matrix includes 259 terminals, 103 of which belong to Ctenidae and represent 28 of the current 49 described genera. We estimated divergence times by including fossils as calibration points and biogeographic events, and used the phylogenetic hypothesis obtained to reconstruct the evolution of the eye conformation in the retrolateral tibial apophysis (RTA) clade. Ctenidae and its main lineages originated during the Paleocene-Eocene and have diversified in the tropics since then. However, in some analyses Ctenidae was recovered as polyphyletic as the genus Ancylometes Bertkau, 1880 was placed as sister to Oxyopidae. Except for Acantheinae, in which the type genus Acantheis Thorell, 1891 is placed inside Cteninae, the four recognized subfamilies of Ctenidae are monophyletic in most analyses. The ancestral reconstruction of the ocular conformation in the retrolateral tibial apophysis clade suggests that the ocular pattern of Ctenidae has evolved convergently seven times and that it has originated from ocular conformations of two rows of four eyes (4-4) and the ocular pattern of lycosids (4-2-2). We also synonymize the monotypic genus Parabatinga Polotov & Brescovit, 2009 with Centroctenus Mello-Leitão, 1929. We discuss some of the putative morphological synapomorphies of the main ctenid lineages within the phylogenetic framework offered by the molecular phylogenetic results of the study.

Abba, a new monotypic genus of orb-weaving spiders (Araneae, Araneidae) from Australia

A new monotypic genus in the orb-weaving spider family Araneidae Clerck, 1757 is described from Australia: Abbagen. nov., with Abba transversa (Rainbow, 1912) comb. nov. as the type species. It differs from all other genera in the family by somatic characters, specifically a patch of approximately five long spines on the prolateral surface of the first leg in males and an abdominal colouration with a pair of two central spots dorsally on a creamy-white surface. Specimens of A. transversacomb. nov. have been collected in Queensland and New South Wales, where the species is largely summer-mature. We also provide a genus level summary of all Australian Araneidae, currently consisting of 230 described species and eight subspecies in 46 genera.

The new Australian leaf-curling orb-weaving spider genus Leviana (Araneae, Araneidae)

The new Australian orb-weaving spider genus Levianagen. nov. is described to include five species, all known from both sexes: Leviana dimidiata (L. Koch, 1871) comb. nov. (type species) (= Epeira sylvicola Rainbow, 1897 syn. nov.), L. cincinnatasp. nov., L. foliumsp. nov., L. minimasp. nov. and L. mulieraria (Keyserling, 1887) comb. nov. Male pedipalp morphology, specifically the presence of a single patella spine and the median apophysis forming an arch over the radix, place Levianagen. nov. in the informal Australian ‘backobourkiine’ clade; however, the genus differs from all other genera of this group by the presence of a spine inside the basal median apophysis arch of the male pedipalp, an epigyne that is wider than long with a scape that is approximately as long as the epigyne (but often broken off) and a lack of humeral humps on the elongate ovoid abdomen. In addition, unlike any other backobourkiine, Levianagen. nov. incorporate a rolled leaf as retreat into the periphery of their web. Levianagen. nov. species exhibit only a moderate sexual size dimorphism with female to male ratios between 1.3 and 1.7. Levianagen. nov. occurs in eastern Australia from northern Queensland in the north to Victoria in the south, with a single tropical species, L. mulierariacomb. nov., spreading into northern Western Australia.

Castanheira P. Revision of the new Australasian orb-weaving spider genus Salsa (Araneae, Araneidae)

A new Australasian genus in the orb-weaving spider family Araneidae Clerck, 1757 is described to include seven species: Salsafuliginata (L. Koch, 1871) comb. nov. (type species; = Epeirarubicundula Keyserling, 1887) syn. nov.) (Australia, introduced to New Zealand); S.brisbanae (L. Koch, 1867) comb. nov. (Australia); S.canalae (Berland, 1924) comb. nov. (New Caledonia); S.neneba sp. nov. (Papua New Guinea); S.recherchensis (Main, 1954) comb. nov. (Australia); S.rueda sp. nov. (Australia); and S.tartara sp. nov. (Australia; Lord Howe Island endemic). Salsa gen. nov. belongs to the Australasian informal backobourkiine clade and differs from other genera of this clade by a distinct abdominal shape (single posterior abdominal tubercle) and ventral colouration (pale lateral spindle-shaped bands), male pedipalp morphology (C-shaped median apophysis that has teeth-like tubercles inside the basal arch) and the shape of the female epigyne scape (partially translucent and generally shorter than the epigyne plate). Based mainly on male pedipalp morphology within the backobourkiines, Salsa gen. nov. has closest morphological affinities with Acroaspis Karsch, 1878 and Socca Framenau, Castanheira & Vink, 2022.

A new genus of Australian orb-weaving spider with extreme sexual size dimorphism (Araneae, Araneidae)

The new Australian orb-weaving spider genus Mangrovia in the family Araneidae Clerck, 1757 is described. It is characterised by extreme sexual size-dimorphism (eSSD) with females (total length 8–10 mm) ca. 3 to 5 times larger than males (2.5–3 mm). Whilst Mangrovia shares with the informal Australian ‘backobourkiine’ clade a single seta on the male pedipalp patella, the genus is probably more closely related to the ‘zealaraneines’ or associated genera. In addition to eSSD and the single patellar spine, the genus is characterised by a distinct subterminal embolus branch in males. The new genus includes two species: the type species Mangrovia albida (L. Koch, 1871) comb. nov. (= Epeira fastidiosa Keyserling, 1887, new syn.) from Queensland and Mangrovia occidentalissp. nov. from Western Australia. Both species are apparently coastal and occur in mangroves, but also in riparian woodland. Spiders were found resting in rolled-up leaves adjacent to their orb-web.

Monophyly, Taxon Sampling, and the Nature of Ranks in the Classification of Orb-Weaving Spiders (Araneae: Araneoidea)

We address some of the taxonomic and classification changes proposed by Kuntner et al. (2019) in a comparative study on the evolution of sexual size dimorphism in nephiline spiders. Their proposal to recircumscribe araneids and to rank the subfamily Nephilinae as a family is fundamentally flawed as it renders the family Araneidae paraphyletic. We discuss the importance of monophyly, outgroup selection, and taxon sampling, the subjectivity of ranks, and the implications of the age of origin criterion to assign categorical ranks in biological classifications. We explore the outcome of applying the approach of Kuntner et al. (2019) to the classification of spiders with emphasis on the ecribellate orb-weavers (Araneoidea) using a recently published dated phylogeny. We discuss the implications of including the putative sister group of Nephilinae (the sexually dimorphic genus Paraplectanoides) and the putative sister group of Araneidae (the miniature, monomorphic family Theridiosomatidae). We propose continuation of the phylogenetic classification put forth by Dimitrov et al. (2017), and we formally rank Nephilinae and Phonognathinae as subfamilies of Araneidae. Our classification better reflects the understanding of the phylogenetic placement and evolutionary history of nephilines and phonognathines while maintaining the diagnosability of Nephilinae. It also fulfills the fundamental requirement that taxa must be monophyletic, and thus avoids the paraphyly of Araneidae implied by Kuntner et al. (2019).

Photoreflectance/scattering measurements of spider silks informed by standard optics

The silks of certain orb weaving spiders are emerging as high-quality optical materials. This motivates study of the optical properties of such silk and particularly the comparative optical properties of the silks of different species. Any differences in optical properties may impart biological advantage for a spider species and make the silks interesting for biomimetic prospecting as optical materials. A prior study of the reflectance of spider silks from 18 species reported results for three species of modern orb weaving spiders (Nephila clavipes, Argiope argentata and Micrathena Schreibersi) as having reduced reflectance in the UV range. (Modern in the context used here means more recently derived.) The reduced UV reflectance was interpreted as an adaptive advantage in making the silks less visible to insects. Herein, a standard, experimental technique for measuring the reflectance spectrum of diffuse surfaces, using commercially available equipment, has been applied to samples of the silks of four modern species of orb weaving spiders: Phonognatha graeffei, Eriophora transmarina, Nephila plumipes and Argiope keyserlingi. This is a different technique than used in the previous study. Three of the four silks measured have a reduced signal in the UV. By taking the form of the silks as optical elements into account, it is shown that this is attributable to a combination of wavelength-dependent absorption and scattering by the silks rather than differences in reflectance for the different silks. Phonognatha graeffei dragline silk emerges as a very interesting spider silk with a flat 'reflectance'/scattering spectrum which may indicate it is a low UV absorbing dielectric micro-fibre. Overall the measurement emerges as having the potential to compare the large numbers of silks from different species to prospect for those which have desirable optical properties.

Towards a synthesis of the Caribbean biogeography of terrestrial arthropods

BACKGROUND

The immense geologic and ecological complexity of the Caribbean has created a natural laboratory for interpreting when and how organisms disperse through time and space. However, competing hypotheses compounded with this complexity have resulted in a lack of unifying principles of biogeography for the region. Though new data concerning the timing of geologic events and dispersal events are emerging, powerful new analytical tools now allow for explicit hypothesis testing. Arthropods, with varying dispersal ability and high levels of endemism in the Caribbean, are an important, albeit understudied, biogeographic model system. Herein, we include a comprehensive analysis of every publicly available genetic dataset (at the time of writing) of terrestrial Caribbean arthropod groups using a statistically robust pipeline to explicitly test the current extent of biogeographic hypotheses for the region.

RESULTS

Our findings indicate several important biogeographic generalizations for the region: the South American continent is the predominant origin of Caribbean arthropod fauna; GAARlandia played a role for some taxa in aiding dispersal from South America to the Greater Antilles; founder event dispersal explains the majority of dispersal events by terrestrial arthropods, and distance between landmasses is important for dispersal; most dispersal events occurred via island hopping; there is evidence of 'reverse' dispersal from islands to the mainland; dispersal across the present-day Isthmus of Panama generally occurred prior to 3 mya; the Greater Antilles harbor more lineage diversity than the Lesser Antilles, and the larger Greater Antilles typically have greater lineage diversity than the smaller islands; basal Caribbean taxa are primarily distributed in the Greater Antilles, the basal-most being from Cuba, and derived taxa are mostly distributed in the Lesser Antilles; Jamaican taxa are usually endemic and monophyletic.

CONCLUSIONS

Given the diversity and deep history of terrestrial arthropods, incongruence of biogeographic patterns is expected, but focusing on both similarities and differences among divergent taxa with disparate life histories emphasizes the importance of particular qualities responsible for resulting diversification patterns. Furthermore, this study provides an analytical toolkit that can be used to guide researchers interested in answering questions pertaining to Caribbean biogeography using explicit hypothesis testing.

Generic and family transfers, and numina dubia for orb-weaving spiders (Araneae, Araneidae) in the Australasian, Oriental and Pacific regions

As part of a current revision of the Australasian and Pacific orb-weaving spider fauna (family Araneidae Clerck, 1757), a number new combinations are proposed in the generaAcroaspisKarsch, 1878 (3 species),CarepalxisL. Koch, 1872 (1 species),CyclosaMenge, 1866 (5 species), andNeosconaSimon, 1864 (7 species):Acroaspislancearia(Keyserling, 1887),comb. n.,A.mamillana(Keyserling, 1887),comb. n.,A.scutifer(Keyserling, 1886),comb. n.,Carepalxisfurcifera(Keyserling, 1886),comb. n.;Cyclosaanatipes(Keyserling, 1887),comb. n.;Cyclosaapoblepta(Rainbow, 1916),comb. n.;Cyclosaargentaria(Rainbow, 1916),comb. n.;Cyclosalichensis(Rainbow, 1916),comb. n.;Cyclosapoweri(Rainbow, 1916),comb. n.;Neosconadecolor(L. Koch, 1871),comb. n.;Neosconaenucleata(Karsch, 1879),comb. n.;Neosconaflavopunctata(L. Koch, 1871),comb. n.;Neosconafloriata(Hogg, 1914),comb. n.;Neosconagranti(Hogg, 1914),comb. n.;Neosconainusta(L. Koch, 1871),comb. n.; andNeosconanotanda(Rainbow, 1912),comb. n.

The following two Australian species, currently placed inAraneus, are not Araneidae but comb-footed spiders (family Theridiidae Sundevall, 1833):Anelosimusdianiphus(Rainbow, 1916),comb. n.andTheridionxanthostichus(Rainbow, 1916),stat. and comb. n.

The following six species are considerednumina dubiaas their type material is immature or otherwise unidentifiable (e.g. partly destroyed):AraneusacachmenusRainbow, 1916;AraneusagastusRainbow, 1916;AraneusexsertusRainbow, 1904;AraneussuavisRainbow, 1899;Carepalxiscoronata(Rainbow, 1896); andHeurodesturritusKeyserling, 1886.Heurodesfratellus(Chamberlin, 1924) is considered anomen dubiumandHeurodesporcula(Simon, 1877) is returned toEriovixiaArcher, 1951,Eriovixiaporcula(Simon, 1877).

Type material of predominantly Australian species described by E. v. Keyserling (1 species), W. J. Rainbow (10 species), A. T. Urquhart (8 species), and C. A. Walckenaer (2 species) is here considered destroyed or otherwise lost. As it is impossible to identify these species from their original descriptions and considering the known spider fauna from their respective type localities, they are all considerednumina dubia:AnepsiacrinitaRainbow, 1893;Epeiradiabrosis(Walckenaer, 1841);EpeiradiversicolorRainbow, 1893;EpeirafictaRainbow, 1896;EpeirahamiltoniRainbow, 1893;Epeiralacrymosa(Walckenaer, 1841);EpeiraleaiRainbow, 1894;EpeiramortoniUrquhart, 1891;EpeiranotacephalaUrquhart, 1891;EpeiraobscurtaUrquhart, 1893;EpeiraphalerataUrquhart, 1893;EpeirapronubaRainbow, 1894;EpeirararaKeyserling, 1887;EpeirasingularaUrquhart, 1891;Epeirasub-flavidaUrquhart, 1893;EpeirasimilarisRainbow, 1896 (=AraneusurquhartiRoewer, 1942 replacement name);EpeiraventriosaUrquhart, 1891; andEpeiraviridulaUrquhart, 1891.