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Figure 18. Anelosimus eximius. A in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 18. Anelosimus eximius. A, tip of cymbium of the expanded palp; note depressed tip (arrow), the light sclerotization of the cymbial tip is a synapomorphy of Anelosimus (26-1). B, male SPR; curvy rows (159-1) are characteristic of some Anelosimus. C, the much less pronounced female picks. D, male SPR area; note also proprioreceptic setae (PR, left arrow points toward a dorsal (11 o'clock) proprioreceptor, 163-1). E, female spinnerets. F, female PLS and PMS. G, male PMS. Scale bars: A–D, 50 Mm; E–G, 20 Mm.

Figure 17. Anelosimus eximius, male palp. A in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 17. Anelosimus eximius, male palp. A, mesial; note hooked TTA tip (arrow, 85-1). B, ventral. C, ectal. D, mesial tip of palp. E, view of expanded palpal sclerites. F, details of SC (70-1) and TTA with a hooked tip (arrow). G, conductor rising out of the side of the SC, the SC was interpreted as the C by Levi & Levi (1962) and Coddington (1990a). Scale bars: A-G, 100 Mm.

Figure 16. Anelosimus analyticus. A in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 16. Anelosimus analyticus. A, female prosoma, front view. B, C, male stridulatory picks. B, left side; note inverse position of top spine (arrow). C, right side, same animal. D, E, female spinnerets. D, left field. E, colular setae (arrow). F, female tarsal comb. G, details of the comb's serrated bristles. Scale bars: A, 100 Mm; B–D, G, 20 Mm; E, F, 50 Mm.

Figure 23. Anelosimus rupununi, female. A, PLS. B, PMS. C, ALS. D, fourth tarsal claws. E in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 23. Anelosimus rupununi, female. A, PLS. B, PMS. C, ALS. D, fourth tarsal claws. E, tarsal comb on fourth tarsus. F, details of serrated setae. Scale bars: A–D, F, 20 Mm; E, 100 Mm.

Figure 19. Anelosimus eximius. A, epiandrous gland spigots. B in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 19. Anelosimus eximius. A, epiandrous gland spigots. B, epigynum; note ridges on epigynal plate (arrows, 3-1). C, prolateral cheliceral margin. D, retrolateral cheliceral margin. E, male fourth tarsal claws. F, female prosoma. Scale bars: A, C–E, 20 Mm; B, 50 Mm; F, 100 Mm.

Figure 22. Anelosimus rupununi. A–D, male palp. A in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 22. Anelosimus rupununi. A–D, male palp. A, mesial; note bifurcated MA (75-1). B, ventral. C, ectal. D, distal tip. E, cheliceral promarginal teeth. F, epiandrous gland spigots. G, epigynum; note acute upper wall of bursa (arrow, 6-1). Scale bars: A–D, 100 Mm; G, 50 Mm; E, F, 20 Mm.

Figure 25. Anelosimus studiosus, female. A, spinnerets. B, ALS. C, PLS. D, PMS. E in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 25. Anelosimus studiosus, female. A, spinnerets. B, ALS. C, PLS. D, PMS. E, colular setae (arrow); note absence of colulus (172-1). F, cheliceral teeth. Scale bars: A, E, F, 100 Mm; B–D, 20 Mm.

Figure 24. Anelosimus studiosus. A–C, male palp. A, ventral. B, dorsal. C in Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae)

Figure 24. Anelosimus studiosus. A–C, male palp. A, ventral. B, dorsal. C, tibia; note three trichobothria (arrows, 18-1, 19-1). D, male abdominal stridulatory picks. E, details. F, epiandrous gland spigots. G, epigynum. Scale bars: A–C, 100 Mm; D, G, 50 Mm; F, 20 Mm; E, 10 Mm.

opencc-zeroMar 2020View details →

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Global diversification of Anelosimus spiders driven by long distance overwater dispersal and Neogene climate oscillations

Vicariance and dispersal events, combined with intricate global climatic history, have left an imprint on the spatiotemporal distribution and diversity of many organisms. Anelosimus cobweb spiders (Theridiidae), are solitary-social organisms with a cosmopolitan distribution in temperate- to-tropical areas. Their evolutionary history and the discontinuous distribution of species richness suggest that 1) long distance overwater dispersal, and 2) climate change during the Neogene (23–2.6 Ma), may be major factors in explaining their distribution and diversification. Here we test these hypotheses, and explicitly test if global Miocene/Pliocene climatic cooling in the last 8 Ma affected Anelosimus radiation in parallel in South America and Madagascar. To do so, we investigate the phylogeny and spatiotemporal biogeography of Anelosimus through a culmination of a 20-year comprehensive global sampling at the species level (69 species, including 84% of the known 75 species worldwide, represented by 268 individuals) using nucleotide data from seven loci (5.5 kb). Our results strongly support the monophyly of Anelosimus with an Oligocene (~30 Ma) South American origin. Major clades on other continents originate via multiple, long-distance dispersal events, of solitary or subsocial—but not social—lineages, from the Americas. These intercontinental dispersals were to Africa, Madagascar (twice), and SE Asia/Australasia. The early diversification of Anelosimus spiders coincides with a sudden thermal increase in the late Oligocene (~27–25 Ma), though no causal connection can be made. Our results, however, strongly support the hypothesis that global Neogene climatic cooling in the last 8 Ma drove Anelosimus radiation in parallel in S. America and Madagascar, offering a rare empirical evidence for diversification of a socially diverse group driven by an interplay between long distance dispersal and global Neogene climatic changes.

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Data from: Limited role of character displacement in the coexistence of congeneric Anelosimus spiders in a Madagascan montane forest

Evolutionary and ecological theory predicts that closely related and similar species should coexist infrequently because speciation is more likely to occur allopatrically than sympatrically, and because co-occurring species with similar traits may compete for limited resources, leading to competitive exclusion or character displacement. Here we study the unusual coexistence of 10 similar congeneric species of Anelosimus spiders within a small forest fragment in Madagascar. We asked if these species radiated in sympatry or allopatry, and if there was evidence for local-scale character displacement in body size and other species-level traits. We sampled ∼ 350 colonies (6346 individuals) along a 2800 m transect. We identified colonies using morphology and DNA barcoding, and tested the monophyly of local and regional species assemblages with time-calibrated phylogenies. We used null model analysis and phylogenetic signal inference to test for patterns of segregation in body size, microhabitat, phenology, and seasonality of coexisting species. We found that all species belong to a Madagascan clade that radiated during the Pliocene, but that contemporary local assemblages are non-monophyletic. This is consistent with allopatric speciation during periods of global cooling and expansion of grasslands, and subsequent species assembly as forest fragments re-expanded and coalesced. We found no evidence for character displacement, except for overdispersion and even spacing in phenology: species were segregated by instars in a manner consistent with resource partitioning or maintenance of reproductive isolation. Overdispersion or even spacing in phenology may contribute to coexistence either through resource partitioning or mate recognition. However, there was no support for a scenario of resource partitioning and divergence of body size or other correlated morphological characters. These traits are better explained by evolutionary forces operating during speciation, rather than ecological forces operating during local community assembly.

opencc-zeroDec 2014View details →

FIGURES 14A–C. Anelosimus nelsoni n in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 14A–C. Anelosimus nelsoni n. sp. A, male pedipalpus, ventral (C conductor, E embolus, EB 'embolic division b', MA median apophysis, TTA theridiid tegular apophysis); B, epigynum, ventral; C, epigynum cleared, dorsal (CD copulatory ducts, FD fertilization ducts, S spermathecae), line sketch above shows trajectory of the copulatory ducts to the spermathecae. Scale bars (left for pedipalpus, right for epigyna): 100 m.

FIGURES 2A–E in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 2A–E. Photographs of webs of A. kohi. A–C, colonies of different sizes; A, web containing female with large juveniles; B, female with small juveniles; C, female with egg sac. D–E, female guarding egg sac. The leaves are taken from a small web the female typically attaches two leafs (D) to form a retreat, one or both leafs may also be folded (E). Inside the retreat the spider guards the egg sac surrounded by a thin silk envelope (E).

FIGURES 3A–I. Anelosimus kohi, color polymorphism. A in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 3A–I. Anelosimus kohi, color polymorphism. A, female, dark morph from Singapore; B, female, dark morph from Malaysia; C, male, dark morph from Singapore; D, male light morph from Malaysia; E–G, female with egg sac, light morph from Malaysia, note how egg sac is clasped with the cheliceral fangs and palpal claws; H, female with egg sac, light morph from Singapore; I, female unusual pale morph from Singapore.

FIGURES 6A–F. Anelosimus biglebowski n in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 6A–F. Anelosimus biglebowski n. sp., male pedipalpus (C conductor, E embolus, MA median apophysis, ST subtegulum, T tegulum, TTA theridiid tegular apophysis). A, prolateral; B, prolateralventral; C, ventral; D, retrolateral; E, details of C and TTA, prolateral; F, clasp of distal sclerites, ventral. Scale bars: A–D, 100 m, E–F, 20 m.

FIGURES 10A–F. A–C, A. monskenyensis n in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 10A–F. A–C, A. monskenyensis n. sp. A, pedipalpus, ventral (C conductor, E embolus, MA median apophysis, ST subtegulum, T tegulum, TTA theridiid tegular apophysis). B, epigynum ventral; C, epigynum cleared, dorsal (FD fertilization ducts, S spermathecae). D–F, A. sulawesi n. sp. D, pedipalpus, ventral; E, epigynum ventral; F, epigynum cleared, dorsal (CD copulatory duct). Scale bars (upper for pedipalpi, lower for epigyna): 100 m.

FIGURES 13A–G. Anelosimus kohi Yoshida, 1993. A in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 13A–G. Anelosimus kohi Yoshida, 1993. A, epigynum, ventral; B, epiandrous gland fusules; C, female prosoma, dorsal; D, female posterior lateral and posterior median spinnerets, left side (AC aciniform spigots, AG aggregate spigots, CY cylindrical spigots, FL flagelliform spigots; mAP minor ampullate spigots); E, female anterior lateral spinnerets and colular area (arrow), uniquely in A. kohi no colular setae are present. F, male stridulatory pick row; G, female pedipalpal claw, lateral. Scale bars: C, E, 100 m; A–B, 50 m; D, F–G, 10 m.

FIGURES 12A–F. Anelosimus kohi Yoshida, 1993 in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 12A–F. Anelosimus kohi Yoshida, 1993, male pedipalpus (C conductor, dh distal haematodocha, E embolus, MA median apophysis, ST subtegulum, T tegulum, TTA theridiid tegular apophysis). A, prolateral; B, ventral, note size of tibia compared to the pedipalpal bulb; C, retrolateral; D, details of sclerites, prolateralventral; E, details or bulb, ventral; F, details of bulb, retrolateralventral. Scale bars: A–E, 100 m; F, 50 m.

FIGURES 18A–E. A–B, A. agnar n in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 18A–E. A–B, A. agnar n. sp. A, epigynum, ventral; B, epigynum cleared, dorsal. C–D, A. linda n. sp. C, epigynum, ventral; D, epigynum cleared, dorsal (CD copulatory ducts, FD fertilization ducts, S spermathecae). E, Anelosimus dude n. sp., female opisthosoma ventral, showing setae around the pedicel and the transparency of the cuticle anterior to the epigynum. Scale bar for epigyna: 100 mm.

FIGURES 5A–F. A–C, Anelosimus biglebowski n in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 5A–F. A–C, Anelosimus biglebowski n.sp. A, male pedipalpus, ventral (C conductor, E embolus, MA median apophysis, ST subtegulum, T tegulum, TTA theridiid tegular apophysis); B, epigynum ventral, C, epigynum cleared, dorsal (CD copulatory duct, FD fertilization duct, S spermathecae). D–F, A. dude n. sp. D, male pedipalpus, ventral; E, epigynum ventral, F, epigynum cleared, dorsal. Scale bars (upper for pedipalpi, lower for epigyna): 100 m.

FIGURES 11A–H. Anelosimus kohi Yoshida, 1993. A–B in New species of Anelosimus (Araneae: Theridiidae) from Africa and Southeast Asia, with notes on sociality and color polymorphism

FIGURES 11A–H. Anelosimus kohi Yoshida, 1993. A–B, pedipalpus of light color morph (C conductor, E embolus, MA median apophysis, ST subtegulum, T tegulum, TTA theridiid tegular apophysis). A, ventral; B, prolateral. C–D, pedipalpus of dark color morph; C, ventral; D, prolateral. E–F, epigynum of light color morph; E, ventral; F, cleared, dorsal. G–H, epigynum of dark color morph; G, ventral; H, cleared, dorsal (CD copulatory ducts, FD fertilization ducts, S spermathecae). Scale bars (left for pedipalpi, right for epigyna): 100 m.