Spider taxonomy

Spider taxonomy is that part of taxonomy that is concerned with the science of naming, defining and classifying all spiders, members of the Araneae order of the arthropod class Arachnida with about 46,000 described species. However, there are likely many species that have escaped the human eye to this day, and many specimens stored in collections waiting to be described and classified. It is estimated that only one third to one half of the total number of existing species have been described.[1]

Paintings of Araneus angulatus from Svenska Spindlar of 1757, the first major work on spider taxonomy

Arachnologists currently divide spiders into two suborders with about 114 families.

Due to constant research, with new species being discovered every month and others being recognized as synonyms, the number of species in the families is bound to change and can never reflect the present status with total accuracy. Nevertheless, the species numbers given here are useful as a guideline – see the table of families at the end of the article.

HistoryEdit

Spider taxonomy can be traced to the work of Swedish naturalist Carl Alexander Clerck, who in 1757 published the first binomial scientific names of some 67 spiders species in his Svenska Spindlar ("Swedish Spiders"), one year before Linnaeus named over 30 spiders in his Systema Naturae. In the ensuing 250 years, thousands more species have been described by researchers around the world, yet only a dozen taxonomists are responsible for more than a third of all species described. The most prolific authors include Eugène Simon of France, Norman Platnick and Herbert Walter Levi of the United States, Embrik Strand of Norway, and Tamerlan Thorell of Sweden, each having described well over 1,000 species.[2]

Overview of phylogenyEdit

At the very top level, there is broad agreement on the phylogeny and hence classification of spiders, which is summarized in the cladogram below. The three main clades into which spiders are divided are shown in bold; as of 2015, they are usually treated as one suborder, Mesothelae, and two infraorders, Mygalomorphae and Araneomorphae, grouped into the suborder Opisthothelae.[3][4] The Mesothelae, with about 140 species in 8 genera as of October 2020, make up a very small proportion of the total of around 49,000 known species. Mygalomorphae species comprise around 7% of the total, the remaining 93% being in the Araneomorphae.[note 1]

Araneae (spiders)

Mesothelae

Opisthothelae

Mygalomorphae

Araneomorphae

Hypochiloidea

Austrochiloidea

Haplogynae

Entelegynae

The Araneomorphae are divided into two main groups: the Haplogynae and the Entelegynae. The Haplogynae make up about 10% of the total number of spider species, the Entelegynae about 83%.[note 1] The phylogenetic relationships of the Haplogynae, Entelegynae and the two smaller groups Hypochiloidea and Austrochiloidea remain uncertain as of 2015. Some analyses place both Hypochiloidea and Austrochiloidea outside Haplogynae;[5] others place the Austrochiloidea between the Haplogynae and the Entelegynae;[6][7] the Hypochiloidea have also been grouped with the Haplogynae.[8] Earlier analyses regarded the Hypochiloidea as the sole representatives of a group called the Paleocribellatae, with all other araneomorphs placed in the Neocribellatae.[9]

The Haplogynae are a group of araneomorph spiders with simpler male and female reproductive anatomy than the Entelegynae. Like the mesotheles and mygalomorphs, females have only a single genital opening (gonopore), used both for copulation and egg-laying;[10] males have less complex palpal bulbs than those of the Entelegynae.[11] Although some studies based on both morphology and DNA suggest that the Haplogynae form a monophyletic group (i.e. they comprise all the descendants of a common ancestor),[12][8] this hypothesis has been described as "weakly supported", with most of the distinguishing features of the group being inherited from ancestors shared with other groups of spiders, rather than being clearly indicative of a separate common origin (i.e. being synapomorphies).[13] One phylogenetic hypothesis based on molecular data shows the Haplogynae as a paraphyletic group leading to the Austrochilidae and Entelegynae.[14]

The Entelegynae have a more complex reproductive anatomy: females have two "copulatory pores" in addition to the single genital pore of other groups of spiders; males have complex palpal bulbs, matching the female genital structures (epigynes).[12] The monophyly of the group is well supported in both morphological and molecular studies. The internal phylogeny of the Entelegynae has been the subject of much research. Two groups within this clade contain the only spiders that make vertical orb webs: the Deinopoidea are cribellate – the adhesive properties of their webs are created by packets of thousands of extremely fine loops of dry silk; the Araneoidea are ecribellate – the adhesive properties of their webs are created by fine droplets of "glue". In spite of these differences, the webs of the two groups are similar in their overall geometry.[15] The evolutionary history of the Entelegynae is thus intimately connected with the evolutionary history of orb webs. One hypothesis is that there is a single clade, Orbiculariae, uniting the orb web makers, in whose ancestors orb webs evolved. A review in 2014 concluded that there is strong evidence that orb webs evolved only once, although only weak support for the monophyly of the Orbiculariae.[16] One possible phylogeny is shown below; the type of web made is shown for each terminal node in order of the frequency of occurrence.[17]

Entelegynae

Eresoidea, RTA clade – no web; substrate-defined web

Orbiculariae

Deinopoideaorb web

Nicodamidaeaerial sheet web

Araneoideaorb web; aerial sheet web; cobweb; no web

If this is correct, the earliest members of the Entelegynae made webs defined by the substrate on which they were placed (e.g. the ground) rather than suspended orb webs. True orb webs evolved once, in the ancestors of the Orbiculariae, but were then modified or lost in some descendants.

An alternative hypothesis, supported by some molecular phylogenetic studies, is that the Orbiculariae are paraphyletic, with the phylogeny of the Entelegynae being as shown below.[18]

Entelegynae

Araneoideaorb web; aerial sheet web; cobweb; no web

RTA clade – no web; substrate-defined web

Deinopoidea, Oecobiidaeorb web; substrate-defined web

On this view, orb webs evolved earlier, being present in the early members of the Entelegynae, and were then lost in more groups,[19] making web evolution more convoluted, with different kinds of web having evolved separately more than once.[16] Future advances in technology, including whole-genome sampling, should lead to "a clearer image of the evolutionary chronicle and the underlying diversity patterns that have resulted in one of the most extraordinary radiations of animals".[16]

Suborder MesothelaeEdit

Mesothelae resemble the Solifugae ("wind scorpions" or "sun scorpions") in having segmented plates on their abdomens that create the appearance of the segmented abdomens of these other arachnids. They are both few in number and also limited in geographical range.

 
Digitally enhanced image of a Sphodros rufipes that shows the nearly perfectly vertical orientation of the fangs, a prime characteristic of the Mygalomorphae.

Suborder OpisthothelaeEdit

Suborder Opisthothelae contains the spiders that have no plates on their abdomens. Opisthothelae is divided into two infraorders, Mygalomorphae and Araneomorphae, which can be distinguished by the orientation of their fangs. It can be somewhat difficult on casual inspection to determine whether the fang orientation would classify a spider as a mygalomorph or araneomorph. The spiders that are called "tarantulas" in English are so large and hairy that inspection of their fangs is hardly necessary to categorize one of them as a mygalomorph. Other, smaller, members of this suborder, however, look little different from the araneomorphs. (See the picture of Sphodros rufipes below.) Many araneomorphs are immediately identifiable as such since they are found on webs designed for the capture of prey or exhibit other habitat choices that eliminate the possibility that they could be mygalomorphs.

Infraorder MygalomorphaeEdit

 
Megaphobema robustum, one of the many kinds of spiders called "tarantulas"

Spiders in infraorder Mygalomorphae are characterized by the vertical orientation of their fangs and the possession of four book lungs.

Infraorder AraneomorphaeEdit

 
Photograph showing orientation of the fangs of the Araneomorphae.

Most, if not all, of the spiders one is likely to encounter in everyday life belong to infraorder Araneomorphae. It includes a wide range of spider families, including the orb-weaver spiders that weave their distinctive webs in gardens, the cobweb spiders that frequent window frames and the corners of rooms, the crab spiders that lurk on flowers waiting for nectar- and pollen-gathering insects, the jumping spiders that patrol the outside walls of buildings, and so on. They are characterized by having fangs whose tips approach each other as they bite, and (usually) having one pair of book lungs.

Classification above familiesEdit

Spiders were long classified into families that were then grouped into superfamilies, some of which were in turn placed into a number of higher taxa below the level of infraorder. When more rigorous approaches, such as cladistics, were applied to spider classification, it became clear that most of the major groupings used in the 20th century were not supported. Many were based on shared characters inherited from the ancestors of multiple clades (plesiomorphies), rather than being distinctive characters originating in the ancestors of that clade only (apomorphies). According to Jonathan A. Coddington in 2005, "books and overviews published prior to the last two decades have been superseded".[20] Listings of spiders, such as the World Spider Catalog, currently ignore classification above the family level.[20][21]

At the higher level, the phylogeny of spiders is now often discussed using informal clade names, such as the "RTA clade",[22] the "Oval Calmistrum" clade or the "Divided Cribellum" clade.[23] Older names previously used formally are used as clade names, e.g. Entelegynae and Orbiculariae.[24]

Table of familiesEdit

Key
Genera 1 ≥2 ≥10 ≥100
Species 1–9 ≥10 ≥100 ≥1000
Spider families[note 2]
Family Genera Species Common name Example
Mesothelae
Liphistiidae 8 138 segmented spiders Kimura spider
Opisthothelae: Mygalomorphae
Actinopodidae 3 115 Missulena (mouse spiders)
Anamidae 9 99 Aname diversicolor (black wishbone spider)
Antrodiaetidae 4 37 folding trapdoor spiders Atypoides riversi
Atracidae 3 35 Australian funnel-web spiders Illawarra wisharti
Atypidae 3 54 purseweb spiders Sphodros rufipes (red-legged purseweb spider)
Barychelidae 42 294 trapdoor baboon spiders Sason sundaicum
Bemmeridae 4 47 Spiroctenus personatus
Ctenizidae 2 5 cork-lid trapdoor spiders Cteniza sauvagesi
Cyrtaucheniidae 8 107 wafer trapdoor spiders Amblyocarenum nuragicus
Dipluridae 8 93 funnel-web tarantulas Spruce-fir moss spider (Microhexura montivaga)
Entypesidae 3 37 Entypesa andohahela
Euagridae 13 86 Euagrus formosanus
Euctenizidae 8 77 Aptostichus simus
Halonoproctidae 6 93 Ummidia algarve
Hexathelidae 7 45 venomous funnel-web tarantulas Hexathele hochstetteri
Hexurellidae 1 4
Idiopidae 22 412 Idiosoma nigrum (black rugose trapdoor spider)
Ischnothelidae 5 26
Macrothelidae 1 38
Mecicobothriidae 1 2 dwarf tarantulas
Megahexuridae 1 1
Microhexuridae 1 2
Microstigmatidae 12 41 Envia garciai
Migidae 11 102 tree trapdoor spiders Moggridgea rainbowi
Nemesiidae 22 184 funnel-web trapdoor spiders Aname atra (black wishbone spider)
Paratropididae 5 17 baldlegged spiders Paratropis tuxtlensis
Porrhothelidae 1 5
Pycnothelidae 6 81
Stasimopidae 1 47
Theraphosidae 147 987 tarantulas Goliath birdeater (Theraphosa blondi)
Opisthothelae: Araneomorphae
Agelenidae 87 1341 araneomorph funnel-web spiders Hobo spider (Eratigena agrestis)
Amaurobiidae 49 274 tangled nest spiders Callobius claustrarius
Ammoxenidae 4 18
Anapidae 58 233
Anyphaenidae 56 574 anyphaenid sac spiders Hibana velox (yellow ghost spider)
Araneidae 178 3058 orb-weaver spiders Zygiella x-notata
Archaeidae 5 90 pelican spiders Madagascarchaea gracilicollis
Arkyidae 2 38
Austrochilidae 3 10 Hickmania troglodytes
Caponiidae 19 124 Diploglena capensis
Cheiracanthiidae 14 362
Cithaeronidae 2 8
Clubionidae 15 638 sac spiders Clubiona trivialis
Corinnidae 70 793 dark sac spiders Castianeira sp.
Ctenidae 48 515 wandering spiders Phoneutria fera
Cyatholipidae 23 58
Cybaeidae 20 268 Diving bell spider (Argyroneta aquatica)
Cycloctenidae 8 80
Deinopidae 3 68 net-casting spiders Deinopis subrufa (rufous net-casting spider)
Desidae 60 296 intertidal spiders Phryganoporus candidus
Dictynidae 52 470 Nigma walckenaeri
Diguetidae 2 15 coneweb spiders
Drymusidae 2 17 false violin spiders
Dysderidae 25 578 woodlouse hunter spiders Woodlouse spider (Dysdera crocata)
Eresidae 9 100 velvet spiders Eresus sandaliatus
Filistatidae 19 182 crevice weavers Southern house spider (Kukulcania hibernalis)
Gallieniellidae 10 68
Gnaphosidae 161 2546 flat-bellied ground spiders Drassodes cupreus
Gradungulidae 7 16 large-clawed spiders Progradungula carraiensis (Carrai cave spider)
Hahniidae 23 351 dwarf sheet spiders
Hersiliidae 16 182 tree trunk spiders Hersilia savignyi
Homalonychidae 1 3
Huttoniidae 1 1 Huttonia palpimanoides
Hypochilidae 2 14 lampshade spiders Hypochilus thorelli
Lamponidae 23 192 White-tailed spider (Lampona spp.)
Leptonetidae 21 355 Tooth Cave spider (Tayshaneta myopica)
Linyphiidae 619 4670 dwarf / money spiders Linyphia triangularis
Liocranidae 32 290 liocranid sac spiders
Lycosidae 124 2430 wolf spiders Lycosa tarantula
Malkaridae 13 57 shield spiders
Mecysmaucheniidae 7 25
Megadictynidae 2 2
Mimetidae 8 154 pirate spiders Oarces reticulatus
Miturgidae 29 136 long-legged sac spiders
Myrmecicultoridae 1 1
Mysmenidae 14 158 spurred orb-weavers
Nesticidae 16 279 scaffold web spiders Nesticella marapu
Nicodamidae 7 27
Ochyroceratidae 10 166 midget ground weavers Theotima minutissima
Oecobiidae 6 119 disc web spiders Oecobius navus
Oonopidae 114 1864 dwarf hunting spiders Oonops domesticus
Orsolobidae 30 188
Oxyopidae 9 438 lynx spiders Peucetia viridans (green lynx spider)
Pacullidae 4 38
Palpimanidae 19 155 palp-footed spiders
Penestomidae 1 9
Periegopidae 1 3
Philodromidae 31 536 philodromid crab spiders Philodromus dispar
Pholcidae 94 1812 daddy long-legs spiders Pholcus phalangioides
Phrurolithidae 15 247
Physoglenidae 13 72
Phyxelididae 14 66
Pimoidae 4 53 Pimoa cthulhu
Pisauridae 51 353 nursery web spiders Pisaura mirabilis
Plectreuridae 2 31
Psechridae 2 61
Psilodercidae 11 224
Salticidae 647 6230 jumping spiders Zebra spider (Salticus scenicus)
Scytodidae 5 245 spitting spiders Scytodes thoracica
Segestriidae 4 136 tubeweb spiders Segestria florentina
Selenopidae 9 260 wall spiders Selenops radiatus
Senoculidae 1 31
Sicariidae 3 169 recluse spiders Brown recluse (Loxosceles reclusa)
Sparassidae 89 1253 huntsman spiders Delena cancerides
Stenochilidae 2 13
Stiphidiidae 20 125 Tartarus mullamullangensis
Symphytognathidae 8 74 dwarf orb-weavers Patu digua
Synaphridae 3 13
Synotaxidae 1 11
Telemidae 14 97 long-legged cave spiders
Tetrablemmidae 27 145 armored spiders
Tetragnathidae 50 986 long jawed orb-weavers Leucauge venusta (orchard spider)
Theridiidae 124 2511 cobweb spiders Redback spider (Latrodectus hasselti)
Theridiosomatidae 19 129 ray spiders Theridiosoma gemmosum
Thomisidae 169 2150 crab spiders Misumena vatia (goldenrod crab spider)
Titanoecidae 5 54 Goeldia obscura
Toxopidae 14 82
Trachelidae 19 246
Trechaleidae 17 131
Trochanteriidae 21 171
Trogloraptoridae 1 1 Trogloraptor marchingtoni
Udubidae 4 15
Uloboridae 19 287 hackled orb-weavers Uloborus walckenaerius
Viridasiidae 2 7
Xenoctenidae 4 33
Zodariidae 87 1165 ant spiders Zodarion germanicum
Zoropsidae 27 183 Zoropsis spinimana

NotesEdit

  1. ^ a b Species counts from World Spider Catalog (2020, Currently valid spider genera and species), family classification from Coddington (2005, p. 20).
  2. ^ Unless otherwise shown, currently accepted families and counts based on the World Spider Catalog version 21.5 as of 31 October 2020.[25] In the World Spider Catalog, "species" counts include subspecies. Assignment to sub- and infraorders based on Coddington (2005, p. 20) (when given there).

ReferencesEdit

BibliographyEdit

  • Agnarsson, Ingi; Coddington, Jonathan A. & Kuntner, Matjaž (2013). "Systematics : Progress in the study of spider diversity and evolution". In Penney, David (ed.). Spider research in the 21st century: trends & perspectives. Manchester, UK: Siri Scientific Press. ISBN 978-0-9574530-1-2.
  • Blackledge, Todd A.; Scharff, Nikolaj; Coddington, Jonathan A.; Szüts, Tamas; Wenzel, John W.; Hayashi, Cheryl Y. & Agnarsson, Ingi (2009). "Reconstructing web evolution and spider diversification in the molecular era". Proceedings of the National Academy of Sciences. 106 (13): 5229–5234. Bibcode:2009PNAS..106.5229B. doi:10.1073/pnas.0901377106. PMC 2656561. PMID 19289848.
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  • Coddington, Jonathan A. & Levi, Herbert W. (1991). "Systematics and evolution of spiders (Araneae)". Annual Review of Ecology and Systematics. 22: 565–592. doi:10.1146/annurev.es.22.110191.003025. JSTOR 2097274.
  • Eberhard, W.G. & Huber, B.A. (2010). "Spider genitalia: precise manoeuvers with a numb structure in a complex lock" (PDF). In Leonard, Janet L. & Córdoba-Aguilar, Alex (eds.). The evolution of primary sexual characters in animals. Oxford University Press. ISBN 978-0-19-971703-3. Retrieved 2015-09-20.
  • Griswold, C.E.; Ramirez, M.J.; Coddington, J.A. & Platnick, N.I. (2005). "Atlas of phylogenetic data for entelegyne spiders (Araneae: Araneomorphae: Entelegynae) with comments on their phylogeny" (PDF). Proceedings of the California Academy of Sciences. 56 (Suppl. 2): 1–324. Retrieved 2015-10-11.
  • Hormiga, Gustavo & Griswold, Charles E. (2014). "Systematics, Phylogeny, and Evolution of Orb-Weaving Spiders". Annual Review of Entomology. 59 (1): 487–512. doi:10.1146/annurev-ento-011613-162046. PMID 24160416.
  • Michalik, Peter & Ramírez, Martín J. (2014). "Evolutionary morphology of the male reproductive system, spermatozoa and seminal fluid of spiders (Araneae, Arachnida)–Current knowledge and future directions". Arthropod Structure & Development. 43 (4): 291–322. doi:10.1016/j.asd.2014.05.005. PMID 24907603.
  • Platnick, Norman I. & Raven, Robert J. (2013). "Spider Systematics: Past and Future". Zootaxa. 3683 (5): 595–600. doi:10.11646/zootaxa.3683.5.8. PMID 25250473.
  • Ramírez, Martín J. (2014). The morphology and phylogeny of dionychan spiders (Araneae, Araneomorphae). Bulletin of the American Museum of Natural History. 390. hdl:2246/6537.
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External linksEdit