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Canadian Spider Diversity and Systematics

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Canadian Spider Diversity and Systematics Vol. 18, No. 1 16 Canadian Spider Diversity and Systematics Robb Bennett British Columbia Ministry of Forests, 7380 Puckle Road, Saanichton BC V8M 1W4 Introduction collected. Recent revisions have added consid- It can be stated accurately that spiders erable numbers of species to some groups, par- are to be found everywhere (with apologies to ticularly those with predominantly cryptic, William Morton Wheeler who originally made ground-dwelling members (e.g. Gnaphosidae – this claim for ants). Spiders, unique among all 63 species (Dondale 1979) versus 100 species organisms in their modes of silk production and (Platnick and Dondale 1992)). Such groups usage and of reproduction, are common (if of- have historically been passed over in favour of ten inconspicuous) predatory arthropods in all those with larger, showier, or otherwise more terrestrial and many aquatic ecosystems obvious members (Alderweireldt and Jocqué throughout Canada. From marine intertidal 1993). Many genera within some cryptic spider zones to tundra and rocky peaks, and all points groups with considerable numbers of Nearctic between, the ardent araneologist is always close species such as Linyphiidae, Dictynoidea, and to a wealth of species and numerous specimens Amaurobioidea still await serious revision and of great intrinsic and biological interest. within these groups may lie numbers of un- Among all organisms, spiders form the seventh known species with Canadian representatives. largest order. Furthermore, spiders are ruthless Still, the number of spider species known or es- storm troops in the matriarchal anarchy that is timated to be awaiting discovery in Canada is the arthropod world: theirs is the most diverse, relatively unchanged from Dondale’s estimate female-dominated, entirely predatory order on – there are probably at most 1,500 spider spe- the face of the earth. As such, spiders are key cies in Canada. This is about 35% and 4% of the components of all ecosystems in which they world total numbers of spider families (108) live. and described species (nearly 40,000) respec- tively, not a bad representation for a land mass Twenty years ago, Dondale (1979) listed repeatedly bulldozed in the Pleistocene. 33 spider families with 1256 known Canadian Coddington and Levi (1991) have estimated a species. He estimated another 144 unrecorded world total of 170,000 spider species and that or undescribed species were likely part of the 20% and 80% respectively of the world and Canadian fauna. Araneology is blessed with Nearctic spider fauna have been described. some of the very best systematists in the world and in the intervening years spider taxonomy Although Canada’s araneofauna is rea- and systematics have been highly active fields sonably well known, precious little is known of (e.g. see the Introduction in Platnick 1997). the behaviour, ecology, habitat associations and Canada’s spider record now stands at 38 fami- other aspects of the biology of the majority of lies: two families have dropped out of the list species. Furthermore, in spite of a rapidly grow- (one does not occur in Canada and the other is ing interest world-wide in many aspects of spi- generally considered a subfamily), five families der biology (e.g. ecology, sexual selection, be- have been added through the apparent resolu- haviour, taxonomy, and systematics) as well as tion of polyphyletic and paraphyletic groups, in habitat-based spider inventories (see Intro- one family was apparently missed or perhaps duction in Platnick 1997), there is currently not included in Theridiidae, and one family one professional araneologist in Canada and the (Bennett and Brumwell 1996) has been newly vast majority of Canadian habitats have yet to Vol. 18, No. 1 17 Fig. 1. Male Cybaeus multnoma Chamberlin and Ivie (RTA Clade, Dictynoidea, Cybaeidae). Scale bar=2mm. Individuals of about two dozen species of this Holarctic genus are dominant but poorly known generalist predators in the forest floor arthropod community of the Pacific Northwest, especially in coastal regions. In Canada, six species are known to occur in British Columbia (with one species apparently endemic to the Rocky Mountains of BC and Alberta), one species may occur in southeastern Canadian forests. Many species of Cybaeus (most notably in Japan and unglaciated regions of the Pacific Northwest) have ex- tremely restricted ranges and are known from only a few specimens. be seriously sampled for spiders. Biologists sects and Arachnids houses a large, world-class seeking reliable identifications of Canadian spi- spider collection and taxonomic library. The ders are forced to use the services of a small federal government has effectively declared handful of amateur specialists located in On- spider studies to be irrelevant to the agricultural tario, Saskatchewan, Alberta, and British Co- needs of the nation (C. D. Dondale pers. lumbia or seek help outside the country. Under comm.) and little use is now made of this re- the auspices of Agriculture and Agri-Food Can- source. ada, the Canadian National Collection of In- 18 Newsletter of the Biological Survey of Canada (Terrestrial Arthropods) Table: Classification of spider families with Canadian representatives (modified from Dondale 1979 and following Coddington and Levi 1990 and Platnick 1997) and estimated numbers of species in Canada. With greater knowledge of forest litter and canopy spiders, the number of species found in Canada should approach 1,500. Species* Species* ORDER ARANEAE Suborder Opisthothelae “RTA Clade” (cont’d) Infraorder Mygalomorphae Dionycha Fornicephalae Anyphaenidae 7 Atypidae 1 Liocranidae 18 Antrodiaetidae 2 Clubionidae 35 Tuberculotae Corinnidae 11 Mecicobothriidae 1 Gnaphosidae 100 Dipluridae 1 Zoridae 1 Infraorder Araneomorphae Philodromidae 47 Neocribellatae Thomisidae 68 Araneoclada Salticidae 110 Haplogynae Amaurobioidea “Scytodoidea” Amaurobiidae 30 Scytodidae 1 Titanoecidae 4 Telemidae 1 Agelenidae 11 Pholcidae 3 Orbiculariae Dysderoidea Deinopoidea Segestriidae 1 Uloboridae 3 Dysderidae 1 Araneoidea Entelegynae Nesticidae 2 Palpimanoidea Theridiidae 100 Mimetidae 6 Theridiosomatidae 1 Eresoidea Mysmenidae 1 Oecobiidae 1 Pimoidae 1 “RTA Clade” Linyphiidae >500 Lycosoidea Tetragnathidae 23 Lycosidae 110 Araneidae 74 Pisauridae 7 Oxyopidae 2 TOTAL ~1400 Dictynoidea Dictynidae 75-80 Cybaeidae 11 Hahniidae 16 *Approximate number of species in Canada (1999 estimate) All spiders produce and use silk and can dominate the former grouping. The latter is a di- be divided roughly into two behavioural group- verse assemblage dominated by the “RTA ings based on this usage: those that use their silk clade” with major families including the to snare prey and those that don’t. salticids (jumping spiders), lycosids (wolf spi- Orbicularians, especially the araneoids (primar- ders), thomisids (one family of crab spiders), ily sheet-web, orb-web, and cob-web weavers) and gnaphosids (ground spiders). However, us- Vol. 18, No. 1 19 age of silk for prey capture is not phylogeneti- der family in Canada in terms of numbers of cally constrained and numerous groups span the species and often are extremely abundant. On gap. For instance many amaurobioid and the world stage, they are second in diversity dictynoid species (common and widespread in only to salticids. Many years ago, Bristowe Canada) utilize greatly reduced webs (e.g. see (1938) made a well reasoned estimate of over Bennett 1985) and rely upon sit, wait, and 2.25 million spiders (mostly linyphiids) per pounce strategies. Other species within these acre of grassy meadow in late summer in Eng- groups build large and characteristic capture land. He also cited a study which produced webs. Among the fascinating but mostly un- 159,000 spiders per acre from the soil alone of a common Canadian tarantula kin similar habitat. (These figures should be kept (Mygalomorphae) atypids (purse-web spiders), from the poor arachnophobes who recoil from diplurids (funnel-web tarantulas), and the small handful of spiders they encounter an- mecicobothriids (no common name) use silk in nually.) The bulk of linyphiid diversity is made prey capture. Antrodiaetid mygalomorphs up of erigonine species. Dondale (1979) listed (folding-trapdoor spiders) sit in the entrance of over 300 erigonine linyphiids in Canada with an excavated burrows and wait for hapless crea- estimate of 50 remaining to be recorded or de- tures to come near enough to be grabbed and scribed. These species are characterized by dragged deep into the dim recesses of their re- their undistinguished appearance and small to treats and repeatedly stabbed to death (big-city minute size: not only are a majority of downtown terror is far exceeded by the nightly erigonines tiny, most of them look alike. Usable mayhem on a seemingly peaceful suburban taxonomic keys are virtually non-existent and British Columbia lawn). Linyphiidae (includ- most genera and species are very difficult to de- ing Erigonidae of various authors) and termine even for the specialist. Identification is Salticidae, the major family in each behavioural based largely upon microscopic characters of grouping on a world-wide basis, are very diffi- the very complex male genitalia; in contrast, fe- cult taxonomically and have many genera in males usually are unremarkable morphologi- need of revision and large numbers of undes- cally and often are unidentifiable if not col- cribed species. Following is a summary of the lected with male conspecifics. diversity, abundance, and systematics of Can- Few comprehensive spider
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