2001. The Journal of Arachnology 29:367±377 LIFE-CYCLES OF FOUR SPECIES OF PARDOSA (ARANEAE, LYCOSIDAE) FROM THE ISLAND OF NEWFOUNDLAND, CANADA J. R. Pickavance: Biology Department, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3X9. email: [email protected] ABSTRACT. Populations of four species of Pardosa, P. fuscula, P. groenlandica, P. hyperborea and P. moesta, were sampled during summer 1997 on the west coast of the Island of Newfoundland, Canada. Measurements of carapace width indicated that all four species ®t a biennial life-cycle model where new individuals join the population in summer, live through the following winter, grow throughout the next year, live through the next winter, and then mature, breed and die in the year following their second winter. All species showed only one de®ned recruitment of new spiderlings during the sampling period, but at least two species may have extended periods of recruitment and some individuals may have an extended life-cycle. Keywords: Lycosidae, Pardosa, life-cycle At the beginning of the 20th century the intermediates between strictly annual and conventional wisdom about araneomorph spi- strictly biennial (e.g. Eason & Whitcomb der life-cycles was that most were annuals, ei- 1965; Toft 1976, 1979; Dondale 1977; Strat- ther spring breeders or summer-autumn breed- ton & Lowrie 1984). ers (Emerton 1902). Palmgren (1939) In addition to such permutations of the an- provided one of the ®rst exceptions when he nual/biennial theme, the plasticity of spider described the two-year cycle of Dolomedes life history has been demonstrated. For ex- ®mbriatus (Clerck 1757) where juveniles ample, the same species may change from an- overwintered twice. Cloudsley-Thompson nual to biennial depending on geographical lo- (1955) concluded that individuals of all three cation, such as Philodromus cespitum that was British species of Amaurobius C. L. Koch annual on the warmer Niagara Peninsula, On- 1837 lived for about two years, overwintered tario, Canada (Putman 1967), but biennial in twice, and spent their second winter as adults. colder Nova Scotia, Canada (Dondale 1961). Hackman (1957) described a similar two-year Pardosa lugubris (Walckenaer 1802) was an- cycle for Trochosa ruricola (De Geer 1778). nual in the Netherlands (Vlijm et al. 1963) but Dondale's (1961) seminal work presented biennial in Scotland, and this was attributed quantitative data for ®ve species of spiders in to differences in summer temperatures (Edgar Nova Scotia, Canada: Araniella displicata 1971a, 1972). In addition, individuals of the (Hentz 1847), Philodromus rufus Walckenaer same population may extend their life-cycle 1826, P. cespitum (Walckenaer 1802) and Eris under particular circumstances. Edgar (1972) militaris (Hentz 1845) were shown to be true showed that P. lugubris in the Netherlands biennials, while Pelegrina proterva (Walcken- varied between annual and biennial depending aer 1837) was annual. He also concluded that on environmental conditions. Workman nine other widespread and abundant spiders (1978) showed that in Norfolk, U.K., Trocho- were biennials. In the last decades of the 20th sa terricola Thorell 1856, usually biennial century a number of studies have not only with the second overwintering as adults, was clearly demonstrated annual and biennial life occasionally triennial when juveniles hatched histories for several different species, but also from late or second cocoons overwintered reported permutations of these two basic life- three times before breeding in their fourth cycles. That is, within these two general cat- year. Leech (1966) suggested that even more egories there are species that mature and breed extended life-cycles may occur in particularly at different times of year and species that are cold conditions. He surmised that two species 367 368 THE JOURNAL OF ARACHNOLOGY from Hazen (Ellesmere Island, NWT, Cana- ducted in boreal forest dominated by ®r and da), Pardosa glacialis (Thorell 1872) and Al- spruce (indicative of lower summer tempera- opecosa exasperans (O. Pickard-Cambridge tures) (Ecological Strati®cation Working 1877), had a life-span of six or seven years, Group 1995). Leech (1966) reported from the but that surmise was based on the unsupported Canadian arctic at approximately 828N. Some assumption that each of the estimated six or European work has been conducted at lati- seven instars lasted one year. These points tudes farther north than Insular Newfound- raise a number of questions. Do spider species land. For example, Toft (1976) reported from not yet examined have similar life histories to Denmark and Edgar (1971a) from Scotland, those already described? Do species in places both at approximately 568N. However, climate not yet examined have similar life histories to is not simply determined by latitude, and the those in known places? Do species at latitudes generally more temperate European climate is farther north than some of those previously indicated by the beech woods of the former examined show extended life histories, for ex- study and the oak woods of the latter. ample intermediate between those document- ed in Nova Scotia (Dondale 1961) and those METHODS hypothesised on Ellesmere Island (Leech Species and localities.ÐFour species of 1966)? Pardosa C. L. Koch 1847 (Lycosidae) were The Island of Newfoundland is an appro- chosen for this study: P. fuscula (Thorell priate location to examine these questions. 1875), P. groenlandica, P. hyperborea (Tho- The life histories of the species in this study rell 1872) and P. moesta. Full descriptions of have not been described before with the fol- these species can be found in Dondale & Red- lowing exceptions. Ricards (1967) reported ner (1990). They were chosen both because the life history of what he called P. groenlan- the taxonomy of most Canadian lycosids is dica (Thorell 1872) in Montana, and Schmoll- well established (Dondale & Redner 1990) so er (1970) reported on what he called P. tristis conclusions could be con®dently assigned to Keyserling 1887 (identi®ed as P. groenlandi- individual species and preliminary investiga- ca by Dondale 1999) in Colorado. But as tions in 1995 and 1996 found dense popula- Dondale (1999) pointed out, both authors tions of these species. Such dense populations were in fact dealing with complexes of two or lend themselves to sampling by hand as op- more species, not monospeci®c populations of posed to using pitfall traps. Pitfall traps are P. groenlandica, so their conclusions have useful measures of activity and have a long limited signi®cance. Buddle (2000) reported history of employment in ecological studies, the life-cycle of Pardosa moesta Banks 1892 but they are selective in trapping different spe- in Alberta, and his observations are directly cies and different life-stages (Berghe 1992; relevant here. Life histories of spiders on the Topping & Sunderland 1992). Island of Newfoundland have essentially nev- The Island of Newfoundland is in the boreal er been investigated. Hackman (1954) report- shield ecozone where the climate is heavily ed 220 species from the Island, but drew con- in¯uenced by arctic currents, many areas are clusions for only one: Trochosa terricola was exposed to particularly harsh climatic condi- described as biennial, although the data pre- tions and the landscape is dominated by sented could support other interpretations. spruce-®r forest with extensive peatlands. The present study sites on the Island of Within that ecozone, the populations of this Newfoundland, at approximately 508N, are study were in, or immediately adjacent to, the farther north than previous life history work northern peninsula ecoregion (South 1983; with the following exceptions. Buddle (2000) Ecological Strati®cation Working Group and Zimmerman & Spence (1998) reported 1995). life-cycles of lycosids and a pisaurid, respec- The populations chosen were all in Gros tively, from approximately 548N in central Al- Morne National Park, Newfoundland, and were berta. However, both these studies were con- therefore largely protected from human inter- ducted at the George Lake area dominated by ference. The P. fuscula population was on an hardwoods such as aspen (indicative of higher extensive peatland immediately below and summer temperatures) in the boreal transition around the highest land on top of Partridge- region, whereas the present study was con- berry Hill behind the community of Woody PICKAVANCEÐPARDOSA LIFE-CYCLES 369 Point (49830.29N, 57856.99W). The P. groen- July 7, 99; August 14, 143; September 14, 88. landica population was at the back of a pebble- P. hyperborea: June 5, 74; July 3, 75; August cobble beach immediately north of the mouth 11, 55; September 15, 66. P. fuscula: June 5, of Baker's Brook (49839.59N, 57857.79W). The 48; July 9, 135; August 11, 54; September 15, P. hyperborea population was on the extensive 104. P. groenlandica: May 15, 60; June 1 and treeless heath on the higher parts of Partridge- 2 combined, 37; July 4, 68; August 12, 62; berry Hill behind Woody Point (49830.09N, September 13, 74. Spiders were caught with 57856.69W). The P. moesta population was on an aspirator and transferred to snap-cap plastic the treeless coastal meadow immediately above vials. Only one spider was put in each vial to and behind the beach at Lower Head, Shallow avoid intraspeci®c aggression and cannibal- Bay (49857.39N, 57846.29W). Voucher speci- ism. Spiders were taken to the laboratory, mens are deposited in the Newfoundland Mu- placed in a deep-freeze