Multiple reproductive events in female wolf spiders Pardosa hyperborea and Pardosa furcifera in the Low-Arctic: one clutch can hide another

Abstract

Changing abiotic conditions can affect the phenology of animals and plants with implications for their reproductive output, especially in rapidly changing regions like the Arctic. For instance in arthropods, it was recently shown that females of the spider species Pardosa glacialis (Thorell, 1872) (Lycosidae) are able to produce two clutches within one growing season in years when snowmelt occur particularly early. This phenomenon could be widespread in northern latitudes, and here we investigated the voltinism of two other very abundant species of wolf spiders in the Low-Arctic, Pardosa hyperborea (Thorell, 1872) and Pardosa furcifera (Thorell, 1875), over the period 2015 -2017. While a bimodal pattern in the clutch size frequency distribution was only revealed for P. hyperborea, we were able to show that both species can produce a second clutch over the active season by using information on the embryonic stages. We also observed significantly larger first than second clutches. We argue that information about the embryonic stage can be critical for evaluating evidence of wolf spider populations producing more than one clutch in a season. Our study provides evidence that bivoltinism could be more widespread pattern than expected in Arctic wolf spiders. It remains to be investigated what the trophic consequences of such patterns are in a global warming context. We thus highlight the need for a coordinated framework for such further studies, integrating and relating various functional traits.

Variation in abundance and life-history traits of two congeneric Arctic wolf spider species, Pardosa hyperborea and Pardosa furcifera, along local environmental gradients

“…Høye et al 2009). Young are developing as juveniles and subadults two winters in a row, and mature as adults the third active season where they breed and die (Buddle 2000;Pickavance 2001;Ameline et al 2017;Viel et al 2022).…”

“…Pardosa hyperborea on the one hand, a fairly well studied species (e.g. Pickavance 2001;Viel et al 2022) measuring between 4.5 and 5.6 mm in body length (Paquin and Dupérré 2003), is widespread over boreal and Low-Arctic areas.…”

“…Analyses of the relation between body size and clutch size were made on clearly identified mother/cocoon pairs. However, both P. hyperborea and P. furcifera females have been shown to be able to produce two clutches in one active season with the second clutch being smaller than the first (Viel et al 2022).…”

“…Therefore, in order to avoid potentially mixing smaller second clutches with the larger first clutches, we used the method in Viel et al (2022) to only keep clutches from the first laying episode. Specifically, we found no evidence of differences in date thresholds amongst species and elevations and thus excluded clutches collected after week 31 of the year (i.e.…”

“…This in turn results in distinct spatial variation in arthropod community composition Dahl et al 2018;Hein et al 2019a), a group that constitutes the majority of animal species in the region (Schmidt et al 2017). Similarly, elevation also creates environmental variation and affects species distribution and development (Körner 2007;Hein et al 2019b;Viel et al 2022). At higher elevation, environments become more variable and less predictable, both in terms of abiotic (e.g.…”