Habitat specialization and climate affect arthropod fitness: a comparison of generalist vs. specialist spider species in Arctic and temperate biomes

Abstract

Life history trade-offs are a key notion in evolutionary biology, notably for understanding how selection shapes the diversity of traits among species. Despite the frequent study of such trade-offs, few studies synchronously investigate the effects of multiple factors, such as niche specialization and adaptation to harsh environments. We compared reproduction (fecundity and egg quality) in two sympatric couples (one habitat generalist and one specialist) of congeneric wolf spider species, in both Arctic and temperate habitats. We found that specialist species at both latitudes invested more in clutch size than did generalist species. We interpret this result as an optimization of clutch production. In the Arctic, the specialist was able to invest in fecundity with increasing body size at a much higher rate than the generalist species. In the temperate habitat, both species showed similar strategies: they increased quantity and quality of offspring relative to body size at the same rate. These results are consistent with the hypothesis that Arctic species must develop distinct strategies in order not to overlap each other's ecological niches as a consequence of limited food resources or niche space. We emphasize the need to test the role of plasticity and environmentally mediated effects of competition on arthropod fitness.

Differences in Mobility and Dispersal Capacity Determine Body Size Clines in Two Common Alpine-Tundra Arthropods

“…Our results for body size indicate no linear trend with elevation in P. palustris, even though body size adaptations in response to elevation are a well-described phenomenon in some Pardosa species [74,90]. Our result, no clear linear trend in body size of P. palustris along the elevational gradient, is in line with various previous findings on the body size variation of P. palustris in the research area [27,63,64].…”

Biogeographic position and body size jointly set lower thermal limits of wandering spiders

“…The size of southern spiders, that have higher SCP, seemed to be less related to SCP. This difference in strategy between temperate and colder habitats has been reported in other species from the closely-related family of Lycosidae (Ameline et al 2018). The northern spiders have a shortened breeding season, which can impact life history traits such as body size (Bowden et al 2015).…”

“…In turn, this difference between species might explain the wider northward distribution of D. fimbriatus compared to that of D. plantarius. It indeed appears that specialist species are larger under harsher conditions because they are more adapted to their environment (Ameline et al 2018). A larger size implies a smaller cold resistance here, which might be detrimental in this case.…”

“…For ectotherms, these two rules were first opposed (Voorhies 1996, Mousseau 1997 but it seems that both larger and smaller individuals at northern latitudes is possible and the two rules are eventually not exclusive (Blanckenhorn and Demont 2004), possibly co-existing in close species (e.g. in artic wolf spiders, see Ameline et al 2018). The latitudinal size cline is of importance as body size also influences cold hardiness (Ansart et al 2014), e.g.…”

Broad-scale rather than fine-scale environmental variation drives body size in a wandering predator (Araneae, Lycosidae)

“…Consequently, the driving principles of phenotypic variation in individual-environment interactions are in the focus of current research (e.g., Chevin, Lande, and Mace 2010;Ameline et al 2018;Hein et al 2018). However, knowledge about specific spatial and temporal variations of life history traits remains scarce in invertebrates, especially in cold environments (Homburg et al 2013;Høye and Sikes 2013;Ameline et al 2017). Body size is one of the key features of life history traits research in ectotherms (Angiletta et al 2004;Chown and Gaston 2010;Høye and Hammel 2010), because it is considered a proxy for fecundity, body condition, and survival (e.g., Hodkinson 2005;Bowden, Høye, and Buddle 2013;Penell, Raub, and Höfer 2018).…”