Impact of Habitat Complexity on Body Size of Two Spider Species, Alopecosa cuneata and A. pulverulenta (Araneae, Lycosidae), in River Valley Grasslands

Abstract

Many studies have shown that vegetation structure and habitat complexity affect taxonomic composition, functional diversity, and the number of individuals in spider assemblages. These factors also affect spider body size, but mechanisms responsible for that are still not well understood. In our research, we examined the relationship between the body size of spiders from two species -Alopecosa cuneata and A. pulverulenta -and environmental factors such as habitat type and habitat complexity. Our research was conducted in the Bug River Valley on 12 plots covering three types of habitats: mesic meadow, sandy grassland, and xerothermic grassland. Spiders were collected in 2007-08 from April to mid-November using pitfall traps. In total we measured 334 males and 168 females of Alopecosa cuneata and 315 males and 104 females of A. pulverulenta. The generalized linear mixed model revealed that individuals of Alopecosa cuneata as well as A. pulverulenta reached larger sizes in more complex vegetation, whereas the habitat type did not affect the spider body size. One of the likely mechanisms responsible for a larger body size in more complex habitats is predator pressure. Birds as the main predators of spiders, being selective in their choice of prey, may collect larger spiders with higher intensity than smaller ones. We suggest that more complex habitats with dense vegetation provide better shelter for large spiders, which allows them to avoid predators. Our results indicate that habitat complexity may be an important determinant of body size distribution in spider assemblages.

Reproductive phenology of the spider Micrommata ligurina (C.L. Koch, 1845) (Araneae; Sparassidae) across an elevational gradient in Northeast Algeria

“…Although we have not measured the size of adults across elevation, it is reasonable to predict that the size of ectotherms increases in colder conditions because individuals spend longer time growing (Angilletta et al, 2004;Valenzuela-Sánchez et al, 2015). Many studies have shown that several others factors affect spider body size such as predators being selective in their choice of prey, habitat complexity, and nutritional quality (Stańska, Stański, 2017;Stańska et al, 2018). Further investigations on the complexity of mechanisms that are responsible for this difference in body size are needed.…”

The latitudinal gradient of functional diversity of Miocene marine mollusks from Chile

“…Regarding environmental heterogeneity and niche‐related processes, for example, the existence of fjords in high‐latitude regions at the South Pacific coast of Chile could be seen as a mechanism generating broader environmental biotopes where more species could fill up their niches for near‐coast marine organisms (Valdovinos et al 2003, Kiel and Nielsen 2010). This is because fjords, as spatially complex habitats, offer ample topographic relief and water depth ranges, availability of refugia (Kiel and Nielsen 2010) and a wide variety of environmental conditions (González‐Wevar et al 2011, Buhl‐Mortensen et al 2012, Stańska et al 2018). As a result, fjords can increase biodiversity and contribute to the formation of inverse latitudinal gradients in taxonomic and functional diversity (Santelices and Meneses 2000, Kiel and Nielsen 2010, Rivadeneira et al 2011, Mannion et al 2014, Moreno et al 2021).…”