Optimal foraging, not biogenetic law, predicts spider orb web allometry

Abstract

The biogenetic law posits that the ontogeny of an organism recapitulates the pattern of evolutionary changes. Morphological evidence has offered some support for, but also considerable evidence against, the hypothesis. However, biogenetic law in behavior remains underexplored. As physical manifestation of behavior, spider webs offer an interesting model for the study of ontogenetic behavioral changes. In orb-weaving spiders, web symmetry often gets distorted through ontogeny, and these changes have been interpreted to reflect the biogenetic law. Here, we test the biogenetic law hypothesis against the alternative, the optimal foraging hypothesis, by studying the allometry in Leucauge venusta orb webs. These webs range in inclination from vertical through tilted to horizontal; biogenetic law predicts that allometry relates to ontogenetic stage, whereas optimal foraging predicts that allometry relates to gravity. Specifically, pronounced asymmetry should only be seen in vertical webs under optimal foraging theory. We show that, through ontogeny, vertical webs in L. venusta become more asymmetrical in contrast to tilted and horizontal webs. Biogenetic law thus cannot explain L. venusta web allometry, but our results instead support optimization of foraging area in response to spider size.

Exploration behaviour and behavioural flexibility in orb-web spiders: A review

“…In general orbweb spiders do not seem to improve their web-building skills with experience and show no major differences in web geometry throughout life (Pasquet et al, 2014), except that old spiders build webs that contain more errors (Anotaux et al, 2012). However, some minor differences are found in that older heavier, spiders build more vertically asymmetric webs, although this difference is likely caused by older spiders also being heavier (Herberstein and Heiling, 1999;Venner et al, 2013;Hesselberg, 2010;Nakata, 2010;Kuntner et al, 2010;Gregoric, 2013) and that early instar juveniles of species that as adults include a free sector often build webs without a free sector (Hesselberg, 2010). Although webbuilding behaviour in spiders appears to be innate, this does not mean that they do not show learning in other aspects.…”

Phylogenetic position and composition of Zygiellinae andCaerostris, with new insight into orb-web evolution and gigantism

“…Peters, ; Witt, Reed & Peakall, ; Eberhard, ; Vollrath & Selden, ; Kuntner & Agnarsson, ; Blackledge et al ., ), and other behavioural questions (e.g. Eberhard, , ; Kuntner, Gregorič & Li, ; Gregorič et al ., ). Moreover, because orb webs are made with nature's toughest biomaterial and covered with glue, orb weavers are central objects of biomaterial research (e.g.…”

Orchard Orbweaver, Orchard Spider Leucauge argyrobapta (White), Leucauge venusta (Walckenaer) (Arachnida: Araneae: Tetragnathidae)

“…Silk for the webs is spun by spinnerets at the tip of the abdomen (Figure 12). Webs are usually horizontal (fewer than 45 degrees of slope) (Alvarez-Padilla and Hormiga 2011) but occasionally are nearly vertical (Evans 2008, Gregoric et al 2013.…”