Sexual selection on jumping spider color pattern: investigation with a new quantitative approach

Abstract

How animals assess information encoded in individual color patches have been extensively studied, yet the role of both individual color patches and gross color pattern (i.e., the combination of color patches) remains understudied. We tested the functioning of both individual color patches and gross color pattern in sexual selection using the jumping spider Siler semiglaucus as a study system. We first quantified sexual dimorphism in S. semiglaucus in both individual patches and gross color pattern using the newly developed quantitative color pattern analysis (QCPA) framework. After detecting sexual differences in color coverage and pattern contrast, we manipulated the abdomen color pattern of males and had them engage in both female mate choice and male contest trials. Females spent more time watching males with lower pattern contrast and greater red coverage during mate assessment, suggesting that they evaluate information from both individual patches and gross color pattern of males. However, male color pattern had no significant effect on the outcomes of male contests. Thus, we suggest that the observed sexual color pattern dimorphism evolved primarily through female mate choice in S. semiglaucus. This is the first study to use QCPA framework to quantify sexual dimorphism in within-pattern conspicuousness from an intraspecific perspective in invertebrates. Our study also highlights the importance of both individual color patches and gross color pattern in sexual selection.

Female preference for males with lower pattern contrast follows Weber's law of proportional processing in jumping spiders

“…Our results confirm our previous finding that S. semiglaucus females show a strong preference for males with abdomens that have lower red/blue pattern contrast (Zhou et al, 2021). Moreover, we demonstrate that females are able to improve their discrimination…”

The jumping spider Saitis barbipes lacks a red photoreceptor to see its own sexually dimorphic red coloration

“…Testing functional hypotheses about animal coloration without knowledge of animal spectral sensitivities has become especially common in the jumping spider (Salticidae) literature over the past 15 years; see, for example, studies of Siler semiglaucus (Zhou et al 2021 ), Evarcha culicivora (Cross et al 2020 ), Maratus volans (Girard et al 2018 ), Habronattus pyrrithrix (Taylor and McGraw 2013 ), Lyssomanes viridis (Tedore and Johnsen 2012 ), Phintella vittata (Li et al 2008 ), and Cosmophasis umbratica (Lim et al 2008 ). In general, jumping spiders’ sexually dimorphic color patterns, dynamic courtship dances, and high-acuity vision make them excellent models for testing hypotheses about sexual selection (Harland et al 2012 ).…”

An Ant-Mimicking Jumping Spider Achieves Higher Predation Probability with Lower Success Rate When Exposed to Ethanol

“…The glass tubes were plugged with cotton to prevent spiders from escaping. All spiders were under controlled environmental conditions (25 ± 1 • C, 80-85% relative humidity, and a 12:12 h light: dark photoperiod, with the lights turning on at 0800 h), following standard protocols described in other salticid studies [40,41]. We fed spiders with 20 fruit flies (D. melanogaster) twice a week and provided water ad libitum until they reached sexual maturity.…”