Do Female Red Flour Beetles Assess both Current and Future Competition during Oviposition?

Abstract

Female insects must assess multiple factors when laying eggs, including both abiotic and biotic conditions of the laying site. Competition may also play a crucial role in the oviposition decisions of females. Competition at oviposition sites may take two forms: current competition between adults for both food and access to sites for oviposition, and future competition between offspring that will hatch and develop at that site. Here, we test whether female red flour beetles (Tribolium castaneum) assess both current and future competition at oviposition sites with a laboratory experiment where we manipulated both the density (current competition) and sex ratio (future competition) of adults at potential oviposition sites. We counted the number of eggs laid in each site to assess oviposition decisions, and then let those eggs develop into adults to determine the fitness consequences of oviposition decisions (measured by the total number of adult offspring produced). Female red flour beetles responded to both density and sex ratio: per capita eggs laid decreased as density increased, but was higher when the sex ratio was male-biased. These oviposition decisions were reflected in the per capita number of adult offspring produced. We provide evidence that female red flour beetles do assess for both current and future competition in their oviposition decisions.

Fitness Landscapes Reveal Context-dependent Benefits of Oviposition Choice

“…1939; Janus 1989). Thus, one way to increase offspring development rate under high resource competition is to decrease fecundity, and T. castaneum females may employ this strategy (Halliday et al . 2019).…”

“…Hence, fecundity and oviposition choice are inextricable; though most prior work on female context has focused on fecundity alone (Awmack & Leather 2002; Berger et al . 2008; Halliday et al . 2019).…”

Tribolium beetles as a model system in evolution and ecology

“…Oviposition is suppressed by conditioning of the medium and increased by egg cannibalism (Sonleitner and Gutherie 1991 ). Recent work has shown that females evaluate current and future competitive conditions when making oviposition decisions (Halliday et al 2019 ). Larval development is slowed by increasing larval and adult density (Park et al 1939 ; Janus 1989 ).…”

Carcass Scavenging Relaxes Chemical-Driven Female Interference Competition

“…In the present work, we tested multiple novel hypotheses vis-à-vis analysing the relative impacts of diverse counter-strategies such as natal resource access, increased dispersal, and carcass scavenging to reduce the density-dependent female interference competition. We used T. castaneum since they are already an established model system to study female competition (Khan et al 2018;Halliday et al 2019). Wild populations of Tribolium beetles are also generalised feeders, show cannibalism (Via 1999) and can survive as natural predator and scavengers of other insects in a range of habitats such as nests of birds or eusocial insects and stored product environments (reviewed in Dawson 1976;Alabi et al 2008).…”