Larval host plant influences male body size and mating success in a tephritid fruit fly

Abstract

In phytophagous insects, the larval host plant may have a profound effect on the biology of the adult stage. This influence has been most widely studied in females, where larval diet may affect their fecundity and survival. Males have been less well studied, with focus on host plant effects on (1) male size and the consequences of variable male size on male mating success, ejaculate, and/or nuptial gifts, or (2) male-produced chemical signals important in sexual communication. The melon fly, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae), is a world-wide agricultural pest that infests plants of the family Cucurbitaceae primarily but also attacks hosts in other unrelated families. The objective of the present study was to investigate whether larval host influenced female choice in Z. cucurbitae and, in particular, test for random mating using adults (Z flies) whose larvae fed on a cucurbit host (zucchini, Cucurbita pepo L.) and adults (P flies) whose larvae fed on a non-cucurbit host (papaya, Carica papaya L., Caricaceae). In field tent trials, both Z and P females mated more often with Z males than P males, and in no-choice laboratory cage trials, mating latency was generally shorter for Z than for P males. Wing vein measurements, made both within and between generations, showed that Z males were consistently larger than P males. Further observations of fly trios -one female plus one large and one small male -revealed that large males dominated in aggressive encounters and exhibited wing fanning (signaling) more often than their smaller counterparts. Although olfactory signals associated with wing fanning were not investigated in the present study, the observed host-mediated difference in male size is, if not solely responsible, certainly an important determinant of the mating patterns described.

One step closer to understanding the ecology of Cameraria ohridella (Lepidoptera: Gracillariidae): The effects of light conditions

“…Rhainds (2015) reports a positive correlation between body size and lepidopteran wing length (and hence mobility, and speed of movement) and the largest individuals are more likely to mate and, in effect, have a higher realised fecundity. Host-dependent differences in male size in the melon fl y, Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae) are important determinants of its mating pattern (Shelly, 2018). In addition, positive relationships between insect body mass and wing parameters are reported in a study on food quality (under different light conditions and with different host plants) and its effect on the microlepidopteran, Yponomeuta evonymellus L. (Lepidoptera: Yponomeutidae) (Łukowski et al, 2017).…”

Crowded developmental environment promotes adult sex-specific nutrient consumption in a polyphagous fly

“…For instance, when larvae are kept in crowded environments and/or poor nutritional conditions there may be a delay in pupation, an increase in mortality rate at the pupal stage, or reduced adult body size [3–16]. Because of the general trend in insects for body size to be positively associated with sexual performance (see e.g., [17–21]), crowding and poor larval nutrition tend to decrease adult sexual attractiveness and reproductive performance, including pre- and post-copulatory competitive ability (for males) and fecundity (for females) [10, 14, 15, 17, 18, 22]. Thus, larval crowding is an important ecological modulator of the strength of evolutionary forces such as sexual selection and sexual conflict [15].…”

Sons from virgin mothers produce more daughters in a haplodiploid mite

“…When we compare male offspring produced by mothers of different mating status, we show that virgin T. ludeni females laid significantly larger male eggs than mated females, and the resultant larger male eggs developed to larger deutonymphs and adults (Table 1). In principle, larger males have advantages in male-male competition (Andersson 1994;Emlen 2008;Hunt et al 2009;Suzaki et al 2013;Shelly 2018). Ohzora and Yano (2008) reveal that although size is not measured, sons from virgin mothers disperse faster and start guarding females sooner than those from mated mothers in T. urticae, suggesting that the former may have better mating success than the latter.…”