Reproductive strategies of two forms of flightless males in a non‐pollinating fig wasp under partial local mate competition

Abstract

1. The underlying basis of alternative male reproductive strategies is either genetic or environmental. Several non-pollinating fig wasp lineages have dimorphic males, typically with winged males that disperse from natal figs to mate and flightless males that seek mating opportunities in natal figs.2. Walkerella sp. from Ficus benjamina has dark and pale wingless males. Observations and experiments in Xishuangbanna, Southern China found that (i) the sex ratio of Walkerella sp. did not vary with foundress number or brood size. (ii) The frequency of dark males increased with brood size and foundress number and they were absent from figs with a single foundress. This produced a higher proportion of dark males at higher densities. (iii) Males of both morphs fought, but injuries to dark males were more frequent. (iv) Dark males were more likely to disperse away from their natal figs and (v) they were more resistant to dehydration.3. Responses to selection are constrained by the genetic options available. Consequently, selection pressures acting on different lineages can produce similar outcomes that are achieved in different ways. Walkerella species lack winged males, but dark males display some of their features, dispersing from natal figs and displaying appropriate physiological and behavioural adaptations. However, dark males also displayed increased levels of damage from fighting -a feature unlikely to be shared with the winged males of other species.

Fighting injuries, fig exit, and dimorphism in two species of sycoryctine fig wasp (Chalcidoidea, Pteromalidae)

“…ex. F. benjamina male wasps (Wang et al 2010). The exit rate of the Philotrypesis males from F. benguetensis (31%) is very close to that of Philotrypesis (35%) from F. ingens (Greeff and Ferguson 1999).…”

“…ex. F. benjamina have low exit rates of 36% and 23%, respectively (Wang et al 2010). Differences in exit rates between intraspecific morphs show that dispersal is likely not influenced by environmental cues but by maternal choices, and these choices may be influenced by environmental factors.…”

“…In congeneric species, very few fight winners were injured, whereas 22% of Philotrypesis losers and 73% of Sycorycteridea losers were injured (Moore et al 2008). As examples for other genera, in Walkerella, the IF was approximately 17% (Wang et al 2010), and in Idarnes wasps, it was approximately 40% (Pereira and Prado 2008). In our study, morph type had no effect on IF for either of the studied species; however, for another species of Philotrypesis for a given mandible size, atypical males were less injured (Moore et al 2009).…”

“…The IF of non-pollinating wasps living in F. benguetensis figs is higher than that of other species; thus, environmental factors might be key for determining the intensity of fights. Indeed, IF is often affected by the number of conspecific males (Murray 1987;Prado 2005, 2008;Wang et al 2010), fight duration (Moore et al 2008), fig diameter (Pereira and Prado 2005, male size (Moore et al 2008;Pereira and Prado 2008), and number of females (Pereira and Prado 2008). Furthermore, injuries can occur only after a certain number of males have hatched (Wang et al 2010).…”

Influence of temperature on the reproductive success of a fig wasp and its host plant

“…The darker coloration typical of day flying fig wasps, compared with night-flying species, suggests that they nonetheless display adaptations to reduce water losses (Compton et al, 1991) and among the other insects that inhabit figs, a non-pollinating fig wasp Walkerella sp. (Pteromalidae) has a specialist male morph adapted for mating outside the figs that is darker in color and more resistant to desiccation than typical males (Wang et al, 2010). Although darker fig wasps are not necessarily more resistant to dehydration (Warren et al, 2010), thermal tolerances may nonetheless limit the distributions of some fig wasps to sub-sets of the distributions of their host plants, with the day-flying Ceratosolen galili, a fig wasp that fails to pollinate its host figs, absent from the western desert areas of the range of F. sycomorus, unlike its night-flying congener C. arabicus (Compton et al, 1991;Warren et al, 2010).…”