The effects of exposure to seaweed on willingness to mate, oviposition, and longevity in seaweed flies

Abstract

Abstract. 1. Large male seaweed flies (Diptera: Coelopidae) are more likely to mate than smaller males. This is due to sexual conflict over mating, by which females physically resist male attempts to copulate. In some species, large males are simply more efficient at overpowering female resistance.2. Female reluctance to mate is likely to have evolved due to the costs of mating to females. In many dipterans, males manipulate female behaviour through seminal proteins that have evolved through sperm competition. This behavioural manipulation can be costly to females, for example forcing females to oviposit in sub-optimal conditions and increasing their mortality.3. Previous work has failed to identify any ubiquitous costs of mating to female coelopids. The work reported here was designed to investigate the effects of exposure to oviposition sites (Fucus algae) on the reproductive behaviour of four species of coelopid. Algae deposition in nature is stochastic and females mate with multiple males in and around oviposition sites. Spermatogenesis is restricted to the pupal stage and there is last-male sperm precedence. It was predicted that males would avoid wasting sperm and would be more willing to mate, and to remain paired with females for longer, when exposed to oviposition material compared with control males. Females were predicted to incur longevity costs of mating if mating increased their rate of oviposition, especially in the presence of algae.4. The behaviour of males of all four species concurred with the predictions; however mating did not affect female receptivity, oviposition behaviour, or longevity. Exposure to algae induced oviposition and increased female mortality in all species independently of mating and egg production. The evolutionary ecology of potential costs of mating to female coelopids are discussed in the light of these findings.

Sex-Biased Phoretic Mite Load on Two Seaweed Flies:Coelopa frigidaandCoelopa pilipes

“…We also determined their wing length using a graticule unit under the same level of magniÞcation. Wing length has been used as the standard index of relative size in numerous previous studies of coelopids (Gilburn et al 1992;Day 1994, 1999;Dunn et al 1999Dunn et al , 2002Crean et al 2000;Edward and Gilburn 2007;Meader and Gilburn 2008).…”

“…Coelopa frigida is an established model organism for research into sexual selection and sexual conßict (Butlin et al 1982;Gilburn and Day 1994, 1996Day et al 1996;Dunn et al 2002;Gilburn 2005, 2006;Edward and Gilburn 2007). The mating behavior of the other common British seaweed ßy, Coelopa pilipes, has also been studied (Crean et al 2000, Dunn et al 2002, Edward and Gilburn 2007, albeit to a lesser extent.…”

“…The mating behavior of the other common British seaweed ßy, Coelopa pilipes, has also been studied (Crean et al 2000, Dunn et al 2002, Edward and Gilburn 2007, albeit to a lesser extent. The two species occur on beaches on which deposits of seaweed, known as wrack beds, are washed up (Dobson 1974), often occurring sympatrically.…”

The effect of an inversion system and the time interval between matings on postcopulatory sexual selection in the seaweed fly, Coelopa frigida

“…After the second mating, females were placed individually in pots of minced seaweed (consisting of mixed Fucus and Laminaria species) to lay eggs until death. Oviposition is stimulated by the presence of seaweed but not mating (Dunn et al, 2002), so the females were maintained with sucrose solution as a source of energy and water to prevent oviposition in the intervening period when there was a 24 h gap between matings. The larvae of each female were allowed to develop to adulthood before being collected and frozen.…”

Extreme Promiscuity in a Mating System Dominated by Sexual Conflict

“…Convenience polyandry occurs when males are able to coerce females into accepting unwanted copulations by increasing the likely costs of rejection beyond the costs of mating. There are a number of insect taxa in which this mating system is common, does not affect female willingness to mate but does stimulate oviposition 48 to a similar extent in both mated and virgin females (Dunn et al, 2002).…”