Forced monogamy in a multiply mating species does not impede colonisation success

Abstract

BackgroundThe guppy (Poecilia reticulata) is a successful invasive species. It is also a species that mates multiply; previous studies have demonstrated that this strategy carries fitness benefits. Guppies are routinely introduced to tanks and troughs in regions outside their native range for mosquito-control purposes, and often spread beyond these initial confines into natural water bodies with negative ecological consequences. Here, using a mesocosm set up that resembles the containers into which single guppies are typically introduced for mosquito control, we ask whether singly-mated females are at a disadvantage, relative to multiply-mated females, when it comes to founding a population. Treatments were monitored for one year.ResultsA key finding was that mating history did not predict establishment success, which was 88% in both treatments. Furthermore, analysis of behavioural traits revealed that the descendants of singly-mated females retained antipredator behaviours, and that adult males showed no decrease in courtship vigour. Also, we detected no differences in behavioural variability between treatments.ConclusionsThese results suggest that even when denied the option of multiple mating, singly-mated female guppies can produce viable populations, at least at the founder stage. This may prove to be a critical advantage in typical introduction scenarios where few individuals are released into enclosed water bodies before finding their way into natural ecosystems.

Extreme fertilization bias towards freshly inseminated sperm in a species exhibiting prolonged female sperm storage

“…If the offspring arising from stored sperm are of lower quality [ 40 ], for example, due to the deleterious effects of ageing (see above), females would benefit by exerting CFC for fresh sperm. In guppies, we do not know whether offspring arising from fertilizations by stored sperm are of lower quality than those arising from fresh sperm, although the observation that a single pregnant female can establish a viable population [ 12 , 13 ] suggests that offspring quality does not decline appreciably across cycles of FSS. Similarly, in natural populations stored sperm have been shown to be fertile well beyond the male's lifetime, suggesting that strong CFC against stored sperm is unlikely [ 9 ].…”

“…However, it could be argued that behavioural interactions between males and females are required to activate stored sperm. However, this argument does not apply to guppies, as females kept in isolation from males are able to produce several successive broods [ 12 , 19 , 20 , 24 ], indicating that fertilization by stored sperm occurs in the absence of any behavioural or visual interaction with males. Furthermore, in experimental designs using natural matings, males and females often mate more than once (consensually or through forced copulations).…”

“…Although sperm storage can be costly [ 10 , 11 ], it is beneficial for females under many circumstances. For example, FSS allows females to produce numerous broods in the absence of males and is therefore an important trait for invasion success of new habitats [ 12 , 13 ], and to maintain within-brood genetic variability when mate availability is low. In addition, across-cycles FSS may have important implications for sperm competition, potentially influencing fertilization dynamics when fresh sperm compete with previously stored sperm ( figure 1 ).…”

Me against who? Male guppies adjust mating behaviour according to their rival’s presence and attractiveness

“…The area covered by orange spots is a strong predictor of female mate choice and of male fitness, while the effect of black and iridescent areas in driving female choice is less clear (Endler & Houde, ; Karino & Matsunaga, ; Magellan et al, ; Reynolds & Gross, ). We recorded individual orange coloration by direct visual evaluation and using a standardized scheme, following Deacon, Barbosa, and Magurran (). This scheme divides the body into 12 sections and considers that a male has a smaller coloured area compared to other males when his colour spots cover fewer body sections (Figure ).…”

“…Scheme of male guppy body sections (main body and tail) used to estimate areas of orange (adapted from Deacon et al, ). The main body area was divided evenly.…”