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. 2012;7(5):e38404.
doi: 10.1371/journal.pone.0038404. Epub 2012 May 31.

Reasons for the Invasive Success of a Guppy (Poecilia Reticulata) Population in Trinidad

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Free PMC article

Reasons for the Invasive Success of a Guppy (Poecilia Reticulata) Population in Trinidad

Caya Sievers et al. PLoS One. .
Free PMC article

Abstract

The introduction of non-native species into new habitats poses a major threat to native populations. Of particular interest, though often overlooked, are introductions of populations that are not fully reproductively isolated from native individuals and can hybridize with them. To address this important topic we used different approaches in a multi-pronged study, combining the effects of mate choice, shoaling behaviour and genetics. Here we present evidence that behavioural traits such as shoaling and mate choice can promote population mixing if individuals do not distinguish between native and foreign conspecifics. We examined this in the context of two guppy (Poecilia reticulata) populations that have been subject to an introduction and subsequent population mixing event in Trinidad. The introduction of Guanapo River guppies into the Turure River more than 50 years ago led to a marked reduction of the original genotype. In our experiments, female guppies did not distinguish between shoaling partners when given the choice between native and foreign individuals. Introduced fish are therefore likely to benefit from the protection of a shoal and will improve their survival chances as a result. The additional finding that male guppies do not discriminate between females on the basis of origin will further increase the process of population mixing, especially if males encounter mixed shoals. In a mesocosm experiment, in which the native and foreign populations were allowed to mate freely, we found, as expected on the basis of these behavioural interactions, that the distribution of offspring genotypes could be predicted from the proportions of the two types of founding fish. This result suggests that stochastic and environmental processes have reinforced the biological ones to bring about the genetic dominance of the invading population in the Turure River. Re-sampling the Turure for genetic analysis using SNP markers confirmed the population mixing process and showed that it is an on-going process in this river and has led to the nearly complete disappearance of the original genotype.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Collection sites at the Northern Mountain Range.
Detail of the Northern Mountain Range map showing the Turure and Oropuche Rivers. Red arrows indicate the sites where fish collection took place. HI: Haskins's introduction, bel w: below waterfall at introduction site, CB: Cumaca Bridge, VR: Valencia Road, Con Qu: Confluence with Quare, TMR: Toco Main Road. Not shown: Haskins's source, Guanapo.
Figure 2
Figure 2. Shoaling times of Guanapo and Oropuche females.
The amount of time focal females from either the Guanapo or Oropuche spent shoaling with fish from their own or the other population. Medians and interquartile ranges are shown.
Figure 3
Figure 3. Male mate choice.
The time focal males from the Guanapo and Oropuche spent in the choice zones with a set of females from either their own or the other population (a) and the number of sigmoid displays they directed towards these females (b). Medians interquartile ranges and outliers are shown.
Figure 4
Figure 4. Percentage of SNPs from the mesocosm experiment.
The percentage of Oropuche nucleotides scored at 14 SNPs across different four loci that distinguished between Guanapo and Oropuche origin for all treatments. Dashed lines at 20, 50 and 80% indicate where a theoretical mean for each treatment would be expected given that only the proportion of introduced fish is important for the distribution of Guanapo and Oropuche allele frequencies. Medians, interquartile ranges and outliers are shown.
Figure 5
Figure 5. Percentage of SNPs from re-sampling the Turure river.
The amount of native Turure and Oropuche allele frequencies estimated at four different loci with 14 SNPs compared to the invading Guanapo allele frequencies. The percentage of the Oropuche state of all SNPs per site was taken in order to illustrate the change of genetic composition across the river Turure. Two sites at the Oropuche were sampled to compare the Turure results to a likely original genotype. N = 10 fish per site, except Oropuche Toco Main Road: n = 3. HS: Haskins's source; HI: Haskins's introduction. Error bars represent 95% CI.

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