Body shape differentiation at global and local geographic scales in the invasive cichlid Oreochromis mossambicus

Abstract

The Mozambique tilapia Oreochromis mossambicus (Teleostei, Cichlidae) has been transplanted worldwide during the 20th century, and now belongs to the list of the most invasive species. Using a geometric morphometric approach, we describe body shape differentiation among 15 populations from native (Mozambique) and invaded (New Caledonia and Guadeloupe) ranges. A dominant phylogeographic signal is detected, despite the broad range of environmental conditions at the local scale. This result suggests that phylogeographic background rather than phenotypic plasticity responding to environmental variation constitutes the main factor correlated with shape divergence. This could result from successive founder events that occurred during the process of colonization of new geographic areas, and therefore strongly suggests heritable phenotypic differentiation. In addition, shape changes along a major axis of divergence hypothetically refer to different swimming abilities, possibly related to divergent functional requirements between the native and invaded ranges. Overall, patterns of contemporary shape diversification in O. mossambicus probably result from both phylogenetic constraints and adaptive divergence processes. We show that critically taking into account recent phylogenetic history of populations as a constraint on rapid phenotypic divergence is necessary for an improved view of contemporary evolution.

A case of complete loss of gill parasites in the invasive cichlid Oreochromis mossambicus

“…1). The samples come from both freshwater ponds or lakes and brackish water mangroves (Firmat and Alibert 2011;Firmat et al 2012), covering the range of the O. mossambicus habitats in New Caledonia. This territory was chosen because O. mossambicus is reported to be established from a unique introduction in 1954 of 40 individuals transferred from the Republic of the Philippines (Froese and Pauly 2011;Marquet et al 2003), suggesting a very low propagule intensity.…”

Condition and morphometric changes in tilapia (Oreochromis sp.) after an eradication attempt in Southern Louisiana

“…Morphology has been shown to change as a result of bottleneck events in fish (Shao et al 2007), including with inbred cichlids (Winemiller and Taylor 1982). For invasive tilapia, the founder effect appeared more important than local selective forces in O. mossambicus (Firmat et al 2012). The question of the relative importance of stochasticity, selection, and plasticity is still speculative at this point and requires further study.…”

“…Of note, Firmat et al (2012) observed a strong effect of phylogenetic history on morphology, regardless of a variety of environmental conditions faced by multiple populations of invasive O. mossambicus. This would indicate the importance of founder effect as opposed to phenotypic plasticity.…”

“…The response variable of this model was all PC components with an eigenvalue > 1 (PC1 -PC5), accounting for 82% of the variance. Previously, centroid size alone has been used as a covariate for similar MANCOVAs, but in this case it was also found to be correlated with standard length (Firmat et al 2012). For our study, it was not highly correlated with standard length (R 2 = 0.028, p = 0.432), therefore both standard length and centroid size were used as covariates in our MANCOVA.…”

“…In addition to predation, other factors can affect fish morphology as well, such as salinity (Collyer et al 2005), water velocity (Imre et al 2002) and stunting (Chizinski et al 2010). A previous study examining tilapia found that invasive Oreochromis mossambicus exhibit a decrease in body depth when compared to their native populations (Firmat et al 2012).…”