Growth pattern and survival in populations of Poecilia vivipara (Teleostei; Poeciliidae) inhabiting an environmental gradient: a common garden study

Abstract

We performed a common garden experiment to assess the existence of genetic differences on growth and body size between two populations of Poecilia vivipara inhabiting extremes of an environmental gradient caused by water salinity in lagoons of Northern Rio de Janeiro State, Brazil: the Campelo lagoon (freshwater) and Açu lagoon (brackish/saltwater). The two populations show extreme differences in average phenotypes for body size, shape and life history (freshwater populations with smaller body size, lower fecundity and larger reproductive allotment). Pregnant females were brought to the lab and the offspring from both groups were kept in a common recirculating system with freshwater. Standard length and survival were measured weekly over a period of 200 days and growth models were fitted and selected with information criteria. The offspring originally from the brackish water lagoon presented larger asymptotic length, higher maximum growth rate but lower survival than the offspring originally from the freshwater lagoon. Potential confounding variables such as density differences due to mortality and maternal effects (offspring size) were included as covariates in comparisons of growth rates between groups.The results are consistent with phenotypic differences among populations having some genetic basis, and with the existence of a trade-off between growth and maintenance due to the high growth/low survival observed in the group that changed from salt to freshwater. Comparisons of captive and natural populations suggest that the influence of environmental factors, such as salinity, food availability, fish density and predation should also be considered relevant to explain phenotypic variation in this system.

Does Body Shape in Fundulus Adapt to Variation in Habitat Salinity?

“…Other studies have revealed links between body shape and salinity. Araújo and Monteiro (2012) found that Poecilia vivipara from areas with higher salinities tend to have deeper body profiles than P. vivipara found elsewhere, a trend that corresponds well with the present study. Although salinity seems to be at least partially responsible for this variation in body shape, Araújo and Monteiro (2012) could not separate variation in body shape due to selection for osmoregulation efficiency from alternative sources of selection.…”

Demographic Expansion and Contraction in a Neotropical Fish during the Late Pleistocene-Holocene

“…Poecilia vivipara successfully colonizes rivers and inland habitats varying in salinity from 0 to 36 parts per thousand [22]; the latter figure actually being equal to the salinity of sea water. Populations of P. vivipara at either extreme of the salinity gradient differ significantly in traits such as body size and shape, fecundity, and reproductive allotment, which are likely determined genetically [38] [39]. Poecilia vivipara also varies markedly in personality traits including boldness, activity, and sociability/shoaling behaviour, which are modulated by environmental factors such as water transparency/visibility, salinity, and dissolved oxygen [40].…”

Body size and allometric shape variation in the molly Poecilia viviparaalong a gradient of salinity and predation

“…In line with these findings, P. latipinna and Gambusia affinis showed larger body size and better body condition in brackish versus freshwater natural environments, suggesting that the latter is physiologically more stressful than the former for these species [ 49 ]. Additionally, a common garden experiment with two populations of P. vivipara inhabiting lagoons with contrasting salinities indicates that populations from brackish environments grow faster and reach larger body sizes than those from freshwater environments and that these differences are partly heritable [ 50 ], suggesting that populations might be genetically adapted to different salinity environments [ 51 , 52 ].…”