Habitat predicts reproductive superfetation and body shape in the livebearing fish Poeciliopsis turrubarensis

摘要: Superfetation, the ability of females to simultaneously carry more than one brood at different developmental stages, is an unusual reproductive strategy that has independently evolved several times in livebearing fish family Poeciliidae. Why this remains uncertain. One hypothesis superfetation a response selective pressures constrain physical space within female which her offspring can develop. This reasonable, because should reduce total volume needed house developing embryos - is, fewer large, fully developed will be held by superfetating (with broods stages) non-superfetating (where all reach stage same time). In study, we explore 'morphological constraint' examining fish, Poeciliopsis turrubarensis. We found populations vary markedly degree superfetation, with individuals carrying from two four distinct across geographic areas. These also occupy range habitat types: some occur slow moving coastal rivers near ocean, while other far inland fast waters drain steep mountain environments. comparing these types environments, find strong association between stream type and populations. Fish have higher levels their counterparts. addition, geometric morphometric analysis revealed are fusiform locations. Combined, lines evidence support hypothesis, suggest life history could driven environmental favor streamlined phenotype.