Poeciliidae Evolution

Biologists at the University of California, Riverside have made an incredible evolutionary discovery that links sexual selection and placentation (Science Daily, 2014). The study of 150 species of Poeciliidae (Figure 1), describes the morphologies of males in species with placentas. Sexual selection- “special case” of natural selection, which acts on an organism’s ability to obtain, or successfully copulate with a mate, is not exceedingly important in species with placentas (Science Daily, 2014). For instance, guppies, platys, swordtails, and mollies (Figure 2), are apart of the family Poeciliidae and are extremely varied: bright colouration, decoration, or courtship display. In this case of Poeciliidae family, the species are non-placental …show more content…
Comparative methods using maximum likelihood in phylogeny were constructed using RAxML 7.0.4, and different phylogenetic comparative methods were used to test for correlated evolutionary traits in Poeciliidae (Pollux et al., 2014). For one, the comparative method is applied to examine the potential conflict-driven shifts in sexual selection associated with the evolution of post-fertilization of maternal care in Poeciliidae fish family (Pollux et al., 2014). It is thought that maternal care intensifies after post-fertilization, which adds to fetal-maternal conflict (Pollux et al., 2014). This as a result causes a reduced reliance of pre-copulatory cues in males; display less developed, or the absence of, traits that facilitate female mate choice before copulation (Pollux et al., 2014). The matrotrophy index, which is the estimated dry mass of the offspring at birth divided by the dry mass of the egg at fertilization, is a measurement of post-fertilization maternal care (Pollux et al., 2014). For example, placentotropic species have matrotrophy index greater than 1, because the embryo utilizes and grows in the uterus, exploiting maternal resources (Pollux et al.,