The three groups had starting densities of50, and 25 larvae per 1. Pen et al. This indicates that zebrafish sex is a genetic trait and the fact that we were able to keep highly skewed sex ratios - and even eliminate one of the two sexes in some cases - suggests the absence of a strong effect by sex chromosomes on sex determination.
Finally, to account for potential discordances between gene trees and the species tree, we used the pseudo-ML approach implemented in the MP-EST program [ 83 ]. Burke AC: Turtles Werneburg I, Sanchez-Villagra MR: Timing of organogenesis support basal position of turtles in the amniote tree of life.
To verify that the decrease was due to selection pressure, we performed a control experiment with the D4F3 family by doing a mass cross for the F 2 generation without any selection Fig. Bayesian relaxed molecular clock time scale. This hypothesis is supported by the persistence of TSD in certain populations of spotted skink Niveoscincus ocellatusa small lizard in Tasmania, where it is advantageous to have females early in the season.
The number of fish was counted every 10 days beginning on day 10 post fertilization. The evolutionary advantages and disadvantages of temperature-dependent sex determination are discussed in Chapter
Adams Despite some larval lethality, the average percentage of dead fish in each density group from experiment 2 did not differ significantly indicating that larval death did not contribute to the observed higher percentage of males in the high density group Table S1 and Fig.
As BEAST implements only uncorrelated relaxed clock models, we used the uncorrelated log normal model. Next, we performed array comparative genomic hybridization aCGH on four families of zebrafish. Turtles have been described as having a conspicuously modified reptile body plan, and termed 'hopeful monsters', representing a successful phenotypic mutant with the potential to establish a new evolutionary lineage [ 2 — 7 ].
A best reciprocal hit BRH strategy was then used to identify orthologs from the contigs of the nine assembled transcriptomes. Our breeding data also indicate the absence of chromosomal sex determination in zebrafish, whereby the inheritance of a particular chromosome would be the predominant determiner of sex.
Larva and juvenile fish were counted every 10 days from 10 dpf up to 30 or 40 dpf for most Table S1 and Fig. Reproduction — Furthermore, our statistical analyses reject any alternative hypotheses to the sister group relationship of turtles to Archosauria Table 2 , thus advancing the resolution of this long-standing controversial issue of vertebrate evolutionary history.
Although the phylogenetic scenario supported by our data would not change the main conclusion that temperature-dependent sex determination evolved multiple times within amniotes, it does provide a basis from which to further investigate the possible adaptive evolutionary value of the temperature-dependent sex determination in amniotes and the evolution of sex chromosomes.