Viviparity In Biology

Reproduction is a vital step in the sustainability of all living things, and the consequences of unsuccessful reproduction can be catastrophic for a species. Therefore, it is not surprising that multiple strategies have evolved over time in order to ensure offspring will be viable and competitive members of a population. One of the basic features of reproductive success is providing offspring an environment with the necessary features for effective development, such as nutrients and water, temperature control and protection from predators. Oviparity and viviparity are two methods that provide developing embryos with the environment they require to successfully develop. Oviparity can be defined as a reproductive mode where a portion of embryonic …show more content…
This study examined the Phrynosomatidae family, due to several suspected origins of viviparity within the family and availability of genetic data for the majority of the species included in the family. Additionally it appeared that the viviparous species did not completely adhere to the cold climate hypothesis, such as oviparous species in colder areas of high elevation. This allowed the authors to examine potential deviations from supporting data. The authors utilized new methods such as phylogenetic logistic regression and Bayesian implementation, which tested relationships between continuous variables and discrete variables. These methods allowed comparison between environmental data and a phylogeny, which was created from data for five mitochondrial and eight nuclear loci. They also attempted to reconstruct the ancestral state of reproduction and environment conditions at that time. The reconstruction was created mainly to address the question of if the conditions viviparity originally evolved in were different than the conditions for populations that remained oviparous. Climate data that was examined in the analysis included averages or midpoints of annual temperature, temperature during the warmest three months of the year, elevation and latitude. The results indicated that higher elevations were associated with oviparity, but this did not contradict the cold climate hypothesis because the higher altitudes were areas like deserts, which also had higher temperatures. The reconstructions of ancestral states were in agreement with the cold climate hypothesis and support that viviparity evolution conditions were at high elevations and low temperatures and latitudes. This also helps to explain the presence of viviparous species in the tropics, as these species are thought to have inhabited the tropical areas after their ancestors evolved