Have superfetation and matrotrophy facilitated the evolution of larger offspring in poeciliid fishes?

Abstract

Superfetation is the ability of females to simultaneously carry multiple broods of embryos, with each brood at a different developmental stage. Matrotrophy is the post-fertilization maternal provisioning of nutrients to developing embryos throughout gestation. Several studies have demonstrated that, in viviparous fishes, superfetation and matrotrophy have evolved in a correlated way, such that species capable of bearing several simultaneous broods also exhibit advanced degrees of post-fertilization provisioning. The adaptive value of the concurrent presence of both reproductive modes may be associated with the production of larger newborns, which in turn may result in enhanced offspring fitness. In this study, we tested two hypotheses: (1) species with superfetation and moderate or extensive matrotrophy give birth to larger offspring compared to species without superfetation or matrotrophy; (2) species with higher degrees of superfetation and matrotrophy (i.e. more simultaneous broods and increased amounts of post-fertilization provisioning) give birth to larger offspring compared to species with relatively low degrees of superfetation and matrotrophy (i.e. fewer simultaneous broods and lesser amounts of post-fertilization provisioning). Using different phylogenetic comparative methods and data on 44 species of viviparous fishes of the family Poeciliidae, we found a lack of association between offspring size and the combination of superfetation and matrotrophy. Therefore, the concurrent presence of superfetation and moderate or extensive matrotrophy has not facilitated the evolution of larger offspring. In fact, these traits have evolved differently. Superfetation and matrotrophy have accumulated gradual changes that largely can be explained by Brownian motion, whereas offspring size has evolved fluidly, experiencing changes that likely resulted from selective responses to the local conditions.

The predictability and magnitude of life‐history divergence to ecological agents of selection: a meta‐analysis in livebearing fishes

“…; Olivera‐Tlahuel et al . ), the costs of provisioning a few large offspring may be proportionally greater than the costs of provisioning many small offspring. This could bias the magnitude of the slope, and further research should investigate the energetic requirement of per capita provisioning among different sizes of clutches and different levels of maternal provisioning.…”

“…In this study, we observed that the slope of the relationship significantly differed from both 0 and À 1. While there is tremendous interspecific variation in the absolute sizes and numbers of offspring produced (Johnson & Bagley 2011;Olivera-Tlahuel et al 2015), increasing the number of offspring by 1 SD should generally be more energetically and ecologically costly than increasing the sizes of each offspring by 1 SD. For example, consider a hypothetical fish with the mean and standard deviation of embryo size (1.9 AE 0.6 mg) and number (10.5 AE 4.7 offspring) estimated from the data set.…”

Placental structures and their association with matrotrophy and superfetation in poeciliid fishes

“…On the other hand, in a moderately matrotrophic species, the embryo's mass increases with progressive developmental stages (MI > 1; Reznick et al, 2002), and the embryo obtains substantial maternal provisioning during development through a placenta. For each study species, we obtained data on the matrotrophy index from previous studies (i.e., Olivera-Tlahuel et al, 2015;Pollux et al, 2014). Extensive matrotrophy refers to species which completely lack yolk, such that all the maternal provisioning occurs during embryonic development and weight at birth may be more than five times greater than at oocyte fertilization (MI > 5; Reznick et al, 2002).…”

Morphological structures for potential sperm storage in poeciliid fishes. Does superfetation matter?

“…Many studies have attempted to find adaptive explanations for superfetation (Frías‐Alvarez & Zúñiga‐Vega, ; Macías‐Garcia & González‐Zuarth, ; Olivera‐Tlahuel, Ossip‐Klein, Espinosa‐Pérez, & Zúñiga‐Vega, ; Pollux et al, ; Travis, Farr, Henrich, & Cheong, ; Zúñiga‐Vega et al, ). However, no study to date has focused on describing the morphological and physiological mechanisms that may allow superfetation to occur.…”