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Animals with biphasic lifecycles often inhabit different visual environments across ontogeny. Many frogs and toads (Amphibia: Anura) have free-living aquatic larvae (tadpoles) that metamorphose into adults that inhabit a range of aquatic and terrestrial environments. Ecological differences influence eye size across species, but these relationships have not yet been explored across life stages in an ontogenetic allometric context. We examined eye-body size scaling in a species with aquatic larvae and terrestrial adults, the common frog Rana temporaria, using a well-sampled developmental series. We found a shift in ontogenetic allometric trajectory near metamorphosis indicating prioritized growth in tadpole eyes. To explore the effects of different tadpole and adult ecologies on eye-body scaling, we expanded our taxonomic sampling to include developmental series of eleven additional anuran species. Intraspecific eye-body scaling was variable among species, with 8/12 species exhibiting a significant change in allometric slope between tadpoles and adults. Traits categorizing both tadpole ecology (microhabitat, eye position, mouth position) and adult ecology (habitat, activity pattern) across species had significant effects on allometric slopes among tadpoles, but only tadpole eye position had a significant effect among adults. Our study suggests that relative eye growth in the preliminary stages of biphasic anuran ontogenies is somewhat decoupled and may be shaped by both immediate ecological need (i.e. tadpole visual requirements) and what will be advantageous during later adult stages. 

Frogs and toads (Amphibia: Anura) display diverse ecologies and behaviours, which are often correlated with visual capacity in other vertebrates. Additionally, anurans exhibit a broad range of relative eye sizes, which have not previously been linked to ecological factors in this group. We measured relative investment in eye size and corneal size for 220 species of anurans representing all 55 currently recognized families and tested whether they were correlated with six natural history traits hypothesized to be associated with the evolution of eye size. Anuran eye size was significantly correlated with habitat, with notable decreases in eye investment among fossorial, subfossorial and aquatic species. Relative eye size was also associated with mating habitat and activity pattern. Compared to other vertebrates, anurans have relatively large eyes for their body size, indicating that vision is probably of high importance. Our study reveals the role that ecology and behaviour may have played in the evolution of anuran visual systems and highlights the usefulness of museum specimens, and importance of broad taxonomic sampling, for interpreting macroecological patterns. 

Objective: Folate in breastmilk has important implications for offspring health and survival given the essential role of this vitamin in DNA synthesis, epigenetic functions, and amino acid metabolism. Yet, little is understood about the variation of folate in breastmilk and transfer across the postpartum year and beyond. Published studies tend to be limited to milk during days/weeks postpartum, and none applied an evolutionary perspective of parental investment. Methods: A secondary analysis of the data and specimens from 200 breastfeeding mothers within 1.5 years postpartum in food-insecure northern Kenya was conducted. ELISA determined folate-binding protein (FOLR1) in cryogenically archived breastmilk and maternal blood specimens, originally collected in 2006. Maternal folate was defined as blood serum FOLR1 multiplied by –1 because elevated FOLR1 is associated with folate deficiency. The concentration of milk FOLR1 was evaluated in relation to maternal folate and 1) infant sex (Trivers-Willard hypothesis), 2) time postpartum and parity (maternal residual reproductive value) using regression models adjusted for covariates. Results indicated: 1) no Trivers-Willard effect; 2) support for time postpartum but not for parity. Maternal folate and time postpartum inversely predicted milk FOLR1. There was an interaction between these variables (p<0.05). Maternal folate improved over time at a varying rate while milk FOLR1 decreased at a relatively steady rate. This inverse relationship became stronger as time advanced. Conclusion: The priority shift from the investment in current offspring toward maternal soma and potential future offspring in this study provides empirical support for the evolutionary hypothesis of parental investment and parent-offspring conflict. This study was funded by NSF (BCS #1638167), and the Wenner-Gren Foundation (Grant #9278). The original data/specimen collection was supported by NSF (BCS #0622358) and the Wenner-Gren Foundation (Grant #7460).