Data from: Maternal diet influences fecundity in a freshwater turtle undergoing population decline

Food availability determines the amount of energy animals can acquire and
allocate to reproduction and other necessary functions. Female animals
that are food-limited thus experience reduced energy available for
reproduction. When this occurs, females may reduce frequency of
reproductive events or the number or size of offspring per reproductive
bout. We assessed how maternal diet affects reproductive output in adult
female Murray River short-necked turtles, Emydura macquarii, from four
wetlands in Victoria. We previously found that turtle diets differ in the
composition of plants and animals between our study wetlands. In this
study, we tested whether differences in turtle diet composition (i.e
plants and animals) at these wetlands were associated with differences in
clutch mass, individual egg mass, bulk egg composition, and hatching
success. We found total clutch mass increased with maternal body size at
each site. At sites where filamentous green algae were scarce and E.
macquarii were carnivorous, females produced smaller clutches relative to
body size compared to females from sites where algae were abundant, and
turtles were more herbivorous. Individual egg mass, bulk egg composition,
and hatching success did not differ across wetlands. Isotopic analysis
revealed a significant positive relationships between the carbon and
nitrogen isotopes (δ13C, δ15N) of the eggs and those of the mothers,
indicating that mothers allocated ratios of carbon and nitrogen isotopes
to their eggs similar to those present in their tissues. Our study
suggests that at sites where females are more carnivorous due to a
relative absence of algae, females produce smaller clutches but other
aspects of their reproduction are not significantly impacted. The
reduction in clutch size associated with differences in the availability
of dietary plants and animals may have long-term consequences for E.
macquarii and other freshwater turtle species that are experiencing
population declines.