La Trobe
Edwards_et_al-2019-Ecology_and_Evolution.pdf (490.41 kB)
Download file

Sexual conflict in action: An antagonistic relationship between maternal and paternal sex allocation in the tammar wallaby, Notamacropus eugenii

Download (490.41 kB)
journal contribution
posted on 25.08.2021, 01:27 authored by Amy Edwards, Elissa Z Cameron, Janine E Deakin, Tariq Ezaz, Jorge C Pereira, Malcolm A Ferguson‐Smith, Kylie RobertKylie Robert
Sex ratio biases are often inconsistent, both among and within species and populations. While some of these inconsistencies may be due to experimental design, much of the variation remains inexplicable. Recent research suggests that an exclusive focus on mothers may account for some of the inconsistency, with an increasing number of studies showing variation in sperm sex ratios and seminal fluids. Using fluorescent in-situ hybridization, we show a significant population-level Y-chromosome bias in the spermatozoa of wild tammar wallabies, but with significant intraindividual variation between males. We also show a population-level birth sex ratio trend in the same direction toward male offspring, but a weaning sex ratio that is significantly female-biased, indicating that males are disproportionately lost during lactation. We hypothesize that sexual conflict between parents may cause mothers to adjust offspring sex ratios after birth, through abandonment of male pouch young and reactivation of diapaused embryos. Further research is required in a captive, controlled setting to understand what is driving and mechanistically controlling sperm sex ratio and offspring sex ratio biases and to understand the sexually antagonistic relationship between mothers and fathers over offspring sex. These results extend beyond sex allocation, as they question studies of population processes that assume equal input of sex chromosomes from fathers, and will also assist with future reproduction studies for management and conservation of marsupials.


We thank Bruce, Alison, Timothy, and Kate Buck for access to their land and animals, for accommodating us on their management rounds and for allowing us to build a field laboratory in their shed. We thank Caroline Paterson and the rangers of Kangaroo Island National Parks for their assistance and guidance with planning fieldwork. We thank Pat Hodgens and the Kangaroo Island Natural Resource Management staff for allowing us access to their brushtail possum cage traps in an attempt to keep our bycatch at bay. Funding was provided by La Trobe University, Department of Ecology, Environment and Evolution Start-up funds to AME, and by La Trobe University Securing Food, Water and Environment Funding Scheme to AME, EZC, and KAR. AE is supported by the School of Life Sciences, La Trobe University Post-Doctoral Fellowship.


Publication Date



Ecology and Evolution






9p. (p. 4340-4348)





Rights Statement

The Author reserves all moral rights over the deposited text and must be credited if any re-use occurs. Documents deposited in OPAL are the Open Access versions of outputs published elsewhere. Changes resulting from the publishing process may therefore not be reflected in this document. The final published version may be obtained via the publisher’s DOI. Please note that additional copyright and access restrictions may apply to the published version.