Sternberg Eleanore D, de Roode Jacobus C, Hunter Mark D
Department of Biology, Emory University, 1510 Clifton Road, Atlanta, GA, 30322, USA.
Center for Infectious Disease Dynamics, Pennsylvania State University, 111 Merkle Building, University Park, PA, 16802, USA.
J Anim Ecol. 2015 Jan;84(1):310-21. doi: 10.1111/1365-2656.12289. Epub 2014 Oct 27.
Multiple generations of hosts are often exposed to the same pathogens, favouring the evolution of trans-generational defences. Because females have more opportunities to transfer protective molecules to offspring, many studies have focused on maternally derived protection. However, males of many species can transfer compounds along with sperm, including chemicals that could provide protection. Here, we assess maternally and paternally derived protection in a monarch butterfly-protozoan parasite system where parasite resistance is heavily influenced by secondary plant chemicals, known as cardenolides, present in the larval diet of milkweed plants. We reared monarch butterflies on medicinal and non-medicinal milkweed species and then measured resistance of their offspring to infection. We also measured cardenolide content in adult monarchs reared on the two species, and in the eggs that they produced. We found that offspring were more resistant to infection when their fathers were reared on medicinal milkweed, while maternal diet had less of an effect. We also found that eggs contained the highest levels of cardenolides when both parents were reared on the medicinal species. Moreover, females reared on non-medicinal milkweed produced eggs with significantly higher levels of cardenolides if they mated with males reared on the medicinal milkweed species. However, we found an equivocal relationship between the cardenolides present in eggs and parasite resistance in the offspring. Our results demonstrate that males reared on medicinal plants can transfer protection to their offspring, but the exact mechanism remains unresolved. This suggests that paternal protection from parasitism might be important, particularly when there are environmental sources of parasite resistance and when males transfer spermatophores during mating.
多代宿主常常会接触相同的病原体，这有利于跨代防御机制的进化。由于雌性有更多机会将保护性分子传递给后代，许多研究都聚焦于母源保护。然而，许多物种的雄性也能随精子传递化合物，包括可能提供保护的化学物质。在此，我们在黑脉金斑蝶 - 原生动物寄生虫系统中评估母源和父源保护，在该系统中，寄生虫抗性受次生植物化学物质（称为强心甾）的严重影响，强心甾存在于马利筋植物的幼虫食物中。我们用药用和非药用马利筋物种饲养黑脉金斑蝶，然后测量它们后代对感染的抗性。我们还测量了在这两种植物上饲养的成年黑脉金斑蝶及其所产卵子中的强心甾含量。我们发现，当它们的父亲在药用马利筋上饲养时，后代对感染更具抗性，而母体饮食的影响较小。我们还发现，当父母双方都在药用物种上饲养时，卵子中的强心甾含量最高。此外，如果在非药用马利筋上饲养的雌性与在药用马利筋物种上饲养的雄性交配，它们所产卵子中的强心甾水平会显著升高。然而，我们发现卵子中存在的强心甾与后代的寄生虫抗性之间存在一种不明确的关系。我们的结果表明，在药用植物上饲养的雄性可以将保护传递给它们的后代，但确切机制仍未解决。这表明父源对寄生虫的保护可能很重要，特别是当存在寄生虫抗性的环境来源以及雄性在交配时传递精包时。
