AUTHOR=Hautier Louis , San Martin Gilles , Jansen Jean-Pierre , Branquart Etienne , Grégoire Jean-Claude 

TITLE=Spiny Prey, Fortunate Prey. Dorsal Spines Are an Asset in Intraguild Interactions among Lady Beetles

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=5

YEAR=2017

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2017.00135

DOI=10.3389/fevo.2017.00135

ISSN=2296-701X

ABSTRACT=<p>The Multicolored Asian Ladybird, <italic>Harmonia axyridis</italic>, is an extremely successful invasive species. Here we suggest that, in addition to many other traits, the dorsal spines of its larvae contribute to their success, as suggested by behavioral observations of agonistic interactions between <italic>H. axyridis</italic> and European coccinellids. In coccinellids, the role of dorsal spines in these interactions has been poorly studied and they could be a physical protection against intraguild predators. Dorsal spines of second instar <italic>H. axyridis</italic> larvae were removed with micro-scissors, which resulted in spineless larvae after molting (spineless group). These larvae were then exposed to starved <italic>Coccinella septempunctata</italic> larvae. Two control categories were also submitted to interactions: <italic>H. axyridis</italic> larvae with all their spines (control group) and with their spines, but injured by pin stings (injured group). Spine removal at the second instar did not hamper <italic>H. axyridis</italic> development. The bite rate by <italic>C. septempunctata</italic> was significantly higher on the spineless <italic>H. axyridis</italic> and more dorsally located compared to the control and injured groups, while no bite rate difference was observed between the injured and the control group. Our results suggest that in addition to behavioral and chemical defenses, the dorsal spines play a significant protective role against bites. Therefore, spines in ladybirds could be considered as a morphological defense against intraguild predation. In <italic>H. axyridis</italic>, these defenses might contribute to its success in food resources already exploited by other guild members and thus further facilitate the invasion of new areas.</p>