The Effect of Ants on Membracid Nymph Growth Patterns: Size and Developmental Rate
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Mutualisms are a symbiotic relationship between two species by which both species benefit from the interaction. Membracid nymphs (Publilia modesta), young treehoppers, are larger when their mutualist partner (Formica obscuripes) is present, but there is little known about by which mechanism the nymphs are growing larger. To investigate the possible mechanism, alternative hypotheses of two possibilities for the nymphs to get larger were investigated. The first possible mechanism is that nymphs grow at a baseline rate, but are larger for a given instar (stage of development). The second hypothesis is that nymphs grow faster (go through instars more quickly). This study investigates the effects of ant attendance on nymph growth by manipulating the . presence or absence of ants with the nymphs during development. Nymphs were sampled weekly for four weeks. Instar and size of the nymphs were determined and analyzed over time with respect to treatment group (ants or no ants). We found that the presence of ants caused the membracid nymphs to develop faster and that size was not affected. Nymph density also did not significantly affect nymph size or instar. These results imply that there is no apparent extra cost to nymphs to grow more quickly, because they are able to preserve their size and still grow at a faster rate. These results also show that mutualisms can facilitate developmental plasticity, which aid in better fitness. Faster development fosters better fitness for an organism due to the shorter window of predation, and better chances of survival.