Interpopulation variation in the trade-off between body-mass gain and age at oviposition in the eastern lubber grasshopper, Romalea microptera

Abstract

Life-history models predict populations under shorter growing seasons will invest earlier and more heavily in reproduction than populations under longer growing seasons. Populations of Romalea microptera inhabit distinctly different climates and differ in mtDNA cytochrome-b gene sequences. Previous work suggested a latitudinal trend in the trade-off among body-mass gain, age at first oviposition, and clutch mass, in populations from Miami FL, Lydia LA, and Athens GA: but this study was confounded by longitudinal variation. Hence, we compared the Miami and Athens populations to a population from Jacksonville, FL, which is equidistant from both, yet under a distinct climate. The Athens population had less body-mass gain and an earlier age at oviposition than the other two populations. When corrected for initial body mass or age at oviposition, the Athens population produced larger clutches. Developmental profiles of juvenile hormone and hemolymph lipids did not differ across populations. In comparison to the Miami population, the Jacksonville population showed a nonsignificantly greater body-mass gain and age at oviposition, in contrast to the latitudinal trend observed previously. These data suggest that reproduction in R. microptera involves a trade-off between body-mass gain and age at oviposition, which is consistent with a current vs future reproduction trade-off.