ANDREWS, A.L.*; HATLE, J.D.; CROWLEY, M.C.; JULIANO, S.A.: Hemolymph protein profiles during egg production in three populations of the Eastern lubber grasshopper
Distant populations of a given organism can be predicted to have reproductive physiologies that are adapted to their local environment. For example, to avoid a reproductive output of zero, populations of univoltine species from locations with shorter growing seasons could be predicted to reproduce sooner than populations from locations with longer growingseasons. In particular, a transition from a developmentally flexible phase to a developmentally inflexible phase (that requires a set amount of time) could be expected to occur sooner in populations from shorter growing seasons. Lubber grasshoppers are univoltine and exhibit low vagility. In addition, they have flexible reproductive timing during the first half of the oviposition cycle but initiate inflexible reproductive timing during the second half of the oviposition cycle. The maximum titer of total hemolymph protein (=TPmax) in lubbers occurs during this inflexible phase. Here, we test whether latitudinally distinct populations of lubbers differ in their timing of reproductive development, as indicated by the timing of TPmax. We predicted that the time from adult eclosion to TPmax (i.e. the flexible phase) would be greatest in Florida, intermediate in Louisiana, and lowest in Georgia lubbers. Contrary to prediction, times from eclosion to TPmax did not differ among the populations. Time from TPmax to oviposition (i.e. the inflexible phase), however, was significantly greater for LA hoppers than GA hoppers. Our data suggest that the duration of the canalized phase differs among populations and raises the possibility that these differences may be adaptive for reproduction in the corresponding local environments. (Supported by NSF grant DB1-9978810 to SAJ.)
