Reproductive life history variation among colour morphs of the pygmy grasshopper Tetrix subulata

Individuals of pygmy grasshoppers (Tetrix subulata [L.] Orthoptera: Tetrigi dae) exhibit genetically coded discontinuous variation in colour pattern. T o determine whether reproductive performance is likely to be affected by co lour pattern, this study investigated variation in body size and reproducti ve life-history characteristics among individuals belonging to five differe nt colour morphs. The proportion of reproductive females (i.e. females with eggs) declined significantly as the season progressed (from 100% in mid-Ma y to 40% in mid-June), but no such seasonal trend was apparent for body siz e, clutch size or egg size. Colour morphs differed significantly in body si ze, and these size differences accounted for most of the variation in clutc h size and egg size. Colour morphs also differed in the regression of egg s ize on clutch size, suggesting that trade-offs between number and size of o ffspring might vary among morphs. Finally, I found a negative relationship across colour morphs between the proportion of females with eggs and averag e clutch size. This suggests that individuals belonging to certain colour m orphs produce a relatively large number of clutches per unit time, at the e xpense of fewer offspring in each clutch, compared to other morphs. Collect ively: my results indicate that different colour morphs of I:subulata may h ave different reproductive strategies. These differences may reflect variat ion in thermoregulatory capacity or differences in probability of survival induced by visual predators. (C) 1999 The Linnean Society of London.