Resource Allocation to Asexual Gemma Production and Sexual Reproduction in South-Western Australian Pygmy and Micro Stilt-Form Species of Sundew (Drosera spp, Droseraceae)

Abstract

Proportional allocations of current total dry matter (DM), N and P to early season asexual gemma production and late-season flowering and seed production were compared for eight pygmy rosette form and three micro stilt-form perennial pygmy sundews (Drosera spp.) in native habitat in south-western Australia. Mean allocations to gemmae for the smaller rosette species were 22% for DM, 60% for N and 38% for P versus 8, 20 and 23% (DM, N, P) respectively for the micro stilt forms. Allocations to mature fully formed seeds were extremely low, 1-8, 4.0 and 5.4% (DM, N, P) for the rosette forms, 0.7, 3-0 and 2.3% respectively for the micro stilt forms. The above values reflect the heavy bias towards gemma production, (8-52 propagules per plant per season across the 11 species) as opposed to that for seed (0-8 fully formed seeds per plant per season). Comparable information for the annual nongemmiferous pygmy sundew D. glanduligera showed end of season allocation of 66, 37 and 29% (DM, N, P) of total plant resource to inflorescences minus seeds, and additional amounts equivalent to 30, 59 and 69% to the 60 seeds produced per plant of this species in the study season. A detailed phenology of resource allocation across a full season of growth in second, third and fourth season plants of the rosette perennial D. closterostigma showed net seasonal losses in the total vegetative resource of N and of P in older plants attributable to apparent over commitment to asexual reproduction during the season of study.