Rates of Pollen Deposition and Removal in Myosotis colonsoi

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Abstract
1. The flowers of Myosotis colensoi are protogynous. The stigma is accessible for pollination for several hours before pollen is presented. One or two days after a flower opens, scales at the mouth of the corolla tube change colour, signalling the start of a protracted post-pollination phase. Flowers in this phase present neither pollen nor receptive stigmas and they are avoided by the principal visitor - a tachinid fly. 2. Hand pollination of protected stigmas shows that they remain receptive throughout the life of the flower. During favourable weather, however, pollen is deposited on most stigmas before the anthers dehisce. The effective female phase is thus shorter than the nominal period based on either the period of stigma receptivity or the end of the period before pollen presentation. The effective male phase is much longer, requiring as many as 12-14 separate visits to complete. 3. Pollen presentation is staggered because the five anthers dehisce sequentially over several hours. This process extends the period over which pollen is removed. 4. Periods of poor weather alter the presentation schedule and pollen removal and deposition rates, lengthen the effective phase durations and cause a partial temporal overlap in sexual functions. These results are discussed with reference to theories of sexual selection.

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