YEAR‐TO‐YEAR CHANGES IN PHENOTYPIC GENDER IN A MONOECIOUS CUCURBIT, APODANTHERA UNDULATA

Abstract

Year‐to‐year variation in phenotypic gender in the monoecious cucurbit, Apodanthera undulata Gray was investigated. Small plants produce no flowers. Larger plants produce only staminate flowers (“male” plants), while a somewhat greater threshold size is necessary for pistillate flower production (cosexual plants). Approximately 85% of the plants that bloomed did not change gender group between years. Two measures of phenotypic gender were used: prospective femaleness, a measure standardized to the population floral ratio, and morphological femaleness, an unstandardized measure. Femaleness of cosexes between years was positively correlated; r values were somewhat greater when using morphological femaleness values. Plants that opened only staminate flowers one year were likely to open only staminate flowers the next year. Similarly, cosexes were likely to be cosexes again the following year, with similar femaleness values. Beyond the threshold size for pistillate flower production, plant size was not correlated with femaleness. These patterns suggest that all plants are male until they reach a certain size and that plants in their cosexual phase may have an intrinsic femaleness tendency due to either genotype or microsite effects.