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Impact of mate availability, population size, and spatial aggregation of morphs on sexual reproduction in a distylous, aquatic plant
Author(s) -
Brys Rein,
Jacquemyn Hans,
Hermy Martin
Publication year - 2007
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.94.1.119
Subject(s) - biology , selfing , fecundity , mating system , heterostyly , pollination , pollen , mating , population , reproductive success , reproduction , natural population growth , sexual reproduction , ecology , botany , zoology , demography , sociology
In distylous, self‐incompatible plants, clonal propagation, unbalanced floral morph frequencies, and reduced population size can interfere with the functioning of distyly by compromising legitimate intermorph pollinations, resulting in reduced reproductive output. Here, we examined the mating system and the impact of mate availability, population size, and spatial aggregation of morphs on reproductive output in the distylous, clonal, aquatic plant Hottonia palustris . Controlled pollinations under greenhouse conditions detected no spontaneous selfing without the action of a pollen vector (autonomous autogamy) and demonstrated very low fruit and seed development after self‐pollination. Intermorph (legitimate) crossings resulted in high reproductive output in both floral morphs (long‐ and short‐styled individuals), whereas intramorph (illegitimate) crossings decreased fruit and seed development by more than 50%, indicating that the species has partial intramorph‐incompatibility. In natural populations, small population size and increasing deviation of floral morph frequencies negatively affected reproductive outcome. Individuals of the majority morph type developed significantly fewer fruit and seeds than individuals of the minority morph type. This rapid decline in fecundity was symmetrical, indicating that regardless of which morph was in the majority, the same patterns of negative frequency‐dependent mating occurred. Increasing spatial isolation between compatible morphs significantly reduced fruit and seed set in both morphs similarly. This study provides clear indications of frequency‐ and context‐dependent mating in natural populations of a distylous plant species.