AUTHOR=Xiang Wen-Qian , Malabrigo Pastor L. , Tang Liang , Ren Ming-Xun 

TITLE=Limited-Distance Pollen Dispersal and Low Paternal Diversity in a Bird-Pollinated Self-Incompatible Tree

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.806217

DOI=10.3389/fpls.2022.806217

ISSN=1664-462X

ABSTRACT=Bird pollination in Asia is regarded as an uncommon phenomenon, and therefore only a few investigations on mating pattern and paternity in fruits of Asian bird-pollinated plants have been conducted. Here we examined spatial genetic structure, pollen dispersal and multiple paternity in a natural population of Bombax ceiba (Malvaceae) in Hainan Island, South China, using simple sequence repeat (SSR) markers. A low genetic diversity (He = 0.351 ± 0.0341 and 0.389 ± 0.043 respectively for adults and offsprings) and bottleneck effects were observed. Genetic kinship was significant within 400 m or in 1800–3800 m. Both mating pattern and paternity analysis confirmed obligate xenogamy and a low multiple paternity in B. ceiba. There was a strongly negative relationship between the frequency of matings and the distance between mating pairs. The average pollen dispersal distance was 202.89 ± 41.01 m (mean ± SE), and the farthest distance of >1 km was recorded. Realized mating events showed an extremely leptokurtic distribution within 1200 m, suggesting that the pollen dispersal distance was consistent with the optimal foraging theory of generalist birds such as Zosterops sp. and Pycnonotus sp. Paternity per tree ranged from two to six and the average effective number of pollen donors per maternal plant was 3.773, suggesting a low level of paternity diversity as compared to other bird-pollinated plants. We concluded that optimal foraging behaviour by generalist birds could explain the leptokurtic pollen dispersal distribution and predominantly near-neighbour matings in Bombax ceiba. The limited pollen dispersal distance and low multiple paternity were consistent with low fruit setting rate (3.27 ± 0.93%) in this self-incompatible tree, which was caused mainly by the restricted flight distance of birds and human disturbances. Low genetic diversity and significant spatial genetic structure might have largely resulted from logging and human collection of fruits.