Data from: Remnant Pachira quinata pasture trees have greater opportunities to self and suffer reduced reproductive success due to inbreeding depression

Habitat fragmentation is extensive throughout the world, converting natural ecosystems into fragments of varying size, density and connectivity. The potential value of remnant trees in agricultural landscapes as seed sources and in connecting fragments has formed a fertile area of debate. This study contrasted the mating patterns of bat-pollinated Pachira quinata trees in a continuous forest to those in pasture through microsatellite-based paternity analysis of progeny. The breeding system was determined by analysis of pollen tube growth and seed production from controlled pollinations. Fitness of selfed and outcrossed seed was compared by germination and seedling growth. There was more inbreeding within pasture trees (outcrossing=0.828±0.015) compared with forest trees (0.926±0.005). Pasture trees had fewer sires contributing to mating events, but pollen dispersal distances were greater than those in the forest. Paternity analysis showed variation in outcrossing rates among pasture trees with high proportions of external and self pollen sources detected. A leaky self-incompatibility system was found, with self pollen having reduced germination on stigmas and slower growth rate through the style. Controlled pollinations also showed a varied ability to self among trees, which was reflected in the selfing rates among pasture trees shown by the paternity analysis (0–80% selfing). Self pollination resulted in lower seed set, germination and seedling growth compared with outcrossing. While remnant trees in agricultural landscapes are involved in broader mating patterns, they show increased but varied levels of inbreeding, which result in reduced fitness.全球范围内生境破碎化现象普遍存在，自然生态系统被分割为面积、密度与连通性各不相同的破碎斑块。农业景观中的残存林木作为种子源及连通破碎斑块的潜在价值，长期以来是学界争论的热点议题。本研究通过对其子代的微卫星（microsatellite）父本分析，对比了连续森林与牧场中蝙蝠传粉的瓜栗（Pachira quinata）的交配模式。本研究通过花粉管生长观测与控制授粉后的结实量分析，确定了该物种的繁育系统。通过种子萌发与幼苗生长指标，对比了自交与异交种子的适合度（fitness）。相较于森林种群的林木（异交率=0.926±0.005），牧场林木的近交程度更高（异交率=0.828±0.015）。牧场林木的交配事件所涉及的父本数量更少，但其花粉扩散距离却大于森林种群。父本分析结果显示，牧场林木间的异交率存在显著差异，研究检测到较高比例的外源花粉与自花花粉来源。本研究发现了一种部分突破型自交不亲和系统：自花花粉在柱头上的萌发率降低，且通过花柱的生长速率更慢。控制授粉实验同样显示，不同林木的自交能力存在差异，这一结果与父本分析所揭示的牧场林木自交率（0~80%自交比例）相一致。相较于异交处理，自花授粉所产生的结实率、种子萌发率与幼苗生长状况均更差。尽管农业景观中的残存林木参与了更广泛的交配模式，但其近交水平整体升高且个体间差异显著，最终导致适合度下降。