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.

生境破碎化在全球范围内普遍发生，将自然生态系统切割为大小、密度与连通性各不相同的片段。农业景观中的残存林木作为种源以及连接生境片段的潜在价值，长期以来都是学界关注的热点争议议题。本研究以蝙蝠传粉的瓜栗（Pachira quinata）为研究对象，通过对子代开展基于微卫星（microsatellite）的父本分析，对比了连续森林与牧场生境中该树种的交配格局；同时通过花粉管生长观测与控制性授粉实验的结籽情况，解析其繁育系统；并通过种子萌发与幼苗生长指标，比较了自交与异交种子的适合度差异。研究结果显示，相较于森林植株（异交率=0.926±0.005），牧场植株的近交程度更高（异交率=0.828±0.015）。牧场植株的交配事件所涉及的父本数量更少，但花粉扩散距离却显著高于森林植株。父本分析表明，不同牧场植株的异交率存在变异，且检测到较高比例的外源花粉与自交花粉来源。本研究发现了存在渗漏现象的自交不亲和系统：自交花粉在柱头上的萌发率更低，且穿过花柱的生长速度更为缓慢。控制性授粉实验同样显示，不同植株的自交能力存在差异，这与父本分析揭示的牧场植株自交率（0~80%）的变异特征相一致。与异交处理相比，自交授粉会导致更低的结籽率、种子萌发率与幼苗生长速率。尽管农业景观中的残存林木拥有更为广泛的交配格局，但其近交水平有所升高且存在个体间差异，最终导致适合度下降。