Frequency-dependent fitness and reproductive dynamics contribute to habitat segregation in sympatric Jewelflowers

Coexistence results from a complex suite of past and
contemporary processes including biogeographic history, adaptation,
ecological interactions, and reproductive dynamics. Here we explore
drivers of local micro-parapatry in which two closely related and
reproductively isolated Streptanthus species (Jewelflower,
Brassicaceae) inhabit continuous or adjacent habitat patches and occur
within seed dispersal range, yet rarely overlap in fine-scale
distribution. We find some evidence for abiotic niche partitioning
and local adaptation, however differential survival across habitats
cannot fully explain the scarcity of coexistence. Competition may
also reduce the fitness of individuals migrating into occupied
habitats, yet its effects are insufficient to drive competitive
exclusion. Experimental migrants suffered reduced seed production and
seed viability at sites occupied by heterospecifics, and we infer that
heterospecific pollen transfer by shared pollinators contributes to
wasted gamete...

共存现象源于一系列复杂的历史与当代过程，包括生物地理历史、适应性演化、生态相互作用及繁殖动态。本文探讨局域微邻域分布（local micro-parapatry）的驱动因素：两种亲缘关系密切且存在繁殖隔离的链荚芥属（Streptanthus）物种（宝石花，十字花科）栖息于连续或相邻的生境斑块中，其分布范围处于种子扩散距离内，但在精细尺度上极少重叠。我们发现了非生物生态位分化（abiotic niche partitioning）与局域适应的部分证据，但不同生境间的生存差异无法完全解释共存现象的稀缺性。竞争或许也会降低迁入已被占据生境的个体适合度，但这种效应不足以引发竞争排斥。实验迁移个体在异种占据的位点上表现出种子产量与种子活力下降，我们推测，共享传粉者介导的异种花粉转移（heterospecific pollen transfer）是配子浪费的原因之一……