Abstract：
AbstractSpatial segregation of closely related species is usually attributed to differences in stress tolerance and competitive ability. For both animals and plants, reproductive interactions between close relatives can impose a fitness cost that is more detrimental to the rarer species. Frequency-dependent mating interactions may thus prevent the establishment of immigrants within heterospecific populations, maintaining spatial segregation of species. Despite strong spatial segregation in natural populations, two sympatric California monkeyflowers (Mimulus nudatus and M. guttatus) survive and reproduce in the other\'s habitat when transplanted reciprocally. We hypothesized that a frequency-dependent mating disadvantage maintains spatial segregation of these monkeyflowers during natural immigration. To evaluate this hypothesis, we performed two field experiments. First, we experimentally added immigrants in varying numbers to sites dominated by heterospecifics. Second, we reciprocally transplanted arrays of varying resident and immigrant frequencies. Immigrant seed viability decreased with conspecific rarity for M. guttatus but not for M. nudatus. We observed immigrant minority disadvantage for both species, but it was driven by different factors-frequency-dependent hybridization for M. guttatus and competition for resources and/or pollinators for M. nudatus. Overall, our results suggest a major role for reproductive interference in spatial segregation that should be evaluated along with stress tolerance and competitive ability.
摘要：
紧密相关物种的空间隔离通常归因于胁迫耐受性和竞争能力的差异。对于动物和植物来说，近亲之间的生殖相互作用可能会带来健康成本，这对稀有物种更为不利。因此，频率依赖的交配相互作用可能会阻止异类种群中移民的建立，保持物种的空间隔离。尽管自然种群存在强烈的空间隔离，当相互移植时，两个同胞加利福尼亚猴花（Mimulusnudatus和M.guttatus）在另一个的栖息地中存活和繁殖。我们假设频率相关的交配缺点会在自然移民过程中保持这些猴花的空间隔离。为了评估这个假设，我们进行了两次现场实验。首先,我们通过实验将不同数量的移民添加到以异特异性为主的地点。第二,我们相互移植了不同的居民和移民频率。guttatus的移民种子活力随物种的稀有性而降低，但对nudatus则没有。我们观察到这两个物种的移民少数民族劣势，但这是由不同的因子-频率依赖性杂交来驱动的。总的来说,我们的结果表明，生殖干扰在空间分离中起着重要作用，应与胁迫耐受性和竞争能力一起进行评估。
