Mechanisms driving patterns of occurrence and co‐occurrence among North American freshwater fishes are poorly understood. In particular, the influence of biotic interactions on coexistence among stream reaches and their effects on regional species distribution patterns is not well understood for congeneric headwater fishes. Occupancy models provide a useful framework for examining patterns of co‐occurrence while also accounting for imperfect detection. Occupancy models may be extended to test for evidence that a dominant species influences the occurrence of a subordinate species and thus evaluate support for the hypothesis that species interactions drive patterns of coexistence. We examined patterns of occurrence and co‐occurrence at the stream‐reach scale among three species of darters (Percidae: Etheostomatinae) that occupy headwater streams within a Gulf Coastal Plain drainage in the south‐eastern U.S.A. We assessed species occurrences at 97 sites in first‐ to third‐order streams on one occasion each and used data from four sub‐reaches sampled with equal effort at each site to estimate species‐specific detection probabilities. Following sampling, a suite of habitat variables was collected at three equidistant points along each of the three transects established within a sub‐reach. Coarse (stream‐segment, catchment, network) scale variables were also incorporated using geospatial data. Single‐species and two‐species occupancy models were used to examine patterns of occupancy and coexistence. The occupancy of each species was influenced by distinct habitat variables. Goldstripe darters (Etheostoma parvipinne) were constrained by a stream size gradient, groundwater input appeared to influence the occurrence of Yazoo darters (Etheostoma raneyi), and local habitat heterogeneity (e.g. variation in depth and current velocity) appeared to influence the occupancy of redspot darters (Etheostoma artesiae). We found no evidence that the presence of one species influenced the occurrence of another within a stream‐reach based on two‐species occupancy models. Rather, species co‐occurrences were best explained as independent occurrences within a stream‐reach according to species‐specific habitat associations. Occupancy modelling may provide a suitable framework for evaluating the influence of biotic interactions among congeneric stream fishes along species‐specific habitat gradients at the stream reach scale. Our study offers insight into how habitat variation can influence coexistence of potential competitors across a large river system.

中文翻译：

---

三种同类源头鱼类共存模式建模

对北美淡水鱼类的发生和共同发生模式的驱动机制知之甚少。特别是，生物相互作用对河流河段共存的影响及其对区域物种分布模式的影响对于同类源头鱼类尚不清楚。占用模型为检查共现模式提供了一个有用的框架，同时也解释了不完美的检测。占用模型可以扩展到测试优势物种影响从属物种出现的证据，从而评估对物种相互作用驱动共存模式的假设的支持。我们检查了三种镖鱼（鲈科：Etheostomatinae）占据美国东南部墨西哥湾沿岸平原排水系统的源头流，我们评估了一级至三级河流中 97 个地点的物种出现情况，并使用了在每个站点以估计特定物种的检测概率。采样后，在子河段内建立的三个断面中的每一个的三个等距点收集了一套栖息地变量。还使用地理空间数据合并了粗略（河流段、集水区、网络）尺度变量。使用单物种和双物种占用模型来检查占用和共存模式。每个物种的占有率受到不同栖息地变量的影响。Goldstripe darters (Etheostoma parvipinne) 受到河流大小梯度的限制，地下水输入似乎影响了 Yazoo darters (Etheostoma raneyi) 的发生，而当地栖息地的异质性（例如深度和水流速度的变化）似乎影响了 redspot darters 的占有率(Etheostoma artesiae)。我们没有发现证据表明一种物种的存在会影响基于双物种占用模型的河流河段内另一种物种的出现。相反，根据物种特定的栖息地关联，物种共生最好解释为河段内的独立事件。占用模型可以提供一个合适的框架，用于评估同属河流鱼类之间沿着河流到达尺度的物种特定栖息地梯度的生物相互作用的影响。