Identification and characterization of Gypsophila paniculata color morphs in Sleeping Bear Dunes National Lakeshore, MI, USA

Gypsophila paniculata (baby’s breath) is an invasive species found throughout much of the northwest United States and western Canada. Recently, plants exhibiting a different color morphology were identified within the coastal dunes along eastern Lake Michigan. The common baby’s breath (G. paniculata) typically produces stems that are purple in color (purple morph), while the atypical morph has stems that are green-yellow (green-yellow morph). The purpose of this study was to characterize these newly identified morphs and determine if they are genetically distinct species from the common baby’s breath in order to assess whether alternative management strategies should be employed to control these populations. Methods. We sequenced two chloroplast regions, rbcL and matK, and one nuclear region, ITS2, from the purple morphs and green-yellow morphs collected from Sleeping Bear Dunes National Lakeshore, MI, USA (SBDNL). Sequences were aligned to reference sequences from other Gypsophila species obtained from the Barcode of Life (BOLD) and GenBank databases. We also collected seeds from wild purple morph and wild green-yellow morph plants in SBDNL. We grew the seeds in a common garden setting and characterized the proportion of green-yellow individuals produced from the two color morphs after five-months of growth. Results. Phylogenetic analyses based upon rbcL, matK, and ITS2 regions suggest that the two color morphs are not distinct species and they both belong to G. paniculata. Seeds collected from wild green-yellow morphs produced a significantly higher proportion of green-yellow individuals compared to the number produced by seeds collected from wild purple morphs. However, seeds collected from both color morphs produced more purple morphs than green-yellow morphs. Discussion. Based upon these results, we propose that the two color morphs are variants of G. paniculata. Given the significant difference in the number of green-yellow morphs produced from the seeds of each morph type, we also suggest that this color difference has some genetic basis. We propose that current management continue to treat the two color morphs in a similar manner in terms of removal to prevent the further spread of this species.

圆锥石头花（Gypsophila paniculata，俗称满天星（baby’s breath））是一种入侵物种，广泛分布于美国西北部大部分区域及加拿大西部。近期，科研人员在密歇根湖东岸的沿海沙丘中发现了该物种中具有不同颜色形态的植株。普通满天星（G. paniculata）的茎通常呈紫色形态型（purple morph），而非典型形态的植株茎则呈绿黄色形态型（green-yellow morph）。本研究旨在对这一新发现的两种形态型进行特征分析，并明确其是否与普通满天星在遗传上属于不同物种，以此评估是否需要采用差异化的管理策略来防控这些种群。

研究方法：我们从采集自美国密歇根州睡熊沙丘国家湖岸（Sleeping Bear Dunes National Lakeshore，简称SBDNL）的紫色形态型（purple morph）与绿黄色形态型（green-yellow morph）植株中，对两个叶绿体区域rbcL、matK以及一个核区域ITS2进行了测序。将测得的序列与从生命条形码数据库（Barcode of Life，简称BOLD）及GenBank数据库中获取的其他石头花属物种的参考序列进行比对。我们还从该区域的野生紫色形态型与野生绿黄色形态型植株上采集了种子，将这些种子置于统一栽培环境中培育，并在生长5个月后，统计两种颜色形态型植株所结种子长出的绿黄色个体占比。

研究结果：基于rbcL、matK及ITS2区域的系统发育分析结果显示，这两种颜色形态型并非独立物种，二者均属于圆锥石头花（G. paniculata）。与野生紫色形态型植株的种子相比，野生绿黄色形态型植株的种子所长出的绿黄色个体占比显著更高。但两种颜色形态型植株的种子长出的紫色形态型个体数量均多于绿黄色形态型个体。

讨论：基于上述结果，我们认为这两种颜色形态型均为圆锥石头花（G. paniculata）的变种。鉴于两种形态型植株的种子所产生的绿黄色形态型个体数量存在显著差异，我们认为该颜色差异具备一定的遗传基础。我们建议当前的防控工作仍可采用统一方式对这两种形态型植株进行移除，以阻止该物种进一步扩散。