如何在不覆盖填充组的情况下更改箱线图点颜色

我正在尝试制作显示数据的三个特征（SiteID、Group 和 TreatmentID）的箱线图。我能够成功表示两个变量（SiteID 和 Group），如下面的代码所示，但是当我尝试更改箱线图中点的颜色以表示我的第三个特征（TreatmentID）时，它会覆盖原始分组. 有人知道我该如何解决这个问题吗？

这是我的代码：

myData <- structure(list(SiteID = structure(c(1L, 1L, 2L, 2L, 3L, 3L, 1L, 1L, 2L, 2L, 3L, 3L), .Label = c("1", "2", "3"), class = "factor"), Group = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("Shale Hills", "Sleepers River"), class = "factor"),  TreatmentID = c("A", "R", "A", "R", "A", "R", "A", "R", "A", "R", "A", "R"), DOCmgkg = c(3.63, 6.43, 7.48, 10.04, 7.3, 8.2, 3.1, 8.1 ,6.36 , 1.8, 4.5, 5.4)), row.names = c("4", "8", "16", "20", "24", "28", "32", "36", "40", "44", "48", "52"), class = "data.frame")

# Bring in plot basics
library(ggplot2)
p<-ggplot(myData, aes(x=SiteID, y=DOCmgkg, fill=Group)) +
  geom_boxplot(position=position_dodge(1))

# Successful attempt at displaying two characteritics
p + geom_point(position=position_dodge(1), pch=21)

# Unsuccessful attempt at displaying three characteritics
p + geom_point(position=position_dodge(1), pch=21, aes(fill=factor(TreatmentID)))

最好的，托马斯