1. Yellow crazy ants (Anoplolepis gracilipes) have invaded the rainforests of Christmas Island and have driven a key indigenous species, the red land crab (Geocarcoidea natalis), to near extinction. Researchers hypothesized that the loss of the red land crab has facilitated the establishment of another invasive species, the giant African land snail (Achatina fulica). The crabs both prey on the snails and potentially compete with the snails over an important food source leaf litter. To test this idea, the researchers set up four kinds of fenced 2m 2m plots. In two of the plots, they placed three red land crabs, and the other two plots contained no land crabs. They also installed a leaf litter excluder over two of the plots, while the other two were able to receive ambient leaf litter as it fell into the plot. These treatments were assigned to plots such that all four combinations of the predator and litter treatments were included. Each combination was replicated ten times (40 plots total). The mesh in the fencing was large enough to allow the land snails to enter the plots, and six months after establishing the plots, the researchers returned and counted the number of land snails within each.

1. Notice that the Excel file contains only 39 of the expected 40 plots. One of the plots that was originally established was destroyed by a falling branch. What complications does this unequal sample size create for the analysis of these data?

2. Create a new variable that is the log10 of the number of land snails in each plot. Use R to test the HOV assumption for both transformed and untransformed data. Which better conforms to ANOVA assumptions?

tree	predator	litter	snails
treeA	absent	ambient	106
treeA	present	ambient	22
treeA	absent	excluded	41
treeA	present	excluded	13
treeB	absent	ambient	30
treeB	present	ambient	12
treeB	absent	excluded	70
treeB	present	excluded	6
treeC	absent	ambient	50
treeC	present	ambient	4
treeC	absent	excluded	28
treeC	present	excluded	7
treeD	absent	ambient	437
treeD	present	ambient	39
treeD	absent	excluded	19
treeD	present	excluded	20
treeE	absent	ambient	412
treeE	present	ambient	2
treeE	absent	excluded	36
treeE	present	excluded	6
treeF	absent	ambient	123
treeF	present	ambient	14
treeF	absent	excluded	100
treeF	present	excluded	20
treeG	absent	ambient	374
treeG	present	ambient	9
treeG	absent	excluded	65
treeH	absent	ambient	120
treeH	present	ambient	9
treeH	absent	excluded	41
treeH	present	excluded	40
treeI	absent	ambient	134
treeI	present	ambient	7
treeI	absent	excluded	11
treeI	present	excluded	6
treeJ	absent	ambient	154
treeJ	present	ambient	54
treeJ	absent	excluded	77
treeJ	present	excluded	35