You need to do two things:
The code:
dtt$model <- factor(dtt$model, levels=c("mb", "ma", "mc"), labels=c("MBB", "MAA", "MCC"))
library(ggplot2)
ggplot(dtt, aes(x=year, y=V, group = model, colour = model, ymin = lower, ymax = upper)) +
geom_ribbon(alpha = 0.35, linetype=0)+
geom_line(aes(linetype=model), size = 1) +
geom_point(aes(shape=model), size=4) +
theme(legend.position=c(.6,0.8)) +
theme(legend.background = element_rect(colour = 'black', fill = 'grey90', size = 1, linetype='solid')) +
scale_linetype_discrete("Model 1") +
scale_shape_discrete("Model 1") +
scale_colour_discrete("Model 1")
However, I think this is really ugly as well as difficult to interpret. It's far better to use facets:
ggplot(dtt, aes(x=year, y=V, group = model, colour = model, ymin = lower, ymax = upper)) +
geom_ribbon(alpha=0.2, colour=NA)+
geom_line() +
geom_point() +
facet_wrap(~model)