For ordinary `tslm()` fits without autoregressive error terms, `anova()`
returns the usual analysis of variance table from [stats::anova.lm()].
For AR-error models fitted through [nlme::gls()], the reported tests are
Wald-style tests of model terms. These test whether each term contributes to
the fitted mean model after allowing for the estimated autocorrelation
structure. Because these models do not use the ordinary independent-error
sum-of-squares decomposition, the compact table reports `Df`, `F value`, and
`Pr(>F)`, but does not report `Sum Sq` or `Mean Sq`. Compare nested AR-error
models with care: `verbose = TRUE` exposes the underlying `nlme` comparison
output rather than recreating an ordinary `lm` ANOVA table.
Use `verbose = TRUE` to see the underlying [nlme::anova.gls()] output.