Morphological attributes and phylogenetic signal
In this work, we quantified four major characters representing ‘size’
(head-body length, hind-foot length, ear length and tail length) and
three characters representing ‘shape’ (tail/head-body ratio,
hind-foot/head-body ratio and ear/head-body ratio) into morphological
analyses. All morphological attributes were quantified by the mean
values of eight (four males and four females) or four (two males and two
females) adult individual specimens measuring (Du et al. 2017).
We examined the phylogenetic signal by estimating Pagel’s lambda (Pagel
1999) and Blomberg’s K (Blomberg et al. 2003). Pagel’s lambda is
a parameter scaling the interspecific covariances under Brownian
evolution and non-sensitive to taxon number (Pagel 1999), whereas
Blomberg’s K is a scaled ratio trait variation than expected under
Brownian motion (Wang & Clarke 2014; Blomberg et al. 2003). The
values of lambda range from zero to one: if lambda = 0, trait evolution
performs independent of the phylogeny; if lambda=1, trait evolve
following a Brownian motion model (Wang & Clarke 2014; Pagel 1999).
Blomberg’s K usually yields positive values (K> 0), and
higher K values indicate stronger phylogenetic signal (Blomberg et
al. 2003): if K = 1, trait evolves following Brownian motion model; if
K > 1, interspecific trait similarity is higher than
expected under Brownian motion model; if K < 1, interspecific
trait divergence is higher than expected under a Brownian model (Wang &
Clarke 2014; Blomberg et al. 2003).