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).