Understanding Muroidea (Rodentia) Species Richness: The Complementary Roles of Adaptive and Non‐Adaptive Diversification

Aim To evaluate environmental drivers of species richness in the Muroidea superfamily and to determine the relative contributions of adaptive and non‐adaptive diversification using organismal or emergent properties, trait variation. Location Global. Time Period 32 million years ago to the present. Major Taxa Studied Muroidea superfamily (Rodentia). Methods We employed piecewise structural equation models (pSEMs) to analyse seven environmental variables across 844 species (~50% of known Muroidea diversity) as potential drivers of species richness. Additionally, we used disparity‐through‐time (DTT) and lineages‐through‐time (LTT) analyses, alongside phylogenetic comparative methods, to identify evolutionary processes influencing diversification patterns. Results Geographic range size, which showed a negative correlation, emerged as the most relevant driver of species richness. DTT and LTT analyses revealed an initial phase of adaptive diversification during Oligocene and early Miocene, marked by lineage accumulation and increasing trait disparity among subclades. From the mid‐Miocene onward, however, the group shifted towards non‐adaptive diversification, characterised by continued lineage accumulation but stable trait disparity, particularly in geographic range size. These findings suggest that while ecological opportunity may have played a key role in early diversification, non‐adaptive processes dominated the later phases of Muroidea evolution. Main Conclusions The evolutionary history of Muroidea reflects an interplay of adaptive and non‐adaptive processes. Early diversification aligns with adaptive theories, but subsequent patterns highlight the importance of geographic and stochastic factors. This nuanced perspective emphasises that diversification mechanisms cannot be solely attributed to ecological opportunity or non‐adaptive processes in understanding species richness and global biodiversity. In this work, we revealed that both types of processes were present along the evolutionary history of the superfamily.