“Ecomorphological convergence following niche shifts in montane ground
beetles (Carabidae: Nebria)”
Abstract
Aim A critical step towards uncovering generalizable patterns of
phenotype-niche relationships is understanding how functional traits
have evolved as species occupy new habitats. Ecomorphological traits
impact how organisms function in their environment and are predictive of
habitat use and niche. Studying ecomorphological variation in the
context of strong environmental filtering can provide opportunities to
understand the role of convergent evolution in forming trait-habitat use
patterns. By integrating a molecular phylogeny, habitat use, and
morphometrics, this study aimed to understand the role of ancestry and
convergent evolution in ecomorphological trait evolution. Location
Montane and alpine streambeds, talus, and snowfields in Holarctic
mountain ranges (0-5000 m. above sea level). Time Period 1970-2021 Major
Taxa Studied Seventy-nine species comprising three species complexes in
the ground beetle genus Nebria (Carabidae: Nebriini). Methods
Morphological measurements including pronotal ratio (widest point
divided by the base), elytral length, elytral ratio (length divided by
width), antennal scape length, and pronotal and elytral shape (Fourier
decomposition) were used in this study, in conjunction with measurements
of habitat use habitat where specimens were collected. Morphological
variation was examined in relation to habitat use and phylogenetic
relatedness, and morphological trait evolution was tested for
convergence. Results Ecomorphological traits are evolving slower than
expected under a null model of Brownian motion evolution. Nebria species
cluster in multivariate morphospace according to relatedness, but
habitat use and relatedness together are the best predictors of
morphological variation. There is evidence for convergence in riparian
species based on morphologicy alone, and additional evidence for
morphological convergence in riparian and alpine species when
phylogenetic distance is considered. Main Conclusions In species
assemblages of Nebria, we found evidence of rapid diversification
followed by a slow rate of ecomorphological evolution, with convergent
evolution playing a significant role in shaping trait-habitat use
patterns and niche acquisition.