Intraspecific trait variation shapes macro-scale patterns ofniche breadth and range size
- 1Department of Life Sciences, Imperial College London, Ascot, UK
Abstract
Morphological variation within species may promote adaptation across ecological and geographic space, perhaps reflecting evolutionary plasticity and adaptability. Based on this concept, species with greater intraspecific variation in morphological traits may be expected to occupy broader ecological niches and larger geographic ranges. However, even in the age of global trait datasets, intraspecific morphological variation remains poorly quantified at broad taxonomic and geographic scales, limiting our understanding of how trait flexibility shapes ecological and biogeographic patterns. Focusing on 161 species of bulbuls, a widespread avian family containing some of the most abundant bird species in the world, along with some of the rarest and most restricted in range, we conducted global-scale sampling of morphological traits. These included beak shape, tarsus length and wing length, associated with dietary niche, foraging strategy and dispersal, respectively. Using phylogenetic models, we tested whether ecological niche breadth and geographical range size are predicted by intraspecific morphological variation quantified from 8,251 museum specimens and 5,627 live captures. Our results demonstrate that morphological trait variation predicts both ecological niche breadth and geographic range size. Furthermore, widespread species exhibit greater morphological variation than restricted-range species even when comparisons are constrained to equivalent geographic extents, consistent with the hypothesis that intraspecific trait variation facilitates range expansion rather than simply accumulating as a consequence of occupying a larger range. These results identify intraspecific morphological variation as a potentially important, yet largely overlooked, predictor of ecological traits and biogeographic distributions in birds.
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BibTeX
@misc{ranganathan2026intraspecific,
title = {{Intraspecific trait variation shapes macro-scale patterns ofniche breadth and range size}},
author = {E. Ranganathan and P. D. Round and J. C. T. Gonzalez and D. V. Pluym and L. L. Powell and B. A. Krochuk and C. J. Nwaogu and C. M. Probst and P. Mikula and K. Z. Bitrus and V. Gattani and A. J. Pierce and S. Y. Chia and J. A. Villamin and J. R. Ali and F. Babarovic and R. C. Urizza and K. Zyskowski and L. J. Musher and M. Irham and B. C. Weeks and S. Manawattana and K. D. Kittelberger and C. R. Bajamunde and G. D. Lorenzana and R. R. B. Perez and V. G. Rohwer and W. Sankamethawee and C. G. Meneses and R. Vijayan and M. L. K. Z. Fabella and M. Bulla and K. M. Pitogo and W. Bunkhwamdi and I. C. Enriquez and C. J. du Toit and J. H. Namion and S. Madhuhansi and E. Steell},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.31.763334},
url = {https://www.biorxiv.org/content/10.64898/2026.10.31.763334v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Intraspecific trait variation shapes macro-scale patterns ofniche breadth and range size
AU - E. Ranganathan
AU - P. D. Round
AU - J. C. T. Gonzalez
AU - D. V. Pluym
AU - L. L. Powell
AU - B. A. Krochuk
AU - C. J. Nwaogu
AU - C. M. Probst
AU - P. Mikula
AU - K. Z. Bitrus
AU - V. Gattani
AU - A. J. Pierce
AU - S. Y. Chia
AU - J. A. Villamin
AU - J. R. Ali
AU - F. Babarovic
AU - R. C. Urizza
AU - K. Zyskowski
AU - L. J. Musher
AU - M. Irham
AU - B. C. Weeks
AU - S. Manawattana
AU - K. D. Kittelberger
AU - C. R. Bajamunde
AU - G. D. Lorenzana
AU - R. R. B. Perez
AU - V. G. Rohwer
AU - W. Sankamethawee
AU - C. G. Meneses
AU - R. Vijayan
AU - M. L. K. Z. Fabella
AU - M. Bulla
AU - K. M. Pitogo
AU - W. Bunkhwamdi
AU - I. C. Enriquez
AU - C. J. du Toit
AU - J. H. Namion
AU - S. Madhuhansi
AU - E. Steell
PY - 2026
DA - 2026/10/31
PB - bioRxiv
DO - 10.64898/2026.10.31.763334
UR - https://www.biorxiv.org/content/10.64898/2026.10.31.763334v1
AB - Morphological variation within species may promote adaptation across ecological and geographic space, perhaps reflecting evolutionary plasticity and adaptability. Based on this concept, species with greater intraspecific variation in morphological traits may be expected to occupy broader ecological niches and larger geographic ranges. However, even in the age of global trait datasets, intraspecific morphological variation remains poorly quantified at broad taxonomic and geographic scales, limiting our understanding of how trait flexibility shapes ecological and biogeographic patterns. Focusing on 161 species of bulbuls, a widespread avian family containing some of the most abundant bird species in the world, along with some of the rarest and most restricted in range, we conducted global-scale sampling of morphological traits. These included beak shape, tarsus length and wing length, associated with dietary niche, foraging strategy and dispersal, respectively. Using phylogenetic models, we tested whether ecological niche breadth and geographical range size are predicted by intraspecific morphological variation quantified from 8,251 museum specimens and 5,627 live captures. Our results demonstrate that morphological trait variation predicts both ecological niche breadth and geographic range size. Furthermore, widespread species exhibit greater morphological variation than restricted-range species even when comparisons are constrained to equivalent geographic extents, consistent with the hypothesis that intraspecific trait variation facilitates range expansion rather than simply accumulating as a consequence of occupying a larger range. These results identify intraspecific morphological variation as a potentially important, yet largely overlooked, predictor of ecological traits and biogeographic distributions in birds.
ER -