Bibliographic record
Abstract
Abstract Abiotic environmental conditions play a key role in driving the size and shape of organisms. Quantifying environment-morphology relationships is important not only for understanding the fundamental processes driving phenotypic diversity within and among species (1), but also for predicting how species will respond to ongoing global change (2). Despite a clear set of expectations motivated by ecological theory (3), broad evidence in support of generalizable effects of abiotic conditions, such as temperature (4), on spatial and temporal intraspecific morphological variation has been limited. Using standardized data from over 250,000 captures of 105 landbird species, we assessed intraspecific shifts in bird morphology since 1989 while simultaneously measuring spatial morphological gradients across the North American continent. Across bird species, we found strong spatial and temporal trends in body size, with warmer temperatures associated with smaller body sizes both at more equatorial latitudes and in more recent years. The magnitude of these thermal effects varied both across and within species, with results suggesting it is the warmest, rather than the coldest, temperatures driving both spatial and temporal trends. Across elevation, we found that body size declines as relative wing length increases, likely due to the benefits that longer wings confer for flight in thin air environments. Our results provide support for both existing and new large-scale ecomorphological gradients and highlight how the response of functional tradeoffs to abiotic variation drives morphological change. Significance Statement Characterizing how the size and shape of organisms varies over space and time is key to understanding the processes that create ecological communities and for predicting how species will respond to climate change. Across more than 100 species of North American birds, we show that within species the size and shape of individuals varies substantially across space and time. Warmer temperatures are associated with smaller body sizes, likely due to the importance of body size for thermoregulation. As the climate continues to warm, these species will likely continue to shrink. We also provide the first large-scale evidence of an increase in wing length with elevation, a pattern that could be attributed to thinner air in high elevation environments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.073 | 0.008 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".