VESTIGIAL ORGANS AS OPPORTUNITIES FOR FUNCTIONAL INNOVATION: THE EXAMPLE OF THE PENSTEMON STAMINODE
Bibliographic record
Abstract
Vestigial organs arise commonly during morphological evolution, but they need not be destined for elimination. Instead, vestigial organs may facilitate functional innovation because their freedom from functional constraints allows them to assume novel roles that their functional progenitor could not perform. We illustrate this vestigial transition between functions with an experimental study of the staminode of Penstemon flowers. Previous phylogenetic and developmental studies indicate that this staminode represents a stamen that was lost phenotypically, but not genetically, and then reappeared in the tribe Cheloneae, to which Penstemon belongs. To assess whether the Penstemon staminode has adopted a novel function(s), we compared pollination of flowers with and without staminodes for two bee-pollinated species, P. ellipticus and P. palmeri, and two hummingbird-pollinated species, P. centranthifolius and P. rostriflorus. The staminode acts differently in the two bee-pollinated species. For P. ellipticus, which represents the basal Penstemon lineage, the staminode hinders pollinator access to nectar, which increases visit duration and pollinator contact with sexual organs, thereby increasing pollen receipt by stigmas and controlling pollen removal from anthers. In contrast, in P. palmeri, the staminode acts as a lever that enhances stigma contact with the pollinator, so that staminode removal reduced pollen receipt, but did not affect pollinator attraction, visit duration, or pollen removal. Unlike in bee-pollinated species. staminode removal from hummingbird-pollinated species did not affect any measured aspect of pollination, indicating that the staminode serves no function in this derived pollination system. These results illustrate several features of vestigial organs: loss of function can be temporary; loss of function facilitates the evolution of novel roles; and functional reinvention will often involve only a single role, thus increasing the chance of both secondary loss of function (bird-pollinated penstemons) and functional switches (P. palmeri).
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".