Phylogeography and genetic characteristics of a putative secondary-contact zone of the loggerhead shrike in central and eastern North America
Bibliographic record
Abstract
The loggerhead shrike (Lanius ludovicianus) is found throughout North America in grassland and open scrub habitats. We previously described four loggerhead shrike management units found in central and eastern North America within the geographic ranges of three subspecies, L. l. migrans, L. l. ludovicianus, and L. l. excubitorides. A contact zone has been suggested to occur between L. l. migrans and L. l. excubitorides. The present study uses mitochondrial DNA sequence data to explore historical, ecological, and geographical factors that may have played a role in the genetic differentiation of these four management units, and examines the evidence for and characteristics of the migransexcubitorides contact zone. Geographically discrete, monophyletic clades were not evident, but the distribution of haplotypes (especially those exceeding 10% overall frequency) indicated some phylogeographic structure that perhaps reflects an intermediate stage of differentiation between paraphyly and reciprocal monophyly. The contact zone between L. l. migrans and L. l. excubitorides is supported by the mixing of haplotypes unique to each of the hybridizing populations and intermediate frequencies of common haplotypes. We interpret these patterns as possibly reflecting the impact of both glacial refugial dynamics and anthropogenic changes to habitat in eastern North America.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".