Persisting at the Edge of Ecological Collapse: The Impact of Urbanization on Fish and Amphibian Communities From Lake Xochimilco
Bibliographic record
Abstract
ABSTRACT Freshwater ecosystems are globally threatened by habitat loss, pollution, and invasive species, all of which are particularly acute in urban areas. To assess the impacts of urbanization on freshwater biodiversity—specifically the effects of alien species on native primary aquatic vertebrates—we investigated the World Heritage Site, Lake Xochimilco in Mexico City. Focusing on fishes and amphibians, we applied environmental DNA metabarcoding using primer pairs targeting mitochondrial 12S and 16S across the remnant lake and collected 14 aquatic environmental variables for sampled sites. Our survey recovered ca. 60% of Lake Xochimilco's historically recorded fish and amphibian species, including rare species and novel taxa not detected by past traditional surveys. However, our findings imply a severely degraded wetland, with alpha diversity indices indicating a low‐diversity ecosystem dominated by alien fishes. Beta diversity analysis revealed a heterogeneous ecosystem that may be driven partially by the presence of alien fish, particularly cyprinids. Environmental variables linked to pollution predicted the presence of non‐native fish families. We also found evidence that some species prefer to occupy different water bodies within the lake remnant. Despite the ongoing degradation of this ecosystem, native and endemic fauna are persisting, although detections were typically rare. We found no evidence of the Critically Endangered axolotl salamanders ( Ambystoma sp.) from wild sites; however, we detected their presence in one wildlife refuge, highlighting the potential of refuges to prevent complete extinction in the wild. We also found evidence of cryptic taxonomic diversity in Lithobates frogs and evidence of endemic genera, including the threatened mexclapique fish ( Girardinicthys viviparus ). These fishes are considered extirpated, suggesting remnant populations persist undetected by traditional surveys. Despite clear evidence of an ecosystem under extreme decline compared to historical biological records, our study demonstrates the potential for restoration, given the presence of native freshwater species and the success of wildlife refuges.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".