Effect of Oceanic Islands on an Insect Symbiont Genome in Transition to a Host-Restricted Lifestyle
Bibliographic record
Abstract
Islands offer unique opportunities to study adaptive radiations and their impacts on host genome evolution. In Hawaiian Pariaconus psyllids, all species harbor the ancient nutritional symbiont Carsonella, while only free-living and open-gall species on younger islands host a second stable cosymbiont, Makana. In contrast, a third cosymbiont, Malihini, appears to be in an early stage of host restriction and genome degradation, making it a valuable model for understanding symbiont evolution during island radiations. Here, we examine Malihini genome evolution across multiple Pariaconus lineages using 16S rRNA sequencing, metagenomics, phylogenetic reconstruction, and microscopy. We find that Malihini is codiversifying with its hosts on the oldest island Kaua'i (kamua group; open- and closed-gall makers) and on the younger islands only in free-living species (bicoloratus group). Comparison of five Malihini genomes-including three newly assembled in this study-shows ongoing genome reduction from a large-genome ancestor (>3,900 protein-coding genes), likely driven by relaxed selection, vertical transmission bottlenecks, and island dispersal over the past 5 million years. On Kaua'i, the galling psyllids appear to depend more heavily on cosymbiont (Malihini) for the biosynthesis of amino acids and B-vitamins than galling species on younger islands-especially closed-gall species, which only have Carsonella. Surprisingly, free-living psyllids on younger islands with all three symbionts show metabolic reliance similar to Kaua'i gall makers. Together, our results demonstrate that island biogeography and host plant ecology shape symbiont losses and codiversification patterns. Malihini represents an early stage of symbiont genome degradation during host restriction, in sharp contrast to its more stable coresidents, Carsonella and Makana.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".