PREreview of Swept ashore: Transoceanic dispersals and the biogeographic origins of Australian gekkonid lizards

Overall Assessment

This manuscript presents an interesting investigation of the biogeographic history of Australian and Pacific gekkonids, with a particular focus on the role of transoceanic dispersal in explaining the distribution of these lineages. The manuscript is very well written, clearly structured, and generally easy to follow. The main conclusion, particularly the possibility of dispersal over distances exceeding 6,000 km, is certainly challenging to conceptualize. However, the authors do a very good job of discussing why such long-distance dispersal may nevertheless be plausible in the groups considered, and the discussion provides useful biological context for interpreting this result.

We particularly appreciated how well thought out the overall analytical strategy is. Although the study relies on a relatively focused set of analytical approaches, the authors use them effectively to uncover complex biogeographic and evolutionary patterns and, importantly, to build a compelling evolutionary narrative from these results. Rather than relying on an unnecessarily large number of analytical methods, the study combines genomic data, phylogenetic inference, divergence-time estimation, and biogeographic modeling in a coherent way to address a clear biological question. We found this combination particularly effective in connecting the phylogenetic patterns with the broader evolutionary history of the group.

We also appreciated the detailed description of the bioinformatic pipelines and the effort to make the analytical workflows transparent and reproducible. Given the genomic nature of the dataset, the processing and preparation of these data represent an important component of the study, and the authors have done a good job of documenting these steps.

Overall, we found the study compelling and potentially valuable for understanding the historical biogeography of gekkonids. Our comments below are mainly intended to improve the transparency of the sampling strategy, clarify several methodological decisions, and ensure that some conclusions are appropriately aligned with the statistical evidence.

Comments and Recommendations

Introduction and framing

1. We recommend clarifying the central question of the study more explicitly at the end of the Introduction. As we understand it, the main question is whether the distribution of gekkonids can be explained by transoceanic dispersal or whether dispersal from eastern Asia through the islands of Melanesia, acting as stepping stones, provides a more plausible biogeographic scenario. Explicitly stating this question would help frame the subsequent analyses.

2. Lines 50–51: the statement “For species capable of flight or dispersal via wind or ocean currents, oceanic dispersal may be common” would benefit from an appropriate reference.

3. Lines 73–75: the wording could be streamlined by removing the repeated “and” before “varanid lizards” and “elapid snakes,” retaining it only before “pythonid snakes.”

4. Lines 79–80: this statement would benefit either from an appropriate reference or from a brief explanation clarifying what is meant by this claim.

5. Lines 114–118: this paragraph appears to introduce methodological details that may be more appropriate for the Materials and Methods section.

6. Line 122: similarly, this sentence appears to introduce a result before the Results section. We suggest either removing it from the Introduction or reframing it as a statement of the study's objectives or expectations.

Sampling and methodology

1. Line 130: the authors state that they included “additional gekkonids throughout the Pacific region to test the monophyly of Australian groups.” We would appreciate some clarification regarding the criteria used to select these additional 17 species. The Introduction emphasizes the importance of incorporating species outside the Australian continent, so it would be useful to explain more explicitly what these additional taxa contribute to the analysis and what limitations remain despite their inclusion. This seems particularly relevant given the possibility of rapid radiation after the Cretaceous and the potential effects of incomplete lineage sorting (ILS) on relationships among these lineages.

2. Lines 131–133: the manuscript states that sampling of Australian species was based on previous studies by Ashman et al. (2018) and Zozaya et al. (2023, 2025). It would be helpful to clarify the basis for this sampling strategy. For example, were species selected based primarily on taxonomy, geographic distribution, availability of vouchers, previous phylogenetic hypotheses, or a combination of these factors? Providing these criteria would make the sampling strategy easier to evaluate and reproduce.

3. Line 171: the manuscript states that details concerning “sample identification, source, summary statistics, and analysis” are provided in the Supplementary Material. However, we could not find information corresponding specifically to “sample identification” in the Supplementary Material. Because the manuscript explicitly refers to some of the sampled taxa as putative species, information on how samples were identified would be particularly valuable. We recommend either adding these details to the Supplementary Material or revising the statement if such information is not available.

4. Lines 184–185: could the authors briefly explain the rationale for this analytical step? The reason for performing this particular procedure was not immediately clear to us.

5. Lines 197–201: the manuscript refers to the “100 fastest evolving AHE loci.” Please clarify how these loci were identified and what criterion was used to classify loci as the fastest evolving.

6. Divergence Dating: the description of the dating strategy currently presented in the Supplementary Material (“Dating Analyses,” lines 1294–1304) is particularly useful for understanding the analytical framework. We understand that some of these details may have been moved to the Supplementary Material because of journal space limitations. Nevertheless, we suggest considering whether at least some of this information could be retained in the main text, as it provides important context for evaluating the divergence-time estimates and the assumptions underlying the dating analyses.

7. Biogeographic modelling: the preferred model includes the founder event parameter J, and the subsequent ancestral range reconstructions and stochastic mapping are therefore based on DEC+J+x. Given the discussion surrounding the behaviour and interpretation of DEC+J models, we think it would be useful to evaluate how strongly the main biogeographic conclusions depend on the inclusion of \(j\). In particular, we suggest comparing the inferred number and direction of colonizations of Australia, the ancestral source areas of the Australian lineages, and the reconstruction of the Christinus dispersal under DEC+x and DEC+J+x. This comparison would help clarify which conclusions are consistently supported across models and which are more dependent on the inclusion of founder event speciation.

Results

1. Figure 2: the confidence/credible interval bars are difficult to distinguish from the background and the phylogeny. We recommend increasing their contrast or otherwise modifying the graphical presentation to make these intervals easier to identify.

2. Lines 351–353: “That the dispersal scalar w did not improve model fit is indicative of environment (land vs. water) not inhibiting gekkonid dispersal.” We suggest revisiting this interpretation. A lack of improvement in model fit does not necessarily demonstrate that the environment does not inhibit dispersal. Rather, it may indicate that the available data do not provide sufficient evidence that incorporating the dispersal scalar improves the model. We therefore recommend tempering this statement or explicitly discussing the limitations of interpreting a non-significant or unsupported model improvement as evidence for the absence of an environmental effect.

Discussion

1. Lines 480–482: we suggest considering the potential relevance of caudal lipid reserves to the discussion of long-distance dispersal. Lipid reserves stored in the tails of gekkonids have been associated with prolonged survival under food deprivation, with some individuals reportedly surviving for several months without food. This physiological trait could provide an additional biological mechanism supporting the plausibility of prolonged oceanic dispersal. The relevance may be particularly interesting given that Christinus marmoratus is among the lineages discussed in relation to the proposed Africa–Australia dispersal history. A potentially relevant reference is Daniels (1984), “The importance of caudal lipid in the gecko Phyllodactylus marmoratus.”

This review was developed collaboratively by members of the DEVL (Diversity and Evolution Laboratory) PREreview Club as part of PREreview’s Review-a-thon, a global initiative organized to celebrate Peer Review Week. Reviewers: Amanda Varago, Carolina Martins, Fabricius Domingos, Felipe José Batista, Júnior Nadaline, Matheus Salles, and Rhamon Malheiro.

Conflict of Interest

The authors declare that they have no competing interests.

Use of Artificial Intelligence (AI)

The authors declare that they did not use generative AI to generate new ideas or substantive content for this review.

Conflitos de interesse

Os autores declaram que não possuem conflitos de interesse.

Uso de Inteligência Artificial (IA)

The authors declare that they did not use generative AI to come up with new ideas for their review.