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The invasion of the giant Madagascar day gecko Phelsuma grandis has increased the threats to the four endemic Mauritian day geckos (Phelsuma spp.) that have survived on mainland Mauritius. We had two main aims: (i) to predict the spatial distribution and overlap of P. grandis and the endemic geckos at a landscape level; and (ii) to investigate the effects of P. grandis on the abundance and risks of extinction of the endemic geckos at a local scale. An ensemble forecasting approach was used to predict the spatial distribution and overlap of P. grandis and the endemic geckos. We used hierarchical binomial mixture models and repeated visual estimate surveys to calculate the abundance of the endemic geckos in sites with and without P. grandis. The predicted range of each species varied from 85 km2 to 376 km2. Sixty percent of the predicted range of P. grandis overlapped with the combined predicted ranges of the four endemic geckos; 15% of the combined predicted ranges of the four endemic geckos overlapped with P. grandis. Levin's niche breadth varied from 0.140 to 0.652 between P. grandis and the four endemic geckos. The abundance of endemic geckos was 89% lower in sites with P. grandis compared to sites without P. grandis, and the endemic geckos had been extirpated at four of ten sites we surveyed with P. grandis. Species Distribution Modelling, together with the breadth metrics, predicted that P. grandis can partly share the equivalent niche with endemic species and survive in a range of environmental conditions. We provide strong evidence that smaller endemic geckos are unlikely to survive in sympatry with P. grandis. This is a cause of concern in both Mauritius and other countries with endemic species of Phelsuma.

The Manapany day gecko Phelsuma inexpectata is a Critically Endangered species endemic to Réunion Island in the Indian Ocean. Studying its geographical distribution and its evolution is important for developing effective biodiversity conservation strategies. We evaluated past and current distributions of P. inexpectata using records from 2008–2020 and through recent, intensive field surveys (230 person-days, 2020–2022). We found that its past distribution has declined by more than 28% (5.12 ha), from 19.44 ha to 14.32 ha. In natural habitats, the distribution of P. inexpectata has been strongly affected, declining by c. 45%, but we identified new areas of occurrence (10.72 ha) through field surveys. Most of these new areas (79%) were found in anthropogenic habitats where the species had not been documented before. The current distribution of P. inexpectata covers c. 24 ha, of which 75% is located in urban areas such as gardens and green urban spaces. Moreover, our field survey showed that at least 10% of its range is now colonized by the invasive gold-dust day gecko Phelsuma laticauda. This survey provides an essential baseline for tracking the future distribution of this threatened species and its potential invasive competitor, and for monitoring how changes to its habitat affect the distribution of P. inexpectata.

The study of gecko adhesion is necessarily interdisciplinary due to the hierarchical nature of the adhesive system and the complexity of interactions between the animals and their habitats. In nature, geckos move on a wide range of surfaces including soft sand dunes, trees, and rocks, but much of the research over the past two decades has focused on their adhesive performance on artificial surfaces. Exploring the complex interactions between geckos and their natural habitats will reveal aspects of the adhesive system that can be applied to biomimetic research, such as the factors that facilitate movement on dirty and rough surfaces with varying microtopography. Additionally, contrasting suites of constraints and topographies are found on rocks and plants, likely driving differences in locomotion and morphology. Our overarching goals are to bring to light several aspects of ecology that are important for gecko–habitat interactions, and to propose a framework for how they can inspire material scientists and functional ecologists. We also present new data on surface roughness and topography of a variety of surfaces, and adhesive performance of Phelsuma geckos on surfaces of varying roughness. We address the following key questions: (1) why and how should ecology be incorporated into the study of gecko adhesion? (2) What topographical features of rocks and plants likely drive adhesive performance? (3) How can ecological studies inform material science research? Recent advances in surface replication techniques that eliminate confounding factors among surface types facilitate the ability to address some of these questions. We pinpoint gaps in our understanding and identify key initiatives that should be adopted as we move forward. Most importantly, fine details of locomotor microhabitat use of both diurnal and nocturnal geckos are needed.

Aim To investigate whether the frequently advocated climate‐matching species distribution modeling approach could predict the well‐characterized colonization of Florida by the Madagascar giant day gecko Phelsuma grandis. Location Madagascar and Florida, USA. Methods To determine the climatic conditions associated with the native range of P. grandis, we used native‐range presence‐only records and Bioclim climatic data to build a Maxent species distribution model and projected the climatic thresholds of the native range onto Florida. We then built an analogous model using Florida presence‐only data and projected it onto Madagascar. We constructed a third model using native‐range presences for both P. grandis and the closely related parapatric species P. kochi. Results Despite performing well within the native range, our Madagascar Bioclim model failed to identify suitable climatic habitat currently occupied by P. grandis in Florida. The model constructed using Florida presences also failed to reflect the distribution in Madagascar by overpredicting distribution, especially in western areas occupied by P. kochi. The model built using the combined P. kochi/P. grandis dataset modestly improved the prediction of the range of P. grandis in Florida, thereby implying competitive exclusion of P. grandis by P. kochi from habitat within the former's fundamental niche. These findings thus suggest ecological release of P. grandis in Florida. However, because ecological release cannot fully explain the divergent occupied niches of P. grandis in Madagascar versus Florida, our findings also demonstrate some degree of in situ adaptation in Florida. Main conclusions Our models suggest that the discrepancy between the predicted and observed range of P. grandis in Florida is attributable to either in situ adaptation by P. grandis within Florida, or a combination of such in situ adaptation and competition with P. kochi in Madagascar. Our study demonstrates that climate‐matching species distribution models can severely underpredict the establishment risk posed by non‐native herpetofauna. Climate‐matching species distribution models (SDMs) are frequently used to predict biotic invasions. Our manuscript details how both release from native‐range competitors and in situ adaptation within the non‐native range have enabled the day gecko Phelsuma grandis to flourish in Florida under bioclimatic conditions classified as highly unsuitable by an otherwise‐well‐performing climate‐matching SDM. By identifying the large discrepancy between the predicted and observed range of P. grandis in Florida, our study highlights the shortcomings of climate‐matching SDMs as conservation management tools, while also providing valuable empirical evidence of the ecological and evolutionary processes underpinning this discrepancy.

The Manapany day gecko, Phelsuma inexpectata, is a critically endangered reptile endemic to Reunion Island (Southwestern Indian Ocean region). In the present study, we provide the first in-depth insights into the genetic diversity and population structure of the species across its main geographic range, limited to a narrow 14-km littoral fringe in the south of the island. We used two mitochondrial genes and twenty microsatellite loci to genotype 452 geckos sampled in anthropized and natural sites. Compared to other insular species of the Phelsuma genus, P. inexpectata displays a low genetic diversity with nine mitochondrial haplotypes detected, and based on the nuclear markers, a mean number of alleles (Na) of 2.8 ± 0.3, and an observed (Ho) and expected heterozygosity (He) reaching a maximum of 0.353 ± 0.053 and 0.345 ± 0.046 per site, respectively. For most sites, no significant deviations from Hardy-Weinberg equilibrium were detected. Along the limited distribution of P. inexpectata, isolation-by-distance patterns and geographical population structures were found with low first-generation migrants between sites. Genetic diversity distribution and structure are likely shaped by historical processes, including the fragmentation and isolation of relict populations, and anthropogenic-mediated colonization of novel habitats. The fine-scale population differentiation and genetic structuring, combined with the limited dispersal capacity of P. inexpectata, highlight the vulnerability of local gecko populations to extinction in the face of habitat fragmentation and loss. The low genetic diversity of P. inexpectata could limit its evolutionary potential and make it vulnerable to stochastic changes in its environment. Hence, efforts to conserve the genetic diversity should be strengthened, notably in natural sites harboring an original and remarkable genetic diversity.

DNA barcoding of non-avian reptiles based on the cytochrome oxidase subunit I (COI) gene is still in a very early stage, mainly due to technical problems. Using a newly developed set of reptile-specific primers for COI we present the first comprehensive study targeting the entire reptile fauna of the fourth-largest island in the world, the biodiversity hotspot of Madagascar. Representatives of the majority of Madagascan non-avian reptile species (including Squamata and Testudines) were sampled and successfully DNA barcoded. The new primer pair achieved a constantly high success rate (72.7-100%) for most squamates. More than 250 species of reptiles (out of the 393 described ones; representing around 64% of the known diversity of species) were barcoded. The average interspecific genetic distance within families ranged from a low of 13.4% in the Boidae to a high of 29.8% in the Gekkonidae. Using the average genetic divergence between sister species as a threshold, 41-48 new candidate (undescribed) species were identified. Simulations were used to evaluate the performance of DNA barcoding as a function of completeness of taxon sampling and fragment length. Compared with available multi-gene phylogenies, DNA barcoding correctly assigned most samples to species, genus and family with high confidence and the analysis of fewer taxa resulted in an increased number of well supported lineages. Shorter marker-lengths generally decreased the number of well supported nodes, but even mini-barcodes of 100 bp correctly assigned many samples to genus and family. The new protocols might help to promote DNA barcoding of reptiles and the established library of reference DNA barcodes will facilitate the molecular identification of Madagascan reptiles. Our results might be useful to easily recognize undescribed diversity (i.e. novel taxa), to resolve taxonomic problems, and to monitor the international pet trade without specialized expert knowledge.

Wild geckos are a significant source of human salmonellosis. We swabbed the cloacas of 37 non-native synanthropic geckos (Gekko gecko, n = 16; Phelsuma grandis, n = 21) from southern Florida, USA, and assayed swab DNA extracts using quantitative polymerase chain reaction of the invA gene. Salmonella enterica was detected in both species with a pooled prevalence of 13.5% (5/37; 95% CI 5.3–27.1%), indicating the potential for zoonotic transmission. Implications for human health in the region are discussed.

Nearly 90% of flowering plants depend on animals for reproduction. One of the main rewards plants offer to pollinators for visitation is nectar. Nesocodon mauritianus (Campanulaceae) produces a blood-red nectar that has been proposed to serve as a visual attractant for pollinator visitation. Here, we show that the nectar’s red color is derived from a previously undescribed alkaloid termed nesocodin. The first nectar produced is acidic and pale yellow in color, but slowly becomes alkaline before taking on its characteristic red color. Three enzymes secreted into the nectar are either necessary or sufficient for pigment production, including a carbonic anhydrase that increases nectar pH, an aryl-alcohol oxidase that produces a pigment precursor, and a ferritin-like catalase that protects the pigment from degradation by hydrogen peroxide. Our findings demonstrate how these three enzymatic activities allow for the condensation of sinapaldehyde and proline to form a pigment with a stable imine bond. We subsequently verified that synthetic nesocodin is indeed attractive to Phelsuma geckos, the most likely pollinators of Nesocodon. We also identify nesocodin in the red nectar of the distantly related and hummingbird-visited Jaltomata herrerae and provide molecular evidence for convergent evolution of this trait. This work cumulatively identifies a convergently evolved trait in two vertebrate-pollinated species, suggesting that the red pigment is selectively favored and that only a limited number of compounds are likely to underlie this type of adaptation.

Color traits in animals play crucial roles in thermoregulation, photoprotection, camouflage, and visual communication, and are amenable to objective quantification and modeling. However, the extensive variation in non-melanic pigments and structural colors in squamate reptiles has been largely disregarded. Here, we used an integrated approach to investigate the morphological basis and physical mechanisms generating variation in color traits in tropical day geckos of the genus Phelsuma. Combining histology, optics, mass spectrometry, and UV and Raman spectroscopy, we found that the extensive variation in color patterns within and among Phelsuma species is generated by complex interactions between, on the one hand, chromatophores containing yellow/red pteridine pigments and, on the other hand, iridophores producing structural color by constructive interference of light with guanine nanocrystals. More specifically, we show that 1) the hue of the vivid dorsolateral skin is modulated both by variation in geometry of structural, highly ordered narrowband reflectors, and by the presence of yellow pigments, and 2) that the reflectivity of the white belly and of dorsolateral pigmentary red marks, is increased by underlying structural disorganized broadband reflectors. Most importantly, these interactions require precise colocalization of yellow and red chromatophores with different types of iridophores, characterized by ordered and disordered nanocrystals, respectively. We validated these results through numerical simulations combining pigmentary components with a multilayer interferential optical model. Finally, we show that melanophores form dark lateral patterns but do not significantly contribute to variation in blue/green or red coloration, and that changes in the pH or redox state of pigments provide yet another source of color variation in squamates. Precisely colocalized interacting pigmentary and structural elements generate extensive variation in lizard color patterns. Our results indicate the need to identify the developmental mechanisms responsible for the control of the size, shape, and orientation of nanocrystals, and the superposition of specific chromatophore types. This study opens up new perspectives on Phelsuma lizards as models in evolutionary developmental biology.

Invasion risks may be influenced either negatively or positively by climate change, depending on the species. These can be predicted with species distribution models, but projections can be strongly affected by the source of the environmental data (climate data source, Global Circulation Models GCM and Shared Socio-economic Pathways SSP). We modelled the distribution of Phelsuma grandis and P. laticauda, two Malagasy reptiles that are spreading globally. We accounted for drivers of spread and establishment using socio-economic factors (e.g., distance from ports) and two climate data sources, i.e., Climatologies at High Resolution for the Earth’s and Land Surface Areas (CHELSA) and Worldclim. We further quantified the degree of agreement in invasion risk models that utilised CHELSA and Worldclim data for current and future conditions. Most areas identified as highly exposed to invasion risks were consistently identified (e.g. in Caribbean and Pacific Islands). However, projected risks differed locally. We also found notable differences in quantitative invasion risk (3% difference in suitability scores for P. laticauda and up to 14% for P. grandis) under current conditions. Despite both species native distributions overlapping substantially, climate change will drive opposite responses on invasion risks by 2070 (decrease for P. grandis, increase for P. laticauda). Overall, projections of future invasion risks were the most affected by climate data source, followed by SSP. Our results highlight that assessments of current and future invasion risks are sensitive to the climate data source, especially in islands. We stress the need to account for multiple climatologies when assessing invasion risks.