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New data on Dierogekko (Squamata: Gekkota: Diplodactylidae), with the description of a new species from Île Baaba, Province Nord, New Caledonia
Abstract
The diplodactylid gecko genus Dierogekko is endemic to the northern Grande Terre of New Caledonia and the adjacent ultramafic offs-hore islands. All species are allopatric except D. poumensis and D. inexpectatus, both of which occur on Sommet Poum. The validity of the latter species, described on the basis of a single female, is confirmed by a recently collected series of specimens from Paevala. Dierogekko inexpectatus appears limited to the northern portion of Sommet Poum, where it is restricted to closed forest remnants. Based on its tiny area of occurrence and existing threats from mining, wildfires, invasive weeds, and a diversity of invasive animals, it is assessed as Critically Endangered. A molecular phylogenetic analysis of Dierogekko confirms previously proposed relationships and reveals a new species level taxon from Île Baaba, off the northern tip of the Grande Terre. The specimen is known from a single female, but is distinguished from its congeners by its small size (<38 mm SVL) and narrow, divided subdigital scansors. It is separated from all other Dierogekko by an uncorrected ND2 divergence of 6-15% (Tajima-Nei distance 6-17%). It is vulnerable to wildfires, habitat degra-dation and introduced mammalian predators and fire ants and is considered to be Critically Endangered.
... The former species possessed an intermediate claw position (Fig. 1B) but had only a single row of precloacal pores. The latter species has subsequently been removed from Bavayia, and placed in Dierogekko, a genus of small, nimble geckos endemic to northern New Caledonia, which has since been recognized as a radiation of at least nine species, mostly occurring in allopatry in vegetation on ultramafic surfaces Skipwith et al. 2014). and the B. ornata Group, the last including B. ornata and B. septuiclavis (Wright 1999;Bauer et al. 2012b;Skipwith et al. 2016Skipwith et al. , 2019Bernstein et al. 2021). ...
... Etymology: The specific epithet is a patronym honoring our friend and colleague Anthony (Tony) Hume Whitaker (1944Whitaker ( -2014, indefatigable British-born Kiwi herpetologist and wildlife biologist who left us too soon. Tony and his wife Viv contributed greatly to New Caledonian herpetology, particularly that of the far north, where their tireless efforts turned up many novel lizards, including this species. ...
... For example, the Panié Massif, Koniambo, Néhoué and adjacent areas, and the northern offshore islands . And, as in Bavayia, sympatry is rare within a single clade, occurring only in the relatively distantly related D. poumensis and D. inexpectatus (Skipwith et al. 2014). However, it should be noted that patterns of microendemism are not fully congruent between genera. ...
Bavayia Roux, 1913 is the most speciose of the gecko genera endemic to New Cale- donia, with 13 recognized species. The presence of many undescribed taxa has been signaled by previous studies using mito-nuclear data sets and by a comprehensive DNA barcoding study. However, the conservative morphology of the group has hin- dered formal description of additional species. We examined more than 2000 speci- mens of Bavayia from throughout New Caledonia and its satellite islands and includ- ed ~600 specimens in a phylogenetic analysis of the mitochondrial ND2 gene. Our tree topology was consistent with previous, though less comprehensive, results from other molecular data sets and supported our recognition of 28 new species in the genus, bringing the total diversity to 41 species distributed in 12 well-supported clades. Although variation in size, precloacal pores and arrangement of apical scan- sors of the first digit are useful characters to diagnose the species of Bavayia, many taxa are supported only by subtle differences in coloration pattern, which is typical- ly characterized by alternating brownish and whitish markings.
In situ radiation and microendemism in New Caledonia is common in both geck- os and skinks, but Bavayia is exceptional, accounting for 30% of the known terres- trial herpetofauna. Although as many as five Bavayia species may occur in sympatry, these are almost always representatives of different clades within the genus. Most species and some entire clades are endemic either to ultramafic substrates (seven to the large southern ultramafic block, usually one or two to the isolated ultramafic massifs of the north) or to massifs or portions of the Chaîne Centrale on volcano-sed- imentary substrates. We consider the radiation of Bavayia, which has been dated to the Early Miocene, to represent a “non-adaptive radiation” with many of the species distributed allopatrically and lacking genetic continuity but living similar lifestyles and retaining plesiomorphic features. Of the 41 species of Bavayia 36 are in IUCN Threatened categories and, of these, 29 are Endangered or Critically Endangered. Wildfire, agriculture, mining and introduced species implicated in habitat destruc- tion, predation and competition are among the greatest current threats to Bavayia spp.
... The systematics and taxonomy of the New Caledonian lizard fauna are still dynamic, with 45 species being described or undergoing taxonomic change in the past two decades, almost doubling the endemic lizard fauna Smith et al. 2007;Skipwith et al. 2014;Sadlier et al. 2009Sadlier et al. , 2014aSadlier et al. , 2014bSadlier et al. , 2014cSadlier et al. , 2015. The molecular phylogenies generated by these studies have been based primarily on the mitochondrial gene NADH dehydrogenase subunit 2 (ND2). ...
... Our sampling consists of 601 lizard specimens from New Caledonia, representing 100 of the 107 currently described species, 95 of which are native. Tissue samples from widespread and systematic collection efforts over 35 years used extensively in a diversity of published studies (see Bauer et al. , 2009Bauer et al. , 2012Sadlier et al. 2009Sadlier et al. , 2014aSadlier et al. , 2014bSadlier et al. , 2014cSkipwith et al. 2014 and papers cited therein) were used to obtain genomic DNA. All but seven species of the native New Caledonian lizards were barcoded in this study. ...
... To assess the phylogenetic utility of CO1 trees, maximum likelihood (ML) genealogies of the six most speciose lizard genera were reconstructed to ensure barcoded specimens formed clades that have also been recovered in published, well-supported ND2 and/or multilocus trees using the same specimens Skipwith et al. 2014;Sadlier et al. 2009Sadlier et al. , 2014aSadlier et al. , 2014bSadlier et al. , 2014c. ML methods were used (1) to obtain a point estimate of evolutionary relations, incorporating evolutionary models of nucleotide substitution and evolutionary rate heterogeneity parameters, and (2) draw comparisons to previously published analyses using different markers on the same specimens. ...
New Caledonia is the smallest global biodiversity hotspot, yet has one of the highest levels of endemism for an insular region of its size. Lizards are the dominant vertebrate fauna, and, while ecologically important, can be difficult to identify and many are in decline due to anthropogenic threats. As an aid to facilitate identification, we generated a near-complete DNA barcode dataset for New Caledonian lizards, consisting of 601 mitochondrial CO1 sequences of 100 of the 107 described lizards, and a number of yet undescribed species. We use this dataset to assess the performance of CO1 in delimiting species recognised by other, more extensive data and in recovering phylogenetic signal. Most species had intraspecific genetic distances ≤3.7%. Most comparisons between described species were at least ~5% divergent, with the exception of three pairwise species comparisons showing interspecific distances > 2.5%. Maximum likelihood CO1 trees of the six most speciose genera recovered each as monophyletic and, although discordant with previously published ND2 trees using quantitative topology tests, showed similar patterns of intraspecific and interspecific divergence, supporting the utility of CO1 in taxonomic identification and species delimitation. Some species showed overlap between intra- and interspecific pairwise distances, suggesting cryptic taxa, a finding also supported by species delimitation analyses using GMYC and mPTP. This dataset not only provides the basis for economical and reliable identification of New Caledonian lizards encountered during biodiversity assessments, but also provides a potential tool for investigating the identity of native lizards and their ecosystem interactions, even from partial remains.
... So far, the scarceness and the observed distribution of the species, restricted to the south raises issues about its presence in the other parts of New Caledonia . Additional sampling efforts should be done in other localities, well distant from the current known distribution, as for example in 'maquis minier' located at high-elevations or those located in north-western isolated mountains, on which allopatric speciation events have occurred in plants [96,97], geckos [98,99], skinks [100,101] and grasshoppers [16] . In New Caledonia clear-cut specializations between two sister lineages have been frequently highlighted for different geological substrates in insects (e.g. in caddisflies [14], or in grasshopper [16,102]), in squamata [99,100,101] or in plants (e.g. in Codia sp. ...
... Additional sampling efforts should be done in other localities, well distant from the current known distribution, as for example in 'maquis minier' located at high-elevations or those located in north-western isolated mountains, on which allopatric speciation events have occurred in plants [96,97], geckos [98,99], skinks [100,101] and grasshoppers [16] . In New Caledonia clear-cut specializations between two sister lineages have been frequently highlighted for different geological substrates in insects (e.g. in caddisflies [14], or in grasshopper [16,102]), in squamata [99,100,101] or in plants (e.g. in Codia sp. [103], or Diospyros sp. ...
Few studies have focused on the early colonization of New Caledonia by insects, after the re-emergence of the main island, 37 Myr ago. Here we investigate the mode and tempo of evolution of a new endemic cricket genus, Pixibinthus, recently discovered in southern New Caledonia. First we formally describe this new monotypic genus found exclusively in the open shrubby vegetation on metalliferous soils, named 'maquis minier', unique to New Caledonia. We then reconstruct a dated molecular phylogeny based on five mitochondrial and four nuclear loci in order to establish relationships of Pixibinthus within Eneopterinae crickets. Pixibinthus is recovered as thesister clade of the endemic genus Agnotecous, mostly rainforest-dwellers. Dating results show that the island colonization by their common ancestor occurred around 34.7 Myr, shortly after New Caledonia re-emergence. Pixibinthus and Agnotecous are then one of the oldest insect lineages documented so far for New Caledonia. This discovery highlights for the first time two clear-cut ecological specializations between sister clades, as Agnotecous is mainly found in rainforests with 19 species, whereas Pixibinthus is found in open habitats with a single documented species. The preference of Pixibinthus for open habitats and of Agnotecous for forest habitats nicely fits an acoustic specialization, either explained by differences in body size or in acoustic properties of their respective habitats. We hypothesize that landscape dynamics, linked to major past climatic events and recent change in fire regimes are possible causes for both present-day low diversity and rarity in genus Pixibinthus. The unique evolutionary history of this old New Caledonian lineage stresses the importance to increase our knowledge on the faunal biodiversity of 'maquis minier', in order to better understand the origin and past dynamics of New Caledonian biota.
... Within Dierogekko we failed to resolve the phylogenetic position of D. insularis, and we found a cryptic lineage of D. cf. koniambo that was consistently allied to the D. kaalaensis + D. thomaswhitei clade rather than with putatively conspecific D. koniambo samples ( Skipwith et al., 2014). Bavayia fell out in a polytomy with Paniegekko and a clade containing Eurydactylodes and the large bodied forms formerly placed within Rhacodactylus. ...
... B. sauvagii, B. cyclura, B. montana, B. crassicollis), identified based on external morphology were non-monophyletic as previously suggested by Bauer & Jackman (2006). Within Dierogekko, the strong support we recovered for the D. koniambo and D. inexpectatus complexes agrees with previous studies ( Bauer et al., 2006b;Skipwith et al., 2014). All of our analyses recover two lineages on Massif Koniambo attributed to D. koniambo, one restricted to the type locality (Massif Koniambo) and another from Taavo Pointe de Vavouto (D. koniambo B in Figs 1 & 2) to the north-west. ...
Aim
New Caledonia is a remnant of the land mass Tasmantis that harbours high levels of endemism. Two primary hypotheses have been proposed for the origin of such endemic lineages; the first suggests a vicariant origin arising from the sundering of eastern Gondwana in the Cretaceous. The second posits more recent dispersal and colonization. We use concatenated and coalescent time‐calibrated phylogenies to test whether New Caledonian diplodactylid geckos diversified steadily following an ancient vicariance event or experienced an early burst of diversification followed by a decline in net diversification after long‐distance dispersal.
Location
New Caledonia, Gondwana.
Methods
Phylogenetic relationships were elucidated from a multilocus DNA data set. Divergence times were inferred using relaxed clock Bayesian methods on the concatenated data set and in a multispecies coalescent framework using * beast . In order to elucidate patterns of diversification for the New Caledonian clade we tested models of diversification using laser and ddd .
Results
The divergence of the New Caledonian clade from its Australian sister clade occurred well after Gondwanan fragmentation, and the age of the crown clade is younger than the proposed drowning period of the island. Diversification analyses strongly suggest that the group experienced an early burst of diversification, which has slowed towards the present.
Main conclusions
We demonstrate that the species‐rich diplodactylid geckos endemic to New Caledonia are of recent origin and that the diversification of the clade is consistent with the expectations of a recent radiation. Diversification in this clade does not conform to a constant‐rate model, but rather experienced an initial burst followed by a decline in net diversification. This pattern is consistent with a decline in diversification as ecological niche space was filled. Our results add to the growing body of evidence that recent adaptive radiations have contributed to the remarkable endemism of New Caledonia.
A key area of interest in evolutionary biology has been understanding the role of ecological opportunity in the formation of adaptive radiations, lineages where speciation and phenotypic diversification are driven by open ecological opportunity. Evolutionary theory posits that adaptive radiations should show initial bursts of ecomorphological diversification and rapid speciation, and that these two processes are correlated. Here, we investigate and contrast these predictions across ecomorphologically diverse continental (Australia) and insular (New Caledonia and New Zealand) radiations of diplodactyloid geckos. We test two key hypotheses: (a) that island colonization and the transition to novel niche-space has resulted in increased rates of speciation and trait diversification and (b) that rates of morphological diversification are correlated across multiple trait axes. Surprisingly, we find that speciation rate is homogenous and morphological diversification rates are idiosyncratic and uncorrelated with speciation rates. Tests of morphological integration suggests that while all traits coevolve, constraint may act differentially on individual axes. This accords with a growing number of studies indicating that ecologically diverse and species-rich radiations can show limited or no evidence of exceptional regime shifts in speciation dynamics or morphological diversification, especially in continental contexts.
Australasia harbors very high squamate diversity and is a center of endemicity for a number of major lineages. However, despite this diversity, the diplodactyloid geckos of Australia, New Caledonia, and New Zealand (comprised of three endemic families and >200 species) are the only extant squamates with unequivocal Mesozoic origins in the region. Diplodactyloid geckos also exhibit notable phenotypic and ecological diversity, most strikingly illustrated by the functionally limbless pygopods. Here, we present the first phylogenomic analyses of the pattern and timing of diplodactyloid evolution, based on a dataset of more than 4000 ultraconserved elements (UCEs) from 180 species. These analyses fully resolve nearly all nodes, including a number of intergeneric relationships that have proven problematic in previous studies. The hypothesis that New Caledonia and New Zealand clades represent independent post-KT boundary colonization events of Tasmantis from Australian ancestors is confirmed. Phylogenetic relationships recovered here further highlight contrasting patterns of diversity, most strikingly between insular and/or morphologically highly derived clades that have diversified rapidly, as opposed to other species poor and phylogenetically divergent relictual lineages on mainland Australia. Our new timetree suggests slightly older branching times than previous analyses and does not find a mass extinction event in the early Cenozoic. Finally, our new phylogeny highlights caudal variation across the clade. Most strikingly, the distinctive leaf-tail morphology shown by one family may in fact be plesiomorphic.
A new species of skink in the genus Epibator is described from Île
Walpole, a small, isolated, raised vegetated limestone platform, ∼200km ESE of southern New Caledonia. The new species is distinguished from its congeners Epibator nigrofasciolatus and E. greeri primarily by its coloration and pattern (both species), differences in scalation (greeri), and substantial genetic differentiation (nigrofasciolatus). The new species is the only extant endemic terrestrial vertebrate on Walpole. The island is small (<1.7km2), and has a long history of past human occupation (over the last 2,500 years, including European-era exploitation for guano), resulting in degradation of the vegetation cover and introduction of invasive animal species, most significantly ants (Little Fire Ant, Yellow Crazy Ant) and rats (Pacific Rat). The species’ very limited distribution in combination with the threats posed by invasive species place it at a level of risk sufficient to be considered as Critically Endangered under IUCN Red List criteria.
Introduced species of mammals have now been removed from many islands around New Zealand, thus providing singular opportunities for ecological restoration. If island restoration is to be attempted, the way island biota originate and the precise effects of introduced organisms must be identified. Plants introduced to the New Zealand archipelago may have transitory effects, but others may modify forest structure and disrupt succession. Goats have been the most destructive introduced herbivore on islands. Among introduced predators, cats have extirpated colonies of seabirds, and rats (depending on species) affect invertebrates, lizards, and birds. Ecological theories and concepts that may help with island restoration projects include: the keystone species concept, in which the effects of one species on others is disproportionate relative to its abundance; the "intermediate predator" hypothesis, where removal of the top introduced predator may lead to rebound effects of intermediate predators; and ecological chain reactions, where local extinction of some species can cause complicated multiple effects. Problems with restoration of islands may be encountered because of meagre data on the previous effects of pests (such as predators), use of non-seral species in revegetation projects, proliferations of indigenous or introduced species that have unforeseen community effects, and inexplicable difficulties with some translocations. A restoration case study in the continental Mercury Islands and on Cuvier Island showed success with removal of introduced mammals and demonstrates the various effects of introduced browsers, grazers, and predators. A contrasting case study is provided by oceanic Mangere Island in the Chatham Islands where 22 species of avifauna have been lost, seven as permanent extinctions. Restoration targets for some New Zealand islands can be clarified by palaeoecological studies of Maori (Polynesian) middens and natural deposits. Understanding the role of disturbance in island systems may also help clarify restoration targets. When exotic keystone species are introduced, physical disturbance may be overridden by biotic disturbance. This replacement in turn has implications for trophic structure. With high levels of biotic disturbance, continental islands may be changed from relatively species-rich bottom-up food webs to species-poor top-down trophic cascades. These possibilities can be tested with an experimental approach to restoration, although such experiments may be hard to interpret because of difficulties with replicates and controls. Ecological restoration on New Zealand islands has potential to replace damaged or lost communities, expand the ranges of relict populations, reduce the selective influence of exotic (keystone) species on indigenous species, help in understanding how the systems are formed, provide opportunities for educational and scientific investigation, and act as a testing ground for new technologies against pests.
MrBayes is a program for the Bayesian inference of phylogeny. This manual explains Bayesian inference of phylogeny and how to use the program. The program has a command-line interface and should run on a variety of computer platforms. Note that the computer should be reasonably fast and should have a lot of memory (depending on the size of the data matrix, the program may require hundreds of megabytes of memory). The program is optimized for speed and not for minimizing memory requirements. This manual is divided into two parts. The first section gives an overview of the program with a brief tutorial to help you get started and the second section introduces Bayesian inference and presents some of the theory behind the program. Conventions used in this manual What you see on the screen and what is in the input file is in a sans serif font. What you type is in a bold font.
Over the last four decades the eradication of rats from islands around New Zealand has moved from accidental eradication following the exploratory use of baits for rat control to carefully planned complex eradications of rats and cats (Felis catus) on large islands. Introduced rodents have now been eradicated from more than 90 islands. Of these successful campaigns, those on Breaksea Island, the Mercury Islands, Kapiti Island, and Tuhua Island are used here as case studies because they represent milestones for techniques used or results achieved. Successful methods used on islands range from bait stations and silos serviced on foot to aerial spread by helicopters using satellite navigation systems. The development of these methods has benefited from adaptive management. By applying lessons learned from previous operations the size, complexity, and cost effectiveness of the campaigns has gradually increased. The islands now permanently cleared of introduced rodents are being used for restoration of island‐seabird systems and recovery of threatened species such as large flightless invertebrates, lizards, tuatara, forest birds, and some species of plants. The most ambitious campaigns have been on remote subantarctic Campbell Island (11 300 ha) and warm temperate Raoul Island (2938 ha), aimed to provide long‐term benefits for endemic plant and animal species including land and seabirds. Other islands that could benefit from rat removal are close inshore and within the natural dispersal range of rats and stoats (Mustela erminea). Priorities for future development therefore include more effective methods for detecting rodent invasions, especially ship rats (Rattus rattus) and mice (Mus musculus), broader community involvement in invasion prevention, and improved understanding of reinvasion risk management.
The constant accumulation of sequence data poses new computational and methodological challenges for phylogenetic inference, since multiple sequence alignments grow both in the horizontal (number of base pairs, phylogenomic alignments) as well as vertical (number of taxa) dimension. Put aside the ongoing controversial discussion about appropriate models, partitioning schemes, and assembly methods for phylogenomic alignments, coupled with the high computational cost to infer these, for many organismic groups, a sufficient number of taxa is often exclusively available from one or just a few genes (e.g., rbcL, matK, rDNA). In this paper we address scalability of Maximum-Likelihood-based phylogeny reconstruction with respect to the number of taxa by example of several large nested single-gene rbcL alignments comprising 400 up to 3,491 taxa. In order to test the effect of taxon sampling, we employ an appropriately adapted taxon jackknifing approach. In contrast to standard jackknifing, this taxon subsampling procedure is not conducted entirely at random, but based on drawing subsamples from empirical taxon-groups which can either be user-defined or determined by using taxonomic information from databases. Our results indicate that, despite an unfavorable number of sequences to number of base pairs ratio, i.e., many relatively short sequences, Maximum Likelihood tree searches and bootstrap analyses scale well on single-gene rbcL alignments with a dense taxon sampling up to several thousand sequences. Moreover, the newly implemented taxon subsampling procedure can be beneficial for inferring higher level relationships and interpreting bootstrap support from comprehensive analysis.
The program MODELTEST uses log likelihood scores to establish the model of DNA evolution that best fits the data.
AVAILABILITY: The MODELTEST package, including the source code and some documentation is available at http://bioag.byu. edu/zoology/crandall_lab/modeltest.html.
The computation of large phylogenetic trees with statistical models such as maximum likelihood or bayesian inference is computationally extremely intensive. It has repeatedly been demonstrated that these models are able to recover the true tree or a tree which is topologically closer to the true tree more frequently than less elaborate methods such as parsimony or neighbor joining. Due to the combinatorial and computational complexity the size of trees which can be computed on a Biologist's PC workstation within reasonable time is limited to trees containing approximately 100 taxa.
In this paper we present the latest release of our program RAxML-III for rapid maximum likelihood-based inference of large evolutionary trees which allows for computation of 1.000-taxon trees in less than 24 hours on a single PC processor. We compare RAxML-III to the currently fastest implementations for maximum likelihood and bayesian inference: PHYML and MrBayes. Whereas RAxML-III performs worse than PHYML and MrBayes on synthetic data it clearly outperforms both programs on all real data alignments used in terms of speed and final likelihood values. Availability
RAxML-III including all alignments and final trees mentioned in this paper is freely available as open source code at http://wwwbode.cs.tum/~stamatak
stamatak@cs.tum.edu.
Unlabelled:
RAxML-VI-HPC (randomized axelerated maximum likelihood for high performance computing) is a sequential and parallel program for inference of large phylogenies with maximum likelihood (ML). Low-level technical optimizations, a modification of the search algorithm, and the use of the GTR+CAT approximation as replacement for GTR+Gamma yield a program that is between 2.7 and 52 times faster than the previous version of RAxML. A large-scale performance comparison with GARLI, PHYML, IQPNNI and MrBayes on real data containing 1000 up to 6722 taxa shows that RAxML requires at least 5.6 times less main memory and yields better trees in similar times than the best competing program (GARLI) on datasets up to 2500 taxa. On datasets > or =4000 taxa it also runs 2-3 times faster than GARLI. RAxML has been parallelized with MPI to conduct parallel multiple bootstraps and inferences on distinct starting trees. The program has been used to compute ML trees on two of the largest alignments to date containing 25,057 (1463 bp) and 2182 (51,089 bp) taxa, respectively.
Availability:
icwww.epfl.ch/~stamatak
Unlabelled:
A key element to a successful Markov chain Monte Carlo (MCMC) inference is the programming and run performance of the Markov chain. However, the explicit use of quality assessments of the MCMC simulations-convergence diagnostics-in phylogenetics is still uncommon. Here, we present a simple tool that uses the output from MCMC simulations and visualizes a number of properties of primary interest in a Bayesian phylogenetic analysis, such as convergence rates of posterior split probabilities and branch lengths. Graphical exploration of the output from phylogenetic MCMC simulations gives intuitive and often crucial information on the success and reliability of the analysis. The tool presented here complements convergence diagnostics already available in other software packages primarily designed for other applications of MCMC. Importantly, the common practice of using trace-plots of a single parameter or summary statistic, such as the likelihood score of sampled trees, can be misleading for assessing the success of a phylogenetic MCMC simulation.
Availability:
The program is available as source under the GNU General Public License and as a web application at http://ceb.scs.fsu.edu/awty.
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Since the 1930s the common house gecko, Hemidactylus frenatus, a sexual species, has been inadvertently introduced to many tropical Pacific islands. Using mark-recapture censuses and visual gecko searches we found that Lepidodactylus lugubris, an asexual gecko previously common on these islands, is nearly 800% more abundant on buildings in the urban/suburban environment on islands that lack H. frenatus than it is on islands where H. frenatus is present. On buildings in Hawaii and Fiji that have been surveyed in different years, the proportion of H. frenatus relative to L. lugubris has significantly increased over time. The degree of numerical dominance is also related to climate and habitat: L. lugubris is relatively more common on the more mesic, cooler, windward sides of large islands compared to the more arid sides of islands and in general H. frenatus does not penetrate forest habitats, where L. lugubris remains one of the most common geckos. Overall, buildings with external electric lights have more geckos than unlit buildings. Where the two species occur on the same buildings H. frenatus is closer, on average, to the prime feeding sites near lights that attract insects. In the absence of H. frenatus, L. lugubris is found closer to the lights. We hypothesize that the previously demonstrated agonistic dominance of H. frenatus over L. lugubris (Bolger and Case 1992) is likely to lead to competitive superiority when insect prey are concentrated into patches that are structurally simple (like flat building walls with lights), allowing easy detection of prey and intruders.
Here we present results of an assessment of the threat that is represented by the spread of the introduced little fire ant for the lizard fauna in sclerophyll forest. The lizard fauna comprises nine endemic lizard species and one introduced, three of which are very scarce, and one is only known from the study site. As such, this ecosystem is of high conservation value for native lizards. However, a quantitative sampling of lizards, at both ground and canopy levels indicates threats from the invasive little fire ant, Wasmannia auropunctata (Roger). During a quantitative field survey 51 specimens belonging to 7 insectivorous species were captured. Between invaded and non-invaded plots, there is a sharp decrease in the overall abundance of this insectivorous guild (38 specimens versus 13). This decrease is especially marked for the two dominant species, Bavayia cyclura and Caledoniscincus austrocaledonicus (respectively from canopy and ground level). Their abundance is approximately one third of that encountered in forest without invasive ants. The means by which W. auropunctata impacts upon this vertebrate fauna remains unclear possibilities include: direct predation, monopolisation of resources (food or sheltering) or both. Nevertheless, these results represent the first quantitative assessment of an impact by W. auropunctata on higher trophic levels in a New Caledonian context. It also highlights the significant changes induced by W. auropunctata in the functional structure of native ecosystems. The spread of this exotic ant represents a major and immediate threat to the rich endemic New Caledonian herpetofauna, and more generally for the whole native fauna.
The level of inter- and intraspecific aggression between three species of gekkonid lizards was investigated with laboratory contests between pairs of individuals. Two of these species, Lepidodactylus lugubris and Hemidactylus garnotii, are asexual parthenogens. The third species, Hemidactylus frenatus, is sexual and has been implicated in an apparent competitive exclusion of the asexual species in the urban ‘house gecko niche’ on tropical Pacific islands. Hemidactylus frenatus males were more likely to approach and bite an asexual female and less likely to be spatially displaced by the approach of an asexual female than vice versa, suggesting that competitive exclusion is at least partially caused by behavioural interactions. Sexual males are more aggressive than sexual females in interspecific encounters with asexual females, so the presence of males in the sexual population increases the competitive advantage of the sexual population over that of the asexual population. Recent studies of aggression in Cnemidophorus lizards have shown reduced aggression in asexual species compared with that of closely related sexual species, and reduced aggression intra-clonally versus inter-clonally in the asexual species. As in Cnemidophorus, sexual H. frenatus females were more aggressive towards each other than were asexual H. garnotii females belonging to a single clone. However, no difference was found between intra- and inter-clonal aggression in two genetic clones of L. lugubris. The potential for interspecific predation of juveniles as an interference mechanism was also evaluated experimentally. Hemidactylus frenatus was capable of preying on L. lugubris hatchlings but the reverse was not true. This is also consistent with the observed competitive superiority of H. frenatus in the field.
A native asexual gecko, Lepidodactylus lugubris, declines numerically when the sexual gecko Hemidactylus frenatus invades urban/suburban habitats throughout the Pacific. Previous studies showed that the competitive displacement occurs rapidly and is facilitated by clumped insect resources. Five lines of evidence suggest that the mechanism of displacement is primarily due to differences in the ability of each species to exploit insect resources. (1) These species show nearly complete diet overlap. (2) Insects are a limiting resource for both geckos as evidenced by positive demographic effects with increased insect abundance. (3) Hemidactylus frenatus depletes insect resources to lower levels than L. lugubris, which results in reduced rates of resource acquisition in L. lugubris. (4) This reduced resource acquisition translates into significant reductions in the body condition, fecundity, and survivorship of L. lugubris individuals. (5) Evidence for interference (and other) mechanisms does not account for these negative demographic effects on L. lugubris. Interspecific competition is stronger than intraspecific competition for L. lugubris, with increasing L. lugubris density having negligible effect on H. frenatus, mirroring the asymmetry of the large-scale displacement. The superior harvesting ability of H. frenatus is most pronounced when insects are clumped spatially and temporally, and is attributable to a variety of species-specific traits such as their larger body size, faster running speed, and reduced intraspecific interference while foraging. We conclude that clumped resources can increase interspecific exploitation competition, and this mechanism may contribute to species turnover when human environmental alterations redistribute resources.
Established populations of the unisexual gecko, Lepidodactylus lugubris, decline around man-made lights when the bisexual gecko, Hemidactylus frenatus, invades the environment. Some of the decline in L. lugubris numbers could occur through the process of exploitative competition for food resources. Our experiments were designed to see if other variables were important in the decline. We found that L. lugubris were more likely to use a hiding platform in enclosures with 2 rather than 1 platform when conspecific or heterospecific pairs of geckos were housed in an enclosure. Additionally, when two H. frenatus were housed in the same enclosure, they maintained closer proximity to each other than when their cagemates were L. lugubris. L. lugubris developed and laid more eggs when housed with another L. lugubris than when housed with either a female or male H. frenatus. Most interestingly, L. lugubris housed in enclosures previously occupied by H. frenatus males required more time for egg development and laying than geckos housed in enclosures previously occupied by another L. lugubris. In conclusion, variables in addition to food competition may influence the declines in L. lugubris numbers when an area in which they are established is invaded by the bisexual gecko, H. frenatus. L. lugubris numbers may decline in response to their reluctance to share a hiding place with another gecko, leaving them more vulnerable to predators. Additionally, L. lugubris fecundity may be negatively affected by the exudates from H. frenatus femoral pores or the odors of their feces.
How introduced reptiles cause the loss of endemic reptiles is poorly understood and currently there are no available techniques for dealing with this major conservation issue. We addressed both these problems by investigating the role of the introduced house gecko Hemidactylus frenatus in causing the catastrophic decline and extinction of the endemic night gecko Nactus populations of the Mascarene Islands and how this introduced species can be excluded from habitats on the basis of morphology. Competition for enemy free space was tested in experimental enclosures and showed that H. frenatus displace the endemic Nactus coindemirensis and Nactus durrelli from favoured positions close to and from refugia, thus increasing the risk of predation and exposure to stochastic events. The ability of H. frenatus to grip substrates with their pad-bearing toes was examined, and we demonstrated that naturally occurring substrates with a greater amount of loose surface material of a higher particulate concentration and size excludes H. frenatus, but not Nactus. These findings support the hypothesis that H. frenatus led to the fragmentation and extinction of the endemic Nactus populations and demonstrate that artificial refugia made of a crumbly substrate may be used to limit future disturbances by this gecko and others like it in the Mascarene Islands and elsewhere.
Survey of the lizard faunas of selected sites in Province Nord Unpublished report to Service de l'Environnement, Direction du Développement économique et de l
- Whitaker A H A Whitaker V
WHITAKER A. H. & WHITAKER V. A. 2007b — Survey of the lizard faunas of
selected sites in Province Nord, New Caledonia. Unpublished report to
Service de l'Environnement, Direction du Développement économique et
de l'Environnement, Province Nord, Koné, Nouvelle-Calédonie. Whitaker
Consultants Limited, Motueka, New Zealand. iv + 24 p.
For permission to visit various massifs and island localities, and for assistance, we are grateful to Claude Paquet of Société Minière du Sud Pacifique. Logistical support and encouragement was provided by Hervé Jourdan of IRD Nouméa and Vivienne Whitaker participated in all the fieldwork
- Aaron M Bauer
Aaron M. Bauer. We particularly thank Joseph Manauté, Christian Papineau, Jean-Jérome Cassan and Van Duong Dang and
the staff at the Antenne DDEE de Koumac. For permission to visit various massifs and island localities, and for assistance,
we are grateful to Claude Paquet of Société Minière du Sud Pacifique. Logistical support and encouragement was provided
by Hervé Jourdan of IRD Nouméa and Vivienne Whitaker participated in all the fieldwork. This research was supported by
grants DEB 0108108 and DEB 0515909 from the National Science Foundation (U.S.A.) to A. M. Bauer and T. Jackman
and by the project BIONEOCAL funded by the Agence Nationale de la Recherche (France).
Biodiversity and Conservation Status of Lizards in Threatened and Restricted Habitats of North-Western New Caledonia
- H Whitaker A
- A Sadlier R
- M Bauer A
- A Whitaker V
WHITAKER A. H., SADLIER R. A., BAUER A. M. & WHITAKER V. A. 2004 -Biodiversity
and Conservation Status of Lizards in Threatened and Restricted Habitats of
North-Western New Caledonia. Report to Direction du Développement
économique et de l'Environnement, Province Nord, Koné, New Caledonia.
Whitaker Consultants Limited, Motueka, New Zealand. vi + 105 p.
Extended survey for Dierogekko inexpectatus, Province Nord
- Whitaker A H A Whitaker V
WHITAKER A. H. & WHITAKER V. A. 2008 — Extended survey for Dierogekko
inexpectatus, Province Nord, New Caledonia. Unpublished report to
Société le Nickel, Nouméa, Nouvelle-Calédonie. Whitaker Consultants
Limited, Motueka, New Zealand. ii + 24 p.
2000 -Premières observations sur les consequences de l'invasion de Wasmannia auropunctata 1863 (Roger) sur les prédateurs superieurs dans les ecosystemes néo-calédoniens
- Jourdan H A Sadlier R
- M Bauer A
JOURDAN H., SADLIER R. A. & BAUER A. M. 2000 -Premières observations sur
les consequences de l'invasion de Wasmannia auropunctata 1863 (Roger)
sur les prédateurs superieurs dans les ecosystemes néo-calédoniens.
Unpublished report to Service de l'Environnement, Direction du Développement économique et de l'Environnement
- H Whitaker A
- A Whitaker V
WHITAKER A. H. & WHITAKER V. A. 2007b -Survey of the lizard faunas of
selected sites in Province Nord, New Caledonia. Unpublished report to
Service de l'Environnement, Direction du Développement économique et
de l'Environnement, Province Nord, Koné, Nouvelle-Calédonie. Whitaker
Consultants Limited, Motueka, New Zealand. iv + 24 p.
Extended survey for Dierogekko inexpectatus, Province Nord
- H Whitaker A
- A Whitaker V
WHITAKER A. H. & WHITAKER V. A. 2008 -Extended survey for Dierogekko
inexpectatus, Province Nord, New Caledonia. Unpublished report to
Société le Nickel, Nouméa, Nouvelle-Calédonie. Whitaker Consultants
Limited, Motueka, New Zealand. ii + 24 p.