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Modelling correlates of microhabitat use of two sympatric lizards: A model selection approach
Abstract
Studies of the ecological characteristics of sympatric species are important for developing and testing ecological theory, but may be of interest also for conservation biology research when the study species are threatened, endemic and with narrow distribution. Here, we studied a particular aspect of the ecology (i.e. microhabitat use) of two sympatric lizards (Archaeolacerta bedriagae, Podarcis tiliguerta) endemic to Sardinia and Corsica (Tyrrhenian islands). We studied this issue by modelling procedures, using fi eld data collected at six study areas in both Sardinia and Corsica. We recorded 18 microhabitat variables for each lizard spot. Th e variables were entered as independent variables in logistic regression analysis with the presence/absence data for the lizards as the dependent variable, and Akaike Information Criterion was applied to select the best models describing the ecological equation of each study species. In total, we based our modelling approach on 296 individuals of A. bedriagae and 182 of P. tiliguerta . Th e general logistic regression models revealed that fi ve distinct variables were signifi cantly correlated to the presence/absence of A. bedriagae, and six to that of P. tiliguerta . We found that three variables were important for only P. tiliguerta , two for only A. bedriagae , and three for both species and with an identical sign. We also found some similarities in microhabitat choice between species. Indeed, some variables were always present in the best models of both A. bedriagae and P. tiliguerta . In general, A. bedriagae was more related to spots with large stones and low vegetation than P. tiliguerta , which, on the contrary, choose spots relatively closer to vegetation. Th e vari-ous reasons explaining the observed similarities and diff erences between species were examined. It is sug-gested that our modelling procedure may be widely used for studies of lizard community ecology, because it easy to use and allows a more-in-depth analysis than normal 'count approaches'. © Koninklijke Brill NV, Leiden, 2009.
... On the contrary, many other techniques are based on a completely different approach, which applies specific algorithms for deriving species environmental needs from point data (e.g. Nix 1986;Carpenter et al. 1993;Manel et al. 1999;Guisan & Zimmerman 2000;Hirzel et al. 2002;Brotons et al. 2004;Segurado & Araújo 2004;Elith et al. 2006;Bombi et al. 2009aBombi et al. , 2009cBombi et al. , 2009d. ...
... In particular, for local initiatives, a deep knowledge of demographic and microhabitat parameters is required, which can produce extremely detailed predictions (e.g. Gracceva et al. 2008;Bombi et al. 2009c). ...
A rapid improvement of Geographic Information Systems (GIS) and geostatistic procedures has occurred in recent decades. Such technology has become an essential instrument for conservation biology. Several methods have been developed for modelling the potential distribution of species by defining the species–environment interactions. This paper proposes a new approach for identifying biodiversity hotspots in Italy. Data (2894) relative to the distribution of 20 species in Sicily derived from the CKmap databank were used. The algorithm MAXENT was applied for predicting the potential distribution of these species within Sicily utilizing climate, land cover, and human impact variables as environmental predictors. The specific distributions were overlapped and spatially summed, through a GIS-assisted overlay technique, for predicting the number of herptiles species across the area of interest with a spatial resolution of 30” of geographic degree. The models produced obtained highly variable validation scores, from relatively low values (Podarcis sicula: AUC = 0.647) up to very good results (Zamenis situlus: AUC = 0.862) according to ecological requirements of the species and faunistic data availability. The northwestern and southeastern coastal and sub-coastal areas were identified as the most species-rich zones of Sicily, and their importance as the priority targets of conservation initiatives was discussed.
... At the light of these considerations we applied habitat suitability modelling techniques to the Bedriaga's rock lizard (Archaeolacerta bedriagae [Camerano, 1885]), a lacertid species endemic to Corsica and Sardinia, in order to fill the gap of knowledge about its distribution and to provide new instruments for its conservation. This species is a rock dwelling lizard widespread from the sea level up to the highest peaks of both islands (Schneider, 1984;Castilla et al., 1989;Bauwens et al., 1990;Vanhooydonck, Van Damme and Aerts, 2000;Bombi and Vignoli, 2004;Bombi et al., 2009). The conservation status of A. bedriagae is poorly known, as well as its biology. ...
... The fieldwork was carried out between June 2000 and April 2005 throughout Sardinia, including satellite islands, with the aim of confirming the species presence in cited locations, defining the exact coordinates of those localities, and identifying new sites. The presence of A. bedriagae was checked in all of the cited localities as well as in other rocky areas that appeared to be a-priori suitable for the particular autoecological requirements of the species (Bombi et al., 2009). Exact coordinates of presence sites were obtained by a GPS (Garmin, GPSmap 76S). ...
Many techniques for predicting species potential distribution were recently developed. Despite the international interest for these procedures, applications of predictive approaches to the study of Italian fauna distribution are exceptionally rare. This paper aimed at: (a) detecting climatic exigencies of A. bedriagae in Sardinia; (b) predicting the Archaeolacerta bedriagae Sardinian potential distribution; (c) identifying the most vulnerable Italian populations of the species. Literature and field data were utilized as presence records. Six modelling procedures (BIOCLIM, DOMAIN, ENFA, GAM, GLM, and MAXENT) were adopted. The species climatic requirements were defined using the WorldClim databank for deriving the environmental predictors. AUC and Kappa values were calculated for models validation. AUC values were compared by using Anova Monte Carlo. The best four models were combined through the weighted average consensus method for producing a univocal output. GAM and MAXENT had the best performances seasonality, which causes the evidenced range fragmentation. Moreover, the general importance of multi-methods approaches and consensus techniques in predicting species distribution was highlighted.
... Consequently, this lizard represents a vertebrate model species for assessing the geographical structuring of species diversity on Corsica and Sardinia. Moreover, this species shows a fragmented distribution, particularly in Sardinia (Delaugerre & Cheylan, 1992; Bombi & Vignoli, 2004; Bombi et al., 2009b), most likely as a consequence of a high degree of ecological specialization to bare rocky habitats (Bombi et al., 2009a). As shown for P. tiliguerta, the patchy occurrence of suitable habitats on both islands, together with the complexity of Corso–Sardinian islands environments, may facilitate the action of stochastic processes (geographic isolation , genetic drift) and adaptive phenomena promoted by local selective forces. ...
... The distribution pattern of A. bedriagae is highly fragmented, especially on Sardinia (Delaugerre & Cheylan, 1992; Bombi & Vignoli, 2004) where four sub-ranges have been identified to date (Fig. 1). These sub-ranges are characterized by peculiar bioclimatic conditions (Bombi et al., 2009b) and occurrence of suitable rocky habitats (Bombi et al., 2009a). Genetic data would suggest a recent or very recent geographic fragmentation of populations. ...
The peculiar bioclimatic and geographic features of Corso–Sardinian islands may provide an ideal scenario for investigating microevolutionary processes, given their large heterogeneity of environments, which could affect dispersal and gene flow among populations, as well as processes of local adaptation. The genetic variation and differentiation among populations of the endemic lizard Archaeolacerta bedriagae were studied by allozyme electrophoresis at 20 presumptive loci. The genetic structure of this species is characterized by relatively high levels of polymorphism and low differentiation among populations. The pattern of genetic differentiation cannot be explained by genetic drift as a function of geographic distance. Genetic distance data show that genetic variation is distributed into three geographically coherent population groups and suggest a recent (Late Pleistocene) origin for the observed geographic fragmentation. The analysis of environmental correlates of allozymic variation indicates a strong correlation of the Idh-1 locus with climatic variables. The frequency of the Idh-1 106 allele is negatively correlated with annual temperature, and positively correlated with annual precipitation. In addition, the observed heterozygosity at this locus decreases towards more arid climatic regimes. The results obtained support the assumption of differential selection acting on Idh-1 allozymes under diverse climates. An association between Idh-1 allozymes and local bioclimatic regimes was also observed for the sympatric lizard Podarcis tiliguerta, suggesting a key role for such selective agents on Idh-1 polymorphism in these two Corso–Sardinian lacertids.
... However , these subspecies are not supported by genetic (Salvi et al., 2009a,b) or morphological data (Salvi et al., 2008). Archaeolacerta bedriagae is a strictly rock-dwelling lizard (Bombi et al., 2009a) and shows several morphological features associated with living on rocky surfaces and the use of narrow crevices as refuges, including flattened head and body, reduced cranial ossification in adults, unkeeled dorsal body scales, and laterally compressed and often kinked toes in the vertical plane (see e.g. Arnold, 1973; Arnold et al., 2007). ...
... The peculiar biology of A. bedriagae could have played a role in the development of the strong phylogeographic structure resulting from allopatric fragmentation . In fact, as a consequence of its rupiculous habits and its bioclimatic requirements (Bombi et al., 2009aBombi et al., , 2009b ), populations tend to be sparsely distributed, with small local effective population sizes, leading to strong genetic-drift effects (Patton and Feder, 1981). The evolutionary scenario underlying the within Lineage B pattern of mtDNA variation is consistent with allozyme data reported in Salvi et al. (2009b). ...
Archaeolacerta bedriagae is a rock-dwelling lizard endemic to the Corso-Sardinian insular system. We investigated the phylogeography of the species by using the mitochondrial ND4 and flanking tRNAs genes from 94 specimens belonging to 19 populations. Phylogenetic, Barrier, and SAMOVA analyses revealed a highly structured pattern characterized by two levels of discontinuities in the geographical distribution of mtDNA diversity: (i) a deep phylogeographic break in Northern Corsica between Lineage A, restricted to northernmost Corsica, and Lineage B widespread all over the remaining range of the species, and (ii) some minor phylogeographic discontinuities within lineage B, which is sub-structured into six closely related haplotype clades with remarkable concordance with geography. The first evolutionary event concerning the split between the two main lineages from an ancestral population occurred in the Upper Pliocene (5.87-3.68 mya), while the divergence within lineage B would have started from the Upper Pleistocene (2.5-1.6 mya), between Corsican and Sardinian populations. Somewhat later (1.7-1.1 mya), the Sardinian ancestral population underwent fragmentation into population groups inhabiting North, Central, and South Sardinia. As inferred from previous allozyme surveys, the divergence among population groups would be driven by allopatric fragmentation, while the discrepancy concerning the major partition into two lineages inferred from mtDNA but not apparent in analysis of allozymes needs further investigation.
... GIS-based distribution modeling provides a powerful tool for predicting species distributions, habitat suitability, and conservation management of ecosystems due to its simplicity and flexibility (Elith et al., 2006;Zhang et al., 2020). It can be used to identify areas of high conservation value for endangered species, guide the search for poorly known species, model the distributions of the species in protected areas, and predict the invasion risks of alien species (Bombi et al., 2009;Lyet et al., 2013;Vences et al., 2017). This is critical for monitoring the populations of threatened and endangered species in their local habitat, selecting conservation priority sites, and developing advanced management policies. ...
Anguis colchica orientalis is an endemic subspecies of the eastern slow worm that lives along the southern coast of the Caspian Sea. This reptile usually inhabits forests in the Talysh and Alborz mountains, Lenkoran and South-Caspian lowlands from –27 to 1890 m above the sea level (a. s. l.). The majority of localities (82%) are scattered across the coastal lowlands and low mountains. In order to study the distribution and estimate ecological preferences of the species, we applied maximum entropy modeling using 108 localities from Azerbaijan and Iran. The range of the subspecies covers mainly coastal lowlands, eastern slopes of the Talysh and northern slopes of the Alborz ridges. Of the parameters included in the model, slope, barren land and precipitation of driest month were the variables with the highest percentage contributions (29, 16, and 10%, respectively). The slow worm does not avoid human-transformed biotopes and is common in some localities. The main threat to Hyrcanian populations of the slow worm is degradation of suitable habitats, primarily a total deforestation.
... There may possibly also be some fine-scale differentiation of habitat selection between the two species involving competition and/or some other distinct community context, which would merit closer investigation. At this scale, very local variables related to microclimate, plant cover, productivity and refuge should be also included to fully understand the underlying variables responsible of segregation, which could be also linked to morphological variables of the species (Bombi et al. 2009, Gomes et al. 2016). The small morphological differences between the two species (Fitze et al. 2011, San-José et al. 2012) may be significant in this regard: in particular, P. hispanicus is somewhat larger and heavier with a broader head whereas P. edwarsianus is slender and proportionately longer-tailed. ...
The Edwards’s sand racer (Psammodromus edwarsianus) was recognised as distinct from the Spanish sand racer (P. hispanicus) a decade ago, but both their distributions and interspecific range limits are poorly defined. Results of sampling both species along 70km of the Conquense Drove Road (Central Spain) indicate a clear North/South segregation, with P. edwarsianus inhabiting the area North of Las Pedroñeras and P. hispanicus the South. The segregation corresponds with lithological and vegetation differences, hard calcareous substrates in the North and softer sandy sedimentary material in the South. The latter is associated with more intensive agricultural land-use in contrast to the persistence of copses and scrub on the calcareous terrain. The results provide new data on the regional distribution of both species. They also highlight the potential value of this species-pair as a model for study of interactions and habitat segregation in lacertids.
... This process has shaped the habitat into the current structure where geckos now occur. Other studies showed that different species may favour forests with different compositions (Bombi et al. 2009;Lisičić et al. 2012;Loos et al. 2012). Our results suggest that C. saiyok prefers disturbed forests with higher tree density but low canopy cover. ...
Deforestation is a major threat to biodiversity worldwide, especially in Southeast Asia. In western Thailand, reptiles are an important part of tropical rainforest ecosystems and karst forests. However, basic ecological studies of many species are largely lacking. Therefore, we studied two sympatric gecko species, Cyrtodactylus saiyok and C. tigroides, that inhabit karst forests and are restricted to western Thailand. We investigated the habitat variables that affect their abundance and body condition in Kanchanaburi Province in western Thailand. We found that the abundance of C. saiyok increased with increasing plant density and decreasing canopy cover. For both study species, body condition was positively correlated with canopy cover. The two species differed in their microhabitat use, and C. tigroides prefers more karst outcrops and stays higher above the ground. Our findings highlight the importance of an intact forest structure for the survival of geckos and thus reiterates that it is crucial to conserve karst forests in Southeast Asia.
... The study of the ecology of the Italian reptile species is particularly advanced for some groups, especially for tortoises (e.g., Chelazzi and Carlà, 1986;Rugiero and Luiselli, 2006), pond turtles (e.g., Rovero and Chelazzi, 1996;Lebboroni and Chelazzi, 1998;Zuffi et al., 2004Zuffi et al., , 2007, as well as for snakes (e.g., Luiselli et al., 1996;Zuffi, 2008;Zuffi et al. 2009;Scali et al., 2011) and lizards (e.g., Perez-Mellado and Corti, 1993;Sacchi et al., 2007;Salvidio and Oneto, 2008;Bombi et al., 2009;Zuffi et al., 2011Zuffi et al., , 2012. ...
Ecological aspects of syntopic geckoes were rarely addressed in the Mediterranean basin. We reported basic information on habitat use, and activity patterns of three species found in syntopy in Cala Violina site (divided in three subareas), a highly touristic beach located in southern Tuscany, central Italy, during 2009-2010. The most abundant species at first capture is Hemidactylus turcicus (94 individuals), while Tarentola mauritanica and Euleptes europaea are less represented (28 animals in both cases). Total captures and recaptures were 175. Sex ratio did not differ from 1:1 in all the species, nor sexes of adults did differ in size. Ambient temperatures did not differ in T. mauritanica and E. europaea, while were different in H. turcicus. Despite the humidity of capture sites did not vary among species, we recorded the highest number of E. europaea at 95% and H. turcicus at 62% humidity. Wind influenced negatively T. mauritanica and H. turcicus presence, not on E. europaea. Higher observation rate took place between 21:00 and 22:00. After 23:00, only Euleptes was active. Height from the ground was different only in H. turcicus. General Linear Models showed that interaction substrate-height at capture was important for Euleptes, not for the other two species. Along the area, E. europaea was more concentrated in the northern patch, while T. mauritanica and H. turcicus distributed more homogeneously. We suggest limitation of human presence for conservation purposes.
... Tyrrhenian wall lizards inhabit semi-open rocky and shrubby areas as well as human constructions (e.g. stone walls) interspersed with vegetation (Vanhooydonck et al. 2000;Bombi et al. 2009). Like most Podarcis lizards, they have a cryptic dorsal coloration and a conspicuous polymorphic ventral coloration with three alternative colour morphs (i.e. ...
Colour signals are ubiquitous in nature but only recently have researchers recognised the potential of ultraviolet (UV)-reflecting colour patches to function as signals of quality. Lacertid lizards often display UV-blue patches on their flanks and black spots over their entire body, both of which are under sexual selection. They also have a cryptic dorsum and some species have a conspicuous, polymorphic ventral coloration. In this study, we use the Tyrrhenian wall lizard Podarcis tiliguerta to investigate the information content of the lateral UV-blue patches and black melanin spots of males by assessing the relationship between colour features and individual quality traits. In addition, we use a visual modelling procedure to examine whether the coloration of the different body parts and different colour morphs can be distinguished by a wall lizard visual system. We found that larger males had more numerous and larger UV-blue patches, with a higher UV chroma, UV-shifted hue, but a lower spectral intensity than smaller males. The extent of black on the throat, dorsum, and flanks also correlated with male body size and size-corrected head length but not with colour features of the UV-blue patches. These results suggest that the UV-blue and melanic colour patches may provide different, non-redundant information about male resource holding potential, and thus act as condition-dependent indicators of male quality. Finally, we found that the different body parts can be chromatically distinguished from each other, and that the UV-blue patches are the most conspicuous while the dorsum is the least conspicuous.
Significance statement
Many animals use their coloration to convey information about their quality as rivals or mates. Yet, until recently researchers have not recognised the potential of ultraviolet colour patches to function as signals of quality. In this study, we first show that male Tyrrhenian wall lizards display ultraviolet-blue and black colour patches that correlate positively with some aspect of their quality such as body or head size. Furthermore, our visual modelling procedure suggests that these lizards are able to distinguish the colours of their body parts from each other, with dorsal colours being the least conspicuous and ultraviolet-blue coloration being the most conspicuous.
... The directions of these lines were determined at random. The point where the lizard was observed initially served as the centre of a circle with a radius of 50 cm, the other three points were each the centre of a 100-cm radius circle (for a schematic representation, see also Bombi et al. 2009). At the place of the first observation of a given lizard, the following habitat variables were recorded: (1) perching rock height, (2) perching rock breadth (the longest side), (3) number of touching neighbouring rocks, (4) distance to the nearest refuge (i.e., a crack large enough to permit a lizard to enter), and (5) distance to the nearest vegetation. ...
Dinarolacerta mosorensis and D. montenegrina are allopatric and closely related rock lizards endemic to the Dinaric Mountains of the Balkan Peninsula. We analysed their habitat characteristics and relative abundances in the mountains of Montenegro. We found significant differences in structural features of the microhabitat used both between populations of D. mosorensis and the two species. Dinarolacerta mosorensis was associated with relatively more shaded and damper spots on rocks closer to vegetation and leaf litter, while D. montenegrina was found in more open, rocky situations. There were significant differences in relative abundance between the sampling sites. Generally, the studied lizards were more abundant at sites with greater percentage of leaf litter and lower percentages of bare ground and small rocks, despite the lower frequency of available refuges in these places. Our results provide basic information that could assist in the adoption of adequate management practices for protection or restoration of habitat attributes relevant to these vulnerable (D. mosorensis) and endemic species. © 2017 Deutsche Gesellschaft für Herpetologie und Terrarienkunde e.V. (DGHT), Mannheim, Germany.
... In regard to this, the Tyrrhenian wall lizard Podarcis tiliguerta offers an intriguing case study as previous genetic assessments uncovered extraordinarily high level of diversity with contrasting patterns between different genetic markers [21,24]. This species is common and locally abundant across a variety of shrubby and open habitats [35] from the sea level (including tiny islets) up to 1800 m asl in the mountain regions [36]. Based on the current continuous distribution of P. tiliguerta within both Corsica and Sardinia [37,38] and associated with the fact that these two islands were largely and persistently connected into a single landmass during the Pleistocene glaciations [18,39], we may have expected low genetic differentiation between populations with most of the genetic diversity shared within and between the main islands. ...
Background
Mediterranean islands host a disproportionately high level of biodiversity and endemisms. Growing phylogeographic evidence on island endemics has unveiled unexpectedly complex patterns of intra-island diversification, which originated at diverse spatial and temporal scales. We investigated multilocus genetic variation of the Corsican-Sardinian endemic lizard Podarcis tiliguerta with the aim of shedding more light on the evolutionary processes underlying the origin of Mediterranean island biodiversity.
Results
We analysed DNA sequences of mitochondrial (12S and nd4) and nuclear (acm4 and mc1r) gene fragments in 174 individuals of P. tiliguerta from 81 localities across the full range of the species in a geographic and genealogical framework. We found surprisingly high genetic diversity both at mitochondrial and nuclear loci. Seventeen reciprocally monophyletic allopatric mitochondrial haplogroups were sharply divided into four main mitochondrial lineages (two in Corsica and two in Sardinia) of Miocene origin. In contrast, shallow divergence and shared diversity within and between islands was observed at the nuclear loci. We evaluated alternative biogeographic and evolutionary scenarios to explain such profound discordance in spatial and phylogenetic patterning between mitochondrial and nuclear genomes. While neutral models provided unparsimonious explanations for the observed pattern, the hypothesis of environmental selection driving mitochondrial divergence in the presence of nuclear gene flow is favoured.
Conclusions
Our study on the genetic variation of P. tiliguerta reveals surprising levels of diversity underlining a complex phylogeographic pattern with a striking example of mito-nuclear discordance. These findings have profound implications, not only for the taxonomy and conservation of P. tiliguerta. Growing evidence on deep mitochondrial breaks in absence of geographic barriers and of climatic factors associated to genetic variation of Corsican-Sardinian endemics warrants additional investigation on the potential role of environmental selection driving the evolution of diversity hotspots within Mediterranean islands.
... Finally, models and predictors were selected using the Akaike Information Criterion (AIC; Akaike, 1973;Burnham and Anderson, 2002) often used in microhabitat selection modeling (e.g. Bombi et al., 2009). ...
Among vertebrates the concept of ‘‘habitat tree” in temperate forests, involving tree size and microhabitat
occurrence, has been investigated mainly for birds and mammals. However, trees are also used by
many amphibian species or sometimes by whole amphibian families that have evolved adaptations for
living on trees. While there is a self-evident link between arboreal amphibians, which occur mainly in
tropical forests, and trees, the relationship between trees and forest ground-dwelling amphibians is less
widely studied and more difficult to understand. As a consequence, the effect of forestry practices on
amphibian communities are commonly considered at the landscape scale, identifying habitat alteration
and loss as major threats. We provide the first evidence that the combination of forestry practices and
species conservation strategies may act at a smaller scale than those traditionally adopted: the singletree
scale. Our study focused on the Italian endemic spectacled salamander (Salamandrina perspicillata).
In a hectare forest stand in central Italy we marked nearly 400 trees individually and for each we measured
the DBH, the number of buttresses in the stump (BUT) and the number of cavities between soil and
stump (HOL). Salamanders were sampled and individually marked at each tree in eleven sampling occasions,
during 2013 and 2014. We discovered that the concept of ‘‘habitat tree” may also hold for salamanders,
and that DBH and HOL are the best predictors of tree suitability for salamanders. Moreover, using
the number of captures for the same individuals on the same tree, occurring in different years, we were
able to distinguish between trees that act as permanent or temporary shelters for salamanders.
Permanent shelters were not only used by the same individuals in different years, but also hosted a larger
number of salamanders, and were characterized by a larger number of HOL. Our findings may be considered
of importance for drawing up forest management plans and achieving conservation objectives.
During forest harvest operations, for the purpose of salamander conservation we suggest retaining trees
with a larger DBH (>30 cm) and a high number of HOL. Finally, since BUT is highly correlated with HOL
but is less sensitive to variations during time, we suggest this parameter be used as a proxy of HOL.
... Finally, models and predictors were selected using the Akaike Information Criterion (AIC; Akaike, 1973;Burnham and Anderson, 2002) often used in microhabitat selection modeling (e.g. Bombi et al., 2009). ...
... For each surveyed point, we recorded the following variables: presence of bushes, leaf cover, type of soil, slope, distance to the stream, and number, age (juvenile or adult), and sex of individuals found at each location. We used the First Sight Point methodology to characterize the microhabitats (clay, bushes, slope, leaf, aspect, and distance from stream) where we first observed an individual, regardless of the animal remaining at or leaving the site (see Bombi et al. 2009 for more details). We located a total of 20 scorpions during our surveys. ...
We present a first analysis of the ecology and potential distribution of Euscorpius carpathicus (Linnaeus, 1767), a scorpion species endemic to southern Romania, and report on the overwintering habitat selection of this species. Using field data, literature review, species distribution modelling, and habitat selection models, we document the broad scale distribution and ecology of E. carpathicus, as well as habitat selection in the foothills of the Curvature Carpathians, including exclusive microhabitat selection of riverine clay banks. In contrast with other species of the genus that inhabit cracks in cliffs or walls, E. carpathicus has adapted to cracks in clay.
... Finally, models and predictors were selected using the Akaike Information Criterion (AIC; Akaike, 1973;Burnham and Anderson, 2002) often used in microhabitat selection modeling (e.g. Bombi et al., 2009). ...
Forest management can affect small terrestrial vertebrates. As an example, crushing during harvesting operations can be responsible for more than half of the deaths in a given population. Understanding the movement of animals is critical to many aspects of management and conservation. For amphibians with a biphasic life cycle, movements around breeding sites are pivotal for populations reproduction and survival. In this respect, the simplistic assumption that protecting aquatic breeding sites is sufficient for amphibians conservation is now widely surpassed and terrestrial habitats surrounding breeding pools are also considered as priority areas for conservation purposes. However, informed opinions on how large these buffer areas have to be have not reached a consensus, varying from a minimal buffer of about 15 m around pools to a larger buffer up to about 120 m. As a part of the LIFE ManFor C.BD project, annual terrestrial distribution pattern in Salamandrina perspicillata, a semi terrestrial salamander endemic to Italy, was studied. Distribution around the breeding stream during the reproductive time (spring) and after the post breeding migration toward terrestrial shelters (autumn) was investigated. The study was performed on a slope dominated by beech in the Montedimezzo - Pennataro test area. Seven 300-m-long parallel transects, spaced 30 m orthogonal with the breeding stream were identified. We counted salamanders 6 times both in spring and autumn in five 100 m2 plots, spatially distributed every 50 meters along the transect. A total of 161 and 290 salamanders were found in spring and autumn, respectively. Overall mean density of salamander/plot did not vary significantly between the two seasons. However the salamanders distribution in the studied area greatly differed between the two seasons. Results showed that in autumn salamanders are distributed over a large portion of the forest (at least up to 300 m from the stream) while in spring they occurred at higher density in the first hundreds of meters from the breeding sites. Consequently for Salamandrina, but also for other salamanders which have similar bimodal activity seasonal movement patterns, buffer zones should wider in autumn than in spring. For the conservation of Salamandrina the zones in which forest management choices and harvesting operations has to be carefully considered and planned range from a minimum of 100 m in spring up to a maximum of 300 meters from the stream in autumn
... It would be desirable to investigate how P. siculus performs in natural versus anthropogenic habitats (Amo et al., 2006), which physiological responses can be recorded (Davis et al., 2008;French et al., 2008) and how it adapts its morphology to habitat characteristics and environmental change (Herrel et al., 2008). At present we ignore the degree and frequency of adaptive plasticity in P. siculus, and multiple comparisons and experimental analyses are needed (see Bombi et al., 2009). This paper examines the extent of morphological (and likely functional) variation of P. siculus in central Italy. ...
The Italian wall lizard, Podarcis siculus, has a wide distribution. However, information on several aspects of its ecology and biology are scarce, and relate mainly to insular populations. This paper describes the main morphological features of 123 individuals along a geographical gradient (five localities) in northwestern Tuscany (central Italy). Our results show a strong sexual dimorphism in most of the considered parameters, high geographic variation, low interaction between sex and locality and a similar distribution of external parasite load and tail autotomy between the sexes.
... This lizard is endemic to two large Mediterranean islands , Sardinia and Corsica, and their satellite islands and islets: La Maddalena Archipelago and Isola Rossa (Sardinia), and Folaca islet (Corsica). Archaeolacerta bedriagae is a strictly rock-dwelling lizard confined to large rocky outcrops (Bombi and Vignoli, 2004; Bombi et al., 2009); it occurs from the sea level up to the highest mountain peaks (1800 m a.s.l. in Gennargentu Massif, Sardinia, and 2710 m a.s.l. in Mount Cinto, Corsica). Based on weak morphological traits four subspecies have been de- 1 -Department of Environmental Biology, University " Roma Tre " , Viale G. Marconi 446, 00146 Rome, Italy 2 -Museo Civico di Zoologia, Viale U. Aldrovandi 18-I, 00197 Rome, Italy * Corresponding author; e-mail: salvi@uniroma3.it ...
Archaeolacerta bedriagae is a rock lizard endemic to Corsica and Sardinia. Four subspecies have been recozied to date on the basis of morphological traits. Previous allozyme investigations revealed high genetic differentiation among populations of the species. Based on these results some authors hypothesized that more than one species of Archaeolacerta may occur on Corsica and Sardinia. In this paper we investigated allozyme variation at 19 gene loci in 5 populations belonging to all subspecies of A. bedriagae in order to study genetic differentiation among populations from Corsica and Sardinia, and to compare our results with those obtained in previous studies carried out on allozyme variation and taxonomy of the species. Low levels of genetic differentiation (average Nei's D = 0.026) and heterogeneity (mean F ST = 0.147) were found comparing the A. bedriagae populations, and there was no evidence of interruption or restriction of gene flow. This is in agreement with the available molecular and morphometric data, while it is not in accordance with allozyme data reported in the previous studies. Our data do not support the hypothesis of an unrecognized criptic species of Archaeolacerta in Corsica and Sardinia, and indicate that the definitive assessment of the taxonomic status of the A. bedriagae populations requires further investigation.
... Our gap analysis evidences a set of species that are underrepresented in protected areas. Three of these species (Archaeolacerta bedriagae, Euleptes europaea and Tarentola mauritanica) often co-occur in rocky sites of eastern Sardinia (Bombi et al., 2009a; 2009b; Salvi & Bombi, 2010). Thus, future conservation strategies could be facilitated as they should focus on co-occurrence sites. ...
For planning practical measures aimed at biodiversity protection, conservation priorities must be identified at a local scale. Unfortunately, identifying local conservation priorities requires high-resolution data on species distribution, and these are often unavailable. Atlases of species distribution provide data for several groups of organisms in many different areas but are often too coarse in resolution to provide valuable information. We explored the possibility of cross-scale modelling species distributions and we clarified, for the first time, its effect on prioritization exercises. We used different modelling techniques for scaling down atlas data for Sardinian reptiles, validated the outcomes with detailed, field-sampled data, and compared conservation priorities deriving from atlas maps and downscaled models. Doing this, we obtained as a further result the identification of priority species and areas for future conservation strategies. Our results encourage us to experiment further with this approach. Through the downscaling procedure, we obtain high-resolution models with strong variations in predictive performances, although most of the models show satisfactory/excellent scores. This testifies that low-resolution data can be downscaled maintaining low rates of omission and commission errors. Increasing the resolution of distribution maps used for prioritization influences the spatial patterns of priority but does not modify the evaluation of species representation. Overall, we show that atlases can meet the large demand for distribution data by decision makers if appropriate downscaling procedures are adopted. In addition, we provide practical instruments for the conservation of reptiles in Sardinia by identifying priority species and areas that require strict management.
... In addition, the relation of species richness and size of populations with the oases' surface should be clarified. Environmental exigencies of the focal species should be analyzed at the local scale for optimizing measures aimed at increasing habitat suitability in single sites (e.g., Bombi et al. 2009 ). In addition, a deep understanding of all the threatening factors at local, regional, and global levels (e.g., Bovero et al. 2008; D'Amen et al. 2010b) must be obtained for planning the most efficient initiatives to maximize the probabilities of long-term survival. ...
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... Currently, our data on the ecology of the two Seychelles species of Pelusios are too scanty to allow understanding of the deeper aspects of the coexistence ecology of these turtles. More detailed predictions should be based on more detailed environmental data and a deeper knowledge of the population sizes of turtles and on their microhabitat exigencies at the local scale (Bombi et al. 2009). Thus, in situ specific reasearch devoted to highlight such obscure aspects of the field biology of the two Pelusios species are strongly advocated in order to refine the modeling analysis presented here. ...
We report a modeling study on habitat suitability and predicted distribution shifts of two species of Seychelles's freshwater turtles (Pelusios castanoides and Pelusios subniger) under a climate change scenario. We utilized data from the entire species distribution for modeling habitat suitability of the two species under current and future climate conditions, by using the MAXENT algorithm. At the continental scale, it appeared that P castanoides will shift its range towards more coastal areas, whereas P. subniger will move towards more southern sites. In the Seychelles archipelago scale, habitat suitability for P. castanoides will decrease significantly, mainly in the interior areas of Mahé Island. On the contrary, the climatic conditions are predicted to remain suitable for P. subniger, which will enjoy a significantly increased habitat suitability in Seychelles.
Thermoregulation is essential for ectotherms but its relative cost, especially under ongoing climate change, depends on the thermal quality of habitats. Populations at the warm margin of a thermal niche could be negatively affected by environmental temperatures that approach the limits of a species' thermoregulation capacity. This study aims to define the thermal niche of the Bedriaga's rock lizard, Archaeolacerta bedriagae, a rock-dwelling species endemic to the Corsica and Sardinia islands (western Mediterranean Sea), and to investigate its thermoregulation effectiveness at the warm edge of its niche. We collected data on climate, body temperature, and microhabitat temperature throughout the species' range to characterize its thermal niche. We found that A. bedriagae does not occupy the entire climatic space available across its distribution range; rather, it selects temperate climates. Remarkably, thermoregulation effort increases when the habitat thermal quality decreases towards warmer sites. Populations at the warm edge of the thermal niche show the best thermoregulation effectiveness, but they are also more sensitive to the effects of climate change as they may already be at (or beyond) the species' maximum thermal capacity under the current conditions. We observed such a pattern at the extreme hot side of the thermal niche. This study provides key information on the thermoregulatory response of A. bedriagae to ongoing climate change that can be useful to identify populations facing a higher extinction risk either currently or in the near future.
𝗕𝗮𝗰𝗸𝗴𝗿𝗼𝘂𝗻𝗱. The study of convergently acquired adaptations allows fundamental insight into life's evolutionary history. Within lepidosaur reptiles – i.e., lizards, tuatara, and snakes – a fully fossorial ('burrowing') lifestyle has independently evolved in most major clades. However, despite their con-sistent use of the skull as a digging tool, cranial modifications common to all these lineages are yet to be found. In particular, bone microanatomy, although highly diagnostic for lifestyle, remains un-explored in the lepidosaur cranium. This constitutes a key gap in our understanding of their com-plexly interwoven ecology, morphology, and evolution. In order to bridge this gap, we reconstructed the acquisition of a fossorial lifestyle in 2813 lepidosaurs and assessed the skull roof compactness from microCT cross-sections in a representative subset (n = 99). We tested this and five macro-scopic morphological traits for their convergent evolution.
𝗥𝗲𝘀𝘂𝗹𝘁𝘀. We found that fossoriality evolved independently in 54 lepidosaur lineages. Furthermore, a highly compact skull roof, small skull diameter, elongate cranium, and low length ratio of frontal and parietal were repeatedly acquired in concert with a fossorial lifestyle.
𝗖𝗼𝗻𝗰𝗹𝘂𝘀𝗶𝗼𝗻𝘀. We report a novel case of convergence that concerns lepidosaur diversity as a whole. Our findings further indicate an early evolution of fossorial modifications in the amphisbae-nian "worm-lizards" and support a fossorial origin for snakes. Nonetheless, our results suggest distinct evolutionary pathways between fossorial lizards and snakes through different contingen-cies. We thus provide novel insights into the evolutionary mechanisms and constraints underlying amniote diversity and a powerful tool for the reconstruction of extinct reptile ecology.
Sardinia shows a clear lack of herpetological data due to an evident paucity of herpetological surveys. This gap of knowledge is worthy of attention, since Sardinia hosts a rich herpetofauna with a large proportion of endemic species, and distribu-tion data are crucial for targeting conservation efforts. In this paper we provide new distribution data for Sardinian reptiles, with the aim of updating our knowledge on their specific distribution. Data were opportunistically recorded during ten years of field research in Sardinia, carried out in more than twenty campaigns from April 1999 to June 2009. All the eighteen reptile species belonging to the Sardinian fauna were recorded. A total amount of 293 faunistic data were collected from 178 different local-ities covering the entire study area. Within this dataset, 137 faunistic data fall outside known species' ranges as reported in the Atlas of Italian amphibians and reptiles. In conclusion, data presented here produced a remarkable increase of knowledge on Sar-dinian reptiles' distribution. Nevertheless, it should be evidenced that, notwithstand-ing the present updating, the knowledge of Sardinian reptiles' distribution is probably still far from being exhaustive. Thus, further investigations are strongly required for obtaining a complete picture and identifying conservation priorities in terms of iso-lated species/populations and areas of high diversity and endemicity.
The aim of this study was to determine if divergence in habitat use among lacertid lizards is paralleled by morphological differentiation. For 35 lacertid species, we measured body, head and limb dimensions. Habitat use was inferred from the literature: ground-dwelling on open terrain, ground-dwelling in vegetated areas, shrub-climbing, tree-climbing, saxicolous (i.e. rock-climbing). Traditional (i.e. non-phylogenetic) statistical analyses suggest morphological differences among species groups with different habitat use. Ground-dwelling species from open habitats tend to have longer femurs, tibiae and humeri (relative to body length) than other groups. Cursorial (i.e. level-running) species have relatively high heads and trunks compared to climbing species. These differences follow biomechanical predictions and it is tempting to consider them as adaptations to habitat use. However, phylogenetic analyses of the data fail to establish a clear relationship between habitat use and morphology in the data set considered. There is a weak indication that the differences in head and trunk height have evolved as an adaptation to different habitat use, but the differences in relative limb dimensions among species groups with different habitat use vanish. Either adaptation of limb dimensions to habitat use has not occurred in lacertid lizards, or our methods are unable to demonstrate such an adaptation. We show that uncertainties in the topology of the phylogenetic tree used are unlikely to influence the outcome of our study. We also address the fact that habitat use is often similar in different branches of the phylogenetic tree, and the consequences this may have for the power of our statistical analyses.
We modelled the distribution of two genetically differentiated forms of the Golden-striped salamander, Chioglossa lusitanica, in Portugal with the help of a geographical information system. Models were derived with and without the assumption that the contact zone between the forms would be associated with the Mondego river valley and with and without the statistical Bonferroni correction. The model fit was high and ranged from kappa = 0.81-0.99. The southern form appears to live under harsher (but still tolerated) environmental conditions than the northern form (low precipitation, low air humidity, low summer temperatures, a high number of frost months, low NDVI vegetation index) and can be viewed as a mountain form. This is in line with the observation that the southern form has shorter extremities than the northern one.
Autoregressive models for spatial interaction have been proposed by several authors (Whittle [15] and Mead [11], for example). In the past, computational difficulties with the ML approach have led to the use of alternative estimators. In this article, a simplified computational scheme is given and extended to mixed regressive-autoregressive models. The ML estimator is compared with several alternatives.
Podarcis tiliguerta, a Wall Lizard endemic to Corsica and Sardinia, has recently been shown to harbour highly genetically distinct mitochondrial lineages, that may indicate it is in fact a species complex. Here we combine 12S rRNA mtDNA sequences from previous studies with 17 newly gener-ated sequences to better understand genetic diversity within this group. In particular we include samples from the Cerbicale islands, which were quite distinct in an earlier assessment of protein electrophoretic variation. Results confirm that distinct lineages exist on Corsica and Sardinia. The Cerbicale islands appear as part of the Corsican group. A third lineage exists, although at present it is known only from a single specimen from Sardinia. Further morphological and molecular data is needed to revise the taxonomy of this apparent species complex.
In ecology, researchers frequently use observational studies to explain a given pattern, such as the number of individuals in a habitat patch, with a large number of explanatory (i.e., independent) variables. To elucidate such relationships, ecologists have long relied on hypothesis testing to include or exclude variables in regression models, although the conclusions often depend on the approach used (e.g., forward, backward, stepwise selection). Though better tools have surfaced in the mid 1970's, they are still underutilized in certain fields, particularly in herpetology. This is the case of the Akaike information criterion (AIC) which is remarkably superior in model selection (i.e., variable selection) than hypothesis-based approaches. It is simple to compute and easy to understand, but more importantly, for a given data set, it provides a measure of the strength of evidence for each model that represents a plausible biological hypothesis relative to the entire set of models considered. Using this approach, one can then compute a weighted average of the estimate and standard error for any given variable of interest across all the models considered. This procedure, termed model-averaging or multimodel inference, yields precise and robust estimates. In this paper, I illustrate the use of the AIC in model selection and inference, as well as the interpretation of results analysed in this framework with two real herpetological data sets. The AIC and measures derived from it is should be routinely adopted by herpetologists.
Archaeolacerta bedriagae is a polytypic species endemic to Corsica and Sardinia. It represents one of the most peculiar elements of the Italian herpetofauna. This species has a fragmented range in Sardinia. The aim of this paper is to summarise the knowledge on the distribution of this lizard in Sardinia, based both on literature and original records, and to define the conservation status of its populations This research was carried out throughout the entire Sardinian territory, from June 2000 to September 2002. Most of the known sites of occurrence of A. bedriagae were checked, characterised from geomorphologic and florofaunistic points of view and gco-referenced. The surveys carried out explored only the potentially suitable habitats in different hours of the day. Three new localities were discovered, 10 checked sites were confirmed, 12 localities were not confirmed and 43 previously quoted sites were not explored. Two sampling sites were selected for a population study. In the latter two localities, several population parameters, such as density and sex ratio were studied. In the mountain site, a population density twenty limes higher than that found at the sea level site was estimated. Only five species were found to be syntopic with A. bedriagae, Podarcis tiliguerta, Algyroides fitzingeri, Tarentola mauritanica, Chalcides ocellatus and Coluber viridiflavus. The Sardinian subrange includes seven main areas of certain presence, but an underestimation due to their elusivity and the low density of some populations is possible The species generally inhabits areas of scarce interest and difficult for man to reach, though at least in some localities it seems to be disturbed by an increase in tourism. Some conservation actions were proposed.
Nondetection of a species at a site does not imply that the species is absent unless the probability of detection is 1. We propose a model and likelihood-based method for estimating site occupancy rates when detection probabilities are 1. The model provides a flexible framework enabling covariate information to be included and allowing for missing observations. Via computer simulation, we found that the model provides good estimates of the occupancy rates, generally unbiased for moderate detection probabilities (0.3). We estimated site occupancy rates for two anuran species at 32 wetland sites in Maryland, USA, from data collected during 2000 as part of an amphibian monitoring program, Frog-watch USA. Site occupancy rates were estimated as 0.49 for American toads (Bufo amer-icanus), a 44% increase over the proportion of sites at which they were actually observed, and as 0.85 for spring peepers (Pseudacris crucifer), slightly above the observed proportion of 0.83.
Few species are likely to be so evident that they will always be detected at a site when present. Recently a model has been
developed that enables estimation of the proportion of area occupied, when the target species is not detected with certainty.
Here we apply this modeling approach to data collected on terrestrial salamanders in the Plethodon glutinosus complex in the Great Smoky Mountains National Park, USA, and wish to address the question “how accurately does the fitted
model represent the data?” The goodness-of-fit of the model needs to be assessed in order to make accurate inferences. This
article presents a method where a simple Pearson chi-square statistic is calculated and a parametric bootstrap procedure is
used to determine whether the observed statistic is unusually large. We found evidence that the most global model considered
provides a poor fit to the data, hence estimated an overdispersion factor to adjust model selection procedures and inflate
standard errors. Two hypothetical datasets with known assumption violations are also analyzed, illustrating that the method
may be used to guide researchers to making appropriate inferences. The results of a simulation study are presented to provide
a broader view of the methods properties.
We studied, in the field and laboratory, aspects of the thermal biology in two populations of the lizard Podarcis tiliguerta along a 1450 m altitudinal gradient. Body temperatures (Tb) at high altitudes average lower, are more variable, but are more elevated above environmental temperatures than at sea level. Lizards partially reduced the impact of altitudinal changes in thermal loads through presumable subtle behavioural adjustments. A comparison of the thermal preferences in the laboratory, the maximal operative temperatures predicted from a biophysical model, and the activity Tb's at both sites, indicates that the main response to changing environmental conditions is an active shift in thermoregulatory set points. Integration of field Tb's and laboratory data on temperature specific sprint speeds, predicts that the mountainous lizards experience reduced running abilities that are especially acute in the early morning. Despite this impairment of running performance, the thermal sensitivity of running speed has not evolved to match the Tb's experienced by both populations. This result supports the view that the thermal physiology of this lizard is evolutionarily conservative, but the lack of information on the relation between running performance and fitness components impedes rejection of alternative hypotheses.
This chapter gives results from some illustrative exploration of the performance of information-theoretic criteria for model selection and methods to quantify precision when there is model selection uncertainty. The methods given in Chapter 4 are illustrated and additional insights are provided based on simulation and real data. Section 5.2 utilizes a chain binomial survival model for some Monte Carlo evaluation of unconditional sampling variance estimation, confidence intervals, and model averaging. For this simulation the generating process is known and can be of relatively high dimension. The generating model and the models used for data analysis in this chain binomial simulation are easy to understand and have no nuisance parameters. We give some comparisons of AIC versus BIC selection and use achieved confidence interval coverage as an integrating metric to judge the success of various approaches to inference.
Different models of how species are arranged on an environmental gradient result in different amounts of clumping of the species boundaries. A statistical test of the degree to which the boundaries are clumped is presented here and a measure of the variability of inter-boundary distance is discussed. To complement the tests, a method for detecting those portions of the gradient on which the boundaries are most clumped together is described. In addition, a test of the extent to which the upper and lower boundaries of species are intermingled is presented. The methods are illustrated using the arrangements of seaweed species on rocky shores.
Using null model simulations, we tested for non-random patterns of local co-occurrence in 28 congeneric guilds of the Australian avifauna. At the scale of 1° latitude-longitude blocks, species in most guilds co-occurred more often than expected by chance. However, coexistence was significantly less than expected for six of the 28 guilds. In four of these guilds (Climacteris, Cinclosoma, Manorina, and Psophodes), the species were segregated by habitat use and/or geographic range. The remaining two cases were complicated by uncertainty in taxonomy (Malurus) and unreliable field records (Corvus). We also examined distribution patterns in five Australian guilds that are analogs of avian guilds designated by Diamond for the Bismarck Archipelago. For two of the five guilds (Pachycephala and Zosterops), co-occurrence in Australia was less than expected, mirroring an insular pattern of "checkerboard distributions" in the Bismarck Archipelago. For the remaining three guilds (Ptilonopus, Myzomela, and Lonchura), co-occurrence was significantly greater than expected. Overall, our results suggest that competitive-based assembly rules are not important in determining species coexistence within most congeneric guilds of the Australian avifauna, at least at the large spatial scale of our analysis.
Twenty‐four species of lacertid lizards were examined at 31 sites in western Yugoslavia, Greece and Iberia. Comparative observations were made on over 4500 individual lizards, noting such features as times of activity, hunting methods, diet, micro‐ and macro‐habitat, refuges used and body temperature. These data are used as a basis for assessing resource partition in related sympatric species, for finding out whether different systematic groups have characteristic types of niche, and for comparing community structure in the three peninsulas of southern Europe.
Chioglossa lusitanica is a streamside salamander endemic to the northwestern corner of the Iberian Peninsula. In an extensive field survey we found the species to be widely distributed across northwestern Portugal. The distribution data were used to identify macroenvironmental parameters related to the presence of the species in Portugal, and to produce a descriptive distribution model for C. lusitanica. We modelled the species distribution based on five environmental parameters (precipitation, relief, July temperature, number of frost months and hardness of water) selected by logistic regression analysis. The model yielded a high score of correct classification (95%). Excluding parameters unavailable for Spain the model included four parameters (precipitation, relief, July temperature and altitude) and had a 93% correct classification score. Extrapolation of the model to Spain yielded a correct classification of 92% and served as a validation of the modelling technique in an independent area. The models indicate the existence of several potentially suitable areas outside the known distribution of the species, providing clues about the species historical biogeography. The models, through the identification of highly suitable and stable protection regions, may contribute to informed conservation planning.
Podarcis tiliguerta is a lacertid lizard endemic to Corsica, Sardinia and many of their satellite islands. The purpose of this study was to assess the relationships among the various island populations using morphological characters, to assess the usefulness of these characters in phylogenetic studies, and to test the concordance of morphologi- cal and earlier genetical studies. Snout-vent length and 11 pholidotic characters have been studied on 2783 specimens from localities on the two main islands and the majority of their respective satellite islands. Data for males and females are analyzed separately using uni- and multivariate statistical methods; the results are compared to previous genetical analyses. With few exceptions, the two populations, one on Corsica, the second on Sardinia (and their satellite islands), are readily distinguish- able. We argue that the few exceptions may be due to a founder effect and/or genet- ic drift. The male sample from northern Corsica and both sex samples from southern Corsica present unresolved problems because they group with the Sardinian clade. Our results, for the most part, are in accord with those obtained with genetical analy- ses, but further studies are needed to clarify the unresolved questions. Riassunto Podarcis tiliguerta è una specie endemica di Corsica, Sardegna e molte delle loro isole satelliti. Nel presente lavoro sono stati analizzati la lunghezza testa-cloaca e 11 carat- teri della folidosi di 2783 esemplari provenienti da varie località delle isole principali e la maggior parte delle loro isole satelliti. Lo scopo è stato quello di analizzare da un punto di vista morfologico le relazioni tra le varie popolazioni, di verificare l'utilità di questi caratteri negli studi filogenetici e di testare la concordanza tra risultati mor- fologici e genetici. I dati sono stati analizzati, separatamente per maschi e femmine, con metodi di statistica univariata e multivariata, e i risultati sono stati confrontati con precedenti studi genetici. Le due popolazioni di Corsica e Sardegna (e rispettive isole satelliti) risultano piuttosto ben distinguibili, con poche eccezioni dovute proba- bilmente a fenomeni di effetto fondatore e deriva genetica. Il campione di maschi del nord della Corsica e i due campioni di maschi e femmine del sud della Corsica occu- pano una posizione problematica, risultando inclusi nella popolazione sarda. In gen- erale i risultati concordano in larga parte con quelli ottenuti dalle analisi genetiche, ma ulteriori studi sono ritenuti necessari per chiarire alcune delle que-stioni rimaste aperte.
Aim I employed a novel null model and metric to uncover unusual species co‐occurrence patterns in a herpetofaunal assemblage of 49 species collected at discrete elevations along a gradient.
Location Mount Kupe, Cameroon.
Methods Using a construction algorithm that started from a matrix of 0s, a sample null space of 25,000 unique null matrices was generated by simultaneously conserving (1) the number of occurrences of each species, (2) site richness and (3) species range spans derived from the observed incidence matrix. I then compared the number of times each pair of confamilial species co‐occurred in the null space with the same number derived from the observed incidence matrix. Two cases dealing with embedded absences in species ranges were tested: (1) embedded absences were maintained, and (2) embedded absences were assumed to be sampling omissions and were replaced by presences.
Results In the observed absence/presence assemblage there were 147 possible confamilial species pairs. Therefore, 5% or eight were expected by chance alone to have co‐occurrence patterns that differed from chance expectations by chance alone. Of these confamilial species pairs, 38 were congeneric and so 5% or two were expected to differ from chance expectations. For case (1) 16, and for case (2) 17 confamilial species pairs’ co‐occurrence patterns differed significantly from chance expectations. For case (1) nine congeneric species pairs, and for case (2) 10 congeneric pairs differed significantly from chance expectations. For case (1) four, and for case (2) five congeneric species pairs formed checkerboards (patterns of mutual exclusion). Results from case (1) were a proper subset of case (2) indicating that sampling omissions did not alter greatly the results.
Main conclusions I have demonstrated that null models are valuable tools to analyse ecological communities provided that proper models are employed. The choice of the appropriate null space to analyse distributions is critical. The null model employed to analyse birds on islands of an archipelago can be adapted to analyse species along gradients provided an additional range constraint is added to the null model. Moreover, added precision to results can be obtained by analysing each species pair separately, particularly those in the same family or genus, as opposed to applying a community‐wide metric to the faunal assemblage. My results support some of the speculations of previous authors who were unable to demonstrate their suspicions analytically.
The role of interspecific competition as a key factor in the ecology of natural communities where species exploit limited resources is well established, and the study of competition dynamics in snake communities has received much attention in recent years. Twenty years ago, an acclaimed review (Toft 1985) suggested that snakes were atypical among vertebrates because sympatric species usually partition the food niche. Here, I review the articles published in the last two decades with the aim of finding any general geographical or guild patterns and assessing if Toft's main conclusion is still supported by new evidence. Where appropriate, I use Monte Carlo simulations to establish whether observed patterns of niche overlap are real, or if they have occurred by chance. My study shows clear congruence in the patterns of coexistence exhibited by snake communities in different regions of the world, i.e.: (1) cold regions of the northern hemisphere (high latitudes and altitudes) exhibit low species richness and a very low, or even absent, potential for interspecific competition; (2) aquatic snakes that form communities in temperate regions generally partition the food type available and exhibit a broad similarity in habitat use with subtle differences in microhabitat use; (3) terrestrial snake communities in temperate regions are very variable in terms of their coexistence dynamics and show no evidence of generalised patterns; (4) sympatric viperids in Europe, North America and, most interestingly, tropical Asia partition the available habitat but not the prey resource; (5) competition is much stronger in tropical snake communities, and the intensity of this process fluctuates throughout the year being most intense during periods of low food availability; (6) in general, tropical snakes partition the food resource (prey type and/or prey size), but when this resource is not partitioned competitive exclusion can occur.
We propose tests for patterns in meta-community structure. The tests for clustering and nestedness of the occurrences of species and negative co-occurrence patterns provide four important innovations. Firstly, they are not restricted to the analysis of communities along one-dimensional gradients or to the main axis of variation. Secondly, abundance data can also be considered in the null model whereas most previous approaches could consider only presence/absence data. And thirdly, habitat suitability and spatial autocorrelation can be incorporated in the null model so that patterns that might be caused by biotic interactions can be distinguished from patterns which are the result of differences in the suitability or accessibility of sites for the examined organisms. Finally, the test for nestedness is also appropriate if there is more than one set of nested subsets. A re-analysis of 35 data sets with these tests showed the importance of considering the autocorrelation of the occurrences of species in analyses of meta-community structure and demonstrated the advantage of abundance data for tests of clustering of species. With abundance data it could be shown that there is a significant clustering of species, i.e. there are positive associations of species in most meta-communities, even if an environmentally or spatially constrained null model is used for the test. Co-occurrence patterns that might indicate interspecific competition were found in many of the analysed presence/absence data sets. Surprisingly the analysis of abundance data sets provides less evidence for interspecific competition. A hierarchical organization of communities, i.e. nestedness, turned out to be a rare pattern, if the autocorrelation of the occurrences of species is considered.
The concept of evolutionary convergence in morphological traits among phylogenetically unrelated organisms because of their ecological similarities is one of the most venerable in evolutionary ecology, and indeed has attracted the attention of ecologists for a long time. The ‘whip snakes’ are phylogenetically unrelated, morphologically and ecologically convergent species, which are characterized by slender bodies, long tails, large eyes, alertness, diurnality, saurophagy, oviparity, and rapid movement. It has been hypothesized that their morphology has evolved as a response preying on quick-running diurnal prey, mainly lizards. Here I compared two species of saurophagous whip snakes, the European Coluber (Hierophis) viridiflavus and the African Psammophis phillipsii. I explored whether the proximate factors which influence the presence of the two species in their natural habitat are the same in both Mediterranean central Italy (Coluber viridiflavus) and in tropical Nigeria (Psammophis phillipsii). I also used as control two other species of colubrids, Natrix natrix in Italy and Lamprophis fuliginosus in Nigeria. I selected 11 independent variables that are general for both study systems, and that are easily identified for their presence/absence in/around the site of capture of each snake specimen, and then explored the effects of these variables on the presence of the two species using a robust statistical design, i.e. a forward stepwise logistic regression model. My modelling analyses indicated that two variables influenced positively (i.e. the presence of lizards (LIZ) and of tall grass (GRS)), and one influenced negatively (the presence of water bodies (WBS)), the African species' presence. With regard to the European species, only two variables influenced positively and significantly the snakes presence, i.e. LIZ and GRS. Overall, the comparison of the two models clearly showed that both species' presence was influenced exactly by the same variables, despite the different continents and environmental conditions. The two control species were influenced by entirely different variables. Hence, robust modelling statistics revealed a extreme ecological similarity between the phylogenetically unrelated Psammophis and Coluber, clearly indicating that their peculiar morphologies have evolved to prey a rapid moving type of diurnal prey (lizards) in a specific type of microhabitat (tall grass). As there was no significant correlation between LIZ and GRS, hence the positive influence of GRS on both the snake species' presence cannot be considered as a mere correlate of the LIZ variable, but is likely that the peculiar morphological adaptations of these snakes are particularly efficient in this type of microhabitat compared to others.
The analysis of presence–absence matrices with ''null model'' randomization tests has been a major source of controversy in community ecology for over two decades. In this paper, I systematically compare the performance of nine null model algorithms and four co-occurrence indices with respect to Type I and Type II errors. The nine algorithms differ in whether rows and columns are treated as fixed sums, equiprobable, or proportional. The three models that maintain fixed row sums are invulnerable to Type I errors (false positives). One of these three is a modified version of the original algorithm of E. F. Connor and D. Simberloff. Of the four co-occurrence indices, the number of checkerboard com-binations and the number of species combinations may be prone to Type II errors (false negatives), and may not reveal significant patterns in noisy data sets. L. Stone and A. Robert's checkerboard score has good power for detecting species pairs that do not co-occur together frequently, whereas D. Schluter's V ratio reveals nonrandom patterns in the row and column totals of the matrix. Degenerate matrices (matrices with empty rows or columns) do not greatly alter the outcome of null model analyses. The choice of an ap-propriate null model and index may depend on whether the data represent classic ''island lists'' of species in an archipelago or standardized ''sample lists'' of species collected with equal sampling effort. Systematic examination of a set of related null models can pinpoint how violation of the assumptions of the model contributes to nonrandom patterns.
1. Morphological features (i.e. snout–vent length, SVL, mass and limb parameters), locomotor performance (sprint speed, climbing speed, manoeuvrability and endurance) and microhabitat use were measured in three lacertid lizard species. Additionally, microhabitat preference was tested in the laboratory with species kept apart and in combination with each other to assess mutual interference.
2. It was predicted that each species possesses morphological adaptations that allow it to excel in those performance measures relevant in its particular microhabitat.
3. The three species differed in microhabitat use. Lacerta bedriagae was mostly seen on boulders, while Podarcis sicula occurred among vegetation. Podarcis tiliguerta seemed more general in its microhabitat use. The results from the microhabitat preference in the laboratory corresponded well to these field observations.
4. Besides differing in SVL, the three species differed in limb length and diameter, and body mass (all relative to SVL). L. bedriagae has long forelimbs, short hindlimbs and a high body mass, while P. sicula has short forelimbs, long hindlimbs and a low body mass. P. tiliguerta is morphologically intermediate.
5. The differences found in morphology translated partially into performance differences. Only climbing speed and endurance differed among species. L. bedriagae excelled in both cases. Considering its microhabitat use, this seemed adaptive.
6. Unexpectedly, the interference experiments suggested that L. bedriagae is the least competitive of the three species.
Ecologists have identified several kinds of pattern in the distribution of species among sites, including a) nested subsets, b) checkerboards, c) Clementsian gradients, d) Gleasonian gradients, and e) evenly spaced gradients. Most past efforts to diagnose such patterns have focused on only one at a time, often contrasted with a sixth type of pattern, f) “randomness”. While there are statistical tests to distinguish each of the first five patterns from randomness, there are currently no established methods for discriminating among these first five patterns in a given data set. Here we propose a method that will identify which of these possibilities is most prevalent in a site-by-species incidence matrix based on three basic aspects of meta-community structure. Our method is based on first ordinating the incidence matrix to identify the dominant axis of variation and identifying three aspects variation along this dominant axis. The first aspect, “coherence”, is the degree to which pattern can be collapsed into a single dimension. The second, “species turnover”, describes the number of species replacements along this dimension. The third aspect, “boundary clumping”, has to do with how the edges of species boundaries are distributed along this dimension. We present methods for analyzing these three aspects of meta-community structure, use them to identify the six different patterns, and illustrate them with a representative set of cases drawn from previously published data.
There is a long-standing dispute over whether the analysis of species co-occurrence data, typically on islands in an archipelago, can disclose the forces at work in structuring a community. Here we present and utilise three “scores” S, C and T. S gives the mean number of islands shared by a species pair in the presence/absence data under study. The scores C and T are based on the way that a pair of species occurs on a pair of islands. When each species occurs on a different island, this adds to the “checkerboard score” C; if they occupy the same island, this increases the “togetherness score” T.
In judging whether observed values of S, C and T are compatible with a null hypothesis assuming no species interaction, we follow Connor and Simberloff (1979) in generating a “control group” of (constrained) simulated incidence patterns.
Presence/absence matrices can have paradoxical features, in combining a high mutual exclusion by species (checkerboardedness) with a degree of species aggregation that is also high. We show that this is in fact inevitable — that, given the usual contraints, C and T can differ only by a constant. This means that extreme checkerboardedness can be produced by forces making for species aggregation, just as well as by those making for avoidance.
If we restrict our attention to a subset of species, the constraints are less rigid and the S, C and T scores are somewhat freer to vary. We consider the confamilial subsets in the Vanuatu archipelago as likely candidates for revealing any competition forces at work. Calculating the actual S, C and T scores for these subsets, we compare them with the corresponding scores in a sample of simulated colonization patterns.
The actual species-distributions differ significantly from what we would expect if the colonization choices of different species were uncorrelated (save for some biological constraints). The confamilial species of the real world share more islands, and occur in a pattern less checkerboarded, and more aggregated, than their simulation counterparts. This suggests that competition pressures, if they exist, are overcome by countervailing factors.
The method used is applicable in other ways, and to a wider class of problems, in analysing the forces behind community structure.
This paper presents a simple and widely ap- plicable multiple test procedure of the sequentially rejective type, i.e. hypotheses are rejected one at a tine until no further rejections can be done. It is shown that the test has a prescribed level of significance protection against error of the first kind for any combination of true hypotheses. The power properties of the test and a number of possible applications are also discussed.
The history of the development of statistical hypothesis testing in time series analysis is reviewed briefly and it is pointed out that the hypothesis testing procedure is not adequately defined as the procedure for statistical model identification. The classical maximum likelihood estimation procedure is reviewed and a new estimate minimum information theoretical criterion (AIC) estimate (MAICE) which is designed for the purpose of statistical identification is introduced. When there are several competing models the MAICE is defined by the model and the maximum likelihood estimates of the parameters which give the minimum of AIC defined by AIC = (-2)log-(maximum likelihood) + 2(number of independently adjusted parameters within the model). MAICE provides a versatile procedure for statistical model identification which is free from the ambiguities inherent in the application of conventional hypothesis testing procedure. The practical utility of MAICE in time series analysis is demonstrated with some numerical examples.
Atlas de Répartition des Batraciens et Reptiles de Corse
- M Delaguerre
- M Cheylan
Delaguerre, M. and Cheylan, M. ( 1992 ) Atlas de Répartition des Batraciens et Reptiles de Corse. Parc Naturel
Régional de Corse, Ajaccio, France.
Lizard Ecology 109–126 121 Appendix 1. Graphics explaining the distribution of the observed variables between species. r122 P
- L J Vitt
- E R Pianka
- Rp Princeton
- Bombi
Vitt , L.J. and Pianka , E.R. ( 1994 ) Lizard Ecology . Princeton University Press , Princeton . rP. Bombi et al. / Animal Biology 59 (2009) 109–126 121 Appendix 1. Graphics explaining the distribution of the observed variables between species. r122 P. Bombi et al. / Animal Biology 59 (2009) 109–126 rP. Bombi et al. / Animal Biology 59 (2009) 109–126 123 r124 P. Bombi et al. / Animal Biology 59 (2009) 109–126 rP. Bombi et al. / Animal Biology 59 (2009) 109–126 125 r126 P. Bombi et al. / Animal Biology 59 (2009) 109–126
Notes on the biology of the high altitude lizard Lacerta bedriagae
- A M Castilla
- D Bauwens
- R Van Damme
- R Verheyen
Castilla, A.M., Bauwens, D., Van Damme, R. and Verheyen, R. ( 1989 ) Notes on the biology of the high
altitude lizard Lacerta bedriagae. Herpetol. J., 1, 400 -403.
Frammentazione dell'areale in specie del genere Archaeolacerta s.l.: cause ed eff etti
- P Bombi
Bombi, P. ( 2005 ) Frammentazione dell'areale in specie del genere Archaeolacerta s.l.: cause ed eff etti. Ph.D.
Th esis, University "Roma Tre", Rome, Italy.
Tartarughe e sauri d'Italia
- S Bruno
- S Maugeri
Bruno, S. and Maugeri, S. ( 1984 ) Tartarughe e sauri d'Italia. Martello, Florence, Italy.
- P Bombi
P. Bombi et al. / Animal Biology 59 (2009) 109–126
Atlas of Italian Amphibians and Reptiles
- R Sindaco
- G Doria
- E Razzetti
- F Bernini
Sindaco, R., Doria, G., Razzetti, E. and Bernini, F. (Eds.) ( 2006 ) Atlas of Italian Amphibians and Reptiles.
Societas Herpetologica Italica, Polistampa, Firenze.