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Assessing community assembly rules has been a prominent task by community ecologists. Using a turtle family (Pelomedusidae) as a study case, we analyze the structure of their communities from the continental scale to the habitat scale, by using a suite of statistical approaches: (i) GIS modeling of the most complete presence sites dataset (from IUCN/SSC TFTSG archive); (ii) niche overlap and co‐occurrence null models with Monte Carlo simulations; (iii) generalized linear models. We used, after controlling for spatial autocorrelation, continental scale presence data totalling 1698 locality records belonging to 27 species of African Pelomedusidae and local scale data from 58 surveyed stations in eight different countries, totalling 1936 turtle individuals of at least five species (but several taxa are included into one of these "species": the Pelomedusa subrufa complex). At the local scale, the number of co‐occurring Pelomedusidae in Africa ranged from two to three species, although the ranges of up to five total species overlapped at various locations on the continental scale. A simulation study showed that, at the continental scale, the various species co‐occurred following assembly rules that are compatible with interspecific competition by two metrics. At the habitat scale, the mean number of sympatric species was just below two and the maximum number of sympatric species per local site was three, with significant variation among habitat categories (more in forest than in any other habitat). Body size filtering may be also a mechanism that facilitates coexistence of pelomedusid species under sympatric conditions. [ABSTRACT FROM AUTHOR]

The ecology and activity patterns of many tropical vertebrate species are heavily influenced by the seasonal alternance of dry and wet periods. However, the effects of the dry–wet seasonal alternance on feeding habits of tropical vertebrates are poorly known. In this paper, the monthly variations in the diet of the scincid lizard Trachylepis quinquetaeniata were studied, by faecal pellet analysis, in a sandy beach area of southern Togo (West Africa) in relation to both rainfall and temperature‐related variables. The diet was basically insectivorous, with five prey types (Coleoptera adults and larvae, Lepidoptera adults and larvae and Formicidae) being dominant in the pellets. Prey composition was similar between sexes, but varied considerably across months. There was a positive correlation between mean monthly rainfall and number of prey categories eaten in each month. General linear models (GLM) showed that both Simpson and Shannon indices increased with the monthly number of rainy days. GLM also showed that rainfall regime influenced the frequency of eaten Coleoptera adults and larvae and of Lepidoptera adults and larvae, with no effect on Formicoidea. Our study confirms that dietary patterns of tropical lizards are influenced by the wet‐dry‐seasonal alternance, and that both the taxonomic composition of the diet and the dietary diversity metrics are significantly affected. We also demonstrated that rainfall is more important than temperature in determining the dietary variations, and that, among the rainfall‐linked variables, it is the monthly number of rainy days that represents the most important variable. In this paper, the monthly variations in the diet of the scincid lizard Trachylepis quinquetaeniata were studied, by faecal pellet analysis, in a sandy beach area of southern Togo (West Africa) in relation to both rainfall and temperature‐related variables. The diet was basically insectivorous, with five prey types (Coleoptera adults and larvae, Lepidoptera adults and larvae and Formicidae) being dominant in the pellets. Our study confirms that dietary patterns of tropical lizards are influenced by the wet‐dry‐seasonal alternance, and that rainfall is more important than temperature in determining the dietary variations, with the monthly number of rainy days being the most important variable. [ABSTRACT FROM AUTHOR]

Mediterranean streams undergo seasonal reductions in water availability that may affect amphibian demography due to habitat loss and the concentration of individuals in the shrinking aquatic habitats. However, there are few empirical examples of how increased population density experienced by larval stages produces long-term effects on growth and fitness at postmetamorphic stages. We tested the effect of four different larval densities on the demography and growth of the endangered stream-dwelling newt Euproctus platycephalus. By manipulating larval populations in experimental aquaria, we analyzed the short-term effects of density in terms of growth and mortality rates as well as of social behavior. To assess medium- and long-term effects we tested the metamorph individuals after 1 and 3 years, respectively, and adults for maternal effect by assessing the relationship between mean larval size and fecundity. Larval body size and growth rate appeared inversely proportional to larval density. Density affected the incidence of aggressive behavior by increasing the rate of mutilation to arms and tail. One-year-old salamanders raised at the highest larval density grew significantly less. All 3-year-old individuals reached comparable body size and body condition irrespective of initial larval density. Salamanders presented a positive relationship between maternal size and (1) fecundity and (2) larval size. In natural conditions, increased density may cause slower growth and a reduction in the percentage of individuals reaching metamorphosis. Prolonged dry periods and increased water withdrawals for agricultural and industrial practices have almost certainly affected the population dynamics of Sardinian newt populations in the long term. [ABSTRACT FROM AUTHOR]

African elephants ( Loxodonta africana) are ecosystem engineers in African savannahs, but their role in the modifications of the populations of trees by means of their browsing activities has been poorly studied so far in West Africa. We studied the disturbance of elephants to eight selected species of trees in the Nazinga Game Ranch (Burkina Faso), in 54 transects at the end of dry season 2008. We fitted simple models describing the number of dead individuals for each tree species in relation to their initial population density, and in relation to dung-pile density, in the assumption that there should be a positive relationship between elephant density and dung-pile density. Generalized Linear Model analyses and regression analyses showed that the more dense the woodland cover, the least the percentage of damaged plants by elephants. For each plant species, the initial density and density of elephant dung-piles explained a high proportion of the variance in the density of dead individuals. Stochastic models, generated by a purposely created simple computer program written in GW-BASIC programming language, predicted changes in tree and shrub abundance under different assumptions about elephant numbers. The models suggested that elephant browsing may cause considerable change in the selected plant populations, especially with regard to such species as Acacia gourmaensis, Vitellaria paradoxa and Maytenus senegalensis. These changes may possibly increase the meat harvest from controlled hunting activities, thus improving the income for surrounding communities. [ABSTRACT FROM AUTHOR]

In a context of climate change, ecological and physiological adaptations of organisms are of central importance for determining the outcome of niche challenges (e.g., with potential competitors) and species persistence. Typically, long-term data on free-ranging populations are needed to investigate such phenomena. Here, long-term data on a free-ranging population of western whip snakes ( Hierophis viridiflavus: Colubridae) from central Italy were used in order to test the hypothesis that snake feeding frequencies should increase in relation to climate warming, thus positively affecting individual performance because of longer annual activity period, increased daily activity and larger prey base. Data from 231 'female snake-years' of records (including inter-annual recaptures) were collected were collected between 1990 and 2014. The frequency of fed snakes varied remarkably across the study period with a significant increase over the years. There was a significant positive effect of the mean annual temperature on the percentage of fed animals, whereas there was a non-significant relationship between yearly rainfall and percentage of fed animals. There was a positive relationship between mean annual temperature and yearly diversity-of-prey index. No other climatic variables were significantly correlated with yearly diversity-of-prey index. This study supported the hypothesis that global warming may be favorable for thermophilic species (such as H. viridiflavus), as it enhances their foraging performances and hence their feeding frequencies. The same may not be necessarily true for other species which have colder preferenda (e.g., Zamenis longissimus). [ABSTRACT FROM AUTHOR]

Most dietary studies on predator species available in the literature are based on single populations, with no meta-analysis across populations in distinct areas of their range. Here, we performed a systematic review of the available data on the food habits of barn owl ( Tyto alba) across Italy, collected during the last 40 years in relation to the modeled patterns of richness of small mammal communities. The overall dataset came from 212 sites, with multiple surveys for some sites, and a total of 279 samples. There was a significant effect of sample size on niche breadth in each site. There was a significant difference in terms of dietary breadth among six distinct areas of Italy, with diet breadth being lower in Sardinia and higher in Latium-Abruzzi, Tuscany, and North-eastern Italy. Potential small mammal prey diversity was significantly different across distinct study sites, with Apulia and Sardinia having lower diversity than the rest of the sites. Potential small mammal prey diversity affected the niche breadth per site. Overall, the plasticity of the food niche breadth of the barn owl reflected not only local conditions but also more general distribution patterns of small mammal communities. [ABSTRACT FROM AUTHOR]

Habitat loss and fragmentation are recognized as the main causes for the global biodiversity crisis. Most of the studies investigating the issue of habitat fragmentation in vertebrates are cross-sectional, whereas long-term studies are least available. We surveyed bird communities in 17 forest fragments (FF) and a single continuous forest stands (CF) in central Italy twice, 10 years apart (i.e. in 1996 and in 2006). All community parameters showed a contrasting pattern between 1996 and 2006, i.e. an increase of abundance and diversity measures in CF and a decrease or a stability of the same parameters in FF. Insectivorous and migratory bird species were the most prone to population declines associated with fragmented landscapes. Differences in species turnover between CF and FF were due to a higher extinction rate in the latter forest type. There was substantial population increase between 1996 and 2006, especially in FF, of opportunistic predator species like corvids. This fact may be responsible for the observed dropping in species number, evenness and diversity in FF. Hence, we conclude that, in FF, the bird community is far from being either stabilized or resilient, as it is rapidly evolving into a more simplified assemblage, dominated by generalist species. [ABSTRACT FROM AUTHOR]

Islands provide an evolutionary window, where a simplified natural network combined with unusual environmental conditions promote selective processes that trigger rapid changes in biological constituents of a species. The Mediterranean island of Montecristo, Italy, provides such a situation with a reduced fauna and flora compared to the mainland. We measured body size (SVL) and recorded diet of the two snake species occurring on the island, the Asp Viper ( Vipera aspis) and the Western Whip Snake ( Hierophis viridiflavus), and compared these data with populations of conspecifics from the mainland. Compared to mainland populations, the three principal results are: (1) no obvious niche shift along the food or habitat axes between the two snake species; (2) significant body size shift (insular dwarfism) of the whip snake by 30 %, and ca. 10 % in the viper; and (3) arboreal ambushing in the viper to add an alternative diet (birds) compared to mainland populations (more mice) to compensate for the lack of suitable micro-mammals on Montecristo Island. [ABSTRACT FROM AUTHOR]

Interspecific competition has been demonstrated to be an important shaping force for snake communities worldwide, but relatively few studies have investigated its occurrence and extent with island assemblages of snakes. In Sardinia (Mediterranean Sea), two species of whip snakes (Colubridae) co-occur, one of them being abundant and widespread ( Hierophis viridiflavus) and the other being localized and critically endangered ( Hemorrhois hippocrepis). A previous hypothesis suggested that the latter species would be confined to suboptimal habitats by the former species, which is a stronger competitor for food. As a consequence, He. hippocrepis would not only be rare but would also be smaller in body size in Sardinia than in other regions of its range where Hi. viridiflavus does not occur. In 1999-2010, we studied habitat selection, food habits, and body sizes of these two snakes in sympatric populations, applying a suite of statistical tools including null models and Monte Carlo simulations. We observed that dietary habits were different between species (compared to Hi. viridiflavus, He. hippocrepis more frequently preyed upon rodents and less frequently on lizards, and within rodent prey, more frequently upon Rattus and less frequently upon Mus), but not in a way compatible with competitively induced trophic niche partitioning. The two species were similar in terms of prey size and predator-size-prey-size relationships. They also differed in habitat selection (maquis was the preferred habitat for both, but Hi. viridiflavus was found significantly more often than He. hippocrepis in grasslands, cultivations, and artificial pinewoods) but again in a non-competitively directed way. In addition, there was no evidence for the hypothesis that He. hippocrepis was confined to suboptimal habitats. Body sizes were similar between species (with males being significantly larger than females), and Sardinian He. hippocrepis were not smaller than conspecifics inhabiting regions without Hi. viridiflavus. Overall, our study showed that the two species differed in some aspects of their ecology, but these differences could not be due to competitive interactions. The conservation implications of these results are also discussed. [ABSTRACT FROM AUTHOR]

review of several long-term studies has recently suggested that snakes might be declining in large parts of the world. Additional data from other long-term studies are therefore urgently needed in order to assess the generalities of such suggested declines. Based on a 20-year study, we analyzed demographic data on adult dice snakes ( Natrix tessellata) studied in central Italy between 1985 and 2004. Both male and female dice snakes were relatively long-lived, with no significant differences in longevity between the sexes. Individual males and females were observed over a maximum of 10 and 14 years, respectively. However, the among-year recapture rates between the year the snakes were initially captured and the subsequent year (i.e., year 1 to year 2) was significantly lower (45%) than the among-year recapture rates during subsequent years (74%; i.e., year 2 to year 3), suggesting that a large proportion of the snakes at first capture were in fact not resident within our study area, and hence many snakes were migrating in and out of our 2-km stream study site, with no inter-sexual difference in dispersal rates. Sex ratio was virtually equal if we consider the study period as a whole. Significant annual fluctuations were, however, observed through the study. In 1985-1990, 1993-1995, 1998 and 1999 the sex ratio was male-biased, whereas in 2000-2004 female-biased. In terms of both survival and recapture probabilities, model selection showed that Akaike's information criterion favored the model incorporating body size, with the model incorporating year having an intermediate likelihood, and the model with sex included being the most disfavored. Total population number estimates suggest an average 86 adult individuals along the 2 km of stream with only minor annual variations. However, a significant decrease in the number of males occurred during the last 6 years of our study. Thus, further monitoring of this population is warranted in light of the decline of snake populations reported recently. [ABSTRACT FROM AUTHOR]

We examined the guild structure of geckos at a farmbush–rainforest mosaic area in southern Nigeria, during three independent survey periods (i.e. dry season of 1997, 2001, and 2005). We used several simulation descriptors ( C value, V ratio, number of checkerboard species pairs, number of species combinations), generated by Monte Carlo methods, to contrast the actual data matrix with the randomly generated data matrix. We calculated the relative availability and use by species of habitat types and microhabitat types at each of these survey periods and also studied temporal niche aspects. We found that our gecko guild was composed of six species, including native forest specialists as well as native habitat generalists and exotic species linked to human-made habitats. Monte Carlo simulations revealed the occurrence of a structure in the guild under study with regard to habitat type but not with regard to (a) two types of microhabitat uses (i.e. perch height and size of trees) and (b) daily time. The use of simulation analyses also demonstrated that the various species that were similar in terms of habitat use partitioned their microhabitat niche, reducing potential interspecific competition. On the other hand, those species that were clearly separated with regard to habitat type readily frequented the same microhabitats within different habitat types. [ABSTRACT FROM AUTHOR]