Biogeography de madagascar pdf

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biogeography de madagascar pdf

A necessarily complex model to explain the biogeography of the amphibians and reptiles of Madagascar. Jason L. Brown;, Alison Cameron. Has Vicariance or Dispersal. Been the Predominant. Biogeographic Force in. Madagascar? Only Time. Will Tell. Anne D. Yoder and Michael D. Nowak. (), the biogeography of the scorpions of Madagascar has been a complex suggesting that the present representatives of the Madagascar scorpion fauna. Biogeographic Evolution of Madagascar's Microendemic Biota. Lucienne Wilmé1 ,; Steven M. Article; Figures & Data; Info & Metrics; eLetters; PDF. Loading.

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Biogeography de madagascar pdf Nature Communications menu. Science74—78 Specifically, this spatial scale was chosen so that we calculated a landscape-level measure of endemism versus fine-scale regional differences. The major areas of endemism obtained in a 4-class categorization of the originally continuous GDM results Fig. Ecography 3346—50
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IL PIANETA DELLE SCIMMIE 2001 STREAMING VIDEOWEED Moreover, carefully parameterized species distribution models can generate accurate estimates of species ranges 14 and novel, more objective, approaches are being developed to translate patterns of species richness, endemism and turnover for determining those biogeographic regions in greatest need for conservation and protection 2781516 Modifying the t test biogeography de madagascar pdf assessing the correlation between two spatial processes. Response variables: To address this, we randomly sampled 2, points throughout Madagascar from a ca. Climate stability:

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A Nature Research Journal. Pattern and process are inextricably linked in biogeographic analyses, though biogeography de madagascar pdf can observe pattern, we must infer process. Inferences of process are often based on ad hoc comparisons using a single spatial predictor.

Here, we present an alternative approach that uses mixed-spatial models to measure the predictive potential of combinations of hypotheses. Biodiversity patterns are estimated from 8, occurrence records from species of Malagasy amphibians and reptiles. By incorporating 18 spatially explicit predictions biogeography de madagascar pdf 12 major biogeographic hypotheses, we show that mixed models greatly improve our ability to explain the observed biodiversity patterns.

We conclude that patterns are influenced by a combination of diversification processes rather than by a single predominant mechanism. Interpreting the spatial distribution of biodiversity is fundamental to the study of biogeography, macroecology, evolutionary biology and conservation biology 12. Core concepts include local and regional endemism, species richness, and species turnover, of which the two latter correspond to alpha- and beta-diversity as used in big size bebe cool able ecology 34.

Thus, we frequently oversimplify the dynamic and complex interactions among organisms and their environment. Accordingly, it is the default expectation that equivalent barriers for example, rivers, ecotones, climatic transitions will lead to congruent patterns of species endemism, turnover and richness — again, with the underlying assumption that the observation of similar patterns among diverse species reveals a general causal mechanism of diversification across all taxa.

However, there are additional processes by which species richness may be generated that can act in concert with or in opposition biogeography de madagascar pdf biogeographic barriers. For example, climatic factors, environmental stability, land area, habitat heterogeneity, palaeogeography and energy available can be spatially correlated with these barriers but not causally related to diversification Although it seems obvious that such patterns are caused by multiple mechanisms, biogeography researchers often rely on ad hoc and narrative comparisons with spatial distributions of single environmental variables such as centres of historical habitat stability 13climate, topography, vegetation or other assumed barriers to dispersal in searching for an assumed prevalent explanatory factor.

Methodological advances are being developed to address the problems of non-uniformity and non-independence. For example, assessments of spatial biodiversity have typically used simple geographic measures as the unit of analysis, such as the distribution range of individual species, though recent methodological refinements include the integration of phylogenetic relationships among species and their evolutionary age 27.

Moreover, carefully parameterized species distribution models can generate accurate estimates of species ranges 14 and novel, more objective, approaches are being developed to translate patterns of species richness, endemism and turnover for determining those biogeographic regions in greatest need for conservation and protection 2781516 Although biological explanation of these patterns biogeography de madagascar pdf still in its methodological infancy, considerable recent development of conceptual and statistical tools now allows for integrative multivariate approaches to more realistically estimate underlying processes.

This megadiverse microcontinent, initially part of Gondwana, has been isolated from other continents since the Mesozoic. Its current vertebrate fauna is a mix of only a few ancient Gondwanan clades and numerous younger radiations, originating from Cenozoic overseas colonizers arriving mainly from Africa 1920 The extraordinary proportion of family-level endemism in Madagascar, and the long isolation from non-Malagasy sister lineages, provide a unique opportunity to study the mechanisms driving divergence and diversification in situ Over the past decade, numerous mechanisms and models have been formulated to explain biodiversity distribution patterns and species diversification in Madagascar, pertaining to environmental stability or instabilitysolar energy input, geographic vicariance triggered by topographic or habitat complexity, intrinsic traits of organisms or stochastic effects 2324252627282930 Evidence has supported numerous hypotheses, though this evidence has typically been marshalled from limited taxa or groups of taxa with restricted phylogenetic diversity.

Moreover, comprehensive statistical approaches comparing their relative importance are rare We apply an integrative approach to simultaneously test which of the several competing and complementary hypotheses are most strongly correlated with empirical biodiversity patterns Fig. We first translate a total of 12 diversification mechanisms or diversity models into explicit spatial representations.

Our results best agree with the hypothesis that various assemblages of species are under the influence of differing causal mechanisms, and that the distribution of diverse organismal lineages will depend on idiosyncratic factors determined by their specific organismal life-histories combined with stochastic historical factors. Thus, any model that endeavors to explain island-wide patterns must necessarily be complex.

Three types of original data were input into the analyses: These data were used to predict the distributions of species, and the distribution models were used to calculate biogeography de madagascar pdf patterns species richness, corrected weighted endemism and turnover. We then tested for the correlation of these biodiversity patterns with spatial biogeography de madagascar pdf derived from biogeography hypotheses, and used a mixed model to simultaneously test the influences of these hypotheses on the biodiversity patterns.

Species richness is highest in the eastern rainforest for both groups Fig. Spatial patterns of endemism in both groups Fig. Endemism values for reptiles are also high in southwestern Madagascar, symbian sisx application for nokia e63 mobile most arid region of the island. Reptile species richness a and endemism b.

Amphibian species richness c and endemism d. Species richness measures the number of species present. Endemism standardized by the local species richness and reflects the proportion of unique species present within certain areas.

The GDM analyzes compositional turnover of communities biogeography de madagascar pdf jointly for amphibians and reptiles and predicts dissimilarity throughout the landscape based on biogeography de madagascar pdf interpolation of variation in climate and geographic data.

This map depicts a continuous landscape where community similarity is analogous to colour space distance and the more similar colours characterize similar communities. We applied Generalized Dissimilarity Modelling GDM 3334 to identify areas of endemism on the basis of turnover patterns for reptiles and amphibians together. The GDM model captured The top climatic predictors of species turnover and percent of contribution to model were: The major areas of endemism obtained in a 4-class categorization of the originally continuous GDM results Fig.

Our test includes a total ebook pdf marathi jokes 12 predictor hypotheses, some of which focus on the geographical pattern in which species diversity is distributed, but without making any clear assumption about how the species originated for example, the Mid-domain or Topographic Heterogeneity hypotheses. Others explicitly refer to mechanisms of diversification and make predictions about how these processes affected the distribution of species diversity biogeography de madagascar pdf geographical space 36 see Supplementary Methods and Supplementary Table 1 for detailed accounts.

We divided the hypotheses into two categories: The first category includes: The second category includes climate gradient also depicted as a continuous hypothesisRiverine Barrier minor and major riversRiver-Refuge and Watershed. All these hypotheses were transformed into explicit spatial representations Supplementary Note 1Supplemental Data 1 and 2 and used as predictor variables for further analyses.

We calculated unbiased correlation of the continuous predictor and test variables following the method of Dutilleul 37which reduces the degrees of freedom according to the level of spatial autocorrelation between two variables Biogeography de madagascar pdf Table 2.

Measures of reptile and amphibian endemism were both significantly correlated with the Topographic Heterogeneity and Museum hypotheses. Correlations with biogeography de madagascar pdf richness were not tied to measures of endemism. Whereas reptile and amphibian species richness both correlate with the Sanctuary and Museum hypotheses, the reptiles uniquely correlate with the Mid-domain Effect distanceand amphibians uniquely with the Topographic Heterogeneity, Montane Species Pump, Disturbance Vicariance and River-Refuge hypotheses.

In the univariate correlation analyses Table 1we compared the biogeographic zonation of Madagascar as suggested by the GDM analysis of amphibian and reptile distributions Fig. We found biogeography de madagascar pdf predictor variables corresponding to the two Riverine hypotheses and the Gradient hypothesis to be significantly correlated with both the and 4-class GDMs. Only the Watershed hypothesis was not correlated with either classification of the GDM.

Both GDM classifications share the most overlap with the Gradient and the two Riverine hypotheses Given the significant correlation of each of the spatial amphibian and reptile biodiversity patterns with various predictor variables, we used mixed conditional autoregressive spatial models CAR models to test the influences of various predictors simultaneously Supplementary Fig. To avoid over-parameterization, we used AICc corrected Akaike Information Criterionan information-theoretical approach, to compare models with different sets of predictors.

We found that complex models including most of the biogeography hypotheses that were representable as continuous predictor variables performed best, based on the lowest AICc values and consequently used these for further analysis. Detailed contributions of each predictor to the models of species richness, endemism and GDM zonation are summarized in Supplementary Table biogeography de madagascar pdf. The top-five variables contributed For a more simplified graphical representation Fig.

We found relevant influences of the Mid-domain Effect especially on the GDM, and on the species richness and endemism of reptiles However, it is important to point out that almost all the Mid-domain correlation coefficients were negative.

Thus, indicating that factors biogeography de madagascar pdf spatial patterning were those inversely correlated with latitudinal and longitudinal Mid-domain Effects, that is, favouring endemism and richness at the edges rather than centre of the domain. Climate Gradient effects influenced all the models of biodiversity equally, contributing roughly a quarter to each However, in this case, a positive correlation was not expected.

The topography variables contributed positively to the richness and endemism models of amphibians and reptiles, with joint influences of 9.

The Sanctuary and Museum hypotheses each contributed positively to all models, with Museum contributing between 7. The Sanctuary hypothesis also contributed positively to all mixed models, though to a lesser degree than the Museum hypothesis, and with a very low contribution to reptile endemism.

Pie charts correspond to biogeography de madagascar pdf of response variables in each biodiversity model starting at left, clockwise: The included response variables are numbered within each coloured group as follows: Climate gradient: PC1, II. PC2, III.

Climate stability: Precipitation stability, II. Climate stability temperature and precipitation. Topographic Heterogeneity, II. Disturbance Vicariance, III. Montane Species Pump. For all hypotheses except for the climate-gradient variablesa positive correlation was expected between biodiversity metrics.

Pie charts on top row and bottom correspond to contribution of response variables in modeling species richness and endemism, respectively. Response variables: Climate Gradient: Climate Stability: Precipitation Stability, II. Climate Stability temperature and precipitation. The four focal groups: For all hypotheses with exception to the climate-gradient variablesa positive correlation was expected between biodiversity metrics. To assess variation in biogeography patterns among major groups of the Malagasy herpetofauna, we calculated mixed CAR models using the same methods for richness and endemism of four exemplar sub-clades: The top contributors to the models were drastically different for several of these clades Fig.

For instance, the topography variables had strong influences on Boophis richness, with a joint contribution of

biogeography de madagascar pdf

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