Species-area Relationship of Herpetofaunas in West Indies

Species- ara Relationship of Herpetofaunas in western IndiesDe Gao1. Introduction1.1. Biodiversity and crisis on West IndiesOceanic islands, due to their discrete geographic isolation, differ down the stairsstandably from terrestrialecosystem, offer great opportunities for species conservation, and argon regarded as the naturallaboratory for the study of biogeography and evolutionary ecology (Adsersen, 1995 Crawfordand Stuessy, 1997 Ricklefs and Bermingham, 2008). Island home ground heterogeneity and the geneflow prohibition between the island and its neighboring islands or land are the most important drivingforces leading to new species variantiation and formation (Cherry et al. 2002). The colonizedspecies from continents or close islands are then subjected to unique evolutionary processes,for example, geographic isolation, character displacement, and adaptive radiation. Theaccumulated mutations gradually and ultimately make colonized species into new indigenousspecies that a re genetically different from the original one. One of the most distinctive features ofthe biota on oceanic islands is the large number of endemics occurring in small areas (Francisco-Ortega et al. 2000).West Indies was identify as a biodiversity hotspot by Myers et al. (2000). A significantpercentage of the Earths known terrestrial biota is distributed on islands of the West Indies, some(prenominal) of these species are endemic to the region, to individual islands, and even to isolated areas deep down some islands (Hedges, 2001). But a large majority of the vast complex of islands in WestIndies is changing rapidly, resulting in dramatic alterations of habitats, and nearly all of them aremediated by human activities (Powell and Henderson, 2012). Small population size, gene drift,isolated gene flow, and the complexness of island environment have already made the endemicherpetofaunal species easy to be endangered or extinct, human disturbances undoubtedly worsenthe situation. Therefor e, critical conservation concerns in West Indian region are increasinglyimportant and required.1.2. Species-area relationship (SAR)The species-area relationship is one of the most fundamental patterns in macroecology and animportant tool in assessing species diversity, extinction rates and species hotspots (Tjrve, 2009).According to the equilibrium theory (MacArthur and Wilson, 1967), the relationship betweenimmigration and the extinction of species to island depends on the island size and its distance tomainland. MacArthur-Wilsons theory provided trend for numerous studies on species-arearelationships (SARs) that have provided biological interpretations for several taxa and havesuggested factors and mechanisms that can find oneself species richness (Simaiakis et al. 2012).And the theory has an enormous influence on perspectives of species conservation and temperreserves design.The main objective of this chapter is to discuss SARs for herpetofaunas in West Indies regions,with the aim of discover which factors may determine their distribution over the whole paradigm ofisland sizes. We choose to barrack some candidate models including the power model and some sigmoid models to see whether a J- occasiond part exists at the lower end of the curve. Small-island marrow (SIE) holds that, on islands smaller than a certain critical minimum area, one cannotobserve an increase in species number with increasing area (Simaiakis et al. 2012). We choose tofit candidate models including the power model and some sigmoid models to see whether a J-shaped part exists at the lower end of the curve. If the best fitted model has a sigmoid shape, a J-shaped part ordain exist at the lower end, and then we accept SIE. If the best fitted model has aconvex shape, a J-shaped part will not exist at the lower end, and then we deny SIE. There arealso other reasons why it is so important to know the shape of species-area curve. Based on thecurve shape, we could estimate total species di versity from limited numbers of samples, orestimate species extinction as a result of habitat loss and fragmentation (Tjrve, 2003).Candidate species-area models are proposed from two sources. The first source is species-arealiterature which has traditionally fit data with power or exponential models, the minute of arc sourceinvolves a broader search of the literature for models that increased monotonically to anasymptote (Flather, 1996).Although the shape of the curve has been extensively debated over the years, power andexponential curves are the most commonly use and best known ones, lately, an increasingnumber of authors have argued some SARs are perhaps best represented by functions that aresigmoid in arithmetic space and there are also a number of recent studies where sigmoid modelshave been fitted to empirical data (Tjrve, 2003). Some sigmoid models play similar withothers, for instance, the Extreme value function behaves quite similar to the Logistic andGompertz models The Cumulative beta-P distribution behaves similarly to the Weibulldistribution (Tjrve, 2003).2. bringsIn this study, we are trying to act upon 3 questionsQuestion 1 What is the species-area relationship (SAR) for herpetofaunas in West Indies? Is theSAR same for native and invasive species? And is it the same among each animal groupclassification under amphibian and reptile?Question 2 Due to humans help, invasive species are supposed to have a higher dispersal qualification as compared to the native. So, in the linear form of the power model (LogS/LogA) is therea higher z-value for the invasive species than the native species?Question 3 What geographic factors may determine species richness over the whole range ofisland sizes? Are these factors also applicable to other group of islands that located in similarlatitude areas to determine their species richness?3. Material and MethodsData on species occurrences originate from Powell and Henderson (2012). Multiple basemaps inArcMap 10 and ArcGlobe 10 will be apply to digitize islands map. We use different scales todigitize islands with various areas. Fractal Analysis will be used to estimate the perimeters at auniform scale (Farina, 2007). For comparisons of the fit of different models, the Akaikes teaching criterion (AIC) was applied (Burnham and Anderson, 2002). Model selectionanalyses will run using mmSAR package (Guilhaumon et al. 2010) for the R statistical andprogramming environment (R Development Core Team, 2011).Aim 1 Model selectionwe use the 8 most general models composed in mmSAR package (Guilhaumon et al. 2010) tofit the data, which include 5 convex models (Power, Exponential, minus exponential, Monod,Rational function) and 3 sigmoid models (Logistic, Lomolino, Cumulative Weibull).Aim 2 LogS/LogA linear regressionWe analyze the linear function of the LogS/LogA and compare parameter values with vertebratesfrom spherical oceanic islands (Triantis et al. 2012).Aim 3 Find out the geographic factors affect species richness/StepsInitially selected variables areX1 Distance to mainlandX2 Latitude of island centroidX3 Longitude of island centroidX4 Island No. within 0.1kmX5 Island No. within 0.1-1kmX6 Island No. within 1-5kmX7 Island No. within 5-10kmX8 Islands ambit within 0.1kmX9 Islands Area within 0.1-1kmX10 Islands Area within 1-5kmX11 Islands Area within 5-10kmX12 Area of the islandX13 Perimeter of the islandX14 Perimeter/AreaX15 Percentage of vegetationX16 Percentage of human areaX17 Rivers within the islandX18 Invasive spp. within the islandX19 Percentage of invasive spp.X1 and X3 are used to canvass species dispersal from mainland X2 is used to examine thenearness to equator X4, X5, X6, X7 are used to examine stepping stones in each loop circle X8,X9, X10, X11 are used to examine total area of stepping stones in each loop circle X12 is used to examine area effect X13 and X14 are used to examine shape (irregularity) of island X15,X17 are used to examine habitat quality X16, X18 , X19 are used to examine human disturbanceand invasive species.Principal Component Analysis and Hierarchical section Analysis will be made based on theresiduals distribution of LogS/LogA linear regression to examine which geographic factors arethe significant contributions of species richness in West Indies.