Modelling and spatial discrimination of small mammal assemblages: An example from western Sichuan (China)

Abstract

We investigate the relationship between landscape heterogeneity and the spatial distribution of small mammals in two areas of Western Sichuan, China. Given a large diversity of species trapped within a large number of habitats, we first classified small mammal assemblages and then modelled the habitat of each in the space of quantitative environmental descriptors. Our original two step "classify then model" procedure is appropriate for the frequently encountered study scenario: trapping data collected in remote areas with sampling guided by expert field knowledge.In the classification step, we defined assemblages by grouping sites of similar species composition and relative densities using an expert-class-merging procedure which reduced redundancy in the habitat factor used within a multinomial logistic regression predicting species trapping probabilities. Assemblages were thus defined as mixtures of small mammal frequency distributions in discrete groups of sampled sites.In the modelling step, assemblages' habitats and environments of the two sampled areas were discriminated in the space of remotely sensed environmental descriptors. First, we compared the discrimination of assemblage/study areas by linear and non-linear forms of Discriminant Analysis (Linear Discriminant Analysis versus Mixture Discriminant Analysis) and of Multiple Regression (Generalized Linear Models versus Multiple Adaptive Regression Splines). The "best" predictive modelling technique was then used to quantify the contribution of each environmental variable in discriminations of assemblages and areas.Mixtures of Gaussians provided a more efficient model of assemblage coverage in environmental space than a single Gaussian cluster model. However, non-linearity in assemblage response to

Transmission ecosystems ofEchinococcus multilocularisin China and Central Asia

“…The hotspots described above were all located in areas with an actual or potential larger percentage of grassland (Giraudoux et al 1998, 2003, 2013; Raoul et al 2006; Vaniscotte et al 2009). Furthermore, four major communities of small mammals can be identified in those areas which characterize a transmission system (Fig.…”

“…(2006)). It is probable that the small mammal survey we conducted in this area was carried out during a transitory low density phase of small mammal population fluctuation (Vaniscotte et al 2009). However, Rangtang is in the vicinity of a larger scale region where small mammal population densities were higher, and the exposure of Tibetan nomads travelling on the plateau may explain the unexpectedly large human AE prevalence we observed there.…”

Latitudinal Geographical Variation of External and Cranial Measurements inApodemus peninsulae,A. draco, andA. latronum

“…Referring reports on the segregation of their habitats between the two species, A. peninsulae lives in forests or shrub land as well as grassland or farmland in small numbers, while A. draco occupies only forests in Zhang Xiang (around 34°N/104°E: 2,300-2,500 m), southern Gansu (Giraudoux et al 1998 (Vaniscotte et al 2009). Using the same specimens collected by Giraudoux et al (1998Giraudoux et al ( , 2008 and Vaniscotte et al (2009), Ledevin et al (2012 examined character displacement by morphological distance of body sizes (HBL, mandibular size, and the area of first upper molar) between five species of Apodemus (agrarius, uralensis, peninsulae, draco, and latronum) in allopatry versus in sympatry in these localities. However, unfortunately, they sorted out these specimens not by localities with habitats but only by localities, and did not compare the distance of a pair between A. peninsulae and A. draco.…”

“…First, A. sylvaticus inhabits dense woodland as well as open moors with scattered shrubs (Corbet 1966), but A. draco lives not in open fields but in forests (Giraudoux et al 1998;Vaniscotte et al 2009). Second, the distribution of A. sylvaticus is overlapping with that of A. flavicollis in western Europe (Corbet 1966;Niethammer 1978aNiethammer , 1978b, whereas the distribution range of A. draco overlaps partly with A. peninsulae and/or A. latronum in southwestern China as well as northern Myanmar ).…”

“…Apodemus latronum is confined in southwestern China (Qinghai, Sichuan, Yunnan, and eastern Xizang) and northern Myanmar. Additionally, the three species were sometimes collected together in the same locality Giraudoux et al 1998;Vaniscotte et al 2009;.…”