Small mammal assemblages in fragmented shrublands of urban areas of Central Chile

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(1)Urban Ecosyst (2013) 16:377–387 DOI 10.1007/s11252-012-0272-1. Small mammal assemblages in fragmented shrublands of urban areas of Central Chile Ignacio C. Fernández & Javier A. Simonetti. Published online: 25 October 2012 # Springer Science+Business Media New York 2012. Abstract Mediterranean-type ecosystems are one of the most affected environments by habitat loss and fragmentation due to urban development, however only few studies have evaluated the effects of urbanization on the biodiversity of remnant fragments in these ecosystems. This study aims to evaluate the effects of urban development over small mammal assemblages inhabiting isolated forest fragments of an urban area of Chilean Mediterranean zone. We compared abundance and richness of small mammal assemblages of six remnant fragments within an urban matrix, and six fragments similar in area and habitat characteristics with those of urban area, but surrounded by a rural matrix. We found that small mammal assemblages differ considerably among fragments types (urban vs rural), with lack of endemic species from urban fragments and with high proportion of introduced rodents in urban fragments. Furthermore abundance of small mammals was higher in rural than in urban fragments. In urban areas small mammal abundance and richness were not correlated with any of the explanatory variables assessed (woody cover, flora heterogeneity, fragment area, perimeter/area ratio). However in rural fragments small mammal richness was negatively correlated with flora heterogeneity and the abundance of small mammals was positively correlated with perimeter/area ratio. These results reveal important differences within the effects of fragmentation over small mammal assemblages among the two types of fragments assessed. Our findings suggest that in forest fragments isolated by urbanization, larger areas with good quality habitats are not sufficient to maintain native small mammal population. Keywords Habitat fragmentation . Urbanization . Vegetation remnants . Mediterranean ecosystems . Species invasion . Urban ecology. I. C. Fernández (*) Departamento de Ecosistemas y Medio Ambiente, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Casilla 306, Santiago, Chile e-mail: ifernanc@uc.cl J. A. Simonetti Departamento de Ciencias Ecológicas, Universidad de Chile, Las Palmeras 3425, Casilla 653, Santiago, Chile.

(2) 378. Urban Ecosyst (2013) 16:377–387. Introduction Loss and fragmentation of natural habitats are one of the most important drivers of the current rate of species extinction (Tilman et al. 1994). The expansion of land use that accompanies human population growth, including urban development, has led to a steady loss and fragmentation of natural habitats throughout the world (Ellis et al. 2010). In 1900, only 9 % of the world’s human population lived in urban areas, increasing to 50 % by 2000, and is expected to be greater than 66 % by 2025 (McIntyre et al. 2000). The conversion of land for urban development has divided wild habitats into small fragments, isolated by a matrix of inhospitable land uses such as paved roads and housing facilities. This negatively impinges biodiversity by decreasing connectivity and increasing mortality rate, among other factors (Sauvajot et al. 1998; Cavia et al. 2009). Urban development and related human activities have significantly affected Mediterranean-type ecosystems, which are regarded as one of the five most disturbed biomes in the world (Hannah et al. 1995). These ecosystems occur between 31° and 40° north and south of the Equator, and are characterized by warm wet winters and hot dry summers (Vogiatzakis et al. 2006). The five Mediterranean-climate regions of the world (Mediterranean Basin, Central Chile, the Cape Region of South Africa, Southwestern Australia, and parts of California) collectively cover less than 5 % of the Earth's land surface, yet they harbor 20 % of the world’s flora and have exceptionality high rates of endemic flora and fauna (Cowling et al. 1996). Despite their importance for world biodiversity conservation, few studies have evaluated the effects of urbanization and related habitat fragmentation upon the biodiversity of Mediterranean-type ecosystems (Klausmeyer and Shaw 2009). These studies have largely focused on California, the Mediterranean Basin, and south-western Australia (e.g. Soulé et al. 1992; Bolger et al. 1997; Gibb and Hochuli 2002; Crooks et al. 2004), but the impacts of urbanization upon the biota in Mediterranean ecosystems of South Africa and Chile have scarcely been addressed. The Chilean Mediterranean zone harbors more than 80 % of the country’s urban residents. This ecosystem covers around 16 % of the Chilean continental territory, but is home to approximately 50 % of Chile’s vertebrate species, 50 % of the Chilean endemics and over 50 % of the endangered vertebrates, and is regarded as one of the 34 Biodiversity hot-spots of the world (Simonetti 1999; Arroyo et al. 2004). Urban sprawl has fragmented vast expanses of natural habitats, and remnant fragments are threatened by current urban growth rates (Romero and Vásquez 2005). However, no studies have evaluated biodiversity in forest remnants of urban areas of the Mediterranean-type ecosystems in Chile, generating a crucial information gap for developing management strategies for the biota associated with these habitats fragments. Small mammal assemblages may be particularly important in elucidating changes in biodiversity in fragmented forests. Small mammals can play a key role influencing vegetation dynamics (e.g. Gutierrez et al. 1997), and may have strong influences on the presence of a wide array of wildlife, either through competitive interactions or by serving as the prey base for carnivorous species, which are often of greater conservation concern (e.g., Ekernas and Mertes 2006). The persistence of small mammals within fragments will depend on factors such as the area and shape of the remaining fragments and the quality of the surrounding matrix as dispersal habitat (Bierwagen 2007). Furthermore the presence of small mammals in urban remnants might also have implications for human health, as many diseases (such as Hantavirus) are associated with their presence (Torres-Perez et al. 2004). Therefore, understanding changes in.

(3) Urban Ecosyst (2013) 16:377–387. 379. richness and abundance of small mammals in urban remnants may contribute to the development of management strategies for biodiversity conservation in urban areas, as well as to develop plans to avoid potential zoonotic risks. In this study we assessed the small mammal assemblages in forest remnants in urban settings of Santiago de Chile. We compared the richness and abundance of small mammals between remnant fragments surrounded by an urban matrix, and fragments similar in area and habitat characteristics surrounded by a rural matrix. First, to determine whether the effects of fragmentation over small mammal assemblages are dependent on the surrounding matrix, we tested two hypotheses: (1) fragments located in a rural matrix will contain higher richness and abundance of small mammal species than fragments surrounded by urban settings; (2) the proportion of invasive species will be higher in fragments surrounded by urban matrix than those located in a rural setting. Second, we evaluated if (1) abundance and richness of small mammals is positively related to woody vegetation cover and floristic heterogeneity and, (2) if abundance and richness of small mammals is positively related to fragment area and negatively related to perimeter/area ratio (fragment shape index).. Materials and methods Study area The study was carried out on the northeast area of Santiago de Chile (33°20′S-70°32′W), in a residential zone named “La Dehesa” and in a contiguous rural area located at 10 km. to the northwest (Fig. 1). The climate is Mediterranean (with a long dry season) with a mean annual temperature of 13.9 °C, ranging from 22.1 °C in January to 7.7 °C in July. The mean annual precipitation is 356.2 mm. with approximately 80 % of the precipitation taking place in winter months (Rojas et al. 2004). La Dehesa is a relatively new residential zone (less than 30 years old) composed mainly of low density housing, parks, golf courses and forest fragments embedded in the urban landscape. The rural landscape is mainly composed of remnant fragments located in hill tops and riparian areas immersed in a shrub matrix degraded by historical clearance for timber, charcoal and pastures. Currently these fragments are threatened by high development rates of new residential zones (Romero and Vásquez 2005). The original vegetation in both areas is sclerophyllous vegetation, with a predominance of shrub individuals in east, west and equatorial slopes, and a mixture of shrubs and trees in polar-facing slopes (Arroyo et al. 2004). Selection of fragments Small mammal sampling was carried out in 12 fragments, all of them located on polar-facing slopes, half of them in urban areas and the other half in rural ones. Fragments were selected using satellite images on the basis of their area and vegetation cover, in order to have fragments of similar characteristic (Table 1). Two types of fragments were distinguished depending on the surrounding matrix: (1) urban: remnant fragments of native vegetation surrounded in their entire perimeter by urban infrastructure (roads, housing, commercial facilities), and (2) rural: fragments of native vegetation surrounded in all their perimeter by highly degraded shrub community conformed almost entirely by sparse Acacia caven (espino) individuals, and that are at least at one km from an urbanized area. All fragments were at least at 0.5 km from a non-fragmented habitat..

(4) 380. Urban Ecosyst (2013) 16:377–387. Fig. 1 Study area in Central Chile. Grey surface is the current urban area of Santiago de Chile Table 1 Habitat attributes of fragments. Urban and Rural represent the matrix type surrounding the fragment. The four variables shown represent respectively: log. area in hectares; perimeter/area ratio; percentage of fragment area covered by woody vegetation; average number of woody species present in vegetation transects Fragment. Log area. Perimeter/area. Vegetation cover. Flora heterogeneity. Urban 1. 0.155. 0.038. 0.830. 6.250. Urban 2. 0.609. 0.027. 0.938. 5.750. Urban 3. 0.766. 0.033. 0.849. 4.750. Urban 4. 1.135. 0.021. 0.754. 4.750. Urban 5. 1.754. 0.009. 0.742. 4.500. Urban 6. 1.758. 0.008. 0.556. 4.000. mean (S.E.). 1.029 (0.263). 0.023 (0.005). 0.778 (0.053). 5.000 (0.342). Rural 1 Rural 2. 0.093 0.635. 0.042 0.034. 0.898 0.561. 5.250 3.750. Rural 3. 0.863. 0.037. 0.700. 4.750. Rural 4. 1.061. 0.015. 0.579. 2.250. Rural 5. 1.625. 0.009. 0.634. 4.250. Rural 6. 1.732. 0.019. 0.838. 5.500. mean (S.E.). 1.001 (0.252). 0.026 (0.005). 0.702 (0.057). 4.292 (0.485).

(5) Urban Ecosyst (2013) 16:377–387. 381. Explanatory variables We assessed four explanatory variables: area, perimeter/area ratio, woody cover (percent of surface covered by the canopy of trees and/or shrubs), and floristic heterogeneity of forest remnants (Table 1). The fragment’s area and perimeter were calculated from satellite images via Google-Earth-Pro™ GIS tools (available at http://www.google.com/intl/en/earth/businesses). Woody vegetation cover was estimated through line interception method (Eberhardt 1978), with four 50 m’s transects randomly placed in each fragment. Floristic heterogeneity was estimated as the mean number of tree and shrub species present in transects. Small mammal sampling Small mammal richness and abundance were assessed through live captures using Sherman traps. Traps were placed in one transect per fragment. Each transect consisted of 18 double stations (pair of traps) separated by 10 m. Transects were positioned in a disposition that maximizes the distance to the fragment borders. In 2007, three capture sessions (September, October–November and December) of four nights, were conducted for each site, totaling 5,184 trap/nights throughout the study. Captured individuals were identified to species level, individually marked and released at the capture site. We used direct enumeration estimates of small mammal abundance as no assumption of homogeneity of recapture probabilities is required (Simonetti 1986). Results Fragment vegetation Total woody cover was similar in the two habitat types (two tailed t-test; p00.35). Vegetation cover ranged from 56.1 % to 89.8 % in rural fragments, and from 55.6 % to 93.8 % in urban fragments (Table 1). The most frequent species in both fragment types were one endemic tree, Quillaja saponaria (quillay), and two endemic shrub, Lithrea caustica (litre) and Colliguaja odorifera (colliguay). These three species accounted for 68.74 % of relative cover in urban sites, and 72.03 % in rural sites (Table 2). Urban remnants presented higher vegetation richness than rural fragments. While urban fragments harbored a total of 26 species, 16 were found in rural sites. More than half of the plant species recorded in urban fragments were present only in one fragment, and in most cases were represented by only one individual (Table 2). A total of five exotic plant species were found, all of them in urban fragments. The exotic species accounted for 11.85 % of vegetation cover in urban fragments. Rubus ulmifolius (zarzamora) was the most frequent and abundant exotic species, occurring at three out of six urban fragments and accounting for 9.11 % of vegetation cover. Small mammal composition A total of eight small mammal species were recorded, including five species of native rodents, two of them endemics, two introduced rodent species and one endemic marsupial. Six out of these eight species occurred in rural fragments and five were present in urban fragments. Assemblage richness ranged from 1 to 6 species in rural fragments, and from 0 to 4 species in urban fragments, with no captures in two urban fragments (Table 3)..

(6) 382. Urban Ecosyst (2013) 16:377–387. Table 2 Presence and relative coverage of woody species in urban and rural fragments Urban. Rural. NFS. Coverage. NFS. Coverage. Lithraea caustica. 6. 33.05%. 6. 25.88%. Quillaja saponaria. 4. 20.52%. 5. 11.74%. Colliguja odorifera. 4. 15.17%. 5. 34.41%. Rubus ulmifoliusa. 3. 9.11%. np. Acacia caven. 4. 4.84%. 4. Cestrum palqui. 6. 4.52%. 3. Azara dentata Pinus radiataa. 2 1. 4.17% 1.88%. np np. 0% 0%. Baccharis empetrifolia. 1. 1.80%. np. 0%. Kageneckia oblonga. 3. 1.49%. 3. Baccharis pingraea. 2. 0.77%. 1. Salix babylonicaa. 1. 0.39%. np. 0%. Tristerix sp.. 1. 0.27%. np. 0%. Talguenea quinquinervia. 1. 0.27%. np. 0%. Salix humboldtianaa Podanthus mitique. 1 1. 0.26% 0.24%. np 3. 0% 0.67%. Populus nigraa. 1. 0.21%. np. 0%. Colletia spinosissima. 1. 0.21%. np. 0%. Azara celastrina. 1. 0.17%. np. 0%. Trevoa quinquinervia. 1. 0.17%. 1. Berberis chilensis. 1. 0.13%. np. 0%. Azara integrifolia. 1. 0.13%. np. 0%. Porlieria chilensis Proustia cuneifolia. 1 1. 0.13% 0.07%. 3 3. Cuscuta sp.. 1. 0.03%. np. Maitenus boaria. 1. 0.03%. 1. 0.90%. 0% 8.82% 4.33%. 2.30% 2.03%. 0.22%. 3.97% 3.08% 0%. Cissus striata. np. 0%. 1. 1.13%. Aristotelia chilensis. np. 0%. 1. 0.24%. Retanilla trinervia. np. 0%. 1. 0.21%. Escalonia illinita. np. 0%. 1. 0.08%. NFS Number of fragments where the species was present, np not present a Introduced species. Small mammal composition differed between rural and urban fragments (Morista–Horn index 0 0.35). Only three species were present in both fragment types: the two native rodents Abrothrix olivaceus (olive grass mouse) and Phyllotis darwini (Darwin’s leaf eared mouse), and the introduced Rattus rattus (black rat). Furthermore, the three endemic species present in rural fragments, Abrocoma benetti (Bennett’s chinchilla rat), Octodon degus (degu) and Thylamys elegans (mouse opposum), were absent from urban fragments, and the introduced Mus musculus (house mouse) was found only in urban fragments. The native rodent Oligoryzomys longicaudatus (long tailed mouse), which is the principal Hantavirus vector, was absent in rural fragments, but two individuals were captured in an urban fragment (Table 3)..

(7) Urban Ecosyst (2013) 16:377–387. 383. Table 3 Small mammal assemblages in assessed fragments. Small mammal numbers represent individuals captured in each fragment Small mammals species. Distribution. Individuals per fragment Urban. Rural. 1. 2. 3. 4. 5. 6. Total. 1. 2. 3. 4. 5. 6. Total. Endemic. 0. 0. 0. 0. 0. 0. 0. 0. 1. 0. 1. 3. 0. 5. Abrocoma benetti. Endemic. 0. 0. 0. 0. 0. 0. 0. 0. 1. 0. Abrothrix olivaceus. Native. 0. 0. 3. 1. 0. 0. 4. 0. 0. 0. 1. 1. 0. 3. 1. 0. 0. Oligoryzomys longicaudatus Phyllotis darwini. Native Native. 0 0. 0 0. 2 1. 0 0. 0 0. 0 0. 2 1. 0 0. 0 0. 0 1. 1. 0 17. 0 16. 0 2. 0 36. Octodon degus. Endemic. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 5. 5. 0. 10. Rattus rattus. Introduced. 0. 1. 0. 0. 0. 3. 4. 2. 6. 0. 4. 0. 2. 14. Mus musculus. Introduced. 0. 2. 1. 0. 0. 0. 3. 0. 0. 0. 0. 0. 0. 0. 0. 3. 7. 1. 0. 3. 14. 2. 8. 1. 29. 25. 4. 69. Marsupialia Thylamys elegans Rodentia. Total per fragment. Small mammal abundance A total of 83 individuals were captured. Abundance of small mammals was higher in rural than in urban fragments, with 83 % of all captures occurring in rural fragments. Abundance per fragment ranged from 1 to 29 individuals in rural fragments, and from 0 to 7 individuals in urban fragments (Table 3). Phyllotis darwini was the most abundant species in rural fragments, with 36 individuals, accounting for more than 50 % of captures. In urban fragments, only two species, the native A. olivaceus and the introduced R. rattus, reached more than three individuals (Table 3). Introduced rodents were more frequent in urban than rural zones (p<0.05 two sample proportion test). While in urban fragments 50 % of individuals captured were introduced species, in rural remnants this proportion was only 20 %. All introduced rodents captured in rural fragments were R. rattus (Table 3). Small mammal response to vegetation variables Small mammal richness and abundance were unrelated to vegetation cover or to floristic heterogeneity in urban fragments (Fig. 2). In rural fragments small mammal richness was unrelated to vegetation cover, but showed a negative relation to floristic heterogeneity (Fig. 2c, d). Small mammal abundance was not related to vegetation cover or to floristic heterogeneity in rural fragments (Fig. 2a, b). Small mammal response to spatial variables Richness and abundance of small mammal assemblages were not correlated with spatial variables in urban fragments. Neither the area (log transformed) nor the perimeter/area relation of fragments accounted for small mammal abundance and richness in urban fragments (Fig. 3). In rural fragments, small mammal abundance and richness were not.

(8) 384. Urban Ecosyst (2013) 16:377–387. small mammals response. abundance. a). b). 30. Rural: R = 0.40 (p=0.17). 25. Urban: R = 0.03 (p=0.76). 2. 2. Rural: R = 0.62 (p=0.06). 25. Urban: R = 0.06 (p=0.64). 20. 20. 15. 15. 10. 10. 5. 5. 0 50%. 70%. 80%. 2. 90%. 100%. 2. 3. 4. 5. 6. 7. d). 7. Rural: R2 = 0.51 (p=0.11) Urban: R2 = 0.13 (p=0.48). 6. 7. Rural: R2 = 0.79 (p= 0.02) Urban: R2 = 0.01 (p=0.80). 6. 5. 5. 4. 4. 3. 3. 2. 2. 1. 1. 0 50%. 2. 0 60%. c). richness. 30. 0 60%. 70%. 80%. 90%. 100%. 2. 3. vegetation cover. 4. 5. 6. 7. florístic heterogeneity independent variables. Fig. 2 Scatterplots showing relationship between small mammal abundance and richness, and vegetation cover and floristic heterogeneity. (white circle) rural, (black up-pointing triangle) urban. Linear regression coefficient (R2), p-value, and regression lines are shown. Dotted line; rural, dashed line; urban. correlated with fragment area (Fig. 3a, c). Species richness is not correlated to the perimeter/ area ratio of rural fragments, but abundance is negatively correlated to it (Fig. 3b).. a). b). 30. Rural: R2 = 0.16 (p=0.43) Urban: R2 = 0.01 (p=0.86). small mammals response. abundance. 25. 30. 20. 20. 15. 15. 10. 10. 5. 5. 0 4. 5. 6. 0 0,00. richness. c). 0,01. 0,02. 0,03. 0,04. d). 7. Rural: R = 0.13 (p=0.48). 6. Urban: R = 0.05 (p=0.68). 2. 7. Rural: R = 0.56 (p=0.09). 2. 6. Urban: R = 0.13 (p=0.48). 5. 5. 4. 4. 3. 3. 2. 2. 1. 1. 0 4. Rural: R2 = 0.65 (p<0.05) Urban: R2 = 0.06 (p=0.65). 25. 5. 6. 0 0,00. log. area. 2 2. 0,01. 0,02. 0,03. 0,04. perimeter/area independent variables. Fig. 3 Scatterplots showing relationship between small mammal abundance and richness, and log. area and perimeter/area ratio. (white circle) rural, (black up-pointing triangle) urban. Linear regression coefficient (R2), p-value, and regression lines are shown. Dotted line; rural, dashed line; urban.

(9) Urban Ecosyst (2013) 16:377–387. 385. Discussion Small mammal assemblages persisting in remnant fragments of central Chile differ depending if the surrounding matrix is urban or rural. Compared with the fragments immersed in a rural matrix, small mammal assemblages of urban fragments have smaller abundance and richness, lack endemic species, and have a significantly high proportion of invading rodents. This reveals the multiple effects that urbanization might have for wildlife habiting in remnant fragments. In fact habitat loss and fragmentation due to urban development might have significant consequences to wildlife because it results in permanent changes to the environment for which there is little chance for recovery. Furthermore, habitat loss and fragmentation due to urbanization brings with it myriad other threats to remnant habitat fragments that exacerbate impacts on biodiversity (Markovchick-Nicholls et al. 2008). The abundance of small mammals in continuous natural shrublands near to the study area (~0.05 individual/trap-night) is higher than that recorded at rural and urban fragmented landscapes (see Jaksic et al. 1981; Iriarte et al. 1989). That is twice the capture rate of rural fragments (0.026 individual/trap-night), and 10-fold higher of urban fragments (0.005 individual/trap-night). This pinpoint to a consistent reduction of small mammal population in fragmented habitats, also strengthening the difference of fragmentation effects among rural and urban fragments. Factors that may account for a lower abundance in urban fragments include higher predation pressures by pets (Soulé et al. 1992), competitive exclusion by introduced rodents (Tikhonova et al. 2006), and a hard-to-disperse matrix (Verbeylen et al. 2003; Umetsu and Pardini 2007). The abundance of native small mammals is positively correlated with shrub vegetation coverage in central Chile (Meserve 1981; Simonetti 1989; Kelt et al. 1994), however this relation did not hold for any of the two habitats assessed. This fact may be explained because of differences in the fragment’s vegetation structure. The importance of vegetation structure could be supported by the finding of a negative relation of small mammal abundance and richness with floristic heterogeneity in rural fragments. Since higher floristic heterogeneity fragments was related to the presence of shrubs (e.g. C. odorifera, L. caustica and P. chilensis) and trees (e.g. Q. saponaria and A. caven), and lower floristic heterogeneity was related mainly to the presence of shrub species, it seems that small mammals prefer fragments with a high proportion of shrub species that offer protection against predators (Simonetti 1989). The three most abundant species in urban fragments, R. rattus, A. olivaceus and M. musculus are omnivorous (Silva 2005), suggesting that urban remnants are suitable largely for species exhibiting a wide trophic niche. Furthermore, remnant fragments embedded in an urban matrix are invaded by exotic flora, which increases vegetation richness, but decreases coverage of native vegetation (Guirado et al. 2006). These changes might reduce habitat quality for small mammal composition in urban remnants, as endemic small mammals tend to occupy native vegetation areas, whereas invading rodents are suitable to occupy areas of non-native vegetation (Sauvajot et al. 1998; Umetsu and Pardini 2007). Oligoryzomys longicaudatus, the main reservoir of Hanta-virus in Chile, is normally present in natural and rural landscapes of central Chile, but not in urban areas (Torres-Pérez et al. 2004). However our results show their presence only in urban areas. Its absence in rural areas could be explained because O. longicaudatus have high demographic fluctuations, with high abundance in autumn-winter and near zero in spring-summer (the period of our captures), a time where they could move into more humid habitat, such as creeks (Kelt et al. 1994). This yearly habitat shift might also explain its presence in urban settings, where watering of residential and park vegetation might create a suitable habitat for them. Indeed,.

(10) 386. Urban Ecosyst (2013) 16:377–387. the two individuals were recorded next to a residential park, suggesting that urban fragments could offer year-round affordable resources for this zoonotic species. The lack of relationship between small mammal abundance and richness and fragment area suggests a “small island effect”, which characterizes some fragmented systems that are frequently disturbed or have limited habitat diversity (Kelt 2000), and may reflect the protracted human impacts in this region (Aschmann 1991). Furthermore, fragment shape could mask area effects, as irregularly shaped fragments have reduced proportion of suitable core habitat and may be perceived as edge rather than a suitable habitat. Indeed our results show that the perimeter/area ratio was a good predictor for fauna abundance in rural fragments, suggesting that small mammals attempt to reduce contact with the matrix, preferring simple shape fragments that maximize suitable core habitat. This is the first work evaluating the effects of fragmentation by urbanization over small mammals in Chile, so these results might be taken as a first approach to fill the currently existing gap of information in this topic, especially relating to the development of conservation strategies for urban remnants. Our work suggests that, at least at our study scale, remnants isolated-by-urbanization might not be able to support viable populations of native small mammals. If attempts are made to protect the native small mammal fauna of urban remnants, habitat management ought to consider not only fragments with greater sizes, but also their shape, vegetation structure and patch interconnections.. References Arroyo MTK, Marquet P, Marticorena C, Simonetti J, Cavieres L, Squeo F et al (2004) Chilean winter rainfall-valdivian forests. In: Mittermeier RA, Gil PR, Hoffmann M, Pilgrim J, Brooks T, Mittermeier CG et al (eds) Hotspots revisited: earth’s biologically richest and most endangered terrestrial ecoregions. CEMEX, México, pp 99–103 Aschmann H (1991) Human impact on the biota of Mediterranean-climate region of Chile and California. In: Groves RH, Castri FD (eds) Biogeography of Mediterranean Invasions. Cambridge University Press, pp 33–42 Bierwagen BG (2007) Connectivity in urbanizing landscapes: the importance of habitat configuration, urban area size, and dispersal. Urban Ecosyst 10:29–42 Bolger DT, Allison CA, Sauvajot RM, Potenza P, McCalvin C, Tran D et al (1997) Response of rodents to habitat fragmentation in Coastal Southern California. Ecol Appl 7:552–563 Cavia R, Cueto GR, Suarez OV (2009) Changes in rodent communities according to the landscape structure in an urban ecosystem. Landsc Urban Plan 90:11–19 Cowling RM, Rundel PW, Lamont BB, Kalin Arroyo M, Arianoutsou M (1996) Plant diversity in Mediterranean-climate regions. Trends Ecol Evol 11:362–366 Crooks KR, Suarez AV, Bolger DT (2004) Avian assemblages along a gradient of urbanization in a highly fragmented landscape. Biol Conserv 115:451–462 Eberhardt LL (1978) Transect methods for population studies. J Wildl Manag 42:1–31 Ekernas LS, Mertes KJ (2006) The influence of urbanization, patch size, and habitat type on small mammals communities in the New York Metropolitan Region. Wild Metro, New York Ellis EC, Klein Goldewijk K, Siebert S, Lightman D, Ramankutty N (2010) Anthropogenic transformation of the biomes, 1700 to 2000. Glob Ecol Biogeogr 19:589–606 Gibb H, Hochuli DF (2002) Habitat fragmentation in an urban environment: large and small fragments support different arthropod assemblages. Biol Conserv 106:91–100 Guirado M, Pino J, Rodà F (2006) Understorey plant species richness and composition in metropolitan forest archipelagos: effects of forest size, adjacent land use and distance to the edge. Glob Ecol Biogeogr 15:50– 62 Gutiérrez JR, Meserve PL, Herrera S, Contreras LC, Jaksic FM (1997) Effects of small mammals and vertebrate predators on vegetation in the Chilean semiarid zone. Oecologia 109:398–406 Hannah L, Carr JL, Lankerani A (1995) Human disturbance and natural habitat: a biome level analysis of a global data set. Biodivers Conserv 4:128–155.

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