Small Mammals and a Railway in the Atlantic Forest of Southern Brazil
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Edge effects without habitat fragmentation? Small mammals and a railway in the Atlantic Forest of southern Brazil R ICARDO A. S. CERBONCINI,JAMES J. ROPER and F ERNANDO C. PASSOS Abstract Edge effects have been studied extensively in frag- et al., ). Edges between different habitats were once con- mented landscapes, often with conflicting findings. Edge ef- sidered beneficial for biodiversity (Leopold, ;Lay,)but fects may also be important in other situations, such as as studies focused on anthropogenic edges (Chasko & Gates, linear clearings (e.g. along roads, power lines or train ; Harris, ) their detrimental effects became apparent. tracks). We tested for responses of small mammals to a nar- Edges are abrupt transitions between habitats or ecosystems row (c. m) linear clearing created by a railway in the lar- (Yahner, ;Riesetal.,) and their effects include any gest area of Atlantic Forest in southern Brazil. Only two changes that occur as a result of that transition (Murcia, environmental variables, light intensity and train noise, ). Abrupt transitions in vegetation at edges are usually as- were greatest at the edge and decreased with distance from sociated with similarly abrupt changes in climate, with conse- the edge. Temperature differed (greater extremes and more quent impacts on plants and animals (Chasko & Gates, ; variable) only at the edge itself. The few small mammal spe- Sork, ; Palik & Murphy, ;Matlack,; Oliveira et al., cies that were only rarely captured at the edge resulted in an ) as a result of changing resource distribution (Mills et al., apparent edge-effect with respect to species richness. The ;Berg&Pärt,;Ries&Sisk,) and biotic interac- abundance of small mammals, however, was independent tions (Berg & Pärt, ; Fagan et al., ). of distance from the railway. There was no correlation be- Diversity often increases near edges (especially in forest tween resource availability at the tracks and abundance of fragments) as a consequence of invasion by organisms from small mammals. Edge effects were minimal, which suggests areas adjacent to the edge, both the forest interior and the that narrow railways (in contrast with roads) in unfragmen- newly created open area causing the edge (Yahner, ; ted landscapes probably do not have a significant impact Laurance, ; Gascon et al., ; Pardini, ). (if any) on wildlife, as found elsewhere and especially in Conditions near edges are often similar to those of disturbed tropical forests. The use of railways instead of roads is a habitats (Chen et al., ; Cadenasso et al., ) and may potential strategy to minimize the effects of traversing therefore favour invasion by species typical of disturbances important habitats for commercial reasons. (Laurance, ; Pardini, ). Unique resources may be available near edges (Mills et al., ; Berg & Pärt, ; Keywords Atlantic Forest, Brazil, Didelphimorphia, frag- Ries & Sisk, ), also favouring invasion by species that mentation, linear clearing, microclimate, right of way, prefer those resources. Rodentia Edge effects are well known in the context of habitat loss and fragmentation (Yahner, ; Murcia, ; Ries et al., ). However, linear clearings for rights of way (e.g. power lines, roads, railways) also produce edges, often in Introduction otherwise well-preserved landscapes (Laurance et al., dge effects threaten biodiversity in many landscapes ). Studies of the effects of roads and highways on wild- Efragmented as a result of human activities (Harper life have shown that these edges affect the diversity of under- storey birds (Laurance, ) and small mammals RICARDO A. S. CERBONCINI* (Corresponding author), JAMES J. ROPER† and (Goosem, ; Ruiz-Capillas et al., ). However, most FERNANDO C. PASSOS* Programa de Pós-Graduação em Ecologia e studies have addressed these effects where edges are exten- Conservação, Setor de Ciências Biológicas, Universidade Federal do Paraná, sive and obvious. More subtle settings, such as smaller roads Campus Centro Politécnico, 81531-970 Curitiba, Paraná, Brazil E-mail ricardocerboncini@gmail.com and rights of way, remain understudied and may have unex- *Also at: Laboratório de Biodiversidade, Conservação e Ecologia de Animais pected effects as a result of inputs of new resources that Silvestres, Departamento de Zoologia, Setor de Ciências Biológicas, may, in turn, increase diversity (Carthew et al., ). For ex- Universidade Federal do Paraná, Curitiba, Paraná, Brazil ample, agricultural products may fall from trains while in †Also at: Programa de Pós-graduação em Ecologia de Ecossistemas, Universidade de Vila Velha, Vila Velha, Espírito Santo, Brazil transit, introducing plants or providing food for animals. Received July . Revision requested August . Anthropogenic edges in tropical forests are of particular Accepted November . First published online February . concern because of the contrast between the more constant Oryx, 2016, 50(3), 460–467 © 2015 Fauna & Flora International doi:10.1017/S0030605314001070 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.22, on 29 Sep 2021 at 19:51:57, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605314001070 Edge effects without fragmentation? 461 forest interior and the variable temperatures and greater ex- Each group comprised four transects, one of which was at tremes of the adjacent open areas, which may be agricultural, the edge ( m), with c. m between each transect (thus urban or rights of way for road, rail or power lines (Matlack, the last was c. m from the edge). This sampling design ; Pohlman et al., ; Laurance et al., ). As natural was based on the fact that edge effects usually penetrate up areas become increasingly fragmented, understanding the ef- to m in fragments of tropical forest (Kapos, ; fects of fragmentation and edges is important for conser- Matlack, ; Stevens & Husband, ; Laurance et al., vation. An estimated % of the Atlantic Forest is , m ; Oliveira et al., ). Sampling points were estab- from an edge (Ribeiro et al., ). In the future, these lished at m intervals along the m transects. Sampling kinds of edges may be pervasive, and understanding their im- ( days, nights) was carried out monthly during pact on wildlife will be important for appropriate manage- February–July ; storms prevented sampling in March. ment of biodiversity coexisting with small-scale edges. One Sherman trap (H.B. Sherman Traps, Tallahasse, Here we measured the response of small mammals to a USA) was placed at each sampling point. We alternated railway in an otherwise well-preserved natural landscape. six small ( × × mm) and four large ( × × This setting is useful because it minimizes the effects of mm) traps on and above the ground (.– m) on each tran- overdispersion of animals from an anthropogenic matrix sect. Captured animals were handled without anaesthesia, (i.e. farms, rural and urban areas). We tested three hypoth- and marked with a numbered ear tag. All individuals were eses: the railway creates an environmental gradient in the measured (head-and-body length) and weighed. Voucher forest (i.e. an edge effect exists), this edge has consequences specimens collected (licenses Instituto Ambiental do for the small mammals inhabiting the forest, and the new Paraná n°/ and Instituto Chico Mendes de resources introduced by trains hauling agricultural produce Conservação da Biodiversidade n°-) are in the mam- (usually soy and other grains) favour small mammals near mal collection of the Department of Zoology, Federal the edge. By elucidating the impact of this edge within a University of Paraná. Field procedures followed guidelines well-preserved forest we hope to separate edge effects of the American Society of Mammalogists (Sikes et al., from the larger scale of the surrounding matrix. ). Information on the species of small mammals cap- tured is in Cerboncini et al. (). Study site We studied edge effects in Marumbi State Park (Parque Estadual Pico do Marumbi). The Park is in the central portion oftheCoastalMountainRange(SerradoMar)inthestateof Microclimate and environmental conditions Paraná, southern Brazil, and lies within the largest remnant of We measured air temperature (°C), relative humidity Atlantic Forest (Ribeiro et al., ; Fig. ). The climate is (%, thermo-hygrometer, Instrutemp ITHT-), light inten- humid year-round and without a marked dry season (mean sity (lux, Instrutemp ITLD-) and ambient noise (dB, annual rainfall c. , mm and mean annual temperature Instrutemp ITDEC-)atfiverandomlychosenpoints c. °C; Vanhoni & Mendonça, ). The study area is at on all transects once during each sampling period. Noise – m altitude; vegetation is evergreen (Veloso et al., was measured on each transect when a train passed by, ), with emergent trees . m tall and canopy at – which occurred at – hour intervals, day and night. The m. The most common plant families are Bromeliaceae, mean of each variable (except noise from trains) on each tran- Myrtaceae, Rubiaceae, Melastomataceae and Fabaceae sect during each sampling period was used in analyses. (Silva, ; Kaehler et al., ). The Paranaguá–Curitiba rail- An additional m transect perpendicular to the railway way, established in , passes through the Atlantic Forest of was used to measure a temperature gradient. For a fine-scale the Serra do Mar and connects the state capital, Curitiba, with assessment of the microclimate, air temperature was mea- the port of Paranaguá ( km). It is used for commercial sured along this transect