Habitat fragmentation leads to isolation and reduce habitat areas, in addition to a series of negative effects on natural populations, affecting richness, abundance and distribution of animal species. In such a text, habitat corridors serve as an alternative for connectivity in fragmented landscapes, minimizing the effects of structural isolation of different habitat areas. This study evaluated the richness, composition and abundance of small mammal communities in forest fragments and in the relevant vegetation corridors that connect these fragments, located in Southern Minas Gerais, Southeastern Brazil. Ten sites were sampled (five forest fragments and five vegetation corridors) using the capture-mark-recapture method, from April 2007-March 2008. A total sampling effort of 6 300 trapnights resulted in 656 captures of 249 individuals. Across the 10 sites sampled, 11 small mammal species were recorded. Multidimensional scaling (MDS) ordinations and ANOSIM based on the composition of small mammal communities within the corridor and fragment revealed a qualitative difference between the two environments. Regarding abundance, there was no significant difference between corridors and fragments. In comparing mean values of abundance per species in each environment, only Cerradomys subflavus showed a significant difference, being more abundant in the corridor environment. Results suggest that the presence of several small mammal species in the corridor environment, in relatively high abundances, could indicate corridors use as habitat, though they might also facilitate and/or allow the movement of individuals using different habitat patches (fragments).
La fragmentación del hábitat conduce al aislamiento y la reducción de los hábitats, además provoca una serie de efectos negativos sobre las poblaciones naturales, afectando la riqueza, abundancia y distribución de las especies de animales. Dentro de este contexto, los corredores biológicos sirven como una alternativa para la conectividad de los paisajes fragmentados, minimizando los efectos del aislamiento estructural de las áreas con diferentes hábitats. Este estudio evaluó la riqueza, la composición y la abundancia de las comunidades de mamíferos pequeños en fragmentos de bosque y en los corredores de vegetación relevantes que conectan estos fragmentos, localizados en el sur de Minas Gerais, sudeste de Brasil. Diez sitios fueron muestraeados (cinco fragamentos de bosque y cinco corredores biológicos ) usando el método de captura-marcaje-recaptura, desde abril de 2007-marzo de 2008. Un esfuerzo total de muestreo de 6 300 trampas nocturnas resultó en 656 capturas de 249 individuos. En los 10 sitios muestreados, se registraron 11 especies de mamíferos pequeños. Las ordenaciones del escalamiento Multidimensional (MDS) y el ANOSIM basados en la composición de las comunidades de mamíferos pequeños dentro de los corredores y los fragmentos revelan una diferencia cualitativa entre estos dos ambientes. En cuanto a la abundancia, no hubo una diferencia significativa entre los corredores y los fragmentos. Al comparar los valores promedio de abundancia por especie en cada ambiente, sólo Cerradomys subflavus mostró una diferencia significativa, siendo más abundante en el ambiente del corredor biológico. Los resultados sugieren que la presencia de varias especies de mamíferos pequeños en el entorno del corredor biológico, en abundancias relativamente altas, podría indicar el uso de los corredores como hábitat, aunque estos también podrían facilitar y/o permitir el movimiento de individuos que utilizan los diferentes parches de hábitat (fragmentos).
Brazil is among the ]]>
et al. 2005). Despite high rates of deforestation, the Atlantic forest of Brazil host an enormous biological diversity and a very high degree of endemism, being considered one of the most important biodiversity hotspots (Myers et al. 2000, Brooks et al. 2002, ]]>
et al. 2005, Ceballos & Ehrlich 2006). Forest fragmentation and loss of habitat constitute major threats to biodiversity, particularly in tropical regions, where population density and outspread agriculture are increasing rapidly (Saunders et al. 1991, Turner 1996, Cuarón 2000, Fahrig 2003, Bennett et al. 2006). Fragmentation leads to isolation too and triggers a number of negative effects on wildlife populations, affecting the richness, abundance, and ]]>
et al. 2002, Fahrig 2002, Fischer & Lindenmayer 2007, Pardini et al. 2009, vieira et al. 2009). On a broader time scale, fragmentation also affects genetic variability and persistence of populations, potentially leading to local extinctions (Fahrig & Merriam 1994, Gibbs 2001, viveiros de Castro & Fernandez 2004). To survive in fragmented landscapes the individuals need to move between patches of habitat in search of ]]>
et al. 1992, Gascon et al. 1999, Umetsu & Pardini 2007, Passamani & Fernandez 2011a,b). Studies suggest that vegetation corridors could act as habitat or facilitators of dispersion and genetic exchange between populations on fragmented landscapes (Bennett 1990, Aars & Ims 1999, Mech & Hallet 2001). ]]>
One of the focuses of related research has been the use of vegetation corridors by small mammals especially in temperate countries (Hobbs 1992, Aars & Ims 1999, Haddad et al. 2003) while in tropical forests there are few studies (Bennett 1990, Downes et al. 1997, Pardini et al. 2005, Rocha et al. ]]>
et al. 1991, Malcolm 1994, Lidicker 1999, Pardini et al. 2005, Umetsu & Pardini 2007, Passamani & Fernandez 2011a) and their responses, can help researchers understand ecological processes like population dynamics and community structure, and in particular the role of corridors in metapopulation dynamics (Lidicker 1999). Overall, generalist species respond positively to fragmentation, persisting in ]]>
et al. 2008, Pardini et al. 2010). In Southern Minas Gerais, Brazil, the landscape consists of many small forest fragments imersed in an anthropogenic matrix (agricultural crops and pastures) and some of these fragments are connected through vegetation ]]>
Materials and methods ]]>
Study site: The corridor-fragment system studied is located in the municipality of Lavras, in Southern Minas Gerais, Brazil (21º17’15.1’’ S - 44°58’59.3’’ W), at ca. 950m of altitude (Castro 2004). The climate of the region is the Cwa of Koeppen’s classification, with dry winters and wet summers, and the average annual temperature is 20.4°C. The average annual precipitation is 1 460mm, with a rainy season from November through February (Dantas
et al. 2007). The local vegetation is defined as being a disjointed portion of Cerrado biome, inserted into the semideciduous, seasonal Atlantic forest region of Southeastern Brazil (Oliveira-Filho et al. 1994), and the areas sampled are comprised of secondary forests at different regeneration stages. The small mammals were sampled in five forest fragments (F1, F2, F3, F4 and F5) and five vegetation corridors (CA, CB, CC, CD and CE) connecting them (Fig. 1). The ]]>
Sampling: In each fragment, two transects of 100m were established, 50m apart, with one capture station placed along each transect at 20m spacing. Two traps were set in each capture station: one on the ground and one in the ]]>
et al. (2006) and the rodents according to Oliveira & Bonvicino (2006), except Cerradomys subflavus and Calomys cerqueirai, for which the classification proposed by Weksler et al. (2006) and Bonvicino et al. (2010) was used, respectively. Some specimens of all species were collected and hosted to the collection of the Laboratory of Ecology and ]]>
To compare the richness of corridor and fragment sites, rarefaction curves were constructed using EstimateS 8.0 software (Colwell 2008). To evaluate abundance, only the first capture of each individual was considered. To verify if there were differences between the total abundance of fragments and corridors, and between the abundance of each ]]>
Results
A total sampling effort of 6 300 trapnights resulted in 656 captures of 249 individuals, ]]>
Akodon montensis, Calomys cerqueirai, Cerradomys subflavus, Necromys lasiurus, Nectomys squamipes, Oligoryzomys nigripes, Rhipidomys sp., Didelphis albiventris, D. aurita, Gracilinanus microtarsus and Marmosops incanus.
]]>
The rarefaction curves (Fig. 2) produced from the sampling effort of 70 individuals showed that fragments have higher species richness, with around 30% more species sampled than in vegetation corridors. Out of the total number of captures, 59% were rodents and 41% were marsupials, with rodents being more abundant both in corridors (61%) and in fragments (59%). The most abundant species were G. microtarsus (69 individuals), A. montensis (55) and Rhipidomys ]]>
N. squamipes (2) and M. incanus (1) (Table 1).
Considering ]]>
4.48 (SD=±2.34) and in fragments was 3.69 (SD=±1.02), but the difference was not significant (t=0.69, p=0.50). When comparing mean abundance per species in each environment, only C. subflavus showed a significant difference (t=-2.89, p=0.02), being more abundant in corridor ]]>
Fig. 3A). While for the abundance, the MDS did not detect any difference between the small mammal communities in these environments (Fig. 3B). ]]>
Patterns depicted by the MDS analysis for the small-mammal species in the corridor-fragment system were reinforced by the ANOSIM analysis, with corridors differing from fragments in terms of species composition (ANOSIM, Global R=0.27, p=0.03) but not in terms of abundance ]]>
Discussion
These results demonstrate that smallmammal communities present in the corridors and fragments differ ]]>
N. squamipes, N. lasiurus and M. incanus) exclusive to fragments. Nectomys squamipes was detected only in two of the fragments (F3 and F5) that have areas boasting watercourses and permanently flooded soil. This species has semiaquatic habits (Bonvicino et al. 2008); ]]>
N. lasiurus was restricted to another two fragments (F1 and F2), but both fragments showed low abundance. This species appears in open and forested Cerrado formations and in the transitional Cerrado- Atlantic forest ecotone (Bonvicino et al. 2008), it being the dominant species in cerrado and campo sujo habitats, but ]]>
N. lasiurus. The other exclusive species was M. incanus, recorded only once in one of the fragments (F3). Considering our data during a year of study, the presence of M. incanus may be a casual recorded of as individual. Its occasional capture is probably related to an isolated event of ]]>
In the corridor-fragment system, only C. subflavus was more frequent and significantly more abundant in ]]>
et al. (2011) regarding corridors connecting fragments near this area. In addition, the studied corridors harbour a considerable number of species in common with the fragments and similarity in abundance. The presence of small-mammal species in corridor and fragment sites could be related to the fact that corridors effectively play the role of habitats for small-mammal species rather than being mere linking environments for their movement. ]]>
Several studies in temperate countries have pointed to the effectiveness of linear vegetation corridors in preserving small mammals’ fauna. Wegner & Merriam (1979) monitored the movements of small mammals in forest fragments and fencerows in Canada and detected movements of three small-mammal species, most of which occurred between fragments and fencerows, and rarely in cultivated fields. Andreassen et al. ]]>
Microtus oeconomus, observed that corridor presence increases the chance of individuals incorporating more than one habitat patch into their home range. Bolger et al. (2001), in evaluating the use of remnant shrub strips and straight-line revegetated areas connecting forest remainder in California (USA), found no significant difference in the richness of small-mammal species between corridors and forest remainders. Haddad & Tewksbury (2006) evaluated the effects ]]>
It should be noted that, in terms of structure, hedgerows and fencerows in temperate countries resemble the vegetation corridors evaluated in this study, yet they strongly differ in their floristic composition, comprised typically of a ]]>
et al. (2011) has shown the high conservation value of this structure in another fragmented landscape of Southern Minas Gerais. ]]>
In conclusion, corridors seem to be effective in the exchange of individuals between forest fragments, promoting similarity in species composition within both patches and corridors. This can be demonstrated simply by the fact that more than 70% of species present in fragments also appear in corridors. Owing to its effective structural and functional connectivity, the corridor-fragment system studied in this work should ]]>
Acknowledgments ]]>
We would like to thank the Coordenação de Aperfeiçoamento de Pessoal de Ensino Superior (CAPES) for its support; the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA) for the license to collect specimens; Toby A. Gardner for helping to analyze data; and everyone who helped us during the fieldwork, especially Carlos H, Jacinto, Marina S. Pereira, and Adriana L. Gouveia. This study was funded by the Fundação de Amparo à Pesquisa do ]]>
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*Correspondencia Andréa O. Mesquita: Pós-Graduação em Ecologia Aplicada, Universidade Federal de Lavras, Campus Universitário - Lavras, MG - 37200-000, Brazil. andreamesquita.bio@gmail.com Marcelo Passamani: Universidade Federal de Lavras, Setor de Ecologia, DBI, Campus Universitário - Lavras, MG - 37200-000, Brazil/Pós-Graduação em Ecologia Aplicada, Universidade Federal de Lavras, Campus Universitário - Lavras, MG - 37200-000, Brazil. mpassamani@ufla.br 1. Pós-Graduação em Ecologia Aplicada, Universidade Federal de Lavras, Campus Universitário - Lavras, MG - 37200-000, Brazil; andreamesquita.bio@gmail.com 2. Universidade Federal de Lavras, Setor de Ecologia, DBI, Campus Universitário - Lavras, MG - 37200-000, Brazil; mpassamani@ufla.br
Received 12-VIII-2011. Corrected 10-III-2012. Accepted 12-IV-2012.
