Long‐term effects of forest fragmentation on Amazonian ant communities

Abstract

Aim To analyse the effects of forest fragmentation on ant communities in an Amazonian landscape that has been fragmented for over a century.Location The region surrounding the village of Alter do Chão in the Brazilian Amazonian state of Pará (2°30¢ S, 54°57¢ W).Methods Collection of ants and measurements of tree density were performed along transects established in eight sites in continuous forest and in 24 forest fragments surrounded by savanna vegetation. Data on size, perimeter, and degree of isolation (distance to continuous forest and distance to nearest area of forest > 5 ha) of each fragment were obtained from a georeferenced Landsat image of the study area.Results There were significant differences in species richness and composition between fragments and continuous forest, and these differences were not related to intersite variation in vegetation structure (tree density). Fragments supported fewer ant species per plot, and these species tended to represent a nested subset of those found in continuous forests. Fragments had significantly fewer rare species and fewer ant genera. However, fragments and continuous forest had similar numbers of species that also occur in the savanna matrix (i.e. that are not forest specialists). Multiple linear regression analyses indicated that species richness and composition in the fragments are significantly affected by fragment area, but not by fragment shape and degree of isolation. More species were found in larger fragments.Main conclusions Forest fragmentation influences the organization of ant communities in Amazonian savanna/forest landscapes. Forest fragments harboured, on average, 85% of the species found in continuous forest. That these fragments, despite their long history of isolation, support a relatively large complement of the species found in continuous forest is surprising, especially given that in some recently fragmented landscapes the proportion of species surviving in the fragments is lower. Differences in inter-fragment distance and type of matrix between Alter do Chão and these other landscapes may be involved. The fact that fragments at Alter do Chão are surrounded by a natural (rather than an anthropogenic) habitat, and that most of them are less than 300 m from another forest area, may have helped to ameliorate the adverse effects of forest fragmentation.

Consequências ecológicas da fragmentação florestal na amazônia

“…Por exemplo, na amazônia central, fragmentos com menos de 100ha perderam metade das espécies de pássaros de sub-bosque em apenas 15 anos (Ferraz et al 2003). reduções na riqueza de espécies com a fragmentação foram observadas numa grande gama de grupos taxonômicos incluindo primatas (rylands & Keuroghlian 1988), pássaros de subosque (stouffer & Bierregaard 1995a;Ferraz et al 2003), borboletas umbrófilas (Brown & Hutchings 1997), cupins (souza & Brown 1994, besouros (Klein 1989) abelhas euglossinae (Powell & Powell 1987) e formigas (carvalho & Vasconcelos 1999, Vasconcelos et al 2006.…”

“…Também são necessários mais estudos de longo prazo e/ou que façam uso de fragmentos isolados há muitas décadas (e.g. Vasconcelos et al 2006). sabemos que para alguns grupos taxonômicos há uma rápida perda de espécies logo após a fragmentação, mas pouco sabemos como estas taxas variam com o tempo desde o isolamento (e.g.…”

Atlantic Forest Size Effect on Structure and Composition of Soil Arthropods Community, Rj, Brazil

“…This result was obtained comparing larger forest fragments with the smaller ones, such as in areas of Atlantic Rain Forest in the Southern Brazil (DUARTE, 2004) and in the Northeastern Brazil (LEAL et al, 2012) and in the Brazilian Amazonia (VASCONCELOS et al, 2006). The same pattern occurred when comparing native forest fragments of Atlantic Forest with eucalyptus plantations in the state of Rio de Janeiro (CUNHA NETO et al, 2012); and forest fragments with different stages of natural regeneration of Atlantic Forest in the same state (MENEZES et al, 2009;CAMARA et al, 2012).…”

Impact de la fragmentation et de la pression humaine sur la relique forestière de l’Université d’Abobo-Adjamé (Côte d’Ivoire).

“…(2) l'effet de la taille de l'ilot sur la richesse spécifique des fourmis suppose qu'on retrouve plus d'espèces dans les grands fragments comparés aux plus petits. Cet effet détecté dans l'îlot 3, l'a été dans d'autres études dans les zones tropicales et tempérées (Terayma & Murata, 1990 ;Dean & Bond, 1990 ;Brühl et al, 2003 ;Vasconcelos et al, 2006). De plus ces résultats montrent que malgré la forte pression, l'îlot 3 regorge encore un nombre important de fourmis.…”