Metacommunity Dynamics: Decline of Functional Relationship along a Habitat Fragmentation Gradient

Abstract

BackgroundThe metacommunity framework is crucial to the study of functional relations along environmental gradients. Changes in resource grain associated with increasing habitat fragmentation should generate uncoupled responses of interacting species with contrasted dispersal abilities.Methodology/Principal FindingsHere we tested whether the intensity of parasitism was modified by increasing habitat fragmentation in the well know predator-prey system linking the parasitoid Cotesia glomerata (Hymenoptera: Braconidae) to its main host Pieris brassicae (Lepidoptera: Pieridae). We collected information on herbivorous abundance and parasitism rate along an urbanization gradient from the periphery to the centre of Paris. We showed that butterfly densities were not influenced by habitat fragmentation, whereas parasitism rate sharply decreased along this gradient.Conclusions/SignificanceOur results provide novel insights into the mechanisms underlying the persistence of species in highly fragmented areas. They suggest that differential dispersal abilities could alter functional relationships between prey and predator, notably by a lack of natural predators.

Coupling inter‐patch movement models and landscape graph to assess functional connectivity

“…So, in the Île-de-France region, the matrix was not so ''inhospitable'' for P. brassicae within a component because our model (i.e., a combination between dispersal abilities and nature of the landscape between habitat patches) shows that the mean dispersal distance within a component was approximately the mean daily dispersal distance for this species. These results validate the hypothesis previously made by Bergerot et al 2010a showing that dispersal abilities of P. brassicae allows the persistence of this species in this region. We show that the northern part of the study area, which is also the most urbanized, is much more fragmented than its southern part (Fig.…”

“…Pieris brassicae is a common and widespread species across Europe (Bink 1992), which is present in the urbanized region of Île-de-France (Bergerot et al 2010a). We bred individuals in the lab by placing adults captured in the region in an oviposition cage (80 9 80 9 80 cm) with cabbage leaves (Brassica oleracea L.) under incandescent light to maintain a 14L: 10D photoregime.…”

The Spatial Structure of Antagonistic Species Affects Coevolution in Predictable Ways

“…In fact, linear (Bergerot et al 2010), circular (Chisholm et al 2010), modular (Fortuna et al 2008), and star (Economo and Keitt 2008) configurations are common components of the distribution of species assem- Figure 4: Each column shows the stability analyses within hotspots for three specific sets of simulations: A-E, hotspot connectivity simulation within the star configuration; F-J, coldspot organization within the linear configuration; and K-N, connectivity and coldspot organization experiment within the modular configuration. The axes and color code used for the stability plots are the same as those described in figures 2 and 3.…”

Pest management through tropical tree conservation

“…While fragmentation affects species from all trophic levels to some degree, upper trophic level organisms, specifically hymenopteran parasitoids, are often more severely affected than the species they attack (e.g., Klein et al 2006;Antón et al 2007;Bergerot et al 2010). In part this is because many parasitoids, including those of pest tephritids, have movement-ranges that are substantially shorter than those of their hosts (Messing et al 1994(Messing et al , 1995(Messing et al , 1997Nouhuys and Hanski 2002;Thies et al 2005;Bergerot et al 2010). In a Caatinga-Cerrado ecotone in Brazil, the number of tephritid parasitoid species in a patch was higher in areas with adjacent forest fragments (De Souza et al 2012).…”

“…Biodivers Conserv (2014) 23:831-853 837 Table 2 Plants that harbor Anastrepha species larvae and that serve as hosts to parasitoids in Central Veracruz, Mexico (from Lopez et al 1999) Plant species and fruit production per tree These two variables, distance between patches and heterogeneous patch quality, can combine to decrease parasitism with increasing fragmentation so that in general parasitism rates tend to be lower in small patches than in large ones (Kruess and Tscharntke 2000). For example, in France, parasitism of larvae of the butterfly Pieris brassicae by the braconid wasp Cotesia glomerata, declined more rapidly along a fragmentation gradient from the countryside into the center of a large urban area (Paris) than did abundance of the butterfly itself (Bergerot et al 2010).…”