Tracking the effects of one century of habitat loss and fragmentation on calcareous grassland butterfly communities

Abstract

Habitat loss and fragmentation are known to reduce patch sizes and increase their isolation, consequently leading to modifications in species richness and community structure. Calcareous grasslands are among the richest ecosystems in Europe for insect species. About 10% (1,150 ha) of the total area of a calcareous ridge region (Calestienne, Belgium) and its butterfly community was analysed over a timeframe of about 100 years. Since 1905 to present day (2005), the Calestienne region has undergone both calcareous grassland loss and fragmentation: not only did calcareous grassland size decrease and isolation increase, but also, the number of calcareous grassland patches within the landscape increased until 1965, and subsequently decreased, clearly reflecting the effects of fragmentation. These processes have had a profound effect on the butterfly community: extinction and rarefaction affected significantly more often specialist species, which means that generalist species are more and more overrepresented. This ecological drift, i.e. the replacement of specialists by generalists in species assemblages is likely to be a general effect of habitat loss and fragmentation on natural communities.

Native Pollinators in Anthropogenic Habitats

“…Superimposed, the remaining area of calcareous grassland habitat (solid red line), the number of habitat fragments (dashed line), and the connectivity among these (dotted line) show the association between land-use change and species composition. Modified from Polus et al 2007.…”

“…This result concurs with an independent analysis of the ecological characteristics of threatened butterflies (Kotiaho et al 2005). First, the idea that dietary specialist species are the first to disappear is highly supported by multiple studies in different systems across the world (Filippi-Codaccioni et al 2010, Koh & Sodhi 2004, Littlewood 2008, Polus et al 2007, Stefanescu et al 2009, Steffan-Dewenter & Tscharntke 2000; Figure 5). Second, low mobility, measured as wing size, is also associated with negative responses, although this trend is more pronounced in moths than in butterflies (Ockinger et al 2010).…”

“…Few studies have used an across-time design, but those that do have found results broadly consistent with the across-space designs. For example, among butterflies, extinctions occur mainly in specialist species over time (Nilsson et al 2008, Ohwaki et al 2008, Polus et al 2007, Stefanescu et al 2009). In a tropical forest fragmentation experiment, hummingbird species either remained stable or increased following deforestation, and they remained stable for the following 20 years (Stouffer et al 2006).…”

Long-term changes in lowland calcareous grassland plots using Tephroseris integrifolia subsp. integrifolia as an indicator species

“…60 years there has been a well-documented decline in the extent and quality of such grasslands across northwestern Europe (Fuller 1987;Willems 1990;Van Dijk 1991;Critchley et al 2003) and as a consequence a decline in distribution for many calcicolous species (Preston et al 2002;Polus et al 2007). Historical loss has resulted in fragmentation (Fischer and Stöcklin 1997;Hodgson et al 2005), with the result that surviving pieces of grassland are often logistically more difficult to graze and therefore more susceptible to abandonment or changes to grazing pressure that frequently result in an impoverished flora and fauna (Keymer and Leach 1990;Bobbink and Willems 1987;Willems et al 1993;Kahmen et al 2002;Adriaens et al 2006).…”

Garden varieties: How attractive are recommended garden plants to butterflies?

“…Butterflies are an important group of insects that can act as pollinators and environmental indicators but are facing widespread decline (Jennersten 1984;Thomas 2005, Polus et al 2007; Thomas et al 2011;Forister et al 2010). Recent research has drawn attention to the resources butterflies use within their habitat (Dennis et al 2006, Dennis 2010.…”