Microbats in a ‘leafy’ urban landscape: are they persisting, and what factors influence their presence?

Abstract

Urbanization is an extreme form of habitat modification, but retention of native vegetation in bushland reserves may improve the ecological sustainability of cities. We focused on bats (Microchiroptera) and investigated the use of the urban matrix and surrounding bushland in a region of Sydney, Australia, where remnant bushland persists and gardens often support large trees. Ultrasonic surveys were conducted at 40 sites over one summer season in the backyard matrix, bushland remnants and surrounding National Parks to determine which species were present, and the influence of landscape elements and habitat characteristics on activity, species richness and presence of individual species. In total, 15 of the 17 microbat species known from the Sydney region were recorded in the study area. Yet only three of these species, Chalinolobus gouldii, Mormopterus species 2 and Miniopterus schreibersii were present in more than 40% of sites. Bat activity was significantly higher in remnant bushland on shale soils and in backyards, compared with sandstone gully and ridge remnants, or reference sites in nearby National Parks. Furthermore, species assemblages in urban areas were different from assemblages in reference sites. Of all the habitat characteristics examined, the amount of bushland within 0.5-3 km surrounding a site and tree density were the most common predictors of individual species presence, particularly rare species. Area of bushland, hollow abundance and average tree diameter were positively correlated with species richness, while tree diameter was the strongest predictor of total microbat activity.The proximity of large areas of bushland and the many trees remaining in residential areas of the northern 'leafy' suburbs of Sydney allowed the persistence of a range of bat species. The higher bat activity on fertile shale soils indicated that bushland remnants embedded within cities can have high conservation value for bats. Surveys in more urbanized areas of Sydney are needed to test predictions of the models derived in this study.

Temporal Variation of Ecological Factors Affecting Bird Species Richness in Urban and Peri-Urban Forests in a Changing Environment: A Case Study from Milan (Northern Italy)

“…A positive effect of forest patch size on urban biodiversity has been previously found [40][41][42][43]. Our study supports previous findings associated with species-area relationships [44] in urban and in peri-urban landscapes.…”

Urban stress is associated with variation in microbial species composition—but not richness—in Manhattan

“…Species-area relationships, with fewer species in smaller sites, have been observed for microbes (Green et al, 2004;Horner-Devine et al, 2004;Bell et al, 2005) in habitats such as tree holes owing to the greater potential for colonization and quantity and diversity of available resources and habitats. At least for macroorganisms, urban, habitat area has a positive influence on biodiversity (Basham et al, 2010;Shanahan et al, 2011;Beninde et al, 2015). If urban habitat patches act analogously to tree holes, we expect to find fewer microbial species in smaller habitats in cities.…”

Non-random patterns of vegetation clearing and potential biases in studies of habitat area effects

“…Basham et al (2011) reported lower bat activity in well-vegetated protected areas compared with less-vegetated urban areas in the Sydney region of eastern Australia, and suggested that the confounding effects of soil fertility on vegetation extent-a legacy of non-random clearing-may be responsible for this result. Looney et al (2009) proposed that biases in clearing leading to a negative association between remnant area and soil fertility underpinned the lack of relationship between grassland beetle community structure and patch size in prairie remnants in a heavily modified agricultural matrix in the north-western United States.…”

“…Several of these studies (Januchowski et al 2008;Looney et al 2009;Basham et al 2011) highlighted that a lack of an area effect was due to biased vegetation clearing patterns, whereby soil fertility/productivity was negatively correlated with habitat area. Because bigger remnants were associated with poorer quality soils, a positive effect of area on the response variable in these studies was not realised.…”