Ant Diversity in the Urban Mosaic

Urban Ecology has come to the forefront of ecological studies in an attempt to further understand what patterns of biodiversity are present within urban environments. Urban Ecology looks to use the many principles of ecology and apply them to the ever expanding cityscape to understand the roles the physical environment in urban landscapes play on species assemblages (Pickett et al. 2008). Cities are the fastest growing environment of the world today (McIntyre 2000, Pickett et al. 2008). The Global Rural-Urban Mapping Project has shown that urban environments make up more than 3 % of the world’s land surface (Ciesin 2011). In addition to the large spatial extent of urban areas, human populations are clustered in urban environments. According to the 2010 U.S. census, over 71% of the American population may be found within heavily urbanized territories. Despite this knowledge, very little is known about how non-human species interact with urban environments (McIntyre 2000, McKinney 2002, McDonnell and Hahs 2008, Pickett et al. 2008). Traditional ecological thought has treated cities as homogenous species poor environments that destroyed natural areas as they expanded (McIntyre 2000). With further investigation into these “concrete jungles” we may find that instead of a single species poor environment, that there is a mosaic of microenvironments with diverse species assemblages. Urban environments often have a few pockets of untouched natural environment. Additionally, many cities incorporate a large degree of “green space” through the use of gardens and parks. To fully address large cities ecologically, we need to address both city environments as well as their effects on the natural environment they have altered (Pickett et al. 2008). The study of organisms and how they interact with their environment has always been a core component of ecology. The study of ecology has been subdivided into several different fields, including ecosystem ecology, community ecology, population ecology, and organismal ecology, each addressing a unique environmental scale. The largest of these scales addresses the world. The planet is classified into large units called biomes. Each biome helps categorize the various regions of the Earth’s ecosystems based upon the climate and vegetation of the area. Within these biomes, different communities survive and interact with one another (Morin 2009). These various communities are addressed in community ecology which focuses on how different populations interact with one another (Morin 2009). Population ecology focuses on the many individuals within these population and how they interact with other individuals in that same population as well as the environment (Hawley 1950). Each level of ecology allows new insights into organisms and their interactions in the natural world. However, ecological studies have traditionally been restricted to natural environments (McIntyre 2000, Pickett et al. 2008). Despite the many ecological principles we have defined in natural systems, little has been done to understand what principles act on species in urban environments (Blair 1999, McIntyre 2000). Urban environments, for instance, are the only environment that occurs in every biome on the planet. In addition, it is the fastest growing environment worldwide (Svirejeva-Hopkins and Schellnhuber 2006, Martine and Marshall 2007). In light of the expansion of urban environments and the increased presence of non-human species in cities, ecologists have begun to explore the ecological pressures of cities in the relatively new field of urban ecology (Pickett et al. 2008). To understand the ecological patterns and pressures within an environment, cities notwithstanding, organisms are classified into a Linnaean hierarchy. The smallest units used in ecology are species. Organisms may be classified into species using various concepts. The most commonly used species concept in ecology is based on reproductive isolation (Agapow et al. 2004). If two organisms cannot produce viable offspring, then they are considered two separate species (Palumbi 1994, Schluter 2009). Using this species concept, ecologists can examine how ecological pressures affect the diversity in both natural and urban environments. In order to address the diversity of environments, the term biodiversity was coined by W.G. Rosen in 1985. Biodiversity is used to describe the degree of variation of life on the planet. Species distributions and biodiversity are intertwined. Many of the natural environments that have been observed and defined are now broken up by large urban environments that have sprung up over time (Gibb and Hochuli 2002, Coy 2006). In light of shrinking natural environments and the increase of urbanized environments, it has become increasing important to understand what role urban environments play on biodiversity. Cities provide different environmental conditions than similar rural environments (White and McDonnell 1988, Hogsden and Hutchinson 2004). The addition of traffic, pavement, and human interactions may affect how species interact with one another and in turn alter the biodiversity of urban environments (Connell 1961, Hersteinsson and Macdonald 1992).