Genetic structure and diversity of the endangered growling grass frog in a rapidly urbanizing region

Abstract

Two pervasive and fundamental impacts of urbanization are the loss and fragmentation of natural habitats. From a genetic perspective, these impacts manifest as reduced genetic diversity and ultimately reduced genetic viability. The growling grass frog (Litoria raniformis) is listed as vulnerable to extinction in Australia, and endangered in the state of Victoria. Remaining populations of this species in and around the city of Melbourne are threatened by habitat loss, degradation and fragmentation due to urban expansion. We used mitochondrial DNA (mtDNA) and microsatellites to study the genetic structure and diversity of L. raniformis across Melbourne's urban fringe, and also screened four nuclear gene regions (POMC, RAG-1, Rhod and CRYBA1). The mtDNA and nuclear DNA sequences revealed low levels of genetic diversity throughout remnant populations of L. raniformis. However, one of the four regions studied, Cardinia, exhibited relatively high genetic diversity and several unique haplotypes, suggesting this region should be recognized as a separate Management Unit. We discuss the implications of these results for the conservation of L. raniformis in urbanizing landscapes, particularly the potential risks and benefits of translocation, which remains a contentious management approach for this species.

Genetic structure of an abundant small mammal is influenced by low intensity urbanization

“…Further, rarer (i.e. threatened and endangered) or more isolated wildlife may face more issues in urbanizing environments due to genetic drift and reduced gene flow (Reed and Hobbs 2004;Keely et al 2015). This should be of concern to managers and conservation planners.…”

“…Genetic diversity is important for future population viability, particularly in the face of environmental change (Reed and Frankham 2003;Frankham 2005;Lourenco et al 2017). In addition, small populations may experience magnified effects of genetic drift and reduced gene flow (Segelbacher et al 2003;Reed and Hobbs 2004;Frankham 2005;Keely et al 2015). In extreme cases, genetic drift, reduced gene flow, and small population size can lead to inbreeding depression (Keller and Waller 2002;Reed and Frankham 2003;Frankham 2005;Lourenco et al 2017).…”

Review: Toward management of urban ponds for freshwater biodiversity

“…Habitat fragmentation and isolation as a result of urbanization are some of the main threats to amphibian populations (Hamer and McDonnell 2008), and consequently, there is an extensive body of research on this topic. The impact of fragmentation on amphibian populations has been demonstrated at the species level with the use of genetic tools, for example, for the growling grass frog (Litoria raniformis) in the urbanizing landscape of southern Australia (Hale et al 2013, Keely et al 2015, and the common frog (Rana temporaria) in urban sites from Brighton (UK; Hitchings and Beebee 1997). Fragmentation also affects amphibian species richness.…”

“…, Keely et al. ), and the common frog (Rana temporaria ) in urban sites from Brighton (UK; Hitchings and Beebee ). Fragmentation also affects amphibian species richness.…”

Implementation of a parallel algorithm of image segmentation based on region growing

“…Unlike the gradient and Laplacian methods, the edges of the regions that are found by the growing region are perfectly thin and connected. The algorithm is also very stable concerning noise [1][2][3].…”