Figure - available from: Landscape Ecology
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A National scale: study area location within Australia, B regional scale: study fragments (solid triangles) and pseudo-fragments (hollow triangles) across the Little Desert National Park and surrounds, and C landscape scale: study fragments in the agricultural landscape and paired pseudo-fragments (connected with arrows) in the adjacent national park showing proportional sampling. Continuous vegetation of the national park is shaded grey, whilst fragments of remnant native vegetation in the agricultural landscape are hashed grey
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Context
Human disturbance has transformed ecosystems globally, yet studies of the ecological impact of landscape modification are often confounded. Non-random patterns of land clearing cause differing vegetation types and soil productivity between fragments in modified landscapes and reference areas—like national parks—with which they are compared....
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Citations
... To test the feasibility of the wildlife restoration concept, and its utility in risk-spreading, we carried out experimental translocations of two species of agamid in semi-arid, south-eastern Australia. We translocated animals from several sites in the Little Desert National Park, where previous surveys found them to be abundant, to two fragments of remnant vegetation in the adjacent agricultural landscape where surveys found them to be absent or occur in low numbers (Westaway et al., 2024b). Due to the stress and disorientation of the translocation process (Dickens et al., 2010), we predicted translocated animals would show lower survival, body condition, site fidelity, and higher activity areas and movement rates compared to control animals. ...
... Fragments were intensively sampled (one site per ha) with each site containing a 30-m drift fence, three pitfall traps, two funnel traps, as well as artificial refuges (two 1 m 2 pieces of corrugated iron and four ceramic roof tiles). Over 9618 trap-nights, 1736 individuals were recorded across 25 herpetofauna and small mammal species (Westaway et al., 2024b). From this data, we found the mallee tree dragon (Amphibolurus norrisi) and painted dragon (Ctenophorus pictus) to be abundant in the national park and rare or absent in agricultural fragments, thus, making them ideal candidates for translocation. ...
... Yet, their potential as a proactive measure for safeguarding common species in fragmented landscapes has rarely been assessed. We conducted wild-to-wild translocations of two regionally common lizard species into remnant habitat fragments within a semi-arid, agricultural landscape, where reptile populations have likely declined (Westaway et al., 2024b). Notably, survival rates, body condition, movement patterns, and microhabitat use were similar between translocated and control animals. ...
... Despite these issues, small patches can be of high conservation value (Wintle et al. 2019;Riva and Fahrig 2022). Fragments can comprise the last vestiges of contracting species' ranges, and provide 'insurance populations', safeguarded against contagious disturbances like wildfire and disease (Westaway et al. 2024b). Recognizing the high biodiversity value of small fragments raises the question of how to best manage fragmented metapopulations (Lindenmayer 2019). ...
... We expected less differentiation for painted dragon (Ctenophorus pictus) and robust ctenotus (Ctenotus robustus) populations due to their larger body size, potentially facilitating greater dispersal capacity (Jenkins et al. 2007), and tolerance of disturbed landscapes (Read 2002;Shea 2010;Michael et al. 2011). These traits may enable greater gene flow across the agricultural matrix compared to shrubland morethia (Morethia obscura), which has a narrow habitat breadth (Westaway et al. 2024b) and may be sensitive to land modification (Driscoll 2004;Simpson et al. 2023). We predicted lower genomic diversity, and higher levels of inbreeding and relatedness in fragments compared to national park populations for all three species, with greater differences for the painted dragon due to substantially lower population sizes compared to the two skink species (Westaway et al. 2024b) resulting in more rapid genetic drift. ...
... These traits may enable greater gene flow across the agricultural matrix compared to shrubland morethia (Morethia obscura), which has a narrow habitat breadth (Westaway et al. 2024b) and may be sensitive to land modification (Driscoll 2004;Simpson et al. 2023). We predicted lower genomic diversity, and higher levels of inbreeding and relatedness in fragments compared to national park populations for all three species, with greater differences for the painted dragon due to substantially lower population sizes compared to the two skink species (Westaway et al. 2024b) resulting in more rapid genetic drift. ...
Habitat destruction is the most pervasive threat to global biodiversity, leading to widespread population declines and range reductions. Land clearing can leave small, isolated populations persisting in remnant habitat, where demographic factors may erode genomic diversity and diminish adaptive potential. We compared the genomic structure, diversity, inbreeding and effective population sizes of fragmented populations on farms to nearby populations in large, continuous tracts of vegetation (national park) for three terrestrial lizard species in south-eastern Australia. Due to the small spatial scale of the study, observed levels of genomic differentiation among sampling locations were typically very low (FST < 0.1). The farm locality of one species, the painted dragon (Ctenophorus pictus), showed substantially more differentiation to national park localities (FST > 0.05) than the national park localities showed to one another (FST < 0.01), suggestive of genetic isolation due to the agricultural matrix. Genomic diversity and effective population sizes were lower in farm populations compared to national parks for two of the three species, the exception being shrubland morethia (Morethia obscura), where genomic diversity was similar across site types. Inbreeding coefficients were generally comparable between farm and national park populations. Our findings highlight the genetic consequences of land clearing including low population size, low genomic diversity and higher risk of inbreeding depression. Despite these challenges, habitat fragments can maintain high biodiversity value, which can be maximised by management initiatives such as translocations and establishing habitat corridors.
