Dispersal patterns and population structuring among platypuses, Ornithorhynchus anatinus, throughout south-eastern Australia

Abstract

Dispersal patterns can have a major impact on the dynamics and viability of populations, and understanding these patterns is crucial to the conservation and management of a species. In this study, patterns of sex-biased dispersal and waterway/overland dispersal are investigated in the endemic Australian platypus, Ornithorhynchus anatinus, a semi-aquatic monotreme. Analyses of over 750 individuals of south-eastern Australia at thirteen microsatellite loci and two mitochondrial genes, cytochrome b and cytochrome oxidase subunit II, provide genetic insight into dispersal patterns. For the first time, western Victorian individuals are shown to be genetically distinct from other populations in Victoria. Despite distinct morphological differentiation either side of the Great Dividing Range, populations remain genetically similar between coastal and inland areas suggesting gene flow is likely to occur across these ranges. Landscape genetic analyses indicate variability in dispersal patterns between Victorian andTasmanian platypuses with a greater avoidance of overland travel indicated in Victoria compared to Tasmania. Females appear to remain within their natal area or return to breed, maintaining greater genetic structure in maternally inherited mitochondrial DNA in comparison to nuclear DNA and sharing genetic similarity within a short river distance (i.e.  1.4 km). The results of this study provide a valuable spatial framework for the management of wild platypus populations within south-eastern Australia and a baseline for future monitoring of populations that are likely to be impacted by environmental and anthropogenic change.

Insights into platypus population structure and history from whole-genome sequencing

“…STRUCTURE, and FineSTRUCTURE, do involve statistical models which aim to capture features of the data, but none is based on models of historical population dynamics or history.) Our analyses confirm the strong structure previously reported in the species (Gongora et al, 2012;Furlan et al, 2013), with both pronounced di↵erentiation on the mainland in a north-south direction, and separation of the Tasmanian samples from all other groups. Consistent with Furlan et al (2013), we saw little evidence for structure within the Tasmanian samples, which could be due to greater overland migration in this wetter climate.…”

“…Since it appears to be common to collect related individuals when sampling at the same location across several years, it is likely that previous population genetic studies on the platypus (Kolomyjec et al, 2009;Gongora et al, 2012;Furlan et al, 2013) included relatives, but that this was not detected due to the small number of markers used. Some of these studies included individuals in our sequencing study.…”

Postglacial dispersal patterns and mitochondrial genetic structure of the Pyrenean desman (Galemys pyrenaicus) in the northwestern region of the Iberian Peninsula

“…The methodology used here to study these dispersal modes, and the results obtained, open up a promising avenue of research regarding the study of evolutionary and ecological factors that affect dispersal in different semiaquatic species. Thus, these methods can complement previous studies on semiaquatic species that also disperse along rivers or land depending on different ecological factors, such as the Eurasian otter (Pagacz, 2016), the Eurasian beaver (Senn et al, 2014), or the platypus (Furlan et al, 2013), to name a few, and determine to what extent they depend on river and overland dispersal modes. As we have shown here, it is important to note that the results of this isolationby-distance method may be dependent on the size, geography, and ecological features of the area analyzed, and, consequently, different scales may reflect different aspects of the evolutionary history and ecology of semiaquatic species.…”

“…Rivers may also act as barriers to dispersal of aquatic species when their width, depth, and water regimes or the presence of water infrastructures are inappropriate for the species (Bartáková, Reichard, Blažek, Polačik, & Bryja, ; Byrne et al., ; Raeymaekers et al., ). Despite their interest, there are still few studies that have analyzed the effects of river systems on the genetic structure of semiaquatic mammals, in which their degree of dependency on the aquatic medium is crucial for understanding when rivers act as barriers or as dispersal paths (Furlan et al., ; Pagacz, ; Senn et al., ).…”

“…terest, there are still few studies that have analyzed the effects of river systems on the genetic structure of semiaquatic mammals, in which their degree of dependency on the aquatic medium is crucial for understanding when rivers act as barriers or as dispersal paths (Furlan et al, 2013;Pagacz, 2016;Senn et al, 2014).…”