115 kya) and remained geographically separated until after 7 kya when passage through Torres Strait again became possible for marine animals. Evidence for population growth in the widespread lineage, especially after the last glacial maximum, was detected. Dugongs are RNA Synthesis inhibitor widespread in the tropical and subtropical Indo-West-Pacific (Fig. 1) where they generally feed on seagrasses in shallow waters (see Marsh et al. 2011 for references). Dugongs are long-lived (up to 70 yr) and slow-breeding animals (minimum breeding age 7–17 yr, with single calves produced at intervals of 3–6 yr) (Marsh et al. 2011). In Australian waters,

dugongs occur around the northern coasts, from Moreton Bay in southeast Queensland to Shark Bay in Western Australia (Fig. 1). Currently there are no known barriers to

movement within the Australian range. This range is a Holocene phenomenon due to present-day high sea levels. Barriers existed in the past as a result of low sea level stands associated with Pleistocene glacial cycles BKM120 and may have left persisting genetic signals in Australian dugongs. Lowered sea levels, in particular, likely impacted this species in two ways. The first, affecting many marine taxa, was the exposure of land barriers, fragmenting marine populations, influencing the distribution of species and potentially producing phylogeographic structure (e.g., Mirams et al. 2011). The most important land barrier lay between Cape York Peninsula (the northernmost part of mainland Australia) and New Guinea (Fig. 1). Today, these are separated by Torres Strait, which is only 12 m deep (Chivas et al. 2001). Despite substantial fluctuations,

sea levels have rarely been at or above present-day levels during the last 2.5 million years (Shackleton 1987, Lisiecki and Raymo 2005, Raymo et al. 2006). Consequently, Adenosine triphosphate there have probably been few periods when marine organisms have been able to traverse Torres Strait as they can today. To illustrate this, Figure 2a shows historical sea levels over the most recent glacial cycle. A horizontal line at the −12 m level makes it clear that the Torres Strait landbridge was submerged for only a few thousand years after the penultimate glacial period (between about 125 and 115 kya) and then not again until ~7,000 yr ago, after the most recent glacial period. Barriers can also be produced as a result of loss of suitable habitat. The second effect of low sea level stands was the exposure of the Australian continental shelf. The shoreline at the last glacial maximum (LGM), about 18 kya, was on the very steep continental rise. This eliminated much of the shallow-water habitat suitable for growth of seagrasses, in particular along the east coast of Queensland (Hopley et al. 2007).