Large dams limit platypus movement, according to a recent genetic study, with significant conservation implications.
Platypus populations impacted by large river dams
Ronald Bradford/ Via Unsplash
In some Australian states, platypuses are considered a threatened species, and there are general conservation concerns due to the species' well-documented population decline, as per Sciencedaily.
A recent study that was published in Communications Biology looked at the genetic makeup of platypuses in New South Wales's large dammed rivers and nearby free-flowing rivers.
Blood was collected by our Platypus Conservation Initiative researchers at UNSW, and lead author Dr. Luis Mijangos, a former UNSW PhD student who is now at the University of Canberra, extracted the DNA from the blood.
They were able to locate a strong signal stating that genetic differentiation increased quickly between platypuses beneath and above these massive dams by using thousands of molecular markers.
Large dams are a significant hindrance to platypus movement, according to the study. When compared to rivers without dams, platypuses above and below large dams showed greater genetic differentiation.
Importantly, since the dam was built, this genetic differentiation has grown, reflecting the dam's long-term effects.
This is a profound result with important implications for platypus conservation, according to Professor Richard Kingsford, Director of the UNSW Centre for Ecosystem Science and one of the paper's authors.
Due to the restriction on movement caused by the large dams separating the groups of platypuses, there is little to no gene flow among them, which makes these distinct populations more vulnerable to danger.
Increased chances of inbreeding depression, loss of genetic diversity that is adaptive, failure to recolonize areas in which local extinctions had already occurred, and failure to disintegrate to locations with better environmental conditions are all possible consequences.
Dr. Gilad Bino, director of the UNSW Sydney-based Platypus Conservation Initiative, and another study author are aware that numerous threats are causing platypus populations to decline across much of their range in eastern Australia. This research identifies one of the primary threats to this iconic species.
The authors advise that planning for water management and conservation should take into account alternatives to using big dams.
Water storage in off-river reservoirs and the implementation of measures to reduce the impact of dams, such as the artificial movement of individual platypuses among groups above and below dams, or the building of passageways that boost dispersal, could be some of these.
When the exchange of genes between populations is limited, genetic differentiation occurs. The latter may be defined by isolated habitat patches that are divided by ecological or geographic features that severely impede dispersal, such as lakes or ponds in the case of freshwater organisms, as per Heredity.
However, since each patch may offer a continuous habitat spanning greater distances that can be covered by personal dispersal, genetic differentiation could also be seen within continuous populations as matings between individuals are not necessarily random with regards to the distance between individuals.
