From a land down under, stripeys swim across the equator
If you’ve snorkelled around Shelly Beach or Clovelly in Sydney, odds are you’ve seen the beautiful and aptly named stripey (Microcanthus strigatus) – named after its eponymous pattern in brilliant yellow and black. Stripeys are often seen in large schools, marauding around jetties and harbours in the company of other sub-tropical species. They form part of a small family of mostly Australian fishes called footballers. Outside of eastern Australia, stripeys also occur along the Western Australian coast, East Asia, and Hawaii.
Despite their global distribution, these populations are largely disconnected from each other, with the equator serving as a major barrier between populations from each hemisphere. Interestingly, this anti-equatorial pattern is documented for a variety of distantly related fishes, suggesting that historical dispersal events may have shaped the distribution of present day fishes.
Recent studies have shown that these populations are deeply divergent, splitting from each other some half a million to a million years ago during the last Pleistocene glacial cycle. By reconstructing ancestral ranges, we were able to show support for an unusual dispersal pattern, with the ancestral stripey originating along eastern Australia, moving south across the Bass Strait to Western Australia, and then northward to Asia across the equator.
While the relict populations of stripeys today are no longer mixing, several of these populations still carry genetic signatures that echo a historical connection across the oceans. Studies like these highlight the importance of addressing widespread species and the impact they may have towards species conservation and biodiversity management, particularly if populations are genetically distinct.
The Australian Museum has a large repository of species such as the stripey that are housed in the collections. Specimens like these have the potential to shed light on historical processes, opening a window through time in which to study how life on earth has evolved.
Yi-Kai Tea, AMF/AMRI Postgraduate Award recipient
- Tea, Y.K., Van Der Wal, C., Ludt, W.B., Gill, A.C., Lo, N. & Ho, S.Y.W. 2019. Boomeranging around Australia: Historical biogeography and population genomics of th anti-equatorial fish Microcanthus strigatus (Teleostei: Microcanthidae). Molecular Ecology, doi:10.1111/mec.15172.