Recent and rapid assembly of an island species–area relationship threatened by human disturbance

The island species–area relationship (ISAR) describes how larger islands
support more species. Studies on oceanic archipelagos have shown that
ISARs assembled over millions of years have predictable shapes. However,
it remains unclear how rapidly “classic” ISARs develop, and how they are
formed on much younger systems. Here, we compile a dataset for the fish
communities of 79 postglacial peri-Alpine lakes, and report that an ISAR
with a classical shape has formed de novo in less than 15,000 years.
Despite their very young age, these lakes exhibit an ISAR mirroring older
systems, with a characteristic asymptotic shape. Immigration responds
primarily to area and saturates, whereas speciation is primarily driven by
lake depth. This young ISAR has been reshaped by anthropogenic activities,
with species introductions erasing its upper limit. We demonstrate that
ISARs can develop rapidly after habitat formation in semi-isolated
systems, offering insights into the assembly of ecological patterns.