Taxacom: Juan Fernandez Islands and biogeography

[John Grehan]

Dear colleagues,

For anyone interested, copy of the following can be obtained from Michael
Heads:

Heads, M. & Saldivia, P. 2024. The challenging biogeography of the Juan
Fernandez Islands and Coast Range of central Chile explained by new models
of East Pacific  tectonics. Biol. Rev. https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1111%2Fbrv.13121&data=05%7C02%7Ctaxacom%40lists.ku.edu%7C963b18e34fd74e27d5fe08dca9312387%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638571275725050741%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=FOzYgO64vYz%2B9Tdkw9d4KAvs%2F9XzNGNss%2BSMtUh15ws%3D&reserved=0

This article is (in my opinion) the first globally comprehensive assessment
of the biogeographic structure and relationships of the Juan
Fernandez-Coast Range center of endemism. For those interested, I note that
it includes comments on the strengths of the dispersal model and weaknesses
of the vicariance model.

The authors also state:

"The point stressed here is not the old, theoretical debate about
vicariance versus dispersal, but a direct observation – the close spatial
relationship between repeated areas of endemism and major geological
lineaments"

they recommend:

"[I]sland biogeographers should turn from studying the age and extrapolated
ages of individual islands to re-examining the general history and
evolution of subduction zones, spreading centers, fissures, arcs, back-arc
basins and accreted terranes’ (O’Riordan et al., 2010, p. 50)."

And to address misconceptions, that have even posted on Taxacom in the past:

"One misunderstanding about vicariance theory is that it aims to explain
all distribution patterns by vicariance alone (Elias et al., 2024).
However, that would not be possible, unless every area on Earth was
inhabited by just one, endemic species, and no clades overlapped.
Vicariance theory has always acknowledged that overlap is one of the
main phenomena of distribution and is the result of dispersal"

"Another misunderstanding is that vicariance theory rejects dispersal.
Vicariance theory distinguishes between normal, observed dispersal and
chance, long-distance dispersal (LDD), accepting the former and questioning
the latter (Heads, 2014). The distinction between the two processes is now
widely acknowledged (Hackel & Sanmartín, 2021)."

and for Juan Fernandez:

"To summarise, many distributional phenomena in the JFI biota could have
resulted from chance dispersal. But if this was the case there would be
little more to say about the biogeographic patterns – they would have been
caused by unrelated events in different clades at different times."

Cheers, John Grehan


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