[Taxacom] How to generate biogeographic and ecological nonsense

John Grehan calabar.john at gmail.com
Wed Dec 28 22:09:51 CST 2016


Agree absolutely - to the general point that is (I have no judgement to
pass on the authors in particular). The uncritical, pervasive and widely
continuing misrepresentation of minimal divergence estimates as maximal is
the underlying problem here. The Maoricicada example just provides a good
illustration of what results from bad (molecular underestimate) science.

John Grehan

On Wed, Dec 28, 2016 at 10:02 PM, Stephen Thorpe <stephen_thorpe at yahoo.co.nz
> wrote:

> One certainly cannot uncritically accept anything by those authors! Mind
> you, one should not uncritically accept anything by any authors!
>
> Stephen
>
> --------------------------------------------
> On Thu, 29/12/16, John Grehan <calabar.john at gmail.com> wrote:
>
>  Subject: [Taxacom] How to generate biogeographic and ecological nonsense
>  To: "taxacom" <taxacom at mailman.nhm.ku.edu>
>  Received: Thursday, 29 December, 2016, 12:46 PM
>
>  As most list members no doubt
>  appreciate, one cannot use the geological
>  ages of mountains or islands to uncritically make up maximum
>  divergence
>  dates. A good example of the biogeographic mess that is
>  otherwise created
>  (and remains a heavy burden on the scientific integrity of
>  many New Zealand
>  studies) is illustrated by Heads for *Maoricicada* in New
>  Zealand as
>  follows:
>
>
>  “Buckley et al. (2001) calibrated the timeline for
>  phylogeny in*
>  Maoricicada* *campbelli* by assuming that *Maoricicada* was
>  no older than
>  the current alpine habitat (~ 5 Ma), as the genus is mainly
>  alpine. This
>  makes the assumption that taxa currently located in the
>  alpine zone require
>  alpine habitat, and this is not necessarily correct. In any
>  case, *M.
>  lindsayi* occurs at 0-500 m elevation, and *M. campbelli*
>  itself is
>  recorded from 10 to 1580 m (Buckley and Simon, 2007). In
>  fact, most of the
>  “alpine” species of *Maoricicada *are known from some
>  localities below the
>  alpine zone; 10 out of 14 have populations at less than 1000
>  m (around the
>  level of the tree line) and several have populations in the
>  lowlands
>  (Dugdale and Fleming, 1978). These records suggest that
>  *Maoricicada* and
>  at least some of its diversity existed before the present
>  alpine
>  environment developed, surviving in lowland areas of open
>  vegetation. The
>  diverse ancestral complex would have been inherited by the
>  mountains of the
>  Kaikoura orogeny, as they rose. If this was the history, it
>  would undermine
>  a habitat calibration based on the age of the mountains.
>
>
>  Based on the “mountain age” *habitat *calibration,
>  Buckley et al. (2001)
>  calculated that the earliest divergence within *M.
>  campbelli* occurred at
>  2.3 Ma, and they concluded: “We cannot reconcile the
>  earliest date of
>  divergence within M. campbelli with rifting along the Alpine
>  Fault, a
>  process that began to accelerate 10 million years ago.”
>  Yet the young age
>  they calculated for divergence in *M. campbelli* is based on
>  the doubtful
>  assumption they made about the age of the genus.
>
>
>  Buckley et al. (2001) assumed that alpine taxa in
>  Maoricicada could be no
>  older than their alpine habitats. In a subsequent study of
>  the genus,
>  Buckley and Simon (2007) abandoned this method. Instead,
>  though, they
>  calibrated a molecular clock for *Maoricicada *by assuming
>  that related
>  cicadas, endemic on Norfolk Island and Kermadec Islands,
>  could be no older
>  than their current *islands*. But islands are just another
>  habitat type
>  within a region, as are mountains, leaf surfaces, or
>  puddles. The existence
>  of *prior* islands in the region means that calibration
>  using island age,
>  will, as will calibration using habitat age, give dates for
>  clades that are
>  too young by an indeterminate amount. Buckley and Simon
>  (2007) found that
>  *Maoricicada* diverged only in the mid-Miocene. This date is
>  too young (by
>  how much is not known), but at least it confirms that
>  *Maoricicada* existed
>  before the origin of high montane habitats.
>
>
>  Hill et al. (2009) carried out further studies on
>  *Maoricicada campbelli*
>  and confirmed that the main break in *M. campbelli* is
>  between a Central
>  Otago clade and the rest. They wrote “we can only
>  speculated as to what
>  process initiated both the divergence of *M. campbelli *from
>  the rest of
>  Maoricicada at <2.6 Ma, and the main *M. campbelli* split
>  at 1.5-2.1 Ma”
>  (p. 13). As discussed, the “island age” calibration
>  (from Buckley and
>  Simon, 2007) that these dates depend on is flawed.
>
>
>
>  The authors based their conclusions on these dates, but they
>  did not refer
>  to major geological features at the boundaries, such as the
>  Moonlight
>  tectonic zone, and instead suggested that increased
>  sedimentation of river
>  gravel caused by rising mountains produced habitat “into
>  which *M.
>  campbelli *evolved” (p. 14). The new sedimentation and new
>  habitat might
>  explain local range expansion or contraction in the group
>  during the
>  Kaikoura orogeny, but they do not account for the *location*
>  of the mean
>  break in the species.”
>
>
>
>   John Grehan
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>
>  Injecting Intellectual Liquidity for 29 years.
>
>


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