[Taxacom] NZ biogeographer's exam Q3
calabar.john at gmail.com
Sat Jan 28 18:37:00 CST 2017
But the question is why it is not necessary to assume a sea barrier for
taxa *with* a Cook Strait boundary.
On Sat, Jan 28, 2017 at 7:17 PM, Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
> On the other hand, the sea barrier might be the primary factor, followed
> by chance dispersal over the strait to the adjacent land on the other side
> (followed by limited spreading).
> On Sun, 29/1/17, John Grehan <calabar.john at gmail.com> wrote:
> Subject: [Taxacom] NZ biogeographer's exam Q3
> To: "taxacom" <taxacom at mailman.nhm.ku.edu>
> Received: Sunday, 29 January, 2017, 12:37 PM
> NZ biogeographer’s exam Q3
> Why is it not necessary to assume that a Cook Strait
> boundary in a
> terrestrial group is the result of the sea barrier?
> “It is natural to assume that a Cook Strait boundary in a
> terrestrial group
> is the result of the sea barrier. Yet many southern groups
> reach their
> northern limit at the *northern* side of the strait (e.g.,
> the cicada
> strepitans*; Marshell et. al., 2012). In a similar way, many
> groups have their southern limits at the southern side of
> the strait. For
> example,* Hebe parviflora* (PLantaginaceae) is widespread in
> the eastern
> North Island and has its southern limit along the
> northeastern shores of
> the South Island (Marlborough Sounds, Cape Campbell) (Bayly
> and Kellow,
> 2006). These distributions indicate that it is the Cook
> Strait region – not
> the strait itself – that marks the phylogenetic break.
> In a similar pattern to that of these last, terrestrial
> groups, Ross et a.
> (2012) reported a Cook Strait break in the estuarine
> bivalve, *Austrovenus
> stuchburyi*, but noted that the break does not coincide
> exactly with the
> modern strait. Instead, northwest Nelson specimens belong to
> the North
> Island clade, and Wellington specimens are in the South
> Island clades.
> Again, the pattern suggests that the modern topography of
> the Cook Strait
> region is not relevant to the biogeographic break."
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