Fine scale population structure through space and time : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Zoology, Massey University, New Zealand
Loading...
Date
2016
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
Terrestrial
snails,
with
their
diversity
of
interspecific
forms,
have
provided
biologists
with
fantastic
material
to
study
the
evolution
of
ecotypes
and
the
process
of
speciation.
Snails
have
the
advantage
of
shells
that
preserve
well
and
exhibit
trait
variation
readily
perceived
by
taxonomists.
Endemic
to
New
Zealand
is
the
genus
of
giant
carnivorous
Powelliphanta
snails
and
three
species
of
giant
herbivorous
Placostylus.
Both
genera
display
a
range
of
phenotypic
variation
of
shells
within
comparatively
small
geographic
distances.
The
diversity
within
these
snails
has
become
a
matter
of
high
conservation
interest,
as
many
lineages
occupy
small
or
highly
fragmented
ranges
that
render
them
vulnerable
to
ongoing
habitat
loss,
and
predation
by
exotic
pests.
Combining
mitochondrial
sequence
data
and
genotypes
of
microsatellite
loci
I
documented
the
genetic
structure
within
a
species
complex
(Powelliphanta
Kawatiri).
Improved
understanding
of
the
distribution
of
this
complex
and
the
level
of
genetic
diversity
provided
a
picture
of
a
naturally
fragmented
lineage,
restricted
to
a
particular
ecological
zone.
To
investigate
the
evolution
of
Placostylus
ambagiosus
its
mitochondrial
genome
and
that
of
its
sister
species
P.
hongii
were
assembled
and
annotated.
Gene
order
was
consistent
between
the
two
Placostylus
species
although
it
varies
slightly
within
the
wider
Sigmurethra
suborder
due
to
minor
tRNA
rearrangements.
To
distinguish
the
shell
shape
of
spatially
distinct
populations
of
Placostylus
ambagiosus
two-‐
dimensional
geometric
morphometric
methods
were
used.
This
tool
was
used
to
study
shell
shape
evolution
through
time.
Stasis
was
found
to
be
the
most
common
evolutionary
mode,
however
shell
size
followed
a
different
model,
in
one
population,
an
observation
which
would
not
be
expected
if
gene
flow
was
preventing
local
divergence.
Investigation
into
the
genetic
structure
of
Placostylus
ambagiousus
(using
RADseq)
revealed
a
single
admixed
population
illustrating
gene
flow
had
occurred
between
populations
in
the
recent
past.
The
formation
and
maintenance
of
locally
adapted
populations
(ecotypes)
within
Placostylus
ambagiosus
does
not
seem
to
be
prevented
by
gene
flow
within
species.
Description
Listed in 2017 Dean's List of Exceptional Theses
Keywords
Snails, Land snails, Placostylus ambagiosus, Placostylus hongii, Genetics, Population biology, Research Subject Categories::NATURAL SCIENCES::Biology::Organism biology::Systematics and phylogenetics, Dean's List of Exceptional Theses