Divergent lineages in two species of D endrobium orchids ( D . speciosum and D . tetragonum ) correspond to major geographical breaks in eastern Australia
Abstract Aim We investigated genetic divergence among two widespread eastern A ustralian orchids ( D endrobium sect. D endrocoryne ): D endrobium speciosum and D endrobium tetragonum . These orchids are endemic to mesic habitats, with distributional ranges that cross major geographical breaks associ...
Saved in:
Published in | Journal of biogeography Vol. 40; no. 11; pp. 2071 - 2081 |
---|---|
Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
01.11.2013
|
Online Access | Get full text |
Cover
Loading…
Summary: | Abstract
Aim
We investigated genetic divergence among two widespread eastern
A
ustralian orchids (
D
endrobium
sect.
D
endrocoryne
):
D
endrobium speciosum
and
D
endrobium tetragonum
. These orchids are endemic to mesic habitats, with distributional ranges that cross major geographical breaks associated with deep divergences in various fauna. We compared the biogeography of these orchids with other taxa and tested for congruence of divergence date estimations.
Location
Eastern
A
ustralia, latitude 14° S to 34° S.
Methods
Phylogenetic relationships within each species were estimated using maximum parsimony based on sequences of internal transcribed spacer (ITS) regions of nuclear ribosomal
DNA
and the
psb
A–
trn
H spacer region of plastid
DNA
. Divergence dates were inferred by Bayesian relaxed‐clock dating, calibrated on an early Miocene macrofossil,
D
endrobium winikaphyllum
from
N
ew
Z
ealand.
Results
Deep divergences were revealed within each species.
D
endrobium speciosum
includes three major geographical clades (deepest 2.6%
ITS
divergence): a northern Queensland clade, which occurs mainly to the north of the Black Mountain Corridor (
BMC
) in the Wet Tropics; a central Queensland clade; and a southern clade related to the central clade and separated from it by a dry corridor, the St Lawrence Gap (
SLG
). The central and northern lineages show overlap near the
BMC
. Divergence in this area is estimated to date from the Pliocene, possibly late Miocene, 4.3 (2.0–6.9) Ma, and at the
SLG
in the early Pleistocene, possibly late Pliocene, 2.0 (0.6–3.8) Ma.
D
endrobium tetragonum
also includes two clades, deeply divergent (3%) at the
SLG
, estimated as Pliocene in age but possibly latest Miocene, 3.7 (1.8–5.9) Ma.
Main conclusions
D
endrobium
orchids reveal significant divergence associated with geographical breaks in eastern Australia, the
SLG
and
BMC
, patterns broadly concordant with findings for fauna. We infer that divergences were driven by topographical and climatic conditions, with contraction and fragmentation of mesic biomes during periods of drying in the late Neogene. |
---|---|
ISSN: | 0305-0270 1365-2699 |
DOI: | 10.1111/jbi.12145 |