TY  - JOUR
A1  - Breitkopf, Hendrik
A1  - Schlüter, P. M.
A1  - Xu, S.
A1  - Schiestl, Florian P.
A1  - Cozzolino, S.
A1  - Scopece, G.
T1  - Pollinator shifts between Ophrys sphegodes populations: might adaptation to different pollinators drive population divergence?
JF  - Journal of evolutionary biology
N2  - Local adaptation to different pollinators is considered one of the possible initial stages of ecological speciation as reproductive isolation is a by-product of the divergence in pollination systems. However, pollinator-mediated divergent selection will not necessarily result in complete reproductive isolation, because incipient speciation is often overcome by gene flow. We investigated the potential of pollinator shift in the sexually deceptive orchids Ophrys sphegodes and Ophrys exaltata and compared the levels of floral isolation vs. genetic distance among populations with contrasting predominant pollinators. We analysed floral hydrocarbons as a proxy for floral divergence between populations. Floral adoption of pollinators and their fidelity was tested using pollinator choice experiments. Interpopulation gene flow and population differentiation levels were estimated using AFLP markers. The Tyrrhenian O.sphegodes population preferentially attracted the pollinator bee Andrena bimaculata, whereas the Adriatic O.sphegodes population exclusively attracted A.nigroaenea. Significant differences in scent component proportions were identified in O.sphegodes populations that attracted different preferred pollinators. High interpopulation gene flow was detected, but populations were genetically structured at species level. The high interpopulation gene flow levels independent of preferred pollinators suggest that local adaptation to different pollinators has not (yet) generated detectable genome-wide separation. Alternatively, despite extensive gene flow, few genes underlying floral isolation remain differentiated as a consequence of divergent selection. Different pollination ecotypes in O.sphegodes might represent a local selective response imposed by temporal variation in a geographical mosaic of pollinators as a consequence of the frequent disturbance regimes typical of Ophrys habitats.
KW  - adaptation
KW  - ecotypes
KW  - floral scent
KW  - gene flow
KW  - Ophrys
KW  - orchids
KW  - pollinator shift
KW  - sexual deception
KW  - speciation
Y1  - 2013
U6  - https://doi.org/10.1111/jeb.12216
SN  - 1010-061X
SN  - 1420-9101
VL  - 26
IS  - 10
SP  - 2197
EP  - 2208
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Jansen, John D.
A1  - Codilean, Alexandru T.
A1  - Stroeven, A. P.
A1  - Fabel, D.
A1  - Hattestrand, C.
A1  - Kleman, J.
A1  - Harbor, J. M.
A1  - Heyman, J.
A1  - Kubik, P. W.
A1  - Xu, S.
T1  - Inner gorges cut by subglacial meltwater during Fennoscandian ice sheet decay
JF  - Nature Communications
N2  - The century-long debate over the origins of inner gorges that were repeatedly covered by Quaternary glaciers hinges upon whether the gorges are fluvial forms eroded by subaerial rivers, or subglacial forms cut beneath ice. Here we apply cosmogenic nuclide exposure dating to seven inner gorges along similar to 500 km of the former Fennoscandian ice sheet margin in combination with a new deglaciation map. We show that the timing of exposure matches the advent of ice-free conditions, strongly suggesting that gorges were cut by channelized subglacial meltwater while simultaneously being shielded from cosmic rays by overlying ice. Given the exceptional hydraulic efficiency required for meltwater channels to erode bedrock and evacuate debris, we deduce that inner gorges are the product of ice sheets undergoing intense surface melting. The lack of postglacial river erosion in our seven gorges implicates subglacial meltwater as a key driver of valley deepening on the Baltic Shield over multiple glacial cycles.
Y1  - 2014
U6  - https://doi.org/10.1038/ncomms4815
SN  - 2041-1723
VL  - 5
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Lopez-Barquero, Vanessa
A1  - Xu, S.
A1  - Desiati, Paolo
A1  - Lazarian, Alex
A1  - Pogorelov, Nikolai V.
A1  - Yan, Huirong
T1  - TeV Cosmic-Ray Anisotropy from the Magnetic Field at the Heliospheric Boundary
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
KW  - cosmic rays
KW  - magnetic fields
KW  - magnetohydrodynamics (MHD)
KW  - solar wind
KW  - Sun: heliosphere
Y1  - 2017
U6  - https://doi.org/10.3847/1538-4357/aa74d1
SN  - 0004-637X
SN  - 1538-4357
VL  - 842
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -