TY - JOUR

T1 - Herbarium specimens reveal a historical shift in phylogeographic structure of common ragweed during native range disturbance

AU - Martin, Michael D

AU - Zimmer, Elizabeth A

AU - Olsen, Morten T

AU - Foote, Andrew D

AU - Gilbert, M Thomas P

AU - Brush, Grace S

N1 - © 2014 John Wiley & Sons Ltd.

PY - 2014/4

Y1 - 2014/4

N2 - Invasive plants provide ample opportunity to study evolutionary shifts that occur after introduction to novel environments. However, although genetic characters pre-dating introduction can be important determinants of later success, large-scale investigations of historical genetic structure have not been feasible. Common ragweed (Ambrosia artemisiifolia L.) is an invasive weed native to North America that is known for its allergenic pollen. Palynological records from sediment cores indicate that this species was uncommon before European colonization of North America, and ragweed populations expanded rapidly as settlers deforested the landscape on a massive scale, later becoming an aggressive invasive with populations established globally. Towards a direct comparison of genetic structure now and during intense anthropogenic disturbance of the late 19th century, we sampled 45 natural populations of common ragweed across its native range as well as historical herbarium specimens collected up to 140 years ago. Bayesian clustering analyses of 453 modern and 473 historical samples genotyped at three chloroplast spacer regions and six nuclear microsatellite loci reveal that historical ragweed's spatial genetic structure mirrors both the palaeo-record of Ambrosia pollen deposition and the historical pattern of agricultural density across the landscape. Furthermore, for unknown reasons, this spatial genetic pattern has changed substantially in the intervening years. Following on previous work relating morphology and genetic expression between plants collected from eastern North America and Western Europe, we speculate that the cluster associated with humans' rapid transformation of the landscape is a likely source of these aggressive invasive populations.

AB - Invasive plants provide ample opportunity to study evolutionary shifts that occur after introduction to novel environments. However, although genetic characters pre-dating introduction can be important determinants of later success, large-scale investigations of historical genetic structure have not been feasible. Common ragweed (Ambrosia artemisiifolia L.) is an invasive weed native to North America that is known for its allergenic pollen. Palynological records from sediment cores indicate that this species was uncommon before European colonization of North America, and ragweed populations expanded rapidly as settlers deforested the landscape on a massive scale, later becoming an aggressive invasive with populations established globally. Towards a direct comparison of genetic structure now and during intense anthropogenic disturbance of the late 19th century, we sampled 45 natural populations of common ragweed across its native range as well as historical herbarium specimens collected up to 140 years ago. Bayesian clustering analyses of 453 modern and 473 historical samples genotyped at three chloroplast spacer regions and six nuclear microsatellite loci reveal that historical ragweed's spatial genetic structure mirrors both the palaeo-record of Ambrosia pollen deposition and the historical pattern of agricultural density across the landscape. Furthermore, for unknown reasons, this spatial genetic pattern has changed substantially in the intervening years. Following on previous work relating morphology and genetic expression between plants collected from eastern North America and Western Europe, we speculate that the cluster associated with humans' rapid transformation of the landscape is a likely source of these aggressive invasive populations.

KW - Agriculture

KW - Ambrosia/genetics

KW - Bayes Theorem

KW - Cluster Analysis

KW - DNA, Chloroplast/genetics

KW - DNA, Plant/genetics

KW - DNA, Ribosomal Spacer/genetics

KW - Europe

KW - Evolution, Molecular

KW - Introduced Species

KW - Microsatellite Repeats

KW - Molecular Sequence Data

KW - Phylogeography

KW - Sequence Analysis, DNA

KW - Spatio-Temporal Analysis

U2 - 10.1111/mec.12675

DO - 10.1111/mec.12675

M3 - Article

C2 - 24450363

VL - 23

SP - 1701

EP - 1716

JO - Molecular Ecology

JF - Molecular Ecology

SN - 0962-1083

IS - 7

ER -