Heterospecific pollination by an invasive congener threatens the native American bittersweet, Celastrus scandens

Invasive plants have the potential to interfere with native species' reproductive success through a number of mechanisms, including heterospecific pollination and hybridization. This study investigated reproductive interactions between a native North American woody vine (American bittersweet, C...

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Bibliographic Details
Published in:PloS one 2021-03, Vol.16 (3), p.e0248635-e0248635
Main Authors: Zaya, David N, Leicht-Young, Stacey A, Pavlovic, Noel B, Ashley, Mary V
Format: Article
Language:English
Subjects:
Animal behavior
Asymmetry
Biology and Life Sciences
Breeding success
Celastrus orbiculatus
Celastrus scandens
Congeners
Deoxyribonucleic acid
DNA
Ecology and Environmental Sciences
Environmental aspects
Fecundity
Fertilization
Flowers
Hybridization
Hybrids
Indigenous species
Interference
Invasive plants
Measuring instruments
National parks
Plant introduction
Plant reproduction
Pollen
Pollination
Reproduction
Seeds
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Summary:Invasive plants have the potential to interfere with native species' reproductive success through a number of mechanisms, including heterospecific pollination and hybridization. This study investigated reproductive interactions between a native North American woody vine (American bittersweet, Celastrus scandens) and an introduced congener (oriental bittersweet, C. orbiculatus). The decline of C. scandens in the eastern portion of its range is coincident with the introduction and spread of C. orbiculatus, and the two species are known to hybridize. The relationship between proximity and floral production of conspecific and heterospecific males on fertilization and hybridization rates was measured at a field site in northwestern Indiana, USA where both species occur and reproduce. We found that the invasive vine had an extreme advantage in both male and female floral production, producing nearly 200 times more flowers per staminate plant and 65 times more flowers per pistillate plant than the native. Using nuclear microsatellite DNA markers we found that hybridization rates were asymmetric; 39% of the C. scandens seeds tested were hybrids, compared to only 1.6% of C. orbiculatus seeds. The asymmetric hybridization rates were likely not solely due to greater abundance of C. orbiculatus pollen because experimental hand crosses revealed that C. scandens had a higher rate (41%) of heterospecific fertilization than C. orbiculatus (2.4%). We previously reported that few hybrids were observed in the wild, and hybrids had greatly reduced fecundity. Thus, in our system, the threat posed by heterospecific pollen is not replacement by hybrids or introgression, but rather asymmetric reproductive interference. Reproductive interference extended to distances as great as 100 meters, thus, efforts to conserve the native species must reduce its exposure to C. orbiculatus over a relatively large spatial scale.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0248635