Orchid-pollinator interactions and potential vulnerability to biological invasion

Area of Science:

• Ecology
• Conservation Biology
• Entomology

Background:

• Mutualistic plant-pollinator relationships are crucial for biodiversity.
• Environmental changes and emerging threats like biological invasions pose risks to these interactions.
• Laurel wilt disease (LWD) is impacting Palamedes swallowtail butterfly (Papilio palamedes) populations, potentially affecting their primary pollinator role.

Purpose of the Study:

• To assess the reliance of Platanthera ciliaris (orange-fringed orchid) on Papilio palamedes for pollination.
• To evaluate the availability and effectiveness of alternative pollinators for P. ciliaris.
• To predict the impact of P. palamedes decline due to LWD on P. ciliaris reproductive success.

Main Methods:

• Field observations of pollinator visitation and fruit set for P. ciliaris.
• Measurement of nectar spur lengths in P. ciliaris flowers.
• Measurement of proboscis lengths of floral visitors, including P. palamedes and Phoebis sennae.

Main Results:

• Papilio palamedes was the primary pollinator; Phoebis sennae provided minimal supplemental pollination.
• Nectar spur lengths of P. ciliaris flowers matched the proboscis lengths of both butterfly species.
• Moderate fruit set (55%) occurred with pollinators present, but failed (0%) without them, indicating pollination limitation.

Conclusions:

• Platanthera ciliaris is highly dependent on Papilio palamedes for successful reproduction.
• Declines in P. palamedes due to laurel wilt disease pose a significant threat to P. ciliaris persistence.
• This study demonstrates how exotic forest pathogens can indirectly threaten plant-pollinator mutualisms, impacting biodiversity.