Abstract Detail

Conservation Biology

Jolls, Claudia [1], INKSTER, JACLYN [1], Fegley, Erin [1], Havens, Kayri [2], Vitt, Pati [2], Scholtens, Brian [3].

Antagonistic and mutualistic networks of the rare Great Lakes shoreline endemic, Pitcher’s thistle.

Pitcher’s thistle (Cirsium pitcheri, Asteraceae) is a federally threatened perennial, endemic to the Great Lakes dunes and cobble shores. It is monocarpic, growing vegetative for 4-8 years, flowers once (producing capitula or heads as inflorescences), and then dies. Pitcher’s thistle lacks any means of vegetative reproduction. A biological control used to suppress weedy thistles, a univoltine seed-eating weevil (Larinus planus, Curculionidae, Coleoptera), has recently spread to Pitcher’s thistle. After mating, female weevils oviposit eggs in the thistle head; larvae then develop eating ovules and maturing seeds before pupating and emerging as adults that same season. Decreased in plant seed production ranges from 45-100%. Cirsium pitcheri flowers mid-season on the dune landscape and may provide important floral resources for pollinators and other C. pitcheri populations and have modeled effects of weevil seed predation on plant population viability using a demographic data set begun in 1995. We asked 1) What factors may increase vulnerability to seed predation by weevils, 2) Does a low impact deterrent, kaolin clay, hold any promise for weevil control? and 3) What is the role of C. pitcheri as a floral resource in these ecosystems? Intensive temporal monitoring of plants within and among years, including more than 1700 heads at three sites in northern lower Michigan, confirms that L. planus can have significant negative impacts on C. pitcheri seed production, fecundity, and population viability. Kaolin clay slightly reduced probability of oviposition into heads by weevils but did not repel needed insect visitors from C. pitcheri. We also observed all the insect-pollinated flowering species in 50-10 m x 10 m plots for a total of 14,090 minutes of observations between 25 June and 5 August 2015. Pitcher’ thistle was the most visited plant species, by the most insects, in the plant-insect network of 22 angiosperm and 59 insect taxa. Network analysis metrics confirmed highest species strength and connectedness for C. pitcheri. Although rare, Pitcher’s thistle is an important floral resource for this dune ecosystem. Protection of this iconic endemic against non-target impacts from (Larinus planus and an increasing suite of other threats should be a priority for management and conservation.

1 - EAST CAROLINA UNIVERSITY, Department Of Biology, HOWELL SCIENCE COMPLEX, GREENVILLE, NC, 27858-4353, USA
2 - Chicago Botanic Garden, CONS SCI DEPT, 1000 Lake Cook Road, Glencoe, IL, 60022, USA
3 - College of Charleston, Biology, Charleston, SC, 29424, USA

Keywords:
seed predation
pollinator networks
non-target impacts
biological control.

Presentation Type: Oral Paper
Session: 26, Conservation Biology I
Location: 104/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 3:00 PM
Number: 26007
Abstract ID:103
Candidate for Awards:None