Abstract Detail

Ecology

Harritt, Iris Cato [1], Takebayashi, Naoki [2], Wolf, Diana [3], Flint, Paul [4], Ruess, Roger [5].

Geographic variation in phenotypic plasticity of Hoppner’s sedge, Carex subspathacea.

Geese breeding in coastal regions of the Yukon-Kuskokwim River Delta (YKD) in subarctic western Alaska and the Arctic Coastal Plain (ACP) in northern Alaska forage extensively on Hoppner’s sedge (Carex subspathacea) and the availability of this preferred forage has been shown to influence goose population dynamics. Hoppner’s sedge grows as very short (<5 cm tall), dense lawns where individual shoots have high nitrogen concentration. Previous work on the YKD has shown that, in the absence of goose grazing, Hoppner’s sedge grazing lawns converted to Carex ramenskii swards which were described as tall (>10 cm) monotypic stands with low leaf nitrogen concentration. C. ramenskii is considered a poor-quality forage for geese. This conversion, which only occured on the YKD, results in a unique grazing system. We sought to understand the genotypic and environmental influences on these different Arctic and subarctic grazing systems, both of which appear to be based on Hoppner’s sedge. We used genetic sequence capture to describe relatedness between YKD C. subspathacea and C. ramenskii and ACP C. subspathacea. Genetic data clearly showed that what had previously been described as two species (C. subspathacea and C. ramenskii) on the YKD are just different morphologies of Hoppner’s sedge. Further, while there is evidence of some geographic differentiation, all samples from both ACP and YKD grouped together as Hoppner’s sedge when compared to other Carex species. We then used a reciprocal common garden experiment to examine environmental influence (subarctic vs arctic) on morphological plasticity. Ungrazed subarctic Hoppner’s sedge from YKD was phenotypically plastic, and quickly converted to the tall form in the subarctic garden, but remained short in the Arctic garden. Conversely, Hoppner’s sedge from ACP demonstrated very limited plasticity and remained short in both gardens. This suggests that there is a genetic component to the phenotypic plasticity in the growth forms and that environmental conditions influence the expression of this plasticity. This understanding of the functional causes of the phenotypic differences between forage plants is important for predicting the effects of future climate change on grazing systems in both regions.

1 - University of Alaska Fairbanks, Biology and Wildlife, 2090 Koyukuk Dr, Fairbanks, AK, 99709
2 - University Of Alaska Fairbanks, Institute Of Arctic Biology, 2140 Koyukuk Dr., 311 Irving I Bldg, IAB, Fairbanks, AK, 99775, United States
3 - University Of Alaska Fairbanks, Institute Of Arctic Biology, 2140 Koyukuk Drive, PO Box 757000, Fairbanks, AK, 99775, United States
4 - U.S. Geological Survey, Alaska Science Center, 4210 University Dr., Anchorage, AK, 99508
5 - University of Alaska Fairbanks, Institute Of Arctic Biology, 2140 Koyukuk Dr., 311 Irving I Bldg, 311 Irving I Bldg, Fairbanks , AK, 99775

Keywords:
Carex
Geese
Phenotypic plasticity
Grazing Dynamics
climate change.

Presentation Type: Oral Paper
Number: EC08003
Abstract ID:890
Candidate for Awards:None