Abstract Detail

Ecological Section

Marchini, Gina [1], Cruzan, Mitchell [2].

The consequences of gene diversity and nitrogen deposition for competitive success of the newly invasive grass Brachypodium sylvaticum.

Human activity has dispersed many species across continents where they encounter novel biotic and abiotic interactions. Brachypodium sylvaticum (slender false brome) is an invasive perennial bunchgrass rapidly spreading throughout the Pacific Northwest of North America. As B. sylvaticum spreads, secondary bottlenecks and inbreeding may contribute to lag phases and delay population growth. We hypothesize that inbreeding may decrease fitness of homozygous self-fertilizing populations until there is sufficient gene flow to elevate the level of genetic diversity. To investigate whether decreased population genetic diversity (Hs) from bottlenecks and habitat disturbance due to nitrogen deposition affect B. sylvaticum competition with three other perennial bunchgrasses, we grew seeds of Holcus lanatus, Dactylis glomerata, and Elymus glaucus, species commonly found near populations of B. sylvaticum. Plants were grown for 26 months in a randomized competition matrix in a greenhouse. Nitrogen was applied to half the replicates as NO₃NH₄, and fitness of B. sylvaticum individuals was estimated as plant size, which was measured monthly throughout the growing season. Population gene diversity levels ranged from 0 (homozygous inbred population) to 0.34 (outbreeding population). Factors influencing growth and flowering varied over the three growing seasons. While Hs influenced only first season growth the effects of nitrogen did not become significant until the second season, even though nitrogen levels in plots consistently influenced leaf chlorophyll content. By the third growing season a significant nitrogen by Hs interaction is observed as homozygous populations exhibit significantly higher growth in high nitrogen than in low nitrogen. B. sylvaticum performed best in intraspecific competition in the high nitrogen treatment, as there were significant positive effects on growth and flower number. Species identity of competitor significantly influenced B. sylvaticum survival, with survival highest in intraspecific competition, and lowest when grown with another invasive plant (Holcus lanatus). Results suggest that even though competition and genetic variation impact successful colonization, these effects can diminish after establishment. The addition of nutrients such as nitrogen to these habitats increases individual fitness regardless of population heterozygosity, so that limited genetic variation is no longer a barrier to population growth.

Broader Impacts:

1 - Portland State University, Biology, P.O. Box 751, Portland, OR, 97207, United States
2 - Portland State University, Department of Biology, PO BOX 751, PORTLAND, OR, 97207, USA

Keywords:
competition
invasive species
genetic diversity
nitrogen
grasses.

Presentation Type: Oral Paper:Papers for Sections
Session: 14
Location: Newberry/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 2:15 PM
Number: 14002
Abstract ID:330
Candidate for Awards:None