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This is the first record of Eleocharis mutata in Florida, and the second record in the continental USA, suggesting a potential natural range expansion of this species from the Caribbean region. A key to species of Eleocharis subg. Limnochloa in Florida is included, along with a site description of the occurrence, visual aids for identification, and a brief discussion of nativity.

Many studies have investigated the aboveground distributions of C3 and C4 grasses along climatic gradients because they illustrate complex interactions between abiotic and biotic controls on ecosystem functions. Yet few studies have examined belowground components of these distributions, which may present very different patterns compared with aboveground measures. In this study, we surveyed grass species cover and collected soil and root samples from field plots at 100–150-m elevation intervals along a climatic gradient in Hawai‘i. We examined how the relationship between soil carbon isotopic composition (δ13C), a proxy for C4 dominance, and % C4 cover changed along a climatic gradient. We also evaluated root biomass to determine if belowground dominance reflects aboveground patterns under climate variation. Results showed that soil δ13C under predicted C4 dominance in wetter sites. The relationship between % C4 cover and soil δ13C became more negative with increasing mean annual precipitation (MAP) based on a linear mixed-effects model (F 1,34 = 12.25, P

High mountain regions in the tropics have thus far been impacted relatively little by anthropogenic activity or plant invasions, however, they are unlikely to be immune to impacts of global change, including climate change and other anthropogenic disturbances. Changes in fire regimes are known to accelerate the spread of invasive C4 grasses and interactions between changes in fire and climate can alter species distributions. The aim of this study was to compare grass distributions along an elevational gradient in Hawai‘i between 1966–1967 and 2008 to determine whether C4 and C3 grass distributions are shifting upward in response to alterations in fire and climate patterns. Field plots at Hawai‘i Volcanoes National Park were surveyed for grass species and cover at ˜150 m elevation intervals and compared to previous surveys done in 1966–1967. We found that the transition elevation, marking a shift in dominance between C4 and C3 grasses based on relative cover, shifted upward over 40 yr (95% confidence interval = 1476 m ± 130 m in 2008 versus 1200 m ± 106 m in 1966–1967). On the other hand, maximum elevations of all C4 or C3 grasses as a group were not significantly greater than 1966–1967 elevations; however, a subset of C4 (and fewer C3) grasses moved to substantially higher elevations, and these were the species adapted to fire. 100% of fire-adapted grasses moved up in elevation compared to 29% of non-fire adapted species, and the change in elevation of those species (=+454 m) was significantly greater than the change in elevation of non-fire adapted species (p = 0.003). Our study documents an upward expansion of fire-adapted grasses at high elevations in the tropics as an important threat that seems to be compounded by warming trends.

C3 and C4 plants are often reported to differ in functional traits and resource-use strategies, whereas nonnative plants may differ from native plants in functional traits, leading to different resource-use strategies that facilitate their invasion. In this study, we compared root functional traits of native and nonnative C3 and C4 grasses with the prediction that different resource acquisition strategies would be observed among these groups. We examined five root functional traits [mean diameter, specific root length, root tissue density, fine root percentage (diameter P P