title: The carbon and nitrogen ecophysiologies of two endemic tropical orchids mirrors those of their temperate relatives and the local environment.
abstract: Orchids are one of the most widely distributed plant families. However, current research on the ecophysiology of terrestrial orchids is biased towards temperate species. Thus, it is currently unknown whether tropical terrestrial orchids belong to similar trophic guilds as their temperate relatives. To examine the ecophysiologies of two tropical terrestrial orchids, I analysed the carbon and nitrogen stable isotope compositions and nitrogen concentrations of the Hawaiian endemicsAnoectochilus sandvicensisandLiparis hawaiensis. I compared these values with those of surrounding vegetation and their temperate relatives. I found thatA. sandvicensiswas consistently enriched in the heavy isotope of nitrogen (15N) and had higher nitrogen (N) concentrations than surrounding vegetation, and these values were even higher than those of its temperate relatives. Carbon stable isotope composition among populations ofA. sandvicensisvaried by island. These results point to local environment and evolutionary history determining the ecophysiology of this species. WhereasL.hawaiensiswas also enriched in15N and had on average higher N concentrations than surrounding vegetation, these values were not significantly different from temperate relatives, indicating that evolutionary history may be a stronger predictor of this orchid species' ecophysiology than environment. I suggest that both Hawaiian species are potentially partially mycoheterotrophic.
authors.affiliation: Department of Botany , University of Hawaii Manoa , 3190 Maile Way Room 101, Honolulu, HI 96822 , USA.
authors.forename: Nicole A
authors.identifier: 0000-0001-7098-9641
authors.initials: NA
authors.lastname: Hynson
keywords: Hawaii; Orchidaceae; mycorrhiza; rhizoctonia; stable isotopes; tropical ecology