Natural History of -leaf Goldthread ( aspleniifolia) in Juneau, Alaska Authors: Mary F. Willson, and Ellen M. Anderson Source: Northwest Science, 81(2) : 163-165 Published By: Northwest Scientific Association URL: https://doi.org/10.3955/0029-344X-81.2.163

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Mary F. Willson1, 5230 Terrace Place, Juneau, Alaska 99801 and Ellen M. Anderson, P.O. Box 33362, Juneau, Alaska 99801

Natural History of Fern-leaf Goldthread (Coptis aspleniifolia) in Juneau, Alaska

Abstract Fern-leaf goldthread (Coptis aspleniifolia), a coastal rainforest , has variable sex expression, flowering commonly as males, but also as protandrous and protogynous hermaphrodites. Ramets often change sex expression between years; ramets that produced fruit in one year were usually male or sterile the next year. The most common flower visitors were dance flies. Seeds experimentally dispersed by displacement of open follicles or fruiting scapes usually traveled less than 1 m. Experiments to determine resource- or pollen-limitation of fruit and seed set are desirable.

Introduction and recording fruit development. Sixteen ramets were transplanted from the field into pots placed Fern-leaf goldthread (Coptis aspleniifolia Salisb., in a home garden where wild conspecifics also ) is a common understory plant in grew, in order to monitor sex expression more the coastal coniferous rainforest from northern closely. Washington to southern Alaska. It is an evergreen, clonal herb(Tappeiner and Alaback 1989, Pojar Experiments with seed dispersal took place and MacKinnon 1994) with variable sex expres- in the laboratory. Fruiting scapes were held in a sion (some flowers male, others hermaphroditic; mounted alligator clamp and jostled, either by de- Hitchcock et al. 1964). It is largely sympatric pressing separate follicles about 1 cm and releasing with its more widespread congener, C. trifolia them, or by suddenly displacing the entire scape (Hultén 1968). Our study focused on variation in about 10 cm with a broomstraw. The dispersal sex expression, insect visitors to the flowers, and distance of seeds around each experimental scape aspects of seed dispersal. was measured to the nearest cm. Nonparametric statistics are used here, because Study Area and Methods the distribution of the data did not fit the require- ments of parametric statistics. We surveyed 31 populations of goldthread in the City and Borough of Juneau, Alaska, at elevations less than about 400m, from 2001 through 2006, Results documenting sex expression in 100-300 flowering Fern-leaf goldthread usually flowered from late stems per population, collecting insect visitors, April into June at elevations less than about 400m in our area. At the upper end of this range 1 Author to whom correspondence should be addressed. the flowers often emerged through remaining E-mail: [email protected] snow cover.

Northwest Science, Vol.Fern-leaf 81, No. Goldthread 2, 2007 163

© 2007 by the Northwest Scientific Association. All rights reserved.

Downloaded From: https://bioone.org/journals/Northwest-Science on 29 Apr 2019 Terms of Use: https://bioone.org/terms-of-use Access provided by Morton Arboretum Sex Expression The most common floral visitors were dance flies (Diptera, Empididae, Iteaphila, Anthepis- We noted three kinds of flowers: males (stamens copus), some of which were seen to have pollen only), protandrous hermaphrodites (stamens somewhere on their bodies. Less common were matured first, pistils were initially small but other Diptera (Tethinidae [Pelomyia], Scaridae later lengthened and spread their stigmas), and [Lycoriella], Chironomidae [Chironomus, Ortho- protogynous hermaphrodites (pistils longer than cladius], Muscidae [probably Neomyia], Syrphidae stamens, and anthers sometimes did not open [Neoasia, Brachyopa], Phoridae [Puliciphora], at all, rendering the flower functionally female Ceratopogonidae [Isohelea]), Hymenoptera (Brac- only). Both kinds of hermaphrodites were ca- onidae), and Coleoptera (Staphylinidae). pable of fruiting. The proportion of male flowers in 30 populations ranged from 55 to 96%, with Fruiting Effort a median of 72.5%. Protandry ranged from 5 to 39% (median 21%) and protogyny ranged from The number of follicles per infructescence ranged 1 to 31% (median 6%; n = 21 populations). In from 6 to 11, with a median of eight (n = 33); oc- most cases, all flowers on a stem had the same sex casionally entire follicles were aborted. There were expression, but there were occasional exceptions one to eight developed seeds per follicle; some (<<1% of all stems inspected). ovules in several follicles failed to develop. There Six of the potted ramets changed sex expres- was a weak positive correlation, with considerable sion: two that lived for four years changed from scatter, between number of follicles and number hermaphrodite to male and back again; the other of seeds per follicle (Spearman rank correlation four changed from hermaphrodite to male. In coefficient = 0.515,P < 0.05, n = 20). addition, two ramets produced no flowers after On average, only about 28% of the flowers in one season of hermaphrodite flowers, and one the studied populations were potentially capable of was hermaphrodite after two sterile seasons. setting fruit. We lack data on fruit set on the Seven ramets were hermaphrodite for two or three marked in the field, but seven of ten potted ramets consecutive seasons. with hermaphroditic flowers set fruit in 2005.

Flowering Effort Seed Dispersal The number of flowers per stem ranged from one Mature follicles have an opening at the distal end, to three, but the mode and median in 31 popula- from which the seeds exit. Initially, we considered tions were two flowers (see also Hultén 1968); that follicles might be depressed by raindrops or one-flowered stems were very rare (occurring falling conifer needles, thus flipping out the seeds, once or twice in only five populations). Three- but preliminary tests showed that these stimuli flowered stems ranged from 1 to 15% in these were insufficient to disperse the seeds. With a populations (median and mode = 4%) and were stronger stimulus, such as a heavy downpour more often male than hermaphrodite (29 of 31 or falling branches or cones, dispersal might be populations). accomplished (Jim Pojar, Yukon Conservation Individual ramets often changed sex expression Society, Whitehorse, YT, pers. comm.). Seeds between years. Of 134 ramets that retained the from experimentally depressed follicles achieved previous year’s fruiting stalk (i.e., functioning as a maximum dispersal distance of about 104 cm (n female), 95 (71%) were either male or sterile the = 105). The flowering scape elongates after pol- lination (Pojar and MacKinnon 1994), presumably following year (c2 = 12.24, P < 0.001). 1 as an adaptation for seed dispersal. We therefore examined the effect of scape length (height of fol- Insect Visitors licles above the ground) on seed-dispersal distance. From corolla opening to petal drop, flowers lasted As expected, height had a strong effect on dispersal from six to 17 days and were visited by many distance (median 46 cm from a height of 29 cm, kinds of small insects. Even on warm days, how- which is close to the maximum height observed ever, floral visitors were not common; we usually in the field, n = 50; median 18 cm from a height noted fewer than five insects per 200 flowers of 18 cm, n = 55). Sudden lateral displacement of inspected. the entire scape produced a maximum dispersal

164 Northwest Science, Vol. 81, No. 2, 2007

Downloaded From: https://bioone.org/journals/Northwest-Science on 29 Apr 2019 Terms of Use: https://bioone.org/terms-of-use Access provided by Morton Arboretum distance of about 100 cm. Again, height had a North America, male (and male-functioning) flow- notable effect on dispersal distance (median 51 ers often have greater pollinator rewards or larger cm from 24 cm, n =50; median 26 cm from a floral displays than females (e.g., Willson 1979, height of 14 cm, n = 59). 1991), and C. aspleniifolia may fit this pattern. Dispersal of seeds by jostling the fruiting scape Discussion was usually well within a distance of 1m of the Female function (i.e., fruit and seed production in source. Thus, neither this mode of seed dispersal plants) is often limited by resources (e.g., Trivers nor cloning appear to account for the widespread 1972, Willson 1979). The frequency with which occurrence of fern-leaf goldthread in coastal rainforest or its gradual appearance as young fruiting was followed by a season of non-fruit- forest matures. A possible means of achieving ing in fern-leaf goldthread might suggest that longer dispersal might be consumption by deer: resource-limitation often limits female function in fern-leaf goldthread is a forage species for Sitka this species. The 29% of ramets that functioned as black-tailed deer (Hanley and McKendrick 1983), females at least two consecutive years may have but it remains to be seen if the seeds are viable lived in relatively resource-rich locations. The lack after gut passage through deer. It seems clear that of a negative correlation between follicle number the dispersal mechanism is not a splashcup (Pojar and seed number per follicle indicated that there and MacKinnon 1994), as realized later by Pojar was no trade-off between numbers of follicles (Yukon Conservation Society, Whitehorse, YT, and seeds per follicle. One possible interpretation pers. comm.). of this pattern is that ramets capable of fruiting at all could generally produce as many seeds as Coptis aspleniifolia generally flowers earlier permitted by successful pollination. In other words, than the sympatric C. trifolia, although there is seed production by ramets that are not resource some overlap. Coptis aspleniifolia is a forest limited might be limited by pollen deposition. It species, and C. trifolia occurs chiefly in bogs, is also possible that the great scatter in the cor- although again there is some overlap where the relation between follicles and seeds masks a more two habitats intergrade. Dance flies are seen on complex interaction between resource- and pollen- both species, but the radically different structure of the flowers might inhibit successful pollen limitation. Manipulative experiments varying such transfer between the species. resources as light or various minerals, together with experiments designed to test the alternative Acknowledgements hypothesis that pollen deposition limits seed set, would be informative. The tendency for three- We thank R. H. Armstrong for spurring our interest flowered ramets to be predominantly male may in Coptis and M. Schultz, USFS, for identifying indicate that male flowers are relatively cheaper to the insects. B. Sinclair, G. Courtney, and R. Mer- produce than females and that male ramets use this ritt provided advice on the and biology means to increase pollen production and export as of dance flies. J. Pojar graciously commented on a means of competing with other pollen donors. In the draft ms.

Literature Cited Pojar, J., and A. MacKinnon (editors). 1994. Plants of the Pacific Northwest coast. Lone Pine Publishing, Van- Hanley, T. A., and J. D. McKendrick. 1983. Seasonal changes couver, BC. in chemical composition and nutritive values of na- Tappeiner, J. C. II and P. B. Alaback. 1989. Early establish- tive forages in a spruce-hemlock forest, southeastern ment and vegetative growth of understory species in Alaska. USDA Dept. of Agriculture, Forest Service. the western hemlock-Sitka spruce forests of southeast Pacific Northwest Forest and Range Experiment Sta- Alaska. Canadian Journal of Botany 67:318-326. tion Research Paper PNW 312. Trivers, R. L. 1972. Parental investment and sexual selection. In Hitchcock, C. L., A. Cronquist, M. Ownbey, and J. W. Thomp- B. Campbell (editor), Sexual selection and the descent son. 1964. Vascular plants of the Pacific Northwest. Part of man. Pp. 136-179. Aldine, Chicago. 2. University of Washington Press, Seattle, WA. Willson, M. F. 1979. Sexual selection in plants. American Hultén, E. 1968. Flora of Alaska and neighboring territories. Naturalist 113:777-790. Stanford University Press, Stanford, CA. Willson, M. F. 1991. Sexual selection, sexual dimorphism, and plant phylogeny. Evolutionary Ecology 5:69-87. Received 17 August 2006 Accepted for publication 25 January 2007

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