Enzyme Polymorphism in Umbilicaria cylindrica in Northwestern Greenland

Abstract

Living Umbilicaria cylindrica (L.) Del. in the vicinity of Qaanaaq, NW Greenland is of special interest because it is found near sites where subfossils from the same population have recently emerged from beneath glacial ice. Electrophoretically-produced enzyme banding patterns of modern thalli were examined to determine whether isozymes indicated genetic variation within the population. Five enzymes were detected in each of six collection sites and the level of variability based on these was expressed as number of patterns per stand, Complement of the Simpson Index, and the Shannon Diversity Index. As is the case with other lichens examined previously, the U. cylindrica population exhibited appreciable enzyme polymorphism and, thus, potential for evolutionary change. Most enzymes were not detectable in glaciated fossil material, but two bands of esterase showed catalytic activity after approximately 1,350 yr. under ice. Umbilicaria cylindrica (L.) Del. is a variable circumpolar species (Llano 1950) that is common in the Arctic and occurs in a 5 km band of tundra adjacent to the icefield east of Qaanaaq Glacier (Fig. 1), Qaanaaq, NW Greenland (77*28'N, 69*2'W). At the receding margin of the ice, subfossil thalli of the same species were discovered in 1992 (Alstrup 1994) and, based on several samples, carbon dated to approximately 1,350 + 10 yr. This lichen in the vicinity of Qaanaaq is of special interest because it offers a rare opportunity to make phenotypic, ecological, and DNA comparisons between the past and present and to attempt to determine whether evolutionary changes have occurred during the last millennium. To this end, base sequences in mycobiont DNA are presently being investigated (Gargas et al. 1994), and results of a study on secondary chemistry of both recently-emerged and living thalli are now in press (Huneck et al. 1995). The evolutionary potential of any population depends in part on genetic variation, and enzyme polymorphism, which reflects innate variability, has been previously demonstrated in several lichens. The major objective of this study was to determine whether there was populational variation in electrophoretically-generated enzyme banding patterns and, thus, capacity for evolutionary change, in modem U. cylindrica from the Qaanaaq area. Possibilities for studying proteins of dead tissues are limited because of degradation in preserved specimens. Also, finds of fossils and subfossils are infrequent and quantities of available material small. Nev theless, functional enzymes could be of considerable systematic interest. No previous investigations had been made of proteins in deglaciated subfossil lichens, so a second objective was to test for enzyme activity in newly emerging thalli. MATERIALS AND METHODS Samples of Umbilicaria cylindrica were obtained from sites 6-14 (Fig. 1) in unglaciated moraines south of the icefield. In each of the latter sites at least 20 thalli were collected randomly within an area of no more than 3 x 3 m on 7-9 August 1993. When still moist, they were wrapped in ti sue, individually or in small groups, and sent with ice by a sequence of two air carriers to London, Ontario, Canada, arriving in the laboratory after 10 days. Specimens of extant thalli were placed in the University of Western Ontario lichen herbarium and material from three si es reserved for analysis of secondary products. From each of the six remaining sites, ten thalli, each approximately 1-1.5 cm diam., were set aside for DNA extraction in the laboratory of P. DePriest, Smithsonian Institution, U.S.A., and within 24 hr., larger thalli from the same six sites, each up to 2-3 cm diam., were prepared for protein analysis. To remove extracellular phenolics, thalli were washed in excess acetone, and the process was repeated four successive times. It was necessary to combine thalli in pairs to produce samples in the range of 0.38-0.45 g of ground material. From sites 10 and 12, ten samples were available, and from each of the sites 6, 9, 11, and 14, there 0007-2745/95/118-122$0.65/0 This content downloaded from 157.55.39.102 on Mon, 03 Oct 2016 04:50:17 UTC All use subject to http://about.jstor.org/terms 1995] FAHSELT ET AL.: ENZYMES OF UMBILICARIA FROM GREENLAND 119