Morphological Variation of Plants on the Uprising Islands of Northern Russia

Ann. Bot. Fennici 46: 81–89 ISSN 0003-3847 (print) ISSN 1797-2442 (online) Helsinki 30 April 2009 © Finnish Zoological and Botanical Publishing Board 2009 Morphological variation of plants on the uprising islands of northern Russia Anna Serebryanaya1 & Alexey Shipunov2,* 1) San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA 2) Encyclopedia of Life, Marine Biological Laboratory, Woods Hole, MA 02543, USA (corresponding author’s e-mail: [email protected]) Received 20 May 2008, revised version received 16 Feb. 2009, accepted 24 Feb. 2009 Serebryanaya, A. & Shipunov, A. 2009: Morphological variation of plants on the uprising islands of northern Russia. — Ann. Bot. Fennici 46: 81–89. The purpose of our study was to test whether any signifi cant morphological differences exist between island and mainland plant populations of the north European White Sea. Six polymorphic species were studied: Atriplex nudicaulis (Chenopodiaceae), Euphra- sia wettsteinii (Orobanchaceae), Achillea millefolium (Asteraceae), Parnassia palustris (Parnassiaceae), Potentilla egedii (Rosaceae) and Rhodiola rosea (Crassulaceae). Based on the multivariate analyses of our data, we found 10 cases where differences between island and mainland populations are best explained by the existence of short- scale evolutionary processes. These results suggest that plant populations on islands of recent origin may display local morphological divergence in a short evolutionary time frame. Key words: evolution, islands, plant morphology, variation, White Sea Introduction It is known that small-scale morphological differentiation is often subject to natural selec- Islands have been considered natural laborato- tion (Gurevitch 1992, Linhart & Grant 1996) ries for exploring the evolutionary processes and microevolution rates are sometimes surpris- from the times when Charles Darwin discovered ingly high (Cody & Overton 1996, Van Vuren & fi nch diversity on the Galapagos Islands, which Bowen 1999, Bone & Farris 2001). Of particular lead him to the idea of geographical specia- importance to our study is that there is a sig- tion (Darwin 1839, Grant 1996, Emerson 2002, nifi cant geographical variation in certain mor- Whittaker & Fernandez-Palacios 2007). There phological characteristics of plants (Andersson are multiple examples of recent evolutionary 1991, Andersson 1995, Widen 2003, Barrera & studies on islands, and in numerous cases plants Walter 2006). Moreover, many aspects of islands’ are the main objects of research (Soejima et al. fl ora are greatly infl uenced by island surface area 1994, Barrett et al. 1996, Ito et al. 1998, Baldwin and its remoteness from the mainland (McMas- & Sanderson 1998, Stuessy 1998, Ballard 2000, ter 2005, Kalmar & Currie 2006). In general, Stuessy et al. 2006). morphological differences could happen due to 82 Serebryanaya & Shipunov • ANN. BOT. FENNICI Vol. 46 Fig. 1. Map of the region, with designations of all investigated islands. Names of islands with “contrasts” are set in boldface; dots indicate locations of mainland samples. Inset in the upper left corner shows the part of Europe enlarged in the main map. Islands of the Odinokie Ludi archipelago: 29 = Boljshaya Odinokaya Luda, 30 = Malaya Odinokaya Luda, 31 = Srednyaya Odinokaya Luda, 32 = Ochenj Odinokaya Luda. Islands of the Kem’-Ludy archipelago: 65 = Kemludskij, 66 = Perejma, 67 = Korablik, 69 = Korzhnichiha, 70 = Sinopchiha, 76 = Bol’shoj Asaf’ev, 99 = Zhguchij, 100 = Matrasik. Other islands: 2 = Oleniyj, 7 = Ivanjkov, 8 = Rihzhenjkiyj, 10 = Skeletov, 11 = Drakonchik, 23 = Izbyanaya Luda, 42 = Sidorov, 43 = Cherepakha, 49 = Vihsokaya Luda, 52 = Vichennaya Luda, 82 = Morschovec, 90 = Keret’, 91 = Pryaostrov, 92 = Pizhmyak, 93 = Kivsyak, 94 = Lahtak, 96 = Zvezdov, 106 = Gusinyj, 107 = Zelenyj, 110 = Izbyanoj, 111 = Bolshoj Andronin. selection and/or genetic drift (Abdelkrim 2005, sequence of the former depression, many islands Stuessy et al. 2006), and should correlate with the are still rising today with a speed of approxi- remoteness of the island as a measure of isola- mately 5–8 mm per year, and new islands are tion (Mayr 1942, Grant 1996). They could also constantly appearing (Koshechkin 1979, Shipu- be caused by phenotypic variation but that can nov & Abramova 2006). be excluded (at least partly) by using properly The fl ora of these islands is relatively poor selected species and parameters, multiple obser- (Shipunov & Abramova 2006) since the major- vations, and investigations of local variability. ity of plants belong to the northern taiga. Distant To investigate the geographic impact on plant islands are covered with tundra-like fl ora mainly morphology, we chose to study the uprising due to strong winds (Breslina 1987). A variety of islands and islets of Chupa and Kiv gulfs and plants that occur both on the mainland and the Kem’-Ludy archipelago of the big Kandalaksha islands of the White Sea were noted to be taxo- gulf of the north Russian White Sea (Fig. 1). The nomically diverse (Sokoloff & Filin 1996). We history of these islands is unique. During the last chose six herbaceous (two annual and four peren- ice age (12–15 000 years ago) the entire northern nial) species that are common to the studied area Europe was covered with ice, which was around and have the reliable taxonomic diversity under 3 km deep and caused enormous pressure on the the species level: Atriplex nudicaulis (Chenopo- Earth’s crust. As a result, the whole region of diaceae), Euphrasia wettsteinii (Orobanchaceae), the future White Sea sank to form a depression Achillea millefolium (Asteraceae), Parnas- of 0.2–0.3 km deep (Hattestrand & Clark 2007). sia palustris (Parnassiaceae), Potentilla egedii Later, when the climate became warmer, the ice (Rosaceae) and Rhodiola rosea (Crassulaceae). melted, forming the sea and its islands. As a con- For example, Atriplex species are extremely ANN. BOT. FENNICI Vol. 46 • Morphological variation of plants on the uprising islands 83 variable, both morphologically and genetically, 6 landmarks, respectively, situated on the bend and some of their characters can be affected by points of the leaf contour. The coordinates of the environment conditions (Ortiz-Dorda et al. landmarks were written to a data fi le with the 2005, Bouda 2006). Euphrasia is also known for help of a screen digitizer tpsDig (Rohlf 2006). its high morphological variability, especially in The relative warps, characterizing the degree of northern regions (Swann 1973, Yeo 1978, Gus- differences between the specimen and consen- sarova 2005). Many of Achillea species are taxo- sus confi guration, were calculated with tpsRelw nomically problematic, with bottleneck effects (Rohlf 2007) and then used in the overlap analy- having a large impact on variation in several spe- sis (see below). Original coordinates were nor- cies, especially among those in isolated habitats malized using the Procrustes fi t method (α = 0). (Saukel & Langer 1990, Guo et al. 2004, 2005, To explore the variation of plant species 2008). Parnassia palustris can be diploid and within one island we performed a thorough sam- tetraploid (the last form occurs specifi cally in the pling on some islands for Achillea and Rhodiola. northern Europe and alpine habitats), both types We tried to choose multiple sites that belonged show morphological variation, and are often con- to different habitats and were most distant from fused with other species (Borgen & Hultgard each other. This was done to eliminate the pos- 2003). Similar situations exist in Potentilla egedii sibility of small-scale impacts of local conditions (Kamelin 2001) and Rhodiola rosea (Uhl 1952, on the sample populations. The same overlap Sokoloff & Filin 1996). analysis (see below) was used with this kind of Thus, the high variability of the chosen plant data. species set makes them a reliable tool to study The analytical part of our study started with plant variability on islands. Consequently, the the comparison of overlaps derived from princi- goal of our research was to check if plants evolve pal components analysis (PCA) for scaled data differently on the mainland as compared with the (we used scaled data to eliminate the effects of islands, and if the geographical characteristics the different nature of parameters used). For each of the islands (such as height and surface area) species, extreme points on the PCA graph(s) of infl uence these changes. most informative principal components (usually PC1 and PC2, sometimes also PC3) were used for plotting convex hulls, which depicted differ- Materials and methods ent populations (see Fig. 2). In most cases, polygons were intersected and therefore let us calcu- Typically at least one population from each late the percentage of overlap between each pair island was studied. Each sample consisted of of polygons. Since we used polygons instead of approximately 20–25 plants from every popula- original points, we were able to take into account tion (topographically isolated group of plants). the whole norm of reaction and identify the sam- On each plant 7–10 morphological characteris- pling effect. Thus, overlap coeffi cients were cal- tics were measured, and in most cases we used culated for all pairs of populations, along with the parameters that were already known as vari- mean overlap for each population as a measure of able and/or helpful for distinguishing plants on morphological remoteness. We used 20%–25% the intra-species level (Swann 1973, Yeo 1978, of mean overlap as a boundary value for initiating

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