Flora 224 (2016) 42–49

Flora 224 (2016) 42–49 Contents lists available at ScienceDirect Flora journal homepage: www.elsevier.com/locate/flora Fragmentation and environmental constraints influence genetic diversity and germination of Stipa pennata in natural steppes a,∗ a,b a,c a Steffen Heinicke , Isabell Hensen , Christoph Rosche , Dennis Hanselmann , d e b,f Polina D. Gudkova , Marina M. Silanteva , Karsten Wesche a Institute of Geobotany and Botanical Garden, Martin-Luther University of Halle-Wittenberg, Am Kirchtor 1, 06108 Halle (Saale), Germany b German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany c Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, CZ-128 01 Prague, Czech Republic d Institute of Biology, Tomsk State University, Lenina Avenue 36, 634050 Tomsk, Russia e Institute of Botany, Altai State University, Prospekt Lenina 61, 656 049 Barnaul, Russia f Botany Department, Senckenberg Museum of Natural History Görlitz, PO Box 300 154, D-02806, Görlitz, Germany a r t i c l e i n f o a b s t r a c t Article history: Human impact and fragmentation often have negative effects on plant population sizes. This can lead Received 24 November 2015 to declining genetic diversity due to restricted gene flow and genetic bottlenecks, and eventually result Received in revised form 5 June 2016 in reduced reproductive fitness. Environmental conditions can also influence the genetic structure of Accepted 6 June 2016 populations and directly affect their reproduction success. Edited by W. Durka For Stipa pennata, the key species of largely natural steppes in southern Siberia, using AFLP we tested Available online 18 June 2016 whether genetic variability and germination are negatively influenced by fragmentation, and assessed the influence of local environmental conditions. Genetic diversity was moderately high (mean percent- Keywords: Adaptation age of polymorphic bands = 38.4%), with high genetic differentiation occurring between populations AFLP (ST = 0.547). Genetic variation was mainly partitioned (41.8%) between two distinct grassland types. Kulunda-steppe Isolation negatively affected genetic diversity, highlighting that fragmentation had an impact on genetic Population-genetic structure structure. Higher mean precipitation negatively influenced population size, population density and Precipitation genetic diversity. The speed of seed germination was correlated positively with population size and neg- Vegetation atively with vegetation cover, while we found no evidence for negative effects of low genetic diversity on percentage of seed germination. The presence of different genetic groups shows that populations have adapted to a range of environments. Germination speed also differed between groups, as a consequence of maternal effects or of adaption to certain environmental conditions. Our results show that fragmentation can have potentially strong effects even in natural grasslands. We recommend that any future restoration schemes take the observed pronounced genetic differentiation into account. © 2016 Elsevier GmbH. All rights reserved. 1. Introduction to reduced reproductive fitness (Ellstrand and Elam, 1993; Hensen and Oberprieler, 2005; Leimu et al., 2006). However, the rele- In a growing number of threatened species, human medi- vance of such population-wide genetic processes to persistence ated fragmentation significantly constrains population sizes and and conservation in endangered populations remains a topic of increases among-population isolation due to restricted gene flow much debate (Vernesi et al., 2008). Biotic and abiotic factors can (Allendorf et al., 2012; Eckert et al., 2008; Hoffmann and Willi, also have an impact on genetic diversity in populations (Hamasha 2008). Fluctuations, colonisation events and genetic bottlenecks et al., 2013; Huebner et al., 2009; Wang et al., 2006), mainly as (Castric and Bernatchez, 2003) may result in an increased risk of a result of adaptation to environmental conditions. For example, inbreeding, genetic drift and accumulation of deleterious muta- increased drought stress led to increased genetic diversity in Stipa tions (Dudash and Fenster, 2000; Frankham et al., 2002; Young krylovii (Zhao et al., 2006) and Hordeum spontaneum (Nevo et al., et al., 1996), while diminishing genetic diversity is known to lead 1998), while similar habitats can host genetically similar populations (Hamasha et al., 2013; Zhao et al., 2004). A given species’ adaptive potential to particular environmental conditions should ∗ depend heavily on the level of within-population genetic diver- Corresponding author. sity, which can in-turn have a direct bearing on the reproduction E-mail address: steffen [email protected] (S. Heinicke). http://dx.doi.org/10.1016/j.flora.2016.06.003 0367-2530/© 2016 Elsevier GmbH. All rights reserved. S. Heinicke et al. / Flora 224 (2016) 42–49 43 Fig. 1. Global distribution range of Stipa pennata and location of the study populations within the Kulunda steppe. and long-term survival of the population (Bauert et al., 1998; Brook et al., 1965–1992). Its populations have become increasingly frag- et al., 2002; Potvin and Tousignant, 1996). mented throughout their European range (Fig. 1), resulting in Germination is a key stage in reproduction, and is influenced reduced levels of genetic diversity (Durka et al., 2012; Hensen by factors including genetic diversity and/or environmental con- et al., 2010). For S. pennata, high genetic differentiation in its Cen- ditions (Baskin and Baskin, 1998; Gasque and García-Fayos, 2003). tral European range edge is associated with decreasing population Germination behaviour and seed viability are both dependent on sizes and related to populations’ degree of isolation (Wagner et al., species’ capacity to adapt to changing environmental conditions 2012). Moreover, Stipa species are known to develop cleistogamous (Fenner and Thompson, 2005; Ronnenberg et al., 2008). As such, flowers, especially under drier conditions or in more arid regions widely-distributed species in particular show local differentiation (Brown, 1952; Ronnenberg et al., 2011), and cleistogamous flow- in germination behaviour (Fenner and Thompson, 2005). Seed ger- ers of Stipa leucotricha produce a higher ratio of viable seeds than mination is also limited by the environmental conditions required chasmogamous flowers (Call and Spoonts, 1989). to break dormancy (Baskin and Baskin, 2004), and unfavourable Working along a regional climate gradient, we tested (1) climatic conditions can negatively influence germination in certain whether fragmentation of natural steppes in recent decades has plants and lead to diminishing population sizes in the long-term, had a negative effect on genetic diversity and on germination, as which in turn can lead to reduced genetic diversity (Montesinos a proxy for reproductive fitness. Furthermore, we examined (2) et al., 2009). whether genetic structure as well as germination differs among dif- A large share of studies on genetics and germination of grass- ferent steppe habitats. We additionally investigated (3) whether land species originates from European grasslands that have been the regional aridity gradient spanning from the wetter north- fragmented for long periods of time and are largely secondary eastern to the drier south-western part of Siberia is associated with in nature. Genetic structures in novel and peripheral ranges may increasing genetic diversity within populations and, consequently, differ much from those in the natural range (Durka et al., 2012; increased germination. Hensen et al., 2010; Wagner et al., 2012), and effects of fragmentation may thus also differ (Hampe and Petit, 2005). Many 2. Materials and methods European grassland species have native ranges in temperate grasslands, such as steppes and prairies, which cover approximately 8% 2.1. Study species of the global terrestrial surface (White et al., 2000). The steppes of Eurasia are among the world’s largest continuous land biomes. The original description of Stipa pennata by Linnaeus (1753) Gradients in aridity, groundwater availability and edaphic factors was ambiguous, resulting in different species, such as Stipa joannis can cause both small- and large-scale differentiation among natural (Celakovskˇ y),´ occasionally being included under the name. After steppe species (Boonman and Mikhalev, 2005; Box, 2002; Dieterich, Freitag (1985) had determined a new lectotype, S. pennata was 2000). Steppes have, however, been subject to large scale conver- accepted as a separate taxon. sion (Henwood, 1998), which has resulted in severe fragmentation Stipa pennata is a typical grass species of steppes, meadow throughout their distribution range. The Kulunda steppe of south- steppes or forest steppes (Nosova, 1975). It is perennial and 2 western Siberia covers an area of approximately 80,000 km , and tussock-forming and is commonly described as tetraploid (2n = 44; it is a striking example of an ecosystem that has undergone wide- Krasnikov, 1991; Sheidai et al., 2006), which is probably the result ranging land use change. Due to the rising demand for agricultural of a hybridization event (Johnson, 1945). Lemmas typically have crops, approximately 80% of the natural steppes have been trans- an up to 30 cm long bigeniculate awn, which is covered in feath- formed for cultivation (Hoekstra et al., 2005; Meinel, 2002; Wein, ery hairs. Caryopses (hereafter referred to as seeds) are dispersed 1985). As a consequence,

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