Genetic Diversity of the Xerothermic Weevils Polydrusus Inustus and Centricnemus Leucogrammus (Coleoptera: Curculionidae) in Central Europe
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Eur. J. Entomol. 106: 325–334, 2009 http://www.eje.cz/scripts/viewabstract.php?abstract=1458 ISSN 1210-5759 (print), 1802-8829 (online) Genetic diversity of the xerothermic weevils Polydrusus inustus and Centricnemus leucogrammus (Coleoptera: Curculionidae) in central Europe 1 2 3 àUKASZ KAJTOCH , DOROTA LACHOWSKA-CIERLIK and MIECZYSàAW MAZUR 1Institute of Systematics and Evolution of Animals, Polish Academy of Science, Sáawkowska 17 St., Krakow, Poland, e-mail: [email protected] 2Institute of Zoology, Department of Entomology, Jagiellonian University, Ingardena 6 St., Krakow, Poland 3Institute of Biology, Pedagogical Academy, Podbrzezie 3, Krakow, Poland Key words. Curculionidae, weevils, mtDNA, phylogeography, xerothermic habitats Abstract. Phylogeography, genetic diversity, and demography of central European populations of two flightless xerothermic weevils, Polydrusus inustus and Centricnemus leucogrammus, were studied based on the polymorphism of three mtDNA genes (COII, CytB, and ND1). Results indicate that these xerothermic beetles may have different origins. P. inustus is a recent migrant as the parthenogenetic form has a low level of genetic diversity and lacks a geographic population structure. This is probably a result of a recent (before the end of last glaciation) expansion and/or present dispersal mediated by humans. On the other hand, C. leuco- grammus appears to be a relic species as the populations of this species are much more genetically diverse (six distinct clades) and some of the populations are allopatric and others sympatric. They probably diverged and expanded during the last few glaciations. Genetic discontinuities were detected among localities that are now separated by gaps in the distribution. Boundaries (mountains or farmland) separate the populations into three groups: (1) Moravia and Slovakia, (2) the lower Vistula Valley in northern Poland and (3) south-eastern Poland together with western Ukraine. Evidence for recent gene flow was found only among populations from south-eastern Poland and western Ukraine, and between these two groups. One population from northern Poland was surprisingly related to populations in southern Poland, which may be due to extinction of intermediate populations. INTRODUCTION sible that some forest or grassland species may have The present distribution of species in central Europe is adapted to these dry environments and colonized them. a result of their glacial and postglacial history and the An intermediate hypothesis claims that some xerothermic impact of anthropogenic transformations on environ- habitats are natural relicts whereas others are of anthropo- ments. The origin of many species is reconstructed on the genic origin. Consequently, some species should be basis of paleontological, chorological, and genetic data. native to these habitats, persisting for long periods of Most of the species studied occur in the temperate and time, while others should be new migrants. Unlike the boreal zones (Taberlet et al., 1998; Hewitt, 1999; Avise, changes in the distribution of temperate and boreal envi- 2000; Varga, 2003). In contrast, our knowledge of the ronments, steppe-like habitats were common during gla- history of species that inhabit dry environments on the ciations but contracted during warmer periods. Steppe continent (e.g. steppe), is based mainly on paleontological and xerothermic habitats regressed in the Holocene. It is and pollen data (Kowalski et al., 1989; Tarasov et al., possible that present xerothermic habitats are “warm- 2000). Steppe-tundra environments were common in stage refuges” for species that formerly inhabited steppe- Europe in areas between ice sheets in the north, and like environments (Bhagwat & Willis, 2008). mountains or forest zones in the south (Nehring, 1890; Among the most common xerothermic species are Willis & van Andel, 2004). After climate warming, these insects. Faunistic studies on xerothermic insects in central environments started to contract and move: tundra to the Europe are based mainly on the present distribution of north and higher altitudes, steppe to south-eastern areas grasshoppers (Orthoptera) and weevils (Curculionidae) of Europe. At present, areas of potential natural steppe (Liana, 1987; Mazur, 2001). The only examples of phylo- environment in Europe are limited to the Ukraine, Cas- geographic analyses of semi-steppe insects in Europe are pian area, and Pannonian Basin. Xerothermic habitats on butterflies (Lepidoptera), which are highly mobile so similar to steppe exist in many places in western and cen- might have survived glacial periods in more southern tral Europe and the Balkans. These habitats consist refugees and afterwards expanded their range northwards mostly of small patches such as isolated turfs and thickets (Bereczki et al., 2005; Gratton et al., 2008). On the other on steep slopes of hills and along river beds. The origin of hand, there is little knowledge on the history of flightless, these habitats is unclear. They have been considered as xerothermic insects. relicts of steppe-tundra environments. Alternatively, they This paper presents the results of a study of the genetic may have resulted from the deforestation that has diversity of central European populations of two species occurred over the last few thousand years. It is also pos- of weevils from the subfamily Entiminae, Polydrusus inustus Germar, 1824 and Centricnemus leucogrammus 325 (Germar, 1824). P. inustus inhabits an area between the N-10920, N1-J-12533 and LR-N-12866 (Simon et al., 1994). Ural and Caucasus Mts in the east, and south-eastern The cycling profile for the PCR was: 95°C for 4 min, 35 cycles Poland and the eastern slopes of the Carpathians in the of 95°C for 30 s, 50°C for 1 min, 72°C for 2 min, and a final west (Korotyaev, 1996). This species does not live in the extension period of 72°C for 10 min. After purification PCR fragments (QIAquick PCR Purification Kit, Qiagen) were Pannonian Basin. Some isolated populations occur farther sequenced using the BigDye Terminator v.3.1. Cycle to the west and north in Poland (Mazur, 2001). Popula- Sequencing Kit (Applied Biosystems Inc., Foster City, USA) tions of this weevil over most of its range consist of par- and an ABI 3100 Automated Capillary DNA Sequencer. All thenogenetic females and, at least in Poland, they are sequences were deposited in GenBank (accession numbers triploid (Lachowska et al., 2008). Bisexual populations FJ442860-FJ442930, strain numbers correspond to combined are known only from Georgia and Turkey (Korotyaev, haplotypes of COII-CytB-ND1 genes whose numbers are used 1996). These weevils live mostly on Rosacea in xero- in this paper). Sequences were checked and aligned using Bio- thermic habitats but sometimes are also found in dry Edit v.7.0.5.2 (Hall, 1999) and ClustalX (Thompson et. al., wastelands. The main range of C. leucogrammus stretches 1997). No indels (i.e. insertions or deletions) or stop codons from central Asia to southern Poland. A disjunctive part were observed. The three fragments of mtDNA genes obtained (COII, CytB, and ND1) were subjected to a partition- of its range is situated in the Pannonian Basin and along homogenity test (Farris, 1995) using PAUP* 4.10b (Swofford, the Danube valley. Isolated populations are also found 2002), which showed that further analyses could be performed farther to the north – in Pomerania in Poland (Mazur, on combined sequences. Haplotypes were identified and stan- 2001). This species is bisexual and diploid (Petryszak, dard genetic indices such as haplotype diversity (h), nucleotide 1977; Lachowska et al., 2006). It lives exclusively on diversity (S) and number of private haplotypes (Np) for popula- plants in dry and warm xerothermic turfs and steppe. tions were computed using the program DnaSP 4.20.2 (Rozas et These two species are flightless and their ability to dis- al., 2003). perse over great distances limited, especially currently, Phylogeny and phylogeography because of the fragmentation of xerothermic habitats in The Akaike information criterion in MODELTEST (Posada & central Europe. On the other hand, at least for P. inustus, Crandall, 1998) was used to determine the best-fitting nucleo- it is postulated that human mediated dispersal is possible tide substitution model. Parameters of 56 models of sequence as this species might survive in, e.g. strawberry fields evolution were estimated in PAUP* 4.10b (Swofford, 2002). (Mazur, 2001). Low mobility allows their expansion The HKY+I model was chosen for P. inustus and the HKY+I+G routes and range contractions to be assessed over a longer model for C. leucogrammus (Hasegawa et al., 1985). Unrooted perspective. They are also polyphagous, implying that haplotype trees were obtained for each species using Bayesian their present range was not limited by the availability of inference in MrBayes 3.1 (Huelsenbeck & Ronquist, 2001; Ron- quist & Huelsenbeck, 2003). A distribution of posterior prob- food in the past. abilities was produced by allowing four incrementally heated The aim of this study was to describe the phylogeogra- Markov chains (using default heating values) to proceed for 2 × phy, estimate genetic diversity and level of gene flow 107 generations, with sampling occurring every 1 × 103 genera- among central European populations of these two tions. The approximate number of generations needed to obtain weevils, and calculate divergence and expansion times for convergence of the sampled trees was estimated graphically, these populations.