Several Nominal Species in One
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Several nominal species in one An inventory of Norwegian species of Pteromalus (Hymenoptera: Pteromalidae) associated with Asteraceae plants. Master of Science Thesis in Biodiversity and Systematics Jon Peder Lindemann NATURAL HISTORY MUSEUM UNIVERSITY OF OSLO 2016 I II Several nominal species in one An inventory of Norwegian species of Pteromalus (Hymenoptera: Pteromalidae) associated with Asteraceae plants. III © Jon Peder Lindemann 2016 Several nominal species in one. An inventory of Norwegian species of Pteromalus (Hymenoptera: Pteromalidae) associated with Asteraceae plants. Jon Peder Lindemann http://www.duo.uio.no/ Trykk: Reprosentralen, Universitetet i Oslo IV Preface This master thesis was conducted at the Natural History Museum of Oslo in the period 2014- 2016. It has given me the joy of studying biology from a comprehensive and exciting point of view. For this I want to thank my two supervisors, Arild Johnsen and Lars Ove Hansen. Thank you for giving me a great topic within the field of entomological systematics, and for your help and support during the last years! I also want to give a big thanks to Hannes Baur for his expertise and help, crucial for the identification of the Pteromalus material, and for his friendly hospitality during my visit in Bern. Furthermore, thanks to Gunnhild Marthinsen for the distribution of the insect material to Guelph, Jarl Andreas Anmarkrud for performing the lab work, and Karsten Sund for his nice photography’s. You have been of invaluable importance to my master thesis! I also want to thank those who work at the Entomology Collection, including Geir Søli, Hallvard Elven, Dawn Williams and Trude Magnussen, for providing me with what I happened to need of necessary equipment, help and advices, and Leif Aarvik for identifying the moth, Metzneria metzneriella . Additionally, I want to thank the botanist Asbjørn Knutsen for giving me a private tour and lecture on Asteraceae plants at Bømlo. Finally, thanks to Helene Lind Jensen for proofreading, and my mother and father, family and friends for all your support. Tøyen, 30 May 2016 Jon Peder Lindemann V VI Abstract Frequently, DNA studies on parasitic Hymenoptera have revealed host specific cryptic species from complexes previously thought of as single generalist species. The parasitic Hymenoptera genus, Pteromalus , involves members that attack fruit flies (Diptera: Tephritidae) with variable degrees of host specificities, but with one species, P. albipennis , particularly standing out as a generalist. Many members of the genus are also very close morphologically, and the status of some of the species has therefore earlier been questioned. These trends indicate a potential presence of cryptic species, or the opposite, that several nominal species exist within the boundaries of a single species. To test these assumptions, species of Pteromalus were investigated based on morphological determinations, sequence data and their host fruit fly relations. The insects were hatched from different Asteraceae plants, and sequence analyses of the Pteromalus specimens were conducted based on two loci, the mitochondrial COI and nuclear ITS2 regions. Despite large intraspecific genetic variation in the two loci, no clear indication on cryptic species was revealed. This indicates that the observed polymorphism is caused by other factors, such as population size, speciation in reverse, Introgressive hybridization or Wolbachia infection. In two cases, sequence analyses were not able to distinguish between species of Pteromalus , suggesting that what is currently recognized as seven valid species rather exists within the boundaries of two. These results indicate that the two species, P. intermedius and P. albipennis , not constitute complexes of host specific cryptic species, but possess broader ranges of host fruit fly preferences than previously expected. VII VIII Table of Contents Introduction ....................................................................................................... 1 Material and methods ....................................................................................... 5 Study organisms ............................................................................................. 5 Collecting and hatching ................................................................................ 10 Preserving, mounting and identification ....................................................... 13 Material examined ....................................................................................... 14 DNA extraction, amplification and sequencing ............................................. 16 Poor sequencing ........................................................................................... 17 Data analysis................................................................................................. 17 Results ............................................................................................................. 20 Sequence analyses ........................................................................................ 20 Hatching results ............................................................................................ 26 Discussion ........................................................................................................ 29 Several nominals within one species boundary ............................................ 29 Cryptic species .............................................................................................. 31 Intraspecific variation ................................................................................... 31 Host fruit fly relations ................................................................................... 34 Hatching experiences ................................................................................... 35 References ....................................................................................................... 39 Appendix 1 ....................................................................................................... 49 Appendix 2 ....................................................................................................... 54 Appendix 3 ....................................................................................................... 55 Appendix 4 ....................................................................................................... 57 IX X Introduction Taxonomic work on insects has been largely neglected (Wheeler 1990), despite that well above half of the currently described biodiversity is composed of insects (Grimaldi & Engel 2005). This is paradoxical both in an economical view and in the view of a scientist, as natural ecosystems increasingly have been transformed by humans during the last decades (Wheeler & Cracraft 1996, Berntsen & Hågvar 2010), potentially causing a mass extinction (Tilman et al. 1994, Wake & Vredenburg 2008 ). Today, biodiversity loss is considered to be one of the most serious global issues facing humanity (Thomas et al. 2004, Milennium Ecosystem Assessment 2005). Because of this threat, the need to investigate biolodiversity faster is agreed upon and emphasized among biologists, but the way to do taxonomy more efficient and accurate has been under debate (Will & Rubinoff 2004, Will et al. 2005, DeSalle et al. 2005). The use of a single locus marker as a DNA barcode for all animals has been proposed as a promising solution (Hebert et al. 2003a, Savolainen et al. 2005). Several studies have shown that a 648bp region of the mitochondrial cytochrome c oxidase subunit 1 (COI), can be used to distinguish among closely related animal species (Hebert et al. 2003a, Hebert et al. 2003b, Hebert et al. 2004, Hajibabaei et al. 2005, Smith et al. 2005). Today, DNA barcoding has become an easy accessible tool, for species delimitation and identification. Expanding on this, an integrative taxonomy have been proposed, which uses a number of characters and traits, such as morphology, ecology and DNA, to accurately delimit species and taxa at different levels ( Dayrat 2005, Will et al. 2005, Padial 2010, Schlick-Steiner 2010 ). Great effort are being put into finding cryptic species (Bickford et al. 2007), i.e. two or more species that are, or have been, classified under the same nominal due to high morphological similarities (Bickford et al. 2007). Mayr (1963) theoretically facilitated for the increased focus on cryptic species when he introduced the biological species concept. Unlike the traditional morphological species concept (Mayden 1997), the biological species concept with a basic idea that speciation occurs when populations are isolated and gene flow between them has stopped (Mayr 1963, Smith 1966), are consistent with the idea that 1 species can be morphologically indistinguishable. Although cryptic species commonly is associated with the recent development of molecular species delimitation methods, which during the last decades truly have accelerated the rate of publications on this topic (Bickford et al. 2007), the concept has been used for a longer time (Janzon 1984). Compared to the many scientific papers on revealing cryptic animal species, very little is published on the opposite, that two or more nominal species exists within the boundaries of a single species. This may not only have to do with the taxonomical difficulties of many groups, but also the invested taxonomical effort (Bickford et al. 2007). E.g. recent molecular studies on molluscs, which traditionally