A Thesis Submitted to the Faculty of Graduate Studies and Resêarch

LIFE-CYCLE AND ECOLOGICAL IMPACT OF POLISTES VERSICOLOR VERSICOLOR (OLIVIER) (HYMENOPTERA: VESPIDAE) , AN INTRODUCED PREDATORY WASP ON THE GALAPAGOS ISLANDS, ECUADOR by Christine Parent, B.Sc. A thesis submitted to the Faculty of Graduate Studies and Resêarch in partial fulfillrnent of the requirernents for the deg-~ee of Master of Science Department of Biology Carleton University Ottawa, Ontario April 25, 2000 e 2000, Christine Parent National Library Bibliothèque nationale 1+1 ofcanada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395, rue Wellington Ottawa ON K1A ON4 Ottawa ON KI A ON4 Canada Canada Your fik Vorre relëmnw Our fike Notre rsfBrenw The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Biblioîhèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/nlm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fi-om it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son pemiission. autorisation. Abstract This study investigated the ecology (especially the life cycle) of Pol istes versicolor, an introduced predarory wasp on the Galapagos Islands. Emphasis was given to the impact it might have on naturally occurring insects and insect-feeding birds of the Galapagos Islands. The data suggest thalt Polistes versicclor is a food semi-specialist, feeding on various terrestriâl invercebrates, but predominantly on lepidoptera larvae. Study of the colony cycle revealed thaï air teniperâture was significantly related with the nümber of active colonies. However, it could r~otbe established if P. versicolor has a seasonally synchronized cycle. The predatioz pressure of P. versicclor on chs insscz faunâ was estimated to range between 17 and 154.52 g/ha/day of prey insect tissue. Acknowledgements My research was carried out with the permission and scpport of the Servicio del Parque Nacional Galapagos, and the Charles Darwin Research Station. The research was funded by an Innovative Research Grant £rom the Canadisn International Development Agency, and a grant from the Fonds poür la Formâtion de Chercheurs et l'Aide à la Recherche. 1 forenost thank my thesis supervisor, Stewart B. Peck, for his support and guidance throughout this projecc. Speciâl thanks goes to the people of the Inverteb-vate Program at the Charles Darwin Research Station, particularly îo Dr. Chârlotte Caustor! and LSzaro Roque for their constant encouragement and helpful advice. I krve hâi the pleasure to be assisted and work with several enthusias~icpeople chat have now become good friends: Tom, Mzle, Rebecca, Veronica, Camilo, and Marie-Christine. I would most probably hâve completed this project without them, but my stay in the GalEipagos and the fieldwork would not have been so enjoyable. Finally and most irnportantly, 1 ârn very grateful to my farnily and close friends for their suppcrt during the last two years. Very special chanks to my closest cornpz~ion,Icy Veillet, who could not have been more helpful and supportive. Table of Contents Title Page i Acceptance Sheet ii Abs trac t iii Acknowledgements iv Table of Contents List of Tables List of Figures List of Appendices xiii Introduction Methods Study Area Distribution and density of P. versicoZor nests Methods of observation and experimentation Nss ting habi ts Foraging habi ts Foraging range Population dynamics Measure of abiotic and biotic environmental factors Abioiic factors Biotic Factors Table of Contents, continued. Results Descript ion of Polis tes versicolor colonies Distribution and density Foraging activity Growth of colonies Colony cycle Predation pressure Infes~ationby brood predators Predat ion Discussion Description of the colonies Distribution and density Foraging activity Colony growth and colony life-cycle Predation pressure Infestation by broo6 predators and predaticn Conclusions References Tables Figures vii Table of Contents, continued. Appendices viii List of Tables Table Description Paae 1 Landbirds and reptiles occurring on the GalZpagos Islands that are known to feed on insects anci other terrestrial Fnvertebrates. Climatic conditions £rom January to Decemiber 1999 the Galapzgos Islânds Cornparison of support structures for riests of Polis tes versi color. Density of active colonies of Poliçtes versicclor Santa Cruz and Floreana Islands as measured in 1992/1993 and 1999. Prey items in flesh loads of returniq fc,râcers. Proportion of different types of ~O&S fciun~in the crop of retuxning foragers with empty mzndibles. 68 Proportion of the different types of loads (visually identified) of weturni~gforagers. Predation pressure of Polis tes versicolor ori- the insect fauna in diffexent vegetation zones on Santa Cruz Island. List of Tables, continued Table Descri~tion Paqe 9 Proportion of active Polistes versicolor nests that presented signs of moth predation (Taygete sphecophila) . 71 List of Figures Fisure Descri~tion Pase 1 The Galapagos Islands. 73 2 Polistes versicolor. 75 3 Santa Cruz Island and the study sites. 77 4 Vegetation zones found ori high GalSpacos Islan6s. 72 5 Floreana Island and the study s'ries. 81 6 Arrangement of yellow pan traps used to determi~e the f oraging range of Polistes versicolor. 83 Height at which Polistes verçicolor built thelr nests - 85 Density of active colonies of Polis tes versicolor on Sânta Cruz ana Floreana Islands. 87 Meân daily foraging effort of four Pclister versicol or czlonies . 89 Foraging range of Pol istes versi color. 91 Colony developrnent of Polistes versicolor neçt #A2 O . 9 3 Number of adult Polistes versicolor in nest #A20 and mean daily air temperature. List of Figures, continued Fiaure Descript ion Paae 13 Number of active Polistes versicolor nests over a period of five months, from April to August 1994. 97 Population of pupae and mean size of colon: les of Polistes versicolor during a £ive month perioà Sequence of events leading to the growch of Polistes versicolor colonies. Influence of the phase of cne moon on the abundance of adult Sphingidae at a light trap. 103 Influence of meân night the air temporature on the number of adult Sphingidae câptured per night. 105 xii List of Appendices A~~endixDescri~tion Paae 1 Climatic data taken at Bahia Academia, Puerto kyora, Santa Cruz Island, Galapagos. Location and description of ail Polisces versicolor nests found on Santa Cruz and Flore-&rio. Islarids . 118 Data on the development of Polistes versicolor colony #A20. 136 xiii Introduction The prediction of community theory stating that communities should be sâturated wiïh species at levels deîermined by snvironrnental conaitions is a co~troversial one. There is growing evidence that local community saturztion depends on the local environmental conditions (Ricklefs, 1590). According to this idea of bioric sacuration, invasions of continental ecosystorns by newly introàcced species should be very seldom followed by ch- rctâl exclusicn (cr extirpation) of estâblished native cornpecitors. Incroduced species should not be able to easily invade an intact community, especially on continents, becâuse available niches are usuâily alrsrày filled by locally aàapted species. According to the same principle of biotic saturation, islând systems sho~ldbe more vulnerable because they are normally less saturate6 or the native species are less competitive. It is now well known that many ecosystems hâve been altered by the establishment of newly introduced species on many tropical islandç. The archipelago of Hawaii has been the recipient of numerous examples (Howarth, 1985). Generally, the most important effects related tg the introduction of alien species seem to originate in the processes of predation and habitat rnodificâtion, There ore maq- examples of chânge in islând ecosystems worldwide following their invasion by Fntroduced plants and vertebrates (Carlquist, 1974) . However, studies exârniriirq examples of problems related to the introduction of invertebrate species to an island eccsystern are uncornmon. The GalSpagos Islands form a province of the councry of Ecuador. They are locaied 950 km off the weçt coasc cf the South Americàn continent and 1-ie on the equator. Thera are about 30 named islands, and many more srna11 rocks and islets (Figure 1). The oce~nicisolation of the archipelago, its recent origin (it is not more than 3.5 million years old) , and climate have promoteà spsciacion ir. plant and animal groups, conferring upon chem a uniqueness that is now recognized world-wide. The best known illustration of this is provided by Darwin's Finches. From a single ancestral colonization, under the influence of selection and isolation, the finch populations have diverged into 13 different species through the process of adaptive radiation (Lack, 1947; Grant, 1986). Although ltss spectacular, the evolution of some groups of invertebrates has resulted in the formation of several species swarms; the bulimid land snails are an example (Coppois, 1584) as well as the species of the beetle genus Stomion (Fins~ori and Peck, 1997). At least 712 of the 1822 identified insect species inhabiting Galapagos are endemic (Peck et al. , 1998) . Therefore, the total insect fauna of the Galapagos Islands presencs a relatively high level of endemism of about 40%. Some orders show even higher levels of endemism; for example about 67% of the coleopterâns that are founa in the Galapagos cannot be encountered anywhere else in the world. As are al1 other oceanic islands. the Galapâgos are (by definition) isolated, and have naver been connect2d rro other land masses. The proportions of the species represented in various animal groups do not correspond to their proportions as observed on continents (Thornton, 1971).

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