The distribution of a water strider, Aquarius rsmig/s, among habitat patches explained by sex specifie dispersal strategies H. Helen Bang Department of Natural Resource Sciences Macdonald Campus, McGiII University August 2002 A thesis submitled ta the Faculty of Graduate Studies and Research in partial fulfillment of the requirements of the degree Master of Science © H. Helen Bang, 2002 National Library Bibliothèque nationale 1+1 of Canada du Canada Acquisitions and Acquisisitons et Bibliographie Services services bibliographiques 395 Wellington Street 395, rue Wellington Ottawa ON K1A DN4 Ottawa ON K1A DN4 Canada Canada Your file Votre référence ISBN: 0-612-85765-4 Our file Notre référence ISBN: 0-612-85765-4 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 Bibliothèque 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/film, 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 from 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 aturement reproduits sans son permission. autorisation. Canada Abstract A survey of a natural population of Aquarius remigis, a stream dwelling water strider, living in East Turkey Creek, Arizona, USA, revealed that they were mostly found in either pairs consisting of one male and one female, or in small female biased groups. Chi-squared analysis confirmed that this finding was not due to random chance. The sex ratios were manipulated to further test this observation, that is, that the water striders would retum to the most commonly observed sex ratio combinations even after being deliberately rearranged. Pairs of water striders or female biased sex ratios were observed in the experimental pools after a 24 hour period. Behavioural experiments conducted in the laboratory were performed to investigate the possible behavioural interactions that could influence the sex ratios observed in the field. Artificial pools with three water striders, in four sex ratio combinations, and four water striders, in five sex ratio combinations, were used. Male water striders were active in ail experimental pools regardless of sex ratio treatment. Female water striders were less active in male biased pools. Females were, however, more aggressive and active in pools containing only females. Résumé Un aperçu d'une population normale des patineurs Aquarius remigis vivant dans East Turkey Creek, Arizona, Etas-Unis, a indiqué qu'ils ont été trouvés la plupart du temps soit en paire composant d'un mâle et d'une femelle, ou parmi des petites groupes ayant plus de femelles que de mâles. L'analyse chi carré ajusté a confirmé que ces observations n'était pas dû à la chance aléatoire. Les rapports de sexe ont été manipule pour examiner plus profondement l'observation que les patineurs renverraient aux combinaisons le plus généalement observées de rapport de sexe même après une réarrangement délibéré. Après une période de 24 heures, les paires de patineurs ainsi que les groupes de patineurs ayant des rapports décentrés femelles de sexe dans les piscines expérimentales ont été observés. Des expériences comportementales ont été exécutées dans le laboratoire afin d'étudier les interactions comportementales possibles qui pourraient influencer les rapports de sexe observés sur le terrain. Des expériances exploitant des piscines artificielles avec trois patineurs dans quatre combinaisons de rapport de sexe, et quatre patineurs dans cinq combinaisons de rapport de sexe ont été élaborés. Les patineurs masculins étaient actives dans toutes les piscines expérimentales indépendamment du traitement de rapport de sexe. Les patineurs femelles étaient moins actives parmi les piscines avec unplus grand nombres de patineurs par mâle. Les femelles étaient cependant plus agressives et en actives dans les piscines contenant seulement des femelles. 11 Table of Contents Abstract i Resume il Table of contents iii List of tables ....................................................... .. v List of figures vii Acknowledgments viii Introduction ........................................................ .. 1 Literature review .................................................... .. 3 General description ............................................ .. 3 Distribution ................................................... .. 4 Feeding behaviour 5 Territoriality 6 Mating system of Aquarius remigis 7 Mating dynamics: the conflict between male and female water striders 11 The effect of food on mating behaviour ............................ .. 14 Sex ratio, density and dispersal-predictions based on literature ......... .. 15 Methods 16 East Turkey Creek ............................................ .. 16 Survey of the natural population 17 Effect of sex ratio on dispersal - field experiments 17 Dispersal from groups of three water striders 17 Dispersal from groups of four water striders 18 Comparison of male and female water striders .. .................... .. 19 Behavioural observations - laboratory component 19 Marking techniques 21 Data analysis ................................................ .. 22 Results 25 Dispersal experiments: a survey of natural populations 25 Effect of sex ratio on dispersal from groups. ........................ .. 27 Effect of sex ratio on dispersal of males 28 Effect of sex ratio on dispersal of females .......................... .. 28 Effect of sex ratio on occurrence of non-experimental water striders 29 Hl Laboratory behavioural experiments .............................. .. 30 Effect of sex ratio on behaviour offocal males 30 Effect of sex ratio on behaviour of focal females ..................... .. 32 The relationship between behavioural and dispersal experiments 33 Discussion 54 Male dispersal ............................................... .. 54 Female dispersal 56 Dispersal and natural distribution of water striders among pools 58 Conclusion 61 Literature cited 62 IV List of tables Table 1: Observed frequencies and Chi-squared analysis for the movement of water striders, Aquarius remigis, in pools along East Turkey Creek in southeast Arizona 46 Table 2: Observed frequencies and Chi-square analysis of the movement of water striders, Aquarius remigis, where no new individuals arrived, in ail pools along East Turkey Creek in southeast Arizona ................. .. 46 Table 3: The analysis of the movement of focal male water striders, Aquarius remigis, along East Turkey Creek in southeast Arizona 47 a) fram ail pools b) fram ail pools in which no new individuals arrived c) fram those pools in which no new individuals arrived and ail original water striders remained Table 4: The analysis of the movement of focal female water striders, Aquarius remigis, along East Turkey Creek in southeast Arizona .......... .. 48 a) fram ail pools b) from those pools in which no others arrived c) fram those pools in which no others arrived and ail originally marked individuals remained Table 5: The analysis of newly arriving water striders, Aquarius remigis, along East Turkey Creek in southeast Arizona .......................... .. 49 a) newly arriving males and females in ail pools b) newly arriving males in ail pools c) newly arriving females in ail pools Table 6: The effect of sex ratio treatment on the number of attacks made on the focal male by otherwater striders in an artificial pool during a one hour observational Ume period 50 Table 7: The effect of sex ratio treatment on the number of attacks made on the focal male by other male water striders in an artificial pool during a one hour observational time period ............................. .. 50 Table 8: The effect of sex ratio treatment on the number of attacks made on other water striders present in an artificial pool by the focal male during a one hour observational time period 51 v Table 9: The effect of the sex ratio treatment on the attack rate on females by the focal male water strider (per minute of time the male was single) in an artificial pool during a one hour observational time periad ........ .. 51 Table 10: The effect of sex ratio treatment on the attack rate made on the focal female by other water striders (per minute of time the female was single) in an artificial pool during a one hour observational time period ..... 52 Table 11: The effect of sex ratio treatment on the number of attacks made on other water striders by the focal female in an artificial pool during a one hour observational time period 52 Table 12: The effect of sex ratio treatment on the attack rate on the focal female water strider by males (per minute of time the female was single) in an artifici al pool during a one hour observational time period , 53 VI List of figures Figure 1: The percentage of pools containing various numbers of water striders, and the number of individuals per pool of th.e water strider, Aquarius remigis, along East Turkey Creek in southeast Arizona .......... .. 35 Figure 2: The index of pool size versus the number of the water strider, Aquarius remigis, residing in East Turkey Creek in southeast Arizona 37 Figure 3: The percentage of female biased,