Ο όρος φαινοτυπική πλαστικότητα χαρακτηρίζει την ιδιότητα ενός γονότυπου να παράγει ποικίλους φαινότυπους, ως απόκριση στις περιβαλλοντικές συνθήκες στις οποίες υπόκειται (Pigliucci et al. 2006). Αυτή η απόκριση μπορεί να εκφράζεται σε μορφολογικό, βιοχημικό, φυσιολογικό ή αναπτυξιακό επίπεδο (οντογενετική πλαστικότητα), καθώς και στα πρότυπα συμπεριφοράς. Δεδομένης της σημασίας της φαινοτυπικής πλαστικότητας για τις λειτουργικές αποκρίσεις των ατόμων και των πληθυσμών (π.χ. αναλογία φύλου και πληθυσμιακή δομή), η μελέτη του φαινομένου στην ομάδα των ψαριών θεωρείται σημαντική τόσο για τους φυσικούς πληθυσμούς, σε οικολογικό ή εξελικτικό χρόνο, όσο και για τους εκτρεφόμενους. Η ολοκληρωμένη μελέτη της φαινοτυπικής πλαστικότητας, με έμφαση στους υποκείμενους μοριακούς και αναπτυξιακούς μηχανισμούς, μπορεί να δώσει πιο τεκμηριωμένες απαντήσεις στα ερωτήματα που σχετίζονται με τον τρόπο δράσης του φαινομένου στην οικολογία και στην εξέλιξη των ειδών, αλλά και σε πιο πρακτικά ζητήματα, όπως αυτά που αφορούν την εκτροφή ψαριών. Ο κύριος περιβαλλοντικός παράγοντας, υπεύθυνος για την εμφάνιση φαινοτυπικής πλαστικότητας στα ψάρια, φαίνεται ότι είναι η θερμοκρασία ανάπτυξης, η οποία έχει βρεθεί ότι επιδρά στο μεταβολισμό, την ανάπτυξη (Johston 1996, Stickland et al. 1998, Guderley 2004) και τη δομή των μυών (Guderley and Johston 1996, Ochi and Westerfield 2007), τους μεριστικούς χαρακτήρες (Lindsey 1998, Georgakopoulou et al. 2007), το σχήμα του σώματος (Loy et al. 1996, Georgakopoulou et al. 2007), την κολυμβητική ικανότητα (Fuiman and Batty 1997) και την αναλογία φύλου (Pavlidis et al. 2000, Koumoundouros et al. 2002a). Η θερμοκρασία ανάπτυξης, φαίνεται ότι επηρεάζει σημαντικά το ρυθμό αύξησης και διαφοροποίησης των ψαριών, τροποποιώντας το σωματικό μέγεθος όπου επιτελούνται τα διάφορα αναπτυξιακά γεγονότα, φαινόμενο γνωστό ως οντογενετική πλαστικότητα (Koumoundouros et al. 2001, Sfakianakis et al. 2004). Στην παρούσα εργασία εξετάστηκε η επίδραση της θερμοκρασίας πρώιμης ανάπτυξης, στη φαινοτυπική πλαστικότητα του είδους Danio rerio. Εξετάστηκε η αναλογία του φύλου και το σχήμα του σώματος των ψαριών, καθώς και ο ρυθμός ανάπτυξης των νυμφών και των ιχθυδίων κατά τη διάρκεια της εφαρμογής των διαφορετικών θερμοκρασιακών συνθηκών. Παράλληλα έγινε μια προσπάθεια προσδιορισμού του ευαίσθητου στην επίδραση της θερμοκρασίας, οντογενετικού σταδίου. Σύμφωνα με τον πειραματικό σχεδιασμό που ακολουθήθηκε, εξετάστηκε η επίδραση της θερμοκρασίας κατά τη διάρκεια δύο διαφορετικών πρώιμων οντογενετικών περιόδων, διάρκειας 280οd η κάθε 100 μία (28-308οd και 280-560οd). Στην πρώτη οντογενετική περίοδο, τα έμβρυα αφέθηκαν για είκοσι τέσσερις ώρες στους 28οC και στη συνέχεια διαχωρίστηκαν σε τρεις πληθυσμούς ψαριών οι οποίοι υποβλήθηκαν σε τρεις διαφορετικές θερμοκρασιακές συνθήκες (22, 28, 32οC) για μια περίοδο 280οd (28-308od, πρώτη υπό εξέταση οντογενετική περίοδος, ΟΠ1). Στη δεύτερη οντογενετική περίοδο, τα έμβρυα και οι νύμφες διατηρήθηκαν σε κοινές συνθήκες (28οC) μέχρι την 10η ημέρα μετά τη γονιμοποίηση. Στη συνέχεια διαχωρίστηκαν σε τρεις πληθυσμούς ψαριών, οι οποίοι υποβλήθηκαν σε διαφορετικές θερμοκρασιακές συνθήκες (22, 28 και 32οC) μέχρι την 560οd (280-560od, δεύτερη υπό εξέταση οντογενετική περίοδος, ΟΠ2). Και στις δύο περιπτώσεις, μετά το πέρας της περιόδου των 280οd με διαφορετική θερμοκρασιακή επίδραση, η ανάπτυξη πραγματοποιήθηκε σε κοινές συνθήκες (28οC). Τα πειράματα πραγματοποιήθηκαν εις διπλούν. Όλοι οι πειραματικοί πληθυσμοί, προήλθαν από κοινό απόθεμα αυγών. Η διατήρηση και η εκτροφή των νυμφών και των ενήλικων ψαριών πραγματοποιήθηκε βάσει μεθοδολογίας που περιγράφεται στο «The Zebrafish Book» (Westerfield 1995). Το φύλο των ενήλικων ατόμων προσδιορίστηκε μακροσκοπικά, έχοντας ως βάση τους χαρακτήρες της διογκωμένης κοιλιάς των θηλυκών ατόμων και του κίτρινου χρώματος των αρσενικών (Νεοφύτου 2003). Προκειμένου να επιβεβαιωθεί ο μακροσκοπικός προσδιορισμός του φύλου, ακολούθησε ο εγκλεισμός τριάντα συντηρημένων δειγμάτων (Εγκλεισμός σε Τechnovit 7100, τμήση 1-3 μm, χρώση με Polychrome I και II κια μικροσκοπική παρατήρηση των τομών). Για τη μελέτη της επίδρασης της θερμοκρασίας ανάπτυξης στην εξωτερική μορφολογία του σώματος των ενήλικων zebrafish, επιλέχθηκαν τυχαία 30 άτομα ανά φύλο και πειραματικό πληθυσμό, τα οποία υποβλήθηκαν σε ανάλυση γεωμετρικής μορφομετρίας. Με την ίδια μέθοδο αναλύθηκε και το σχήμα του σώματος των νυμφών της πρώτης και της δεύτερης υπό εξέταση οντογενετικής περιόδου, κατά το τέλος της εφαρμογής των διαφορετικών θερμοκρασιακών συνθηκών, στις 308od και στις 560od, αντίστοιχα. Στις νύμφες της πρώτης οντογενετικής περιόδου, ελήφθησαν επιπλέον δείγματα δέκα ημέρες μετά από το τέλος της εφαρμογής των θερμοκρασιακών συνθηκών. Για τη μελέτη του ρυθμού διαφοροποίησης, ελήφθησαν δείγματα νυμφών από κάθε πειραματικό πληθυσμό, μετά από τη λήξη της εφαρμογής των διαφορετικών θερμοκρασιακών συνθηκών. Συγκεκριμένα, από τους πληθυσμούς της ΟΠ1 δείγματα ελήφθησαν στις 588°d, ενώ από τους πληθυσμούς ΟΠ2, στις 560°d. Επίσης, εξετάστηκαν οι μεριστικοί χαρακτήρες των νυμφών της πρώτης και της δεύτερης οντογενετικής περιόδου, αφού προηγήθηκε διπλή χρώση των δειγμάτων με 101 Αλιζαρίνη (Alizarin Red S) και Κυανό της Αλσατίας (Alcian Blue) (Park and Kim 1984). Τα δείγματα φωτογραφήθηκαν ατομικά και μετρήθηκε το μεσουραίο μήκος (FL) του κάθε ατόμου. Στη συνέχεια, μετρήθηκε (1) ο αριθμός των κοιλιακών πλευρών, (2) ο αριθμός των πτερυγιοφόρων και των λεπιδοτριχίων του ραχιαίου και εδρικού πτερυγίου, και (3) ο αριθμός των δερματοτριχίων και των λεπιδοτριχίων του ουραίου πτερυγίου. Ο έλεγχος των διαφορών της αναλογίας φύλου μεταξύ των διαφορετικών πληθυσμών, έγινε με G-test (Sokal and Rohlf 1981). Για τη σύγκριση του σχήματος μεταξύ των δύο φύλων και των διαφορετικών πειραματικών πληθυσμών, εφαρμόστηκε ανάλυση κανονικών συνιστωσών (Canonical Variate Analysis, λογισμικό Statistica, έκδοση 6.0). Τέλος, ο έλεγχος των διαφορών του μέσου μήκους του σώματος μεταξύ των διαφορετικών πληθυσμών, πραγματοποιήθηκε με Mann-Whitney test (μη παραμετρικός έλεγχος), αφού προηγήθηκε ο έλεγχος ομοιοσκεδαστικότητας και κανονικής κατανομής. Η επίδραση της θερμοκρασίας στην αναλογία φύλου αποδείχθηκε στατιστικά σημαντική μόνο κατά την πρώτη οντογενετική περίοδο (p < 0.05, G-test), και όχι κατά τη δεύτερη (p > 0.05, G-test). Ο κατά ζεύγη έλεγχος των διαφορών στην αναλογία φύλου μεταξύ των διαφορετικών θερμοκρασιακών συνθηκών, έδειξε στατιστικά σημαντική επίδραση στην αναλογία φύλου μόνο μεταξύ των 22 και 28οC της ΟΠ1 (28-308οd), όπου η μέση συχνότητα των θηλυκών ατόμων ευνοείται στους 22°C (52,3% έναντι του 37,0% των 28°C, p < 0.05, G-test). Η ίδια συχνότητα εμφανίστηκε αυξημένη και στους 32°C (44,9% έναντι του 37,0% των 28°C), χωρίς ωστόσο να επιβεβαιώνεται και στατιστικά (p > 0.05, Gtest). Σε ότι αφορά τη δεύτερη οντογενετική περίοδο (280-560°d), η μέση συχνότητα των θηλυκών ατόμων στους 22°C (51,9%) και στους 32°C (46,1%), εμφανίζεται αυξημένη σε σχέση με αυτή των 28°C (44,5%), χωρίς ωστόσο οι διαφορές αυτές να είναι στατιστικά σημαντικές (p > 0.05, G-test). Η ύπαρξη μη στατιστικά σημαντικής διαφοράς της αναλογίας φύλου μεταξύ των 28 και 32°C και στατιστικά σημαντικής διαφοράς μεταξύ των 22 και 28°C, υποδεικνύει ότι το πρότυπο απόκρισης της αναλογίας φύλου στην θερμοκρασία πρώιμης ανάπτυξης εμφανίζει ανεξαρτησία στο εύρος 28-32°C και θηλυκοποίηση στους 22°C. Σε όλα τα οντογενετικά παράθυρα που εξετάστηκαν και σε όλες τις πειραματικές επαναλήψεις, τα αποτελέσματα της ανάλυσης των κανονικών συνιστωσών, έδειξαν ότι το φύλο και η θερμοκρασία πρώιμης ανάπτυξης επέδρασαν σημαντικά στο σχήμα του σώματος των ενήλικων ατόμων zebrafish. Η κατά φύλο γεωμετρική ανάλυση του σχήματος, έδειξε ότι η θερμοκρασία ανάπτυξης κατά την ΟΠ1 (28-308od) και ΟΠ2 (280-560od) επιδρά σημαντικά στο σχήμα 102 του σώματος και των δύο φύλων, με τους τρεις πληθυσμούς κάθε οντογενετικής περιόδου και επανάληψης να διαχωρίζονται πλήρως μεταξύ τους κατά μήκος των δύο κανονικών μεταβλητών. Η εξέταση του σχήματος του σώματος των νυμφών της ΟΠ1 (28-308οd), στις 308οd και στις 588 οd, και της ΟΠ2 (280-560οd), στις 560οd, έδειξε ότι η θερμοκρασία ανάπτυξης επηρέασε το σχήμα του σώματός τους. Σε όλες τις, οι διαφορές στο σχήμα οφείλονται τόσο στις ομοιόμορφες συνιστώσες του σχήματος, όσο και στις μη ομοιόμορφες, με τις πρώτες να συμβάλλουν στη νωτοκοιλιακή διεύρυνση ή συμπίεση του σώματος των νυμφών, ανάλογα με την περίπτωση. Ενώ όμως η επίδραση της θερμοκρασίας στο σχήμα του σώματος είναι σημαντική, δε φαίνεται να υπάρχει κάποιο καθορισμένο – σταθερό πρότυπο επίδρασης των κανονικών συνιστωσών. Αυτό πιθανότατα οφείλεται στο ότι δεν είχαν φτάσει όλες οι νύμφες στο ίδιο στάδιο ανάπτυξης κατά τις ημέρες των δειγματοληψιών. Τα δείγματα των νυμφών που λήφθηκαν μετά την έκθεση των πληθυσμών στις τρεις διαφορετικές θερμοκρασιακές συνθήκες, κατά την πρώτη (28-308οd) ή τη δεύτερη (280- 560οd) οντογενετική περίοδο, διαφοροποιήθηκαν σημαντικά ως προς το μέσο μεσουραίο μήκος (FL) των ατόμων. Συγκεκριμένα, η έκθεση στους 22οC οδήγησε σε σημαντική μείωση του FL των ατόμων (p<0.05, Mann Whitney U-test), παρά το ότι τα δείγματα λήφθηκαν στο ίδιο θερμικό άθροισμα. Τα αποτελέσματα έδειξαν, ότι η ανάπτυξη των ψαριών που αφέθηκαν στους 22οC, κατά τη δεύτερη υπό εξέταση οντογενετική περίοδο (280-560οd), καθυστέρησε σε σχέση με τους πληθυσμούς των 28 και 32οC. Αυτό φαίνεται από τα διαγράμματα που αφορούν τον αριθμό των πτερυγιοφόρων και των ακτινών του ραχιαίου πτερυγίου, τον αριθμό των πτερυγιοφόρων και των ακτινών του εδρικού πτερυγίου, καθώς και τον αριθμό των κοιλιακών πλευρών. Συγκεκριμένα, η ολοκλήρωση της ανάπτυξης των πτερυγιοφόρων του ραχιαίου πτερυγίου, των ακτινών του εδρικού και των κοιλιακών πλευρών, καθυστερεί στους 28οC, σε σχέση με τους 32 οC. Η εμφάνιση των ακτινών του ραχιαίου πτερυγίου, καθυστερεί στους 28 οC, σε σχέση με τους 32 οC. Τέλος, η εμφάνιση των πτερυγιοφόρων του εδρικού πτερυγίου, καθυστερεί στους 22 οC, σε σχέση με τους 28 οC. Σε ότι αφορά τα άτομα της πρώτης οντογενετικής περιόδου, οι χαρακτήρες που μελετήθηκαν είτε είχαν εμφανιστεί νωρίτερα από τη λήψη των δειγμάτων, είτε είχε ολοκληρωθεί αργότερα η ανάπτυξή τους. / The term phenotypic plasticity characterizes the property of a genotype to produce different phenotypes in response to distinct environments (Pigliucci et al. 2006). This response can express itself in a morphological, biochemical, physiologic or developmental level (developmental plasticity), or even through changes in the models of behavior. Due to its great importance among individuals in a population at a certain time period or in future generations (e.g. proportion of sex and demographic structure), the study of the phenotypic plasticity in the group of fish is considered significant not only for the natural populations, at the ecological or evolutionary level, but for the cultured populations too. The complete study of phenotypic plasticity, including the underlying molecular and developmental mechanisms, can answer questions related with the way the phenomenon acts in the ecology and species development, but also in more practical applications, such as those that concern aquaculture. One of the most important environmental factors responsible for the appearance of plasticity in fish appears to be the developmental temperature, which affects metabolism, muscle growth (Johston 1996, Stickland et al. 1998, Guderley 2004) and structure (Guderley and Johston 1996, Ochi and Westerfield 2007), meristic characters (Lindsey 1998, Georgakopoulou et al. 2007), body shape (Loy et al. 1996, Georgakopoulou et al. 2007), swimming performance (Fuiman and Batty 1997) and sex ratio (Pavlidis et al. 2000, Koumoundouros et al. 2002a). The developmental temperature influences considerably growth rate and differentiation of fish, modifying the body size as development proceeds. This phenomenon is known as developmental plasticity (Koumoundouros et al. 2001, Sfakianakis et al. 2004). The present study examined the effect of precocious developmental temperature, in phenotypic plasticity of Danio rerio. The Sex ratio and body shape of fish was analyzed, as well as the growth rate of larvae and juveniles during the application of different temperature conditions. At the same time the most sensitive developmental period in the effect of temperature was determined. According to the experimental design, the effect of temperature was examined during two different early developmental periods of 280°d, each (28-308°d and 280-560°d). Two experimental groups of fish were subjected in duplicate to three different temperatures. More specifically, in the first developmental period the embryos were left for twenty four hours in 28°C and then separated in three populations, which were submitted to three different temperature conditions (22, 28 and 104 32°C) for a period of 280°d (28-308°d, first developmental period DP1). In the second developmental period the embryos and the larvae were maintained under common conditions (28°C) up to the 10th day post fertilization. Then they were separated in three populations, which were submitted to three different temperature conditions (22, 28 and 32°C) up to the 560th °d (280-560°d, second developmental period DP2). In both developmental periods that were examined, after the end of the 280°d of temperature effect, fish growth was completed under common conditions (28°C). All the eggs of the experimental populations were obtained from a broodstock of the same genetic origin. The maintenance and the culture of larvae and adult fish were as described in "The Zebrafish Book" (Westerfield 1995). The sex of adult individuals was determined macroscopically using the characters of the swelled abdomen of females and the yellow color of males (Neophytou 2003). In order to confirm the macroscopic determination of sex, thirty fixed samples of zebrafish were enclosed for histology sections (Technovit 7100, sections of 1-3μm and staining with Polychrome I and II) and microscopy. To study the temperature effect on growth and body shape of adult zebrafish, 30 individuals per sex and experimental population were selected randomly and were submitted in geometric morphometrics analysis. The body shape of the larvae of the first and the second developmental period, was analyzed with the same method, at the end of the different temperature conditions, in 308°d and 560°d, respectively. Additional samples were selected in the first developmental period, ten days after the end of the three different temperature regimes. To study the temperature effect on growth rate and differentiation, samples of larvae were obtained from each experimental population, following completion of the different temperature periods. From the populations of DP1, samples were taken at 588°d, while from DP2 samples were obtained at 560°d. The meristic characters of the larvae from the first and second developmental period were examined, after staining of the samples with Alizarin Red and Alcian Blue (Park and Kim 1984). Larvae were photographed and the fork length of each individual was measured (FL). The meristic characters that were examined are (1) the number of ribs (2) the number of pterygiophors and lepidotrichia of the dorsal and the anal fin, and (3) the number of pterygiophors and lepidotrichia of the caudal fin. Sex ratio differences between populations were studied with G-test (Sokal and Rohlf 1981). Canonical Variate Analysis was applied for the comparison of the body 105 shape between the two sexes and between the different experimental populations (Statistica, 6.0). Finally, the differences of medium total length between the different populations was examined with the Mann-Whitney test (non parametric). The sex ratio was significantly affected only at the first developmental period (p < 0.05, G-test), and not at the second (p > 0.05, G-test). The paired control of changes in the sex ratio between the different temperature conditions at DP1 (28-308°d), showed a significant effect only between the populations of 22°C and 28°C (52.3% females in 22°C vs. 37.0% in 28°C, p < 0.05, G-test). The female/male frequency was also increased in the 32°C group (44.9% females in 32°C vs. 37.0% females in 28°C), without however being confirmed as statistically significant (p > 0.05, G-test). Regarding the second developmental period (280-560°d), the medium frequency of the female individuals in the 22°C (51.9%) and 32°C (46.1%) groups, was also increased compared to 28°C (44.5%), although these differences were not confirmed as statistically significant (p > 0.05, G-test). The significant differences in sex ratio between the 22 and 28°C, and the non significant differences between 28 and 32°C indicate that the model of response in sex ratio due to the different developmental temperature shows autonomy in the range of 28-32°C and feminization at 22°C. In both ontogenetic windows that were examined and in all experimental repetitions, the results of the canonical variables showed that sex and developmental temperature significantly affected the bodyshape of the adult individuals. The body shape analysis in accordance with the gender of the individuals, was significantly affected from the developmental temperature at DP1 (28-308°d) and DP2 (280-560°d). The three populations of each ontogenetic period were totally separated amongst them, along the two axes of canonical variables CV1 and CV2. The body shape analysis of the larvae at DP1 (28-308οd), in 308οd and in 588 οd, and at DP2 (280-560οd), in 560οd, indicates that developmental temperature significantly affected their body shape. In all cases, the differences in body shape are contributed from uniform, as much as from non uniform components of shape. Despite the significant effect of developmental temperature in larval body shape, there is not a stable model of the way that canonical variables effect, probably because larvae were not at the same stage of growth during sampling. The total (TL) or the fork length (FL) of the larvae that were analyzed following development at the three different temperatures during the first (28-308°d) or the second (280-560°d) developmental period, was significantly differentiated. The exposure at 22°C 106 led to important reduction of the individuals FL (p < 0.05, Mann-Whitney test), despite the fact that all samples were of the same age. These results showed that the growth of fish that were submitted to 22°C during DP2 (280-560°d) was delayed relative to the populations at 28 and 32°C. This is noticeable from the diagrams that refer to the number of pterygiophors and lepidotrichia of the dorsal fin, the number of pterygiophors and lepidotrichia of the anal fin and the number of ribs. The completion of growth of pterygiophors of the dorsal fin, of lepidotrichia of the anal fin and the abdominal ribs, are also delayed at 28°C vs. 32°C. The appearance of lepidotrichia of the dorsal fin is delayed at 28°C vs. 32°C, as well. Finally, the appearance of pterygiophors of the anal fin is delayed at the 22°C vs. 28°C. Regarding the individuals of DP1, the development of the meristic characters that were studied was completed either earlier or later than the time of sampling, making it difficult to evaluate differences within various groups.

The persistence of a species in the face of environmental change is a function of the extent to which populations respond differently to changes in their environment and the spatial correspondence between the scale of disturbance and the scale of adaptation. The pattern by which a population, or genotype, expresses a range of phenotypes across an environmental gradient is called a norm of reaction. The level of phenotypic plasticity displayed within a population (i.e. the slope of the reaction norm) reflects the short-term response of a population to environmental change while variation in reaction norm slopes among populations reflects the spatial scale of variation in these responses. Using a reaction norm framework, I examined the spatial scale of genetic variation in plasticity for life-history traits in Atlantic cod (Gadus morhua), a marine fish of global biological and socioeconomic importance. Through common-garden experiments, I found evidence of both adaptive and non-adaptive plasticity for larval growth rate and survival in two cod populations that experience contrasting thermal environments in nature. A comparison of these reaction norms with those of four cod populations studied previously revealed significant genetic divergence in adaptive traits at a smaller spatial scale than has previously been shown for a marine fish with no apparent physical barriers to gene flow (<250 km). This fine-scale genetic structure is likely the result of populations being locally adapted to seasonal changes in temperature during the larval stage caused by differences in spawning times and may be maintained by behavioural barriers to gene flow. Implications of variation in life-history trait plasticity to fisheries management in the face of predicted changes in climate are discussed.

The self-fertilizing mangrove rivulus, Kryptolebias marmoratus, is an amphibious fish capable of reversible gill remodelling when moving between aquatic and terrestrial environments. In this thesis I determined how plastic morphological and physiological respiratory traits were integrated during transitions between environments. In two isogenic lineages, I found that behaviour (increased emersion) of individual fish caused gill morphological changes (enlargement of the interlamellar cell mass (ILCM)) that reduced gill surface area. I also found that large ILCMs that formed after 7 d of air exposure increased both gill ventilation and critical oxygen tension (Pcrit) when fish returned to water. These results indicate that large ILCMs reduce aquatic respiratory function, and increased gill ventilation was unable to maintain oxygen uptake at extreme levels of hypoxia. Ultimately, this study highlights the trade-offs in gill structure and function during the transition between air and water, and demonstrates that differences in behaviour can generate morphological variation.

<p>Koi and goldfish have been released into rivers in South Africa since the 1800&rsquo / s for food and sport fish and have since spread extensively. These fish are present in most of the river systems in South Africa and pose an additional threat the indigenous cyprinids in the Western Cape. Monogenean parasites of the genus Gyrodactylus are of particular concern, as their unique biology renders them a possible threat. Gyrodactylus kherulensis and G. kobayashii were identified from koi and goldfish respectively imported from Asia, Europe and locally bred fish. Morphometrics and the use of statistical classifiers, which includes univariate (ANOVA and Kruskal-Wallis), bivariate (Pearson&rsquo / s correlation) and multivariate (Principal Component Analysis) placed the two species within their respective groups. There was some intraspecific variation among the different populations collected from the various locations, especially in the hamulus and ventral bar features, but the marginal hooklets, however, remained static for both helminth species.</p>

The proximate causes triggering nest abandonment are unclear for most species, including the Yellow Warbler (Dendroica petechia), which abandons nests parasitized by cowbirds (via burial or desertion). Cowbird parasitism and rejection of parasitism are costly to some hosts; therefore cues affecting their responses have important evolutionary implications. Manipulative experiments showed that experimentally adding a cowbird egg elicited similar rejection frequencies (2008: 31.8%; 2009: 26.1%) as naturally laid eggs (2008: 27.1%; 2009: 20.0%). In 2008, interaction with an egg-removing model increased the probability of abandonment and the most aggressive individuals were more likely to bury the model cowbird egg. In 2009, eggs added to nests before sunrise were rejected at a frequency (29.7%) similar to eggs added to nests after sunrise (22.9%). Warblers returning to nests after egg addition peered significantly longer at their clutch than at control nests, shuffled their bodies more frequently when on the eggs and spent more time probing eggs with their bill once settled on their parasitized clutch. Furthermore, although non-mimetic blue eggs were not abandoned significantly more frequently than cowbird eggs (blue 31.1% versus cowbird 21.4%), only blue eggs were ejected from some nests. Thus, warblers use both tactile and visual cues to detect the presence of a parasitic egg in their nest. Eggs added to nests were not rejected at a lower frequency than naturally parasitized nests, as was recorded in a previous study. It is difficult to know whether this increase in abandonment of experimental eggs is due to phenotypic plasticity, genetic changes, or other factors. Egg recognition abilities may have changed because I have shown that the warblers’ behaviour changes before versus after egg addition, whereas no changes were recorded in an earlier study. Finally, not all individuals that buried eggs for the first time in 2009 (21.4%) buried again after being re-parasitized (5.3%), when less time remained in the breeding season relative to the first parasitism event. This suggests that egg rejection and host responsiveness in warblers, and likely other avian hosts that use abandonment as a form of rejection, is affected by environmental cues which may act as genetic expressers.

The proximate causes triggering nest abandonment are unclear for most species, including the Yellow Warbler (Dendroica petechia), which abandons nests parasitized by cowbirds (via burial or desertion). Cowbird parasitism and rejection of parasitism are costly to some hosts; therefore cues affecting their responses have important evolutionary implications. Manipulative experiments showed that experimentally adding a cowbird egg elicited similar rejection frequencies (2008: 31.8%; 2009: 26.1%) as naturally laid eggs (2008: 27.1%; 2009: 20.0%). In 2008, interaction with an egg-removing model increased the probability of abandonment and the most aggressive individuals were more likely to bury the model cowbird egg. In 2009, eggs added to nests before sunrise were rejected at a frequency (29.7%) similar to eggs added to nests after sunrise (22.9%). Warblers returning to nests after egg addition peered significantly longer at their clutch than at control nests, shuffled their bodies more frequently when on the eggs and spent more time probing eggs with their bill once settled on their parasitized clutch. Furthermore, although non-mimetic blue eggs were not abandoned significantly more frequently than cowbird eggs (blue 31.1% versus cowbird 21.4%), only blue eggs were ejected from some nests. Thus, warblers use both tactile and visual cues to detect the presence of a parasitic egg in their nest. Eggs added to nests were not rejected at a lower frequency than naturally parasitized nests, as was recorded in a previous study. It is difficult to know whether this increase in abandonment of experimental eggs is due to phenotypic plasticity, genetic changes, or other factors. Egg recognition abilities may have changed because I have shown that the warblers’ behaviour changes before versus after egg addition, whereas no changes were recorded in an earlier study. Finally, not all individuals that buried eggs for the first time in 2009 (21.4%) buried again after being re-parasitized (5.3%), when less time remained in the breeding season relative to the first parasitism event. This suggests that egg rejection and host responsiveness in warblers, and likely other avian hosts that use abandonment as a form of rejection, is affected by environmental cues which may act as genetic expressers.

Temperature variation affects most biological parameters from the molecular level to community structure and dynamics. Current studies on thermal biology assess how populations vary in response to environmental temperature, which can help determine how populations differentially respond to climate change. To date, temperature fluctuation effects on endothermic poikilotherms such as the common eastern bumblebee (Bombus impatiens) are unknown even though bumblebees are the most important natural pollinators in North America. A cold-acclimation experiment with B. impatiens colonies revealed individuals acclimated to 5°C or 10°C at night did not differ in resting metabolic rate, flight metabolic rate, wingbeat frequency, or morphological measurements, compared to the control group. Moreover, an infrared camera showed that all colonies maintained maximum nest temperature consistently above 36.8°C. A latitudinal sampling of flight metabolic rate and morphological measurements of B. impatiens from four locations spanning Ontario (N 45°; W 75°) to North Carolina (N 34°; W 77°) indicated no latitudinal trend in the measured variables. This study shows that bumblebees are well equipped to face a wide range of environmental temperatures, both in the short term and long term, and can use a combination of behavioural and physiological mechanisms to regulate body and nest temperatures. These results are reassuring on the direct effects of climate change on bumblebee ecology, but further studies on the indirect effect of temperature variation on North American bumblebees are required to predict future ecosystem dynamics.

Cyrba algerina is a salticid (Salticidae) spider that lives on the undersides of stones. Two populations were studied, Sintra and Algarve (Portugal), and shown to have similar phenology but different dominant prey. Life cycle in the laboratory was similar for the two populations, but Sintra matured at larger size than Algarve individuals, with these differences potentially having a genetic basis. Sintra individuals used prey-specific prey-capture behaviour against allopatric (Oecobius amboseli) and sympatric (O. machadoi, Trachyzelotes bardiae) spider and insect (bristletails) species. In contrast, Algarve C. algerina only adopted specialised capture behaviour against bristletails. Sintra, but not Algarve, individuals responded to the odour of O. machadoi and T. bardiae, and showed preference for T. bardiae over O. machadoi. Interpopulation variation in the use of specific prey-capture behaviour and in sensitivity to odour cues from prey is directly related to the prey available to individuals from each population, suggesting local adaptation to local prey. Preference for oecobiids seems to be controlled by an experiencetriggered developmental switch. The optics and histology of C. algerina’s principal eye suggest that living in a microhabitat with dim ambient light has favoured sensitivity at the expense of spatial acuity. Short focal length, reduced power of the eye’s diverging lens, and wide, contiguous rhabdomeres, seem to minimise the visual constraints imposed by the low light levels in C. algerina’s microhabitat. While relying solely on vision, C. algerina can detect, identify and capture prey in dim-light conditions under which other salticids perform poorly. C. algerina’s behaviour suggest use of temporal summation to improve its visual performance in dim light.

Hieracium lepidulum is an invasive weed in New Zealand. It colonises a wide range of habitats including pine plantations, scrubland, native Nothofagus forest, and mid-altitude to alpine tussock grassland, where it is competing with indigenous species. Understanding the breeding systems and population genetic structure of H. lepidulum is important for biocontrol, and aids in the understanding of evolutionary colonisation processes. H. lepidulum is a triploid, diplosporous, obligate apomict. This type of reproduction through clonal seed does not involve meiosis or fertilisation, and theoretically populations should contain very low levels of genetic variation, the only source being somatic mutation. Common garden experiments and microsatellite markers were used to determine the population genetic structure of H. lepidulum populations in the Craigieburn Range, Canterbury. Both experiments revealed that populations, sampled from three replicate altitudes within three geographically-separated locations, contained no genetic variation; individuals all possessed the same microsatellite genotype. These results strongly suggest that the Craigieburn Range H. lepidulum individuals reproduce solely by apomixis and populations belong to the same clonal lineage. Populations were also examined for their response to two abiotic environmental ‘stresses’, drought and shade. H. lepidulum populations’ exhibited high drought tolerance, yet appeared to be shade-intolerant. Low levels of reproduction in light-limiting habitats will prevent the invasion of H. lepidulum into closed-canopy forest habitats. H. lepidulum appears to have overcome the reduction in fitness associated with apomictic reproduction by phenotypic plasticity, fixed heterozygosity and polyploidy – all associated with increased vigour, fitness, and the ability to occupy broader ecological niches. This study’s results are hopeful for the development of biocontrol programs involving genotype-specific pathogens but suggest that grazing management may not succeed. The data will be useful for future comparisons of genetic structure during the course of H. lepidulum invasions and will contribute to the management of this invasive weed.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 179-196). Also available for download via the World Wide Web; free to University of Oregon users.