The white perch (Morone americana) is a highly successful invader of freshwater systems, with negative consequences to some resident fishes. White perch are ovivores and may prey upon as well as compete with juvenile sportfishes. Since 1988, an introduced population of white perch has proliferated in the 19,790-ha Kerr Reservoir, NC-VA, potentially threatening popular sport fisheries for largemouth bass (Micropterus salmoides), crappie (Pomoxis spp.), and self-sustaining striped bass (Morone saxatilis). Trophic relationships between white perch and resident sportfish were examined in the Kerr Reservoir system to determine the white perch's impact on them. Striped bass eggs were found in the stomach contents of white perch collected from the Roanoke River during their concurrent spawning runs in May, and at times egg predation was intense (frequency of egg occurrence in white perch individuals up to 100 %). However, modeling simulations indicated that observed densities of white perch in the Roanoke River during the peak spawning period of striped bass (May) were too low to have a substantial effect on striped bass recruitment. Crappie eggs were found in the diets of white perch collected from Kerr Reservoir during April, but the significance of this predation was not determined. Trophic overlap (Schoener's Index) was high (> 0.5) between age-0 white perch and age-0 crappie, largemouth bass, and striped bass in June, but only remained high between white perch and crappie in the remainder of the growing season (July – September). After June, largemouth and striped bass were primarily piscivorous, whereas white perch and crappie remained primarily invertivorous. Trophic overlap was high between adult white perch and adult crappie (> 0.6), but not between white perch and any other species of adult sportfish. The utilization of white perch by adult piscivores (Ictalurids, Pomoxis spp., Moronids, and Percids) as a food source was low (< 2% of diets by weight). Piscivorous sportfish primarily ate clupeids, which are highly abundant in Kerr Reservoir. Analysis of sportfish performance before (1974 – 1987) versus after (1996 – 2005) white perch establishment indicated no change in abundance and growth of striped bass and largemouth bass. Performance data for crappie prior to white perch introductions were unavailable, but observed egg predation by and trophic overlap with white perch suggests that crappie have the highest potential to suffer deleterious interactions with the white perch. Abundance of white bass has significantly declined in years since white perch introductions. Future research in Kerr Reservoir should concentrate on interactions between white perch and these two species. / Master of Science

The release of the seed eating beetle Sulcobruchus subsuturalis for biological control of Caesalpinia decapetala in South Africa has been ongoing since 2000. This is the first post release evaluation of the efficacy of the agent against the weed. The study assessed the phenology of C. decapetala and S. subsuturalis at two sites and included determining the establishment of the beetle on the target weed at 25 study sites. In addition, the effects of S. subsuturalis on seed densities as well as seed germination and seedling recruitment were examined. Furthermore predation by native ants and attacks by native parasitoids were also examined at two release sites. Mature filled pods were available on the tree from September (spring) to March (summer) when the beetle is expected to be reproductively active. The majority of beetle releases by Working for water took place in summer. However the proportion of beetle infested seeds, which were only recovered inside pods in the tree canopy at study sites, was low (0 to 15.5%). Consequently high seed densities and seedling recruitment were observed in the field. In the laboratory, S. subsuturalis did not lay eggs on buried seeds, however seed infestation levels were generally high. Only 8.3% of the seeds containing adults germinated and 6.3% emerged into seedlings. Of the seeds containing larvae, only 14.6% germinated and 2.1% emerged into seedlings. Thus far, S. subsuturalis has failed to maintain high populations on the target weed, possibly due to egg predation by native ants (Crematogaster species, Pheidole megacephala, Messor natalensis and Tetramorium avium) and attacks by native parasitoids. Egg predation reached 100% within 10 days. Egg parasitism by unknown parasitoids ranged between 80 and 93.1% in Limpopo. The parasitic wasp Dinarmus altifrons was recovered once developing inside a C. decapetala seed infested with S. subsuturalis. Further investigations regarding attacks by indigenous parasitoids on S. subsuturalis are required to determine the extent of this problem. Meanwhile releases of S. subsuturalis against C. decapetala should continue. However release efforts need to be improved by (a) using inundative rather than inoculative releases (b) Releasing every year between September and March (summer) and (c) involving land owners, farmers and nature reserve authorities in release activities. Ultimately an additional agent should be sought for release against C. decapetala as the weed may not be the preferred host for S. subsuturalis.

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Made available in DSpace on 2015-04-17T14:55:29Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1643253 bytes, checksum: 663b93e288d71dbedb37bcae9e72b850 (MD5) Previous issue date: 2013-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Damselfishes play key roles in reef environments and are widely used as models in ecological and behavioral studies.During the reproductive period, the damselfishes present strategies involving benthonic spawning. The parental care is performed by the male who, during the days of egg development, expelled all potential predators that try to attack their territory. It was studied here the behavioral ecology during spawning period and the reproductive success of Stegastes sanctipauli, a damselfish endemic to the remote St. Peter and St. Paul s Archipelago (Mid Atlantic Ridge, Brazil). Nest abundance was negatively influenced by depth and abundance of Caranx lugubris, an important damselfish predator. The number of clutches within male s nests was positively influenced by depth, nest area, and substrate inclination, with deeper, bigger and more inclined nests sheltering more clutches. Number of clutches within nests varied along the lunar cycle, peaking at two days before the new moon. Egg loss per clutch per day ranged from 3.5% to 50% and was positively influenced by the initial number of eggs laid by females and moon phase, with highest losses recorded also in the days before the new moon. Frequency of agonistic interactions increased with nest size. Bigger nests, that shelter more clutches, are possibly more attractive to potential egg predators. Species most frequently recorded attempting to predate S. sanctipauli eggs were the conspecifics, heterospecifics damselfishes (Chromis multillineata and Abudefduf saxatilis), Malacoctenus sp. and Halichoeres radiatus. Although, no successful predation events was witnessed, experimental offer of clutches and analysis of bite scars revealed Melichthys niger as the main potential predator of S. sanctipauli eggs. Filial cannibalism of eggs was frequently observed, and may be pointed as a major cause of S. sanctipauli embryo mortality. / Os peixes donzeladesempenham um importante papel nos ambientes recifais e são amplamente utilizados como modelo para estudos comportamentais. Durante o período reprodutivo, as donzelas apresentam estratégias que envolvem desova bentônica. O cuidado parental é realizado pelo macho que, durante o período de desenvolvimento dos ovos, expulsa todos os potenciais predadores que tentam invadir seu território.Neste estudo foi avaliada a ecologia comportamental durante a desova e o sucesso reprodutivo de Stegastes sanctipauli, donzela endêmica do remoto Arquipélago de São Pedro e de São Paulo. A abundância de ninhos foi influenciada negativamente pela profundidade e abundância de Caranx lugubris, um importante predador de donzelas. O número de desovas dentro dos ninhos de cada macho foi positivamente influenciado pela profundidade, área do ninho, e inclinação do substrato. Ninhos mais fundos, maiores e mais inclinados apresentaram um maior número de desovas. O número de desovas variou ao longo do ciclo lunar, atingindo um pico dois dias antes da lua nova. A perda de ovos por desova por dia variou de 3,5% a 50% e foi influenciado positivamente pelo número inicial de ovos desovados pelas fêmeas e pelas fases da lua, com as maiores perdas registradas também nos dias que antecedema lua nova. A frequência de interações agonísticas foi influenciada positivamente pelo tamanho do ninho. Ninhos maiores, que abrigam mais desovas, são possivelmente mais atraentes para potenciais predadores de ovos. As espécies registradas com maior frequência tentando invadir o território de S. sanctipauli foram os próprios coespecíficos, donzelas heteroespecíficas (Chromis multillineata e Abudefduf saxatilis), Malacoctenus sp e Halichoeres radiatus. Apesar de não ter sido registrado sucesso em tentativas de predação de ovos durante as observações comportamentais, a oferta experimental de desovas e análise de cicatrizes de mordidas revelou Melichthys niger como o principal potencial predador de ovos de S. sanctipauli. O canibalismo filial de ovos foi um comportamento frequentemente observado, e pode ser apontadotambém comouma das principais causas de mortalidade embrionária de S. sanctipauli.

Em espécies que exibem cuidado paternal exclusivo, a qualidade esperada do comportamento paternal pode influenciar as decisões de acasalamento das fêmeas e determinar o sucesso de acasalamento dos machos. Nesta tese, investigamos a inter-relação entre o cuidado paternal e a seleção sexual utilizando o opilião Quindina limbata como organismo modelo. Os machos nesta espécie constroem ninhos na forma de taça que são visitados pelas fêmeas na busca de um sítio de oviposição. No primeiro capítulo, nós experimentalmente avaliamos a eficiência do atendimento aos ovos provido pelos machos e testamos se os ninhos desatendidos são adotamos por fêmeas e/ou por machos não relacionados com os ovos. As conclusões mais importantes deste capítulo são: (1) a proteção do macho é crucial para a sobrevivência dos ovos porque ninhos desatendidos são prontamente atacados por predadores; (2) a compensação do cuidado parental por fêmeas é rara, provavelmente porque elas estão associadas aos machos e não aos ninhos; (3) os machos adotam ovos não relacionados com eles e protegem eles tão eficientemente quanto os machos originais, provavelmente porque o cuidado dos ovos é um comportamento selecionada sexualmente. No segundo capítulo, nós testamos a existência de duas táticas alternativas de acasalamento nas fêmeas: residentes, na qual as fêmeas permanecem perto de um ninho, repelem fêmeas conespecíficas e copulam preferencialmente com um único macho dono de ninho, e visitantes, na qual as fêmeas não permanecem espacialmente associadas a ninhos, não repelem conespecíficas e copulam com vários machos donos de ninhos. Também investigamos se a monopolização de ninhos por fêmeas afeta o sucesso reprodutivo dos machos. As conclusões mais importantes deste capítulo são: (1) o comportamento das fêmeas parece ser uma tática reversível, na qual as fêmeas podem mudar de residentes a visitantes durante sua vida, provavelmente em resposta à condição corporal, e (2) a monogamia social imposta pelas fêmeas residentes pode afetar negativamente o grau da promiscuidade dos machos, mas não sua taça de acasalamento. Em conclusão, nós provemos evidência de que a preferência das fêmeas por machos que provem cuidado pode ter favorecido a manutenção do cuidado paternal. Além disso, demonstramos que a monopolização dos melhores machos ou ninhos pode ter favorecido a evolução das táticas alternativas de acasalamento nas fêmeas / In species exhibiting exclusive male care, the expected quality of paternal behavior can influence female mating decisions and thus determine male mating success. In this thesis, we investigated the interplay between paternal care and sexual selection using the harvestman Quindina limbata as model organism. Males of this species build cup-like mud nests that are visited by females in search of an oviposition site. In the first chapter, we experimentally evaluated the efficiency of egg-attendance provided by males and tested if unattended nests are adopted by females and/or unrelated males. The most important conclusions of this chapter are: (1) male protection is crucial for egg survival because unattended nests are promptly attacked by predators; (2) flexible compensation of parental care by females is rare, probably because they are associated to males and not to the nests; (3) males adopt unrelated eggs and protect them as efficiently as original owner males, probably because egg-attendance is a sexually-selected behavior. In the second chapter, we tested the existence of two reproductive tactics in females: resident, in which females remain close to a nest, repel conspecific females, and mate preferentially with a single nest-owner male, and wanderer, in which females are not spatially associated with nests, do not repel conspecific females, and mate with different nest-owner males. We also investigated whether nest monopolization by females may affect males\' reproductive success. The most important conclusions of this chapter are: (1) females\' behavior seems to be a reversible tactic, in which females can switch from resident to wanderer during their lifetime, probably in response to body condition, and (2) the social monogamy imposed by resident females may negatively affect the degree of male promiscuity, but not male\'s mating rate. In conclusion, we provide evidence that female preference for parental individuals may have favored the evolution and maintenance of paternal care. Moreover, we show that the monopolization of the best males or the best nests may have favored the evolution of alternative reproductive tactics in females