<p>Landscape effects on species performance currently receives much attention. Habitat loss and fragmentation are considered major threats to species diversity. Deciduous forests in southern Sweden are previous wooded pastures that have become species-rich communities appearing as islands in agricultural landscapes, varying in species composition. <i>Actaea spicata</i> is a long-lived plant occurring in these forests. In 150 populations in a 10-km² area, I studied pre-dispersal seed predation, seed dispersal and pollination. I investigated spatio-temporal dynamics of a tritrophic system including<i> Actaea</i>, a specialist seed predator, <i>Eupithecia immundata</i>, and its parasitoids. In addition, effects of biotic context on rodent fruit dispersal and effects of flowering time and flower number on seed set, seed predation and parasitization were studied. Insect incidences of both trophic levels were related to resource population size and small <i>Eupithecia</i> populations were maintained by the rescue effect. There was a unimodal relationship between seed predation and plant population size. Seed predator populations frequently went extinct in small plant populations, resulting in low average seed predation. Parasitoids were present in large plant populations but did not affect seed predator density. Seed predators aggregated at edges, relaxing seed predation in patch interiors. Flowering phenology was unrelated to seed set and insect incidence. A higher flower number did not influence seed predation but was associated with higher seed set and a tendency for a higher parasitization rate. In the study on fruit dispersal more fruits were removed inside than outside populations. Within plant populations more fruits were removed from large aggregations. Overall, this thesis underlines the importance of plant-animal interactions during different phases of the life cycle. The spatial configuration of host plants plays an important role for the outcome of plant-animal interactions and trophic cascades.</p>

<p>The tropical palm <em>Mauritia flexuosa </em>has highly nutritious fruits and is an important food resource for both humans and wildlife throughout its geographic range in South America. Unsustainable harvesting threatens wild populations. <em>Mauritia f</em>. occurs primarily in wetlands called Aguajales where it can become the dominating canopy species. Seed predation and dispersal can dramatically affect the survival and distribution of plant species in tropical rainforests (Janzen 1970, Connell 1971, Bleher & Böhning-Gaese 2001, Paine & Beck 2007, Mari et al. 2008). Increased knowledge of seed predation and germination requirements is essential for successful management of this commercially and ecologically important palm. Four experiments were conducted in Manu National Park in southeastern Peru to study: (1) Seed survival in the Aguajal, (2) Quantify seed predators on dry land, (3) Insect visitors and consumers of fruits and seeds, and (4) Germination in greenhouse experiments. Seed survival was significantly higher below water compared to on dry micro sites within the Aguajal. Seeds and fruits placed on dry land were preyed upon by both insects and mammals. Terrestrial insects were the most important predators. Different insects visited fruits and seeds, indicating a successive breakdown of different tissues. Seed survival was also higher below water and/or soil in the greenhouse experiment. This may suggest that the distribution of <em>Mauritia f</em>. is highly influenced by seed predation and that water protects seeds from their insect enemies.</p>

Landscape effects on species performance currently receives much attention. Habitat loss and fragmentation are considered major threats to species diversity. Deciduous forests in southern Sweden are previous wooded pastures that have become species-rich communities appearing as islands in agricultural landscapes, varying in species composition. Actaea spicata is a long-lived plant occurring in these forests. In 150 populations in a 10-km2 area, I studied pre-dispersal seed predation, seed dispersal and pollination. I investigated spatio-temporal dynamics of a tritrophic system including Actaea, a specialist seed predator, Eupithecia immundata, and its parasitoids. In addition, effects of biotic context on rodent fruit dispersal and effects of flowering time and flower number on seed set, seed predation and parasitization were studied. Insect incidences of both trophic levels were related to resource population size and small Eupithecia populations were maintained by the rescue effect. There was a unimodal relationship between seed predation and plant population size. Seed predator populations frequently went extinct in small plant populations, resulting in low average seed predation. Parasitoids were present in large plant populations but did not affect seed predator density. Seed predators aggregated at edges, relaxing seed predation in patch interiors. Flowering phenology was unrelated to seed set and insect incidence. A higher flower number did not influence seed predation but was associated with higher seed set and a tendency for a higher parasitization rate. In the study on fruit dispersal more fruits were removed inside than outside populations. Within plant populations more fruits were removed from large aggregations. Overall, this thesis underlines the importance of plant-animal interactions during different phases of the life cycle. The spatial configuration of host plants plays an important role for the outcome of plant-animal interactions and trophic cascades.

The tropical palm Mauritia flexuosa has highly nutritious fruits and is an important food resource for both humans and wildlife throughout its geographic range in South America. Unsustainable harvesting threatens wild populations. Mauritia f. occurs primarily in wetlands called Aguajales where it can become the dominating canopy species. Seed predation and dispersal can dramatically affect the survival and distribution of plant species in tropical rainforests (Janzen 1970, Connell 1971, Bleher &amp; Böhning-Gaese 2001, Paine &amp; Beck 2007, Mari et al. 2008). Increased knowledge of seed predation and germination requirements is essential for successful management of this commercially and ecologically important palm. Four experiments were conducted in Manu National Park in southeastern Peru to study: (1) Seed survival in the Aguajal, (2) Quantify seed predators on dry land, (3) Insect visitors and consumers of fruits and seeds, and (4) Germination in greenhouse experiments. Seed survival was significantly higher below water compared to on dry micro sites within the Aguajal. Seeds and fruits placed on dry land were preyed upon by both insects and mammals. Terrestrial insects were the most important predators. Different insects visited fruits and seeds, indicating a successive breakdown of different tissues. Seed survival was also higher below water and/or soil in the greenhouse experiment. This may suggest that the distribution of Mauritia f. is highly influenced by seed predation and that water protects seeds from their insect enemies.

Abstract The restoration of degraded landscapes has become one of our most valuable tools for conservation, however there are many factors which can restrict natural regeneration and impede active restoration attempts. The purpose of this study was to investigate three key processes which commonly limit the establishment of forest tree species into abandoned pasture in tropical forests: i) dispersal limitation, ii) seed predation, and iii) competition from the grass sward. Seed dispersal I identified 59 species of birds that were using the grassland habitat. Through 216 hours of focal tree observations I established that isolated trees in the grassland that had larger canopies, and those that were providing a food source (i.e. flowers or fruit) had significantly higher bird visitation rates and average stay lengths. I found evidence of the “perch effect” as patches of remnant trees encouraged more birds into areas of grassland, and the density of seedlings under tree canopies was significantly positively correlated with bird visitations. 95% of the seedlings found beneath tree canopies in grassland were of a different species to that of the tree canopy above them, demonstrating the dispersal of seeds from elsewhere into these microhabitats. 98% of these seedlings are grassland or forest edge species showing forest core species are still dispersal or microsite limited despite the effect of these trees. Seed predation Removal rates of seeds from experimentally laid out seed piles varied among seed species, the habitat the pile was in, and the predator guild able to access the piles. Preliminary results indicate that these trends are driven by the ecology of the seed predator. Removal of seeds by vertebrates was highest in the core forest, while ant predation was constant across all habitats. Vertebrates removed the larger seeds (Entandrophragma angolense and Sterculia tragacantha) while ants preferred the smaller Celtis gomphophylla and Croton macrostachyus. Overall predation rates in grassland were lower than those in the forest, and the presence of remnant trees did not influence predation rates, a positive sign for regeneration and the survival of seeds dispersed into these areas. Competition from the grass sward While the grass sward provides shade for seedlings of forest tree species it is also a harsh environment for them, as the grass competes with seedlings for water. Removing the grass and covering planted seedlings with artificial shading structures significantly increased both the survival and growth of these seedlings. Recommendations From this study I was able to make recommendations for a low input restoration program at Ngel Nyaki. Planting seedlings in small „islands‟ takes advantage of the natural increase in dispersal of seeds under isolated trees, while low seed predation rates increase the chance of survival of these seeds to germination. Planting these seedlings under shade will lead to increases both their growth rates and their survival. Once the secondary forest develops, under-planting seedlings of core forest trees will introduce them to the system, as the natural establishment of these seeds appears to be limited in the current environment. This study has also served to remind us how little we know about this particular forest-grassland system, and has led to the development of ideas for further investigations into several more aspects of regeneration.

Made available in DSpace on 2014-06-11T19:23:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-04-25Bitstream added on 2014-06-13T19:49:55Z : No. of bitstreams: 1 menezes_lccr_me_botib.pdf: 407375 bytes, checksum: 09792894c8ba03182b574501265f8e69 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Mimosa bimucronata (DC.) Kuntze (Fabaceae: Mimosoideae) é uma planta perene, arbórea, altamente ramificada e espinhosa, podendo atingir 8 metros de altura, nativa do Brasil e com reprodução por sementes, e suas sementes, durante a fenofase de frutificação, são intensamente predadas por bruquídeos da espécie Acanthoscelides schrankiae. Porém, há poucos estudos sobre a predação de sementes em M. bimucronata. Apesar de estar localizada em regiões próximas a cursos d’água, M. bimucronata geralmente está envolta por vegetação composta de plantas invasoras herbáceas, na maioria gramíneas, e durante a estação seca é comum a ocorrência de queimadas naturais. No presente estudo investigou-se a hipótese de que o processo germinativo das sementes de M. bimucronata pode ser acelerado após exposição moderada ao fogo. Além disso, estudou-se a relação entre a qualidade das sementes de M. bimucronata e as seguintes variáveis: (1) porcentagem de germinação de sementes sadias provenientes de frutos infestados e não infestados; (2) peso seco de plântulas provenientes de frutos infestados e não infestados; e (3) peso corporal de A. schrankiae. Também foi estudado o efeito da predação de frutos na alocação de recursos e compostos secundários (taninos) nas sementes sadias. Os experimentos relacionados a predação de sementes foram realizados comparando-se duas populações de plantas (Lageado e Rubião), em que 25 plantas foram marcadas ao acaso, sendo 15 pertencentes ao Lageado e 10 a Rubião, e 4 ramos por planta foram ensacados. Os demais ramos ficaram expostos a infestação por bruquídeos. As sementes viáveis dos frutos maduros, coletados dos ramos ensacados e também dos ramos livres, foram utilizadas para as análises dos conteúdos de nitrogênio e taninos, e também para os testes... / Mimosa bimucronata (DC.) Kuntze (Fabaceae: Mimosoideae) is a perennial, arborous, highly branched and spiny plant, reaching a height of 8 m meters high, endemic to Brazil, with seed reproduction. During fructification, M. bimucronata seeds are highly attacked by the bruchid Acanthoscelides schrankiae, although few studies about seeds predation on M. bimucronata are found. Despite being localized on margins of water courses, M. bimucronata is usually surrounded by herbaceous vegetation, mostly grasses, and during the dry season natural burnings are common. This study investigated the hypothesis that the germination process of M. bimucronatai seeds is accelerated after fire treatments. It was also investigated the relationship among the quality of M. bimucronata seeds and the following variables: (1) percentage of germination of viable seeds from infested and non-infested fruits; (2) dry weights of seedlings from infested and non-infested fruits; and (3) body dry weights of A. schrankiae. It was also investigated whether fruit predation affect allocation of resources and secondary compounds (tannins) in viable seeds. Experiments related to seed predation were carried out comparing seeds from two plant populations (Lageado and Rubião). Twenty-five plants were selected at random with 15 from Lageado and 10 from Rubião, and four branches per plant were bagged. The other branches were exposed to predation by bruchids. Viable seeds from mature fruits were collected from bagged and non-bagged branches in order to perform nitrogen and tannins analysis and germination tests. Dry weights of seedlings and adult bruchids were recorded. The results showed that M. bimucronata seeds from non-infested fruits presented better germination than seeds from infested fruits, showing that seed ...(Complete abstract click electronic access below)

Orientador: Marcelo Nogueira Rossi / Banca: Wesley Augusto Conde Godoy / Banca: Lucas Del Bianco Faria / Resumo: Mimosa bimucronata (DC.) Kuntze (Fabaceae: Mimosoideae) é uma planta perene, arbórea, altamente ramificada e espinhosa, podendo atingir 8 metros de altura, nativa do Brasil e com reprodução por sementes, e suas sementes, durante a fenofase de frutificação, são intensamente predadas por bruquídeos da espécie Acanthoscelides schrankiae. Porém, há poucos estudos sobre a predação de sementes em M. bimucronata. Apesar de estar localizada em regiões próximas a cursos d'água, M. bimucronata geralmente está envolta por vegetação composta de plantas invasoras herbáceas, na maioria gramíneas, e durante a estação seca é comum a ocorrência de queimadas naturais. No presente estudo investigou-se a hipótese de que o processo germinativo das sementes de M. bimucronata pode ser acelerado após exposição moderada ao fogo. Além disso, estudou-se a relação entre a qualidade das sementes de M. bimucronata e as seguintes variáveis: (1) porcentagem de germinação de sementes sadias provenientes de frutos infestados e não infestados; (2) peso seco de plântulas provenientes de frutos infestados e não infestados; e (3) peso corporal de A. schrankiae. Também foi estudado o efeito da predação de frutos na alocação de recursos e compostos secundários (taninos) nas sementes sadias. Os experimentos relacionados a predação de sementes foram realizados comparando-se duas populações de plantas (Lageado e Rubião), em que 25 plantas foram marcadas ao acaso, sendo 15 pertencentes ao Lageado e 10 a Rubião, e 4 ramos por planta foram ensacados. Os demais ramos ficaram expostos a infestação por bruquídeos. As sementes viáveis dos frutos maduros, coletados dos ramos ensacados e também dos ramos livres, foram utilizadas para as análises dos conteúdos de nitrogênio e taninos, e também para os testes...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Mimosa bimucronata (DC.) Kuntze (Fabaceae: Mimosoideae) is a perennial, arborous, highly branched and spiny plant, reaching a height of 8 m meters high, endemic to Brazil, with seed reproduction. During fructification, M. bimucronata seeds are highly attacked by the bruchid Acanthoscelides schrankiae, although few studies about seeds predation on M. bimucronata are found. Despite being localized on margins of water courses, M. bimucronata is usually surrounded by herbaceous vegetation, mostly grasses, and during the dry season natural burnings are common. This study investigated the hypothesis that the germination process of M. bimucronatai seeds is accelerated after fire treatments. It was also investigated the relationship among the quality of M. bimucronata seeds and the following variables: (1) percentage of germination of viable seeds from infested and non-infested fruits; (2) dry weights of seedlings from infested and non-infested fruits; and (3) body dry weights of A. schrankiae. It was also investigated whether fruit predation affect allocation of resources and secondary compounds (tannins) in viable seeds. Experiments related to seed predation were carried out comparing seeds from two plant populations (Lageado and Rubião). Twenty-five plants were selected at random with 15 from Lageado and 10 from Rubião, and four branches per plant were bagged. The other branches were exposed to predation by bruchids. Viable seeds from mature fruits were collected from bagged and non-bagged branches in order to perform nitrogen and tannins analysis and germination tests. Dry weights of seedlings and adult bruchids were recorded. The results showed that M. bimucronata seeds from non-infested fruits presented better germination than seeds from infested fruits, showing that seed ...(Complete abstract click electronic access below) / Mestre

The population dynamics of small mammal populations in Punda Maria, Kruger National Park, South Africa was investigated with respect to community size and structure, seed predation and dispersal of several trees. Species populations, community structure and habitat attributes were measured at six sites comprising of 3 habitat types (2 sites per habitat); namely Acaciagrassland, North-facing and South-facing sloped sites. Seasonal variation was investigated at the Acacia sites during late summer (April) and winter months (July). Five habitat attributes were measured; percentages of total cover and herbage, plant litter depth (cm), height of dominant vegetation type measured (m) and edaphic condition were recorded at 15 randomly selected traps per site. Almonds (Prunus dulcis), baobabs (Adansonia digitata), mopane (Colophospermum mopane), and Acacia tortilis seeds were used in the predation and dispersal experiment. North- and South-facing sites were dominated by Aethomys sp. while Acacia sites were dominated by Mastomys natalensis. Seed predation was high at the North-facing slopes, with a significant difference in predation on A. tortilis seeds. Seed dispersal activity was low; no , scatter hoarding was identified; only larder hoarding was observed by Aethomys sp. and M. natalensis at North-facing sites and Acacia sites respectively. Trampling by megaherbivore activity impacted vegetation structure and has negatively affected rodent population and ground activity, particularly at the Acacia sites.

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