No abstract

Few studies of plant-pollinator interactions in fragmented landscapes evaluate the consequences of floral visitor variation on multiple stages of plant reproduction. Given that fragmentation potentially has positive or negative effects on different organisms, and that self-incompatible plant species depend on pollinators for sexual reproduction, differences in floral visitor assemblages may affect certain plant reproductive stages. We evaluated how pollinator assemblage, availability of floral resources, pollination, reproductive output, and seed and seedling performance of Psychotria suterella Muell. Arg. varied among three fragmentation categories: non-fragmented habitats, fragments connected by corridors, and isolated fragments. Richness and frequency of floral visitors were greater in fragments than in non-fragmented sites, resulting mainly from the addition of species typically found in disturbed areas. Although 24 species visited Psychotria suterella flowers, bumblebees were considered the most important pollinators, because they showed the highest frequency of visits and were present in eight out of ten sites. Additionally, the number of pollen tubes per flower per visit was lower in areas without bumblebees. The increased visitation in fragments seemed to enhance pollination slightly. However, fruit and seed output, germination, and seed and seedling mass were similar in non-fragmented sites, connected sites, and isolated fragments. Our results suggested that, even for a self-incompatible species, responses to habitat fragmentation at different stages of plant reproduction might be decoupled from the responses observed in floral visitors, if fruit set is not pollen limited. If all reproductive stages were considered, variation on the small scale was more important than the variation explained by fragmentation category. In spite of its self-incompatible breeding system, this plant-pollinator system showed resilience to habitat fragmentation, mainly as a result of high availability of potential mates to P. suterella individuals, absence of pollen limitation, and the presence of bumblebees (Bombus spp.) throughout this highly connected landscape.

-(Reproductive biology of Psychotria suterella (Rubiaceae) and the approach of ecological scales for flowering and fruiting phenology). Foraging behavior of pollinators and seed dispersers is related to resource heterogeneity in the environment, making it important to know the spatio-temporal variation of resources in order to understand the mutualistic relationships established between plants and animals. Psychotria suterella flowered from January to April, months with highest annual rainfall, and exhibited high synchronism among the populations in the landscape studied. The flowering pattern found on the category of individuals corresponds to that one found in populations and landscape categories. Fructification occurred all year long, with greater availability of mature fruits in May and December; and synchronism was lower in this phenophase than in flowering. Only intermorph pollinations produced fruits and seeds, indicating that this plant species relies on pollen vectors for sexual reproduction. Since there is no evidence of pollen limitation, we consider that differences in fructification among populations could be related to abiotic factors. The overlap between flowering pattern of Psychotria suterella and Bombus brasiliensis foraging activicty, the fact that B. brasiliensis is the most important pollinator of this plant species, as well as the importance of P. suterella for this bee diet, suggest that selective pressures could be acting between these species, underlying this mutualistic interaction.Key words -ecological scales, floral traits, mutualism, pollination, reproductive phenology RESUMO -(Biologia reprodutiva de Psychotria suterella (Rubiaceae) e a abordagem de escalas ecológicas para a fenologia de floração e frutificação). O comportamento de forrageio de polinizadores e dispersores de sementes é influenciado pela heterogeneidade de recursos no ambiente, sendo importante conhecer a variação espaço-temporal dos recursos a fim de compreender as relações mutualistas estabelecidas entre plantas e animais. Na paisagem estudada, a floração de Psychotria suterella ocorreu de janeiro a abril, meses de maior pluviosidade no ano, e apresentou alta sincronia entre as populações. O padrão fenológico de floração encontrado na categoria de indivíduo se assemelhou ao registrado para as categorias de população e paisagem. A frutificação ocorreu durante todo o ano, com maior disponibilidade de frutos maduros em maio e dezembro, havendo menor sincronia entre as populações e entre os indivíduos nesta fenofase do que na de floração. Apenas cruzamentos inter-morfos produziram frutos e sementes, indicando que esta espécie vegetal depende de vetores de pólen para reprodução sexuada. Uma vez que não há indícios de limitação polínica nas populações estudadas, consideramos que as diferenças na frutificação entre as populações poderiam estar associadas a fatores abióticos. A sobreposição entre o padrão de floração anual de Psychotria suterella e a atividade de forrageio de Bombus brasiliensis, o fato de B. bras...

Many studies in the past decade, mostly in temperate countries, have documented the effects of habitat loss and fragmentation on species richness, composition, and abundance and the behaviour of pollinators. Changes in landscape structure are considered to be the primary causes of the limitation of pollination services in agricultural systems. Here, we review evidence of general patterns as well as gaps in knowledge that could be used to support the development of policies for pollinator conservation and the restoration of degraded landscapes. Our results indicate a recent increase in the number of studies on the relationships between pollination processes and landscape patterns, with some key trends already being established. Many authors indicate, for example, that the spatial organization of a landscape has a great influence on the survival and dispersal capacity of many pollinators, as spatial organization affects resource availability and determines the functional connectivity of the landscape. Additionally, the shape, size and spatial arrangement of the patches of each type of natural environment, as well as the occurrence of different types of land use, can create sites with different degrees of connectivity or even barriers to movement between patches, which can deeply modify pollinator flows through the landscape and consequently the success of cross-pollination. However, there are still some gaps, such as in the knowledge of which critical values of habitat loss can lead to drastic increases in pollinator extinction rates, information that is needed to evaluate at what point plant-pollinator interactions may collapse. We also need to concentrate research effort on improving a landscape’s capacity to facilitate pollinator flow (connectivity) between crops and nesting/foraging areas.

Mutualistic interactions between plants and pollinators play an essential role in the organization and persistence of biodiversity. The structure of interaction networks mediates the resilience of local communities and ecosystem functioning to environmental changes. Hence, network structure conservation may be more critical for maintaining biodiversity and ecological services than the preservation of isolated species in changing landscapes. Here, we intensively surveyed seven 36 km 2 landscapes to empirically investigate the effects of forest loss and landscape configuration on the structure of plantpollinator networks in understory vegetation of Brazilian Atlantic Forest. Our results indicate that forest loss and isolation affect the structure of the plant-pollinator networks, which were smaller in deforested landscapes, and less specialized as patch isolation increased. Lower nestedness and degree of specialization (Hʹ 2 ) indicated that the remaining plant and bee species tend to be generalists, and many of the expected specialized interactions in the network were already lost. Because generalist species generate a cohesive interaction core in these networks, these simplified networks might be resistant to loss of peripheral species, but may be susceptible to the extinction of the most generalist species. We suggest that such a network pattern is an outcome of landscapes with a few remaining isolated patches of natural habitat. Our results add a new perspective to studies of plant-pollinator networks in fragmented landscapes, showing that those interaction networks might also be used to indicate how changes in natural habitat affect biodiversity and biotic interactions.

In social insects, nests are very important structures built to provide a protected microhabitat for immature development and food storage and are the places where most interactions between all members of a colony occur. Considering that nest architecture is an important behavioural trait that can clarify essential points of the social level of the species, here we describe the architectural model of the Ponerinae ant Odontomachus chelifer. Five subterranean nests were excavated; one of them filled with liquid cement for extraction of casts of chambers, shafts and tunnels. All nests were found in a woodland area, with Dystrophic Red Latosol soil, associated with roots of large trees and, differently from the pattern currently described for this subfamily, presented a complex structure with multiple entrances and more than one vertical shaft connected by tunnels to relatively horizontal chambers. The number of chambers varied from 24 to 77, with mean volume ranging from 200.09 cm 3 to 363.79 cm 3 , and maximum depth of 134 cm. Worker population varied between 304 and 864 individuals with on average 8.28 cm 2 of area per worker. All nests had at least one Hall, which is a relatively larger chamber serving as a distribution centre of the nest, and to our knowledge, there is no record of Ponerinae species building similar structure. All nests had chambers "paved" with pieces of decaying plant material and on the floor of some of them, we found a fungus whose identification and function are being investigated. Thus, our findings provide evidence to suggest that nests of O. chelifer can be considered complex, due to the great number and organization of chambers, shafts and connections, compared to those currently described for Ponerinae species.

Plant-pollinator networks have been widely used to understand the ecology of mutualistic interactions between plants and animals. While a number of general patterns have been identified, the mechanisms underlying the structure of plant-pollinator networks are poorly understood. Here we present an agent based model (ABM) that simulates the movement of bees over heterogeneous landscapes and captures pollination events, enabling the influence of landscape pattern on pollination networks to be explored. Using the model, we conducted a series of experiments using virtual landscapes representing a gradient of forest loss and fragmentation. The ABM was able to produce expected trends in network structure, from simulations of interactions between individual plants and pollinators. For example, results indicated an increase in the index of complementary specialization (H2’) and a decline in network connectance with increasing forest cover. Furthermore, network nestedness was not associated with the degree of forest cover, but was positively related to forest patch size, further supporting results obtained in the field. This illustrates the potential value of ABMs for exploring the structure and dynamics of plant-pollinator networks, and for understanding the mechanisms that underlie them. We attribute the results obtained primarily to a shift from specialist to generalist pollinators with increasing forest loss, a trend that has been observed in some field situations.

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