ANDRADE FILHO, Fernando César Moura de. Estratégias de fundação colonial de uma vespa social primitiva (Vespidae: Polistinae: Polistes canadensis) em um crescente de aridez. 2015. 32 f. Dissertação (Mestrado em Ecologia e Recursos Naturais)-Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by ELAINE PEREIRA (ellainec.pereira@gmail.com) on 2017-08-03T17:36:44Z No. of bitstreams: 1 2015_dis_fcmandradefilho.pdf: 169632 bytes, checksum: 443882474d1874b76baf286adc4af321 (MD5) / Approved for entry into archive by Jairo Viana (jairo@ufc.br) on 2017-08-04T15:31:46Z (GMT) No. of bitstreams: 1 2015_dis_fcmandradefilho.pdf: 169632 bytes, checksum: 443882474d1874b76baf286adc4af321 (MD5) / Made available in DSpace on 2017-08-04T15:31:46Z (GMT). No. of bitstreams: 1 2015_dis_fcmandradefilho.pdf: 169632 bytes, checksum: 443882474d1874b76baf286adc4af321 (MD5) Previous issue date: 2015 / In some primitively social insects, the absence of distinct morphological castes leads to reproductive plasticity during nest founding. However, environmental constraints select for viable reproductive options. These constraints are well known in temperate locations and distinct from tropical semi-arid environments. We tested the hypothesis that aridity-related constraints on independent nesting decreases the fitness pay-offs to solitary foundresses in a primitively social wasp (Polistes canadensis). 95 colonies were monitored during a six month period in three distinctively arid regions. Colony fail, colony survival and colony reproductive success from each of two (solitary and cooperative) nesting patterns were quantified. Local foundresses population size was larger in less arid locations (Parque do Cocó: n = 142, Pentecoste: n = 86, Serra das Almas: n = 46). In more arid regions, all reproductive successful colonies were founded in the most rainy month of the rainy season (region [GLM: LR = 18.5, d.f. = 2, p < 0.0001***], foundation period [GLM: LR = 5.7, d.f. = 1, p = 0.01*]). Among the foundation period surviving colonies, solitary nesting reproductive success (measured as pupal production) decreased with aridity (nesting strategy [GLM: LR = -6.2, d.f. = 1, p = 0.01*], region [GLM: LR = -18.4, d.f. = 2, p = 0.0001***]). We conclude that aridity constraints reproduction in a primitively social wasp and, in more arid environments, favors the foundations occurred during momentary pulses of high rainfall. / Em insetos sociais primitivos, não existem castas morfológicas diferenciadas e os indivíduos exibem plasticidade reprodutiva ao fundar colônias. Contudo, limitações ambientais podem selecionar quais estratégias de nidificação são viáveis. Os fatores ecológicos que influenciam na fundação colonial em regiões temperadas são bem conhecidos e distintos dos ambientes tropicais semiáridos. Neste contexto, o presente estudo objetiva compreender como a nidificação de vespas sociais tropicais pode ser influenciada por um gradiente de aridez. Populações de Polistes canadensis foram monitoradas durante um período de seis meses em três regiões com distintos níveis de aridez. A falha, a sobrevivência e o sucesso reprodutivo coloniais dos diferentes padrões de nidificação foram quantificados. O tamanho populacional de fundadoras foi maior em locais menos áridos (Parque do Cocó: n = 142, Pentecoste: n = 86, Serra das Almas: n = 46). Em regiões mais áridas, somente as colônias fundadas no mês de maior precipitação conseguiram sobreviver à fase de iniciação colonial. As colônias de fundação associativa foram as que mais sobreviveram em todas as áreas. O sucesso reprodutivo colonial (medido em termos de produção pupal) das fundações solitárias diminuiu com a aridez. A aridez limita as opções reprodutivas de Polistes canadensis e, nos ambientes mais áridos, favorece as nidificações ocorridas em pulsos momentâneos de grande precipitação.

La heterogeneidad de la vegetación y la ambiental se encuentran estrechamente relacionadas. Los gradientes ambientales que surgen de la combinación de diversos factores bióticos y abióticos dentro de un área explican frecuentemente el patrón espacial observado en la vegetación. La importancia de los distintos factores como responsables de la heterogeneidad de la vegetación varía a distintas escalas. A su vez, el rol que cumplan los factores ambientales sobre el patrón de la vegetación dependerá también del ensamble de especies bajo consideración. Procesos como la erosión y la redistribución de agua y otros materiales son controlados por gradientes topoedáficos definidos por la geomorfología. Estos gradientes determinan la habitabilidad de los ambientes por distintas especies. En los ecotonos, el efecto de estos factores adquiere especial relevancia. Allí, las especies están restringidas a áreas fragmentadas en las que la combinación de los distintos factores define ambientes similares a su bioma núcleo. En el NE de Chubut, dentro del ecotono entre las Provincias Fitogeográficas del Monte y Patagónica, la coexistencia espacial de comunidades características de ambas Provincias Fitogeográficas ha dado lugar a discrepancias entre autores en cuanto a la ubicación del límite entre ellas. Esta zona ecotonal coincide con la presencia de sistemas entrelazados de paleocauces y barras pertenecientes a un antiguo abanico aluvial generado por un complejo paleodrenaje del Río Chubut. A nivel regional se han descripto las comunidades típicas de ambas Provincias Fitogeográficas: la comunidad de Larrea divaricata y Stipa spp., típica del Monte Austral y la comunidad de Chuquiraga avellanedae, característica de aquellas áreas más relacionadas a la Provincia Fitogeográfica Patagónica. Los objetivos de esta tesis fueron: 1) describir la heterogeneidad espacial de la vegetación en un área dentro del ecotono entre las Provincias Fitogeográficas del Monte y Patagónica y las principales variables ambientales asociadas a esa heterogeneidad y 2) evaluar el establecimiento de las especies características de ambas Provincias Fitogeográficas en distintos suelos presentes en el área. Para lograr estos objetivos se llevaron a cabo censos de vegetación y muestreos de suelo superficial en geoformas contrastantes (paleocauces y barras). Se evaluó la distribución de los arbustos dominantes en general y de las especies en particular en relación a algunas variables topográficas. Además, se realizaron calicatas en ambas geoformas y se registraron tanto la precipitación como el potencial de agua en el suelo a diferentes profundidades. Por otro lado, se analizaron indicadores espectrales de humedad del suelo para cada estación del año a partir de las imágenes satelitales. Asimismo, se desarrollaron dos experimentos bajo condiciones controladas de invernáculo con el objeto de evaluar el establecimiento de C. avellanedae y L. divaricata en diferentes micrositios de ambas geoformas (paleocauces y barras) bajo distinta disponibilidad hídrica. En este estudio la distribución de las comunidades se asoció fuertemente a la geomorfología. A escala de paisaje, las dos geoformas principales fueron dominadas por comunidades diferentes y presentaron suelos de origen y características distintas. La comunidad de C. avellanedae dominó los paleocauces, topográficamente más bajos. Estos presentaron desarrollo de horizontes argílicos, mayor contenido de materia orgánica, de sales y de yeso, y mayor humedad a lo largo de todo el año. Esta comunidad presentó mayor cobertura vegetal y raíces que exploraron principalmente los primeros 40 cm de profundidad del suelo. La comunidad de L. divaricata dominó las barras, topográficamente más altas con suelos de textura más gruesa, mayor contenido de gravas y carbonatos, y menor humedad. Esta comunidad presentó menor cobertura vegetal y raíces que se extienden a mayor profundidad aunque en superficie su abundancia es menor. Además, en esta comunidad se observó que la densidad de raíces acompañó a las variaciones en la densidad aparente del suelo. En la zona de estudio la diferente distribución de las especies entre geoformas sería fruto de procesos que operan durante etapas tempranas de la vida de las plantas y no consecuencia de mortalidad diferencial luego de un establecimiento homogéneo. A escala de mayor detalle, se observó una influencia favorable de los montículos asociados a los parches de vegetación sobre el establecimiento y el crecimiento de L. divaricata y C. avellanedae, lo que está en concordancia con trabajos previos realizados en zonas áridas y semiáridas. La conjunción de tendencias hacia una temperatura media anual mayor y precipitaciones menores en pulsos más intensos pronosticada en los escenarios de clima futuro para la región intensificaría el patrón observado a escala de paisaje. Aunque esta tendencia no sería favorable para ninguna especie en las barras, perjudicaría más a C. avellanedae en esta geoforma. Por otro lado, pulsos intensos de lluvia podrían aumentar los procesos de escorrentía favoreciendo a C. avellanedae en los paleocauces. De acuerdo a los resultados de este estudio en el extremo sur del ecotono entre las Provincias Fitogeográficas del Monte y la Patagónica la coexistencia en el espacio de horizontes no relacionados pedogenéticamente da lugar a suelos con distintas propiedades, las cuales controlan los patrones de vegetación a través de su efecto sobre el establecimiento de las plántulas. / Vegetation is closely related to environmental heterogeneity. Environmental gradients that result from the interaction among different biotic and abiotic factors frequently explain vegetation patterns, especially in arid and semiarid environments. The relative influence of the different factors responsible for vegetation patterns depends on the scale, and also on the assemblage of species taken into consideration. Erosion processes, as well as redistribution of water and other materials are controlled by topoedaphic gradients defined by geomorphology. These gradients define the environmental suitability for the different species, and become particularly relevant in ecotones, where species are constrained to fragmented areas similar to their core biome. In Northeastern Chubut Province, characteristic species of both the Monte and Patagonic Phytogeographic Provinces coexist in a wide ecotone, causing that different authors disagree on the boundary location between units. Landscape structure in this ecotone is defined by anastomosing systems of paleochannels and bars, part of an ancient alluvial fan of the Chubut River. At a regional scale, two plant communities were described: a community of Larrea divaricata and Stipa spp., typical of the Southern Monte, and a community of Chuquiraga avellanedae, which is more related to the Patagonia Phytogeographic Province. The objectives of this thesis were: 1) to describe the spatial heterogeneity of vegetation at the southern Monte-Patagonia ecotone and the main environmental variables associated with this heterogeneity, and 2) to evaluate the establishment of characteristic species of both Phytogeographic Provinces, in different soils present in the area. To meet the objectives, vegetation and soil surveys were performed at contrasting landforms (bars and palochannels). The distribution of dominant shrubs, irrespective of the species, was evaluated in relation to topographic variables, followed by the evaluation of species distribution. In addition, superficial soil samples, as well as samples from soil pits were taken in both landforms. Precipitation and soil water potential at different depths were also recorded in both landforms, and satellite spectral indices of soil moisture were seasonally analyzed. Finally, seedling establishment in different soils was evaluated by means of two factorial experiments developed under controlled greenhouse conditions. Our results confirmed the existence of a regional ecotone, where plant communities typical from the Monte and Patagonia Phytogeographic Provinces coexist at the landscape scale. In the study area, the presence of this ecotone can be attributed to geomorphology, since soils from the different landforms differed in their origin and characteristics, and were occupied by different plant communities. The community of C. avellanedae dominated on paleochannels, which were topographically lower, presented argilic horizons, and had higher organic matter, salt and gypsum contents, as well as higher humidity throughout the year. Within this community, vegetation cover was higher and root systems developed through the upper 40 cm of soil. In contrast, L. divaricata dominated on bars, which were topographically higher and had coarser soils, with higher gravel and carbonate contents, and lower humidity. This community presented a lower vegetation cover and root systems that developed to a greater depth. Root development was scarce near the surface, and increased with bulk density. Species distribution in the study area would be a consequence of processes operating at early stages in plant life cycle, instead of differential mortality patterns after a homogeneous establishment. A positive effect of soil mounds was observed on seedling establishment and growth, at scales of greater detail. Climate change scenarios predicted higher mean temperatures and lower precipitation, distributed in fewer and more intense rain pulses. Under these conditions, the observed landscape pattern would be intensified. In bars, the predicted trends would be unfavourable for all species, but the effects on C. avellanedae would be comparatively worse, reducing its competitive pressure on L. divaricata in this landform. On the other hand, the higher intensity of rain pulses could increase rainfall runoff processes favouring C. avellanedae in paleochannels. According to these results, at the southern end of the ecotone between Monte and Patagonic Phytogeographic Provinces, the spatial coexistence of pedogenetically unrelated horizons results in soils with different properties, which control vegetation patterns in the study area through their effects on seedling establishment.