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Baccaro F.B.,National Institute of Amazonian Research | De Souza J.L.P.,Programa de Pos Graduacao em Entomologia | Franklin E.,INPA | Landeiro V.L.,National Institute of Amazonian Research | Magnusson W.E.,INPA
Ecological Entomology | Year: 2012

Ants are highly interactive organisms and dominant species are considered to be able to control the species richness of other ants via competitive exclusion. However, depending on the scale studied, inter-specific competition may or may not structure biological assemblages. To date, ant dominance-richness relationships have only been studied in small sample units, where a few dominant colonies could plausibly control most of the sample unit. We conducted a comprehensive survey of terrestrial ant assemblages using bait, pitfall, and litter-sorting methods in three sites in Brazilian Amazonia. Using a spatially structured rarefaction approach, based on sampling units with linear dimensions ranging from 25 to 250 m, the mesoscale patterns of ant dominance-richness relationships (sampling units covering hundreds of meters separated by kilometers) were investigated. Interference-competition models (parabolic or negative linear relationships between species richness and the abundance of dominant ants) tended to be more frequent in smaller sample units or in assemblages sampled with interactive methods, such as baits. Using more inclusive sampling methods, the relationship was generally asymptotic rather than parabolic, with no reduction in species diversity because of the presence of dominants. Random co-occurrence patterns of species within sites support the interpretation of a limited role for present-day competition in structuring these assemblages. Competition from dominant species may reduce species richness in small areas, especially when artificial baits are used, but appears to be less important than environmental constraints in determining ant species richness across scales of hectares and greater in these Amazon forests. Published 2011. This article is a U.S. Government work and is in the public domain in the USA.

Sandoval-Gomez V.E.,Programa de Pos Graduacao em Entomologia | Zacaro A.A.,Federal University of Vicosa
Entomological Science | Year: 2011

Xylographus globipennis Reitter, 1911, a ciid beetle known only from its type locality in Eritrea, has in fact a broad distribution in the Afrotropical region. A redescription of the species is provided, including the description of its male terminalia, based on the lectotype and three paralectotypes, here designated, and specimens from several localities in Democratic Republic of the Congo and in Kenya. The geographic distribution and similarities of external morphological characters of X. globipennis to other African Xylographus species are also discussed. © 2011 The Entomological Society of Japan.

Araujo V.A.,Programa de Pos Graduacao em Entomologia | Freitas F.V.,Federal University of Vicosa | Moreira J.,Programa de Pos Graduacao em Entomologia | Neves C.A.,Federal University of Vicosa | Lino-Neto J.,Federal University of Vicosa
Neotropical Entomology | Year: 2010

Bees can form all levels of social organization, from solitary to advanced eusocial societies. Although 80% of the species exist as solitary species, most researches emphasize social species. This study focuses on the description of the male reproductive system of the solitary bees Thygater analis (Lepeletier) and Melitoma segmentaria (Fabricius) and searches for traits that support behavioral and phylogenetic studies. The reproductive system of males were dissected, fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer pH 7.2 and post-fixed with 1% osmium tetroxide. The tissue was dissected and included for light microscopy. The species presented similar anatomical traits, including paired testicles, seminal vesicles, deferent ducts, accessory glands and an ejaculatory duct. Each testicle was composed of four follicles. In both species, a testicle and a seminal vesicle were surrounded by a joint capsule, forming a seminal vesicle-testicle complex. The two species presented accessory glands with very distinct morphological traits. The anatomic pattern and the histological traits of the reproductive system of the species studied were similar to those described for other bees. In addition, these traits can be used to differentiate species and allow inferences concerning their reproductive biology.

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