Experimental Crosses Between Two Dung Beetle Lineages Show Transgressive Segregation in Physiological Traits.

Physiological traits in insects are intrinsically related to their behavior, fitness, and survival and can reflect adaptations to ecological stressors in different environments, leading to population differentiation that may cause hybrid failure. In this study, we characterized five physiological traits related to body condition (body size, body mass, amount of fat, total hemolymph protein, and phenoloxidase activity) in two geographically separated and recently differentiated lineages of Canthon cyanellus LeConte, 1859 within their natural distribution in Mexico. We also performed experimental hybrid crosses between these lineages to better understand the differentiation process and explore the presence of transgressive segregation over physiological traits in them. We found differences between lineages in all traits except body mass, suggesting selective pressures related to different ecological pressures. These differences were also apparent in the transgressive segregation of all traits in F1 and F2 hybrids, except for phenoloxidase activity. Protein content was sexually dimorphic in both parental lineages but was reversed in hybrids, suggesting a genetic basis for the differences between sexes. The negative sign of transgressive segregation for most traits indicates that hybrids would be smaller, thinner, and generally unfit. Our results suggest that these two lineages may undergo postzygotic reproductive isolation, confirming the cryptic diversity of this species complex.

A new species of Pyrrhosphodrus (Hemiptera: Heteroptera: Reduviidae) from the Caatinga ecosystem in Brazil, with notes on the genus.

A new species of Reduviidae (Hemiptera: Heteroptera) from Caatinga ecosystem, Pyrrhosphodrus caatingensis Lapischies Forero sp. nov., is described. The new species is distinguished from its congeners by its overall reddish coloration with black areas; by the black legs, with femora with a subapical yellowish broad ring, tibiae with apical and subapical yellowish annuli; and genital characters. Comments about the biology, feeding habits, habitus, genitalic images, and a distribution map of the new species are given. In addition, the following synonymy is proposed: Pyrrhosphodrus militaris Stål, 1866 = P. theresina (Berg, 1879), syn. nov. A key to separate the known species of Pyrrhosphodrus Stål, 1866 is provided.

Dung beetle (Coleoptera, Scarabaeidae) assemblage of a highly fragmented landscape of Atlantic forest: from small to the largest fragments of northeastern Brazilian region

Human activities in tropical forests are the main causes of forest fragmentation. According to historical factor in deforestation processes, forest remnants exhibit different sizes and shapes. The aim of the present study was to evaluate the dung beetle assemblage on fragments of different degree of sizes. Sampling was performed during rainy and dry season of 2010 in six fragments of Atlantic forest, using pitfall traps baited with excrement and carrion. Also, we used two larger fragments as control. We used General Linear Models to determine whether the fragments presented distinguished dung beetle abundance and richness. Analysis of Similarities and Non-Metric Multidimensional Scaling were used to determine whether the dung beetle assemblage was grouped according to species composition. A total of 3352 individuals were collected and 19 species were identified in the six fragments sampled. Dung beetle abundance exhibited a shift according to fragment size; however, richness did not change among fragments evaluated. Also, fragments sampled and the two controls exhibited distinct species composition. The distinction on abundance of dung beetles among fragments may be related to different amount of resource available in each one. It is likely that the dung beetle richness did not distinguish among the different fragments due to the even distribution of the mammal communities in these patches, and consequent equal dung diversity. We conclude that larger fragments encompass higher abundance of dung beetle and distinct species. However, for a clearer understanding of effects of fragmentation on dung beetles in Atlantic forest, studies evaluating narrower variations of larger fragments should be conducted.

What is the importance of open habitat in a predominantly closed forest area to the dung beetle (Coleoptera, Scarabaeinae) assemblage?

What is the importance of open habitat in a predominantly closed forest to the dung beetle assemblage? The Atlantic Forest in Brazil is one of the most highly disturbed ecosystems and is mainly represented by fragmented areas. However, in places where human disturbances have ceased, certain areas are showing a natural regeneration pattern. The aim of the present study was to determine how the dung beetle assemblage responds to distinct habitat structures in a fragment of Atlantic Forest. For such, open and closed forest areas were sampled in a fragment of the Atlantic Forest in the northeastern region of Brazil. Pitfall traps baited with excrement and carrion were used to collect the beetles. A total of 7,267 individuals belonging to 35 species were captured. Canthon chalybaeus and C. mutabilis were restricted to open areas. Nearly 90% of the individuals of C. aff. simulans and Deltochilum aff. irroratum were identified in these areas. A higher percentage (> 50%) of Canthon staigi, Dichotomius aff. depressicolis and D. aff. sericeus occurred in closed areas. Abundance differed between areas, with higher values in closed areas. Richness was not influenced by the habitat structure. NMDS ordination exhibited the segregation of areas and ANOSIM confirmed that this variable explained the assemblage of dung beetle species. The findings of the present study validate that open areas are associated to more restrictive conditions, limiting a higher abundance of dung beetle. Although situated near preserved fragments, the studied open areas increase the heterogeneity of the general landscape.