CONSERVATION GENETICS OF NEOTROPICAL POLLINATORS REVISITED: MICROSATELLITE ANALYSIS SUGGESTS THAT DIPLOID MALES ARE RARE IN ORCHID BEES

Allozyme analyses have suggested that Neotropical orchid bee (Euglossini) pollinators are vulnerable because of putative high frequencies of diploid males, a result of loss of sex allele diversity in small hymenopteran populations with single locus complementary sex determination. Our analysis of 1010 males from 27 species of euglossine bees sampled across the Neotropics at 2–11 polymorphic microsatellite loci revealed only five diploid males at an overall frequency of 0.005 (95% CIs 0.002–0.010); errors through genetic nondetection of diploid males were likely small. In contrast to allozyme‐based studies, we detected very weak or insignificant population genetic structure, even for a pair of populations >500 km apart, possibly accounting for low diploid male frequencies. Technical flaws in previous allozyme‐based analyses have probably led to considerable overestimation of diploid male production in orchid bees. Other factors may have a more immediate impact on population persistence than the genetic load imposed by diploid males on these important Neotropical pollinators.     

Influence of temperature and body mass on standard metabolic rate of eastern red-backed salamanders (Plethodon cinereus)

(1) We estimated the standard metabolic rate (SMR) of wild-caught Plethodon cinereus across a range of body masses and ecologically relevant temperatures.     

Partial protection against P. vivax infection diminishes hypnozoite burden and blood-stage relapses

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Nucleic acid enzymes.

Last year provided new structural data, particularly for the group I intron and the Hepatitis delta ribozymes, that were essential for a better understanding of the RNA structure/function relationship. The role of metal ions in catalysis of ribozyme action still remains elusive, however. In vitro selection has continued to be a rich source for obtaining data on new nucleic acid enzyme activities.     

Effector and regulator: Diverse functions of C. elegans C-type lectin-like domain proteins

In C. elegans, 283 clec genes encode a highly diverse family of C-type lectin-like domain (CTLD) proteins. Since vertebrate CTLD proteins have characterized functions in defense responses against pathogens and since expression of C. elegans clec genes is pathogen-dependent, it is generally assumed that clec genes function in C. elegans immune defenses. However, little is known about the relative contribution and exact function of CLEC proteins in C. elegans immunity. Here, we focused on the C. elegans clec gene clec-4, whose expression is highly upregulated by pathogen infection, and its paralogs clec-41 and clec-42. We found that, while mutation of clec-4 resulted in enhanced resistance to the Gram-positive pathogen Bacillus thuringiensis MYBt18247 (Bt247), inactivation of clec-41 and clec-42 by RNAi enhanced susceptibility to Bt247. Further analyses revealed that enhanced resistance of clec-4 mutants to Bt247 was due to an increase in feeding cessation on the pathogen and consequently a decrease in pathogen load. Moreover, clec-4 mutants exhibited feeding deficits also on non-pathogenic bacteria that were in part reflected in the clec-4 gene expression profile, which overlapped with gene sets affected by starvation or mutation in nutrient sensing pathways. However, loss of CLEC-4 function only mildly affected life-history traits such as fertility, indicating that clec-4 mutants are not subjected to dietary restriction. While CLEC-4 function appears to be associated with the regulation of feeding behavior, we show that CLEC-41 and CLEC-42 proteins likely function as bona fide immune effector proteins that have bacterial binding and antimicrobial capacities. Together, our results exemplify functional diversification within clec gene paralogs.     

Purine metabolites in serum of higher primates,including man

Using a new method for simultaneous quantification of hypoxanthine, xanthine, uric acid, and allantoin by means of high-pressure liquid chromatography, purine metabolites of 18 species of higher primates, including man, have been determined. The data thus produced indicate that the serum concentrations of purine metabolites in primates are influenced by nutrition, sexual hormones, and the procedures used in catching the animals for venipuncture. In the Callitrichidae examined, serum concentrations of purines differ significantly from species to species. The results of a nutritional test show that Callithrix jacchus possesses an efficient system for degradation of dietary purines.     

Mountain passes are higher at low latitudes for madicolous insect communities of the Neotropical region

Aim

To test whether spatial turnover patterns of mountain madicolous insect communities in the Southern Hemisphere support the ‘mountain passes are higher in the Tropic’ hypothesis (MPHT). To do this, we compared madicolous communities in the Amazon Mountains (equator) and the Atlantic Forest Mountains (23°S).

Location

Brazil.

Methods

We characterized madicolous insect communities in two elevational gradients between 90 to 3000 m a.s.l. separated by 23° of latitude, totalling 108 sampling sites. Since the MPHT predicts a more intense turnover along elevational gradients at lower latitudes than at higher latitudes, we evaluated beta diversity in the Amazon mountains, at the equator, and in the Atlantic Forest mountains, in the subtropical region. We quantified multiple-site abundance-based dissimilarity to assess whether beta diversity was different between both regions. We also performed constrained ordination (db-RDA) analyses to assess whether community dissimilarity (balanced variation in abundances) was uniquely or jointly explained by environmental, spatial and/or elevational predictors. Additionally, we independently assessed the relationship between community dissimilarity and altitudinal difference in each region and tested for differences in model parameters between regions.

Results

Although we found high species turnover in both regions, the community variation explained by environmental factors and altitude was higher in the Amazon than in the Atlantic Forest, as evidenced by db-RDA and altitudinal difference models. In general, communities were remarkably constrained by spatial predictors, which result from low dispersion capacity of most madicolous insects and low connectivity of madicolous systems. Consequently, the composition of madicolous insects notably diverged between regions, highlighting the complementarity and high conservation value of both systems.

Main Conclusions

Our results indicate that the MPHT explains, at the community level, the differences between low- and high-latitude mountain systems in community turnover along elevational gradients, even within a relatively short latitudinal distance in the Southern Hemisphere.     

How can conserved gene expression allow for variation? Lessons from the dorso-ventral patterning gene muscle segment homeobox

Arthropods are common in marine, freshwater, terrestrial, and even aerial environments. The arthropod nervous systems must be adjusted to the highly diverse behaviour and requirements of the individual arthropod species. This raises the question of how the underlying patterning mechanisms have changed during arthropod evolution to produce the characteristic axonal scaffold on the one hand and allow for variations in neuronal networks on the other hand. Here we show that the overall number of the neural precursor groups/neuroblasts as well as their spatial arrangement in rows and columns is similar in all four arthropod groups indicating a common origin of this pattern. Furthermore, we demonstrate differences in the expression pattern of the columnar gene muscle segment homeobox and both differences in the expression and regulation of the neural subtype specific genes even-skipped and islet. This variation may underlie the evolutionary variations in neural identity in the individual arthropod groups. Furthermore, we discuss to what extent the stereotyped pattern of neural precursors is required for the conserved axonal scaffold and thus might have been constrained along with the underlying patterning mechanisms.