The soil fungus Trichoderma atroviride, a mycoparasite, responds to a number of external stimuli. In the presence of a fungal host, T. atroviride produces hydrolytic enzymes and coils around the host hyphae. In response to light or nutrient depletion, asexual sporulation is induced. In a biomimetic assay, different lectins induce coiling around nylon fibers; coiling in the absence of lectins can be induced by applying cyclic AMP (cAMP) or the heterotrimeric G-protein activator mastoparan. We isolated a T. atroviride G-protein ␣-subunit (G␣) gene (tga1) belonging to the fungal subfamily with the highest similarity to the G␣ i class. Generated transgenic lines that overexpress G␣ show very delayed sporulation and coil at a higher frequency. Furthermore, transgenic lines that express an activated mutant protein with no GTPase activity do not sporulate and coil at a higher frequency. Lines that express an antisense version of the gene are hypersporulating and coil at a much lower frequency in the biomimetic assay. The loss of Tga1 in these mutants correlates with the loss of GTPase activity stimulated by the peptide toxin Mas-7. The application of Mas-7 to growing mycelial colonies raises intracellular cAMP levels, suggesting that Tga1 can activate adenylyl cyclase. In contrast, cAMP levels and cAMP-dependent protein kinase activity drop when diffusible host signals are encountered and the mycoparasitism-related genes ech42 and prb1 are highly expressed. Mycoparasitic signaling is unlikely to be a linear pathway from host signals to increased cAMP levels. Our results demonstrate that the product of the tga1 gene is involved in both coiling and conidiation.

† Background and Aims The Tehuacán Valley in Mexico is a principal area of plant domestication in Mesoamerica. There, artificial selection is currently practised on nearly 120 native plant species with coexisting wild, silvicultural and cultivated populations, providing an excellent setting for studying ongoing mechanisms of evolution under domestication. One of these species is the columnar cactus Stenocereus pruinosus, in which we studied how artificial selection is operating through traditional management and whether it has determined morphological and genetic divergence between wild and managed populations. † Methods Semi-structured interviews were conducted with 83 households of three villages to investigate motives and mechanisms of artificial selection. Management effects were studied by comparing variation patterns of 14 morphological characters and population genetics (four microsatellite loci) of 264 plants from nine wild, silvicultural and cultivated populations. † Key Results Variation in fruit characters was recognized by most people, and was the principal target of artificial selection directed to favour larger and sweeter fruits with thinner or thicker peel, fewer spines and pulp colours others than red. Artificial selection operates in agroforestry systems favouring abundance (through not felling plants and planting branches) of the preferred phenotypes, and acts more intensely in household gardens. Significant morphological divergence between wild and managed populations was observed in fruit characters and plant vigour. On average, genetic diversity in silvicultural populations (H E ¼ 0 . 743) was higher than in wild (H E ¼ 0 . 726) and cultivated (H E ¼ 0 . 700) populations. Most of the genetic variation (90 . 58 %) occurred within populations. High gene flow (Nm FST . 2) was identified among almost all populations studied, but was slightly limited by mountains among wild populations, and by artificial selection among wild and managed populations. † Conclusions Traditional management of S. pruinosus involves artificial selection, which, despite the high levels of gene flow, has promoted morphological divergence and moderate genetic structure between wild and managed populations, while conserving genetic diversity.

The anaiysis of the variability and genetic structure of wild and landrace populations of pepper {Capsicum annuum L.) is important for the management and conservation of valuable genetic resources and to understand the consequences cf domestication on the patterns of neutral genetic variation. For this purpose, 12 popuiations of wild peppers, 3 landrace populations and 7 hybrid populations from northwestern Mexico were studied using microsateliites. On average, 3.62 alíeles per locus were detected in the wild relatives, 3.37 in the landraces, and 3.08 in the hybrids. According to the average vaiues of expected heterozygosity (He), slightly greater genetic diversity was found among the wild relatives (He = 0.466) than in the hybrids (He = 0.440) or the landraces (He = 0.422). In terms of the average number of alíeles per locus and the average expected heterozygosity, reductions of 8.18 and 10.25% were found in the genetic diversity of the landraces and hybrids, respectively, with respect to the wild populations. The genetic differentiation among the populations was the highest among hybrids (Gg.^ = 0.324), followed by landraces (0.309) and wild relatives (the lowest, at 0.208). Cluster analysis clearly demarcated the wild relatives and domesticated populations into different groups. The high levels of genetic diversity found among C. annuum in northwestern Mexico suggest that the wild and landrace populations are a valuable resource that should be conserved.

No abstract

Habitat fragmentation in this landscape is disrupting seed-dispersal-mediated genetic connectivity among extant populations.

• Premise of the study: Microsatellite markers were developed for Spondias radlkoferi to assess the impact of primate seed dispersal on the genetic diversity and structure of this important tree species of Anacardiaceae.• Methods and Results: Fourteen polymorphic loci were isolated from S. radlkoferi through 454 GS-FLX Titanium pyrosequencing of genomic DNA. The number of alleles ranged from three to 12. The observed and expected heterozygosities ranged from 0.382 to 1.00 and from 0.353 to 0.733, respectively. The amplification was also successful in S. mombin and two genera of Anacardiaceae: Rhus aromatica and Toxicodendron radicans.• Conclusions: These microsatellite loci will be useful to assess the genetic diversity and population structure of S. radlkoferi and related species, and will allow us to investigate the effects of seed dispersal by spider monkeys (Ateles geoffroyi) on the genetic structure and diversity of S. radlkoferi populations in a fragmented rainforest.

Intestinal bacteria play an important role in animal health. They extract and process nutrients present in their host's diet, help to develop their host's immune system, and recycle organic compounds, water, and minerals. The gut bacterial diversity is poorly known in wild animals. This study is the first description of the diversity of bacteria along the whole intestine of a wild bird (Passer domesticus). Pyrosequencing of the 16S rRNA gene unveiled a high bacterial diversity, distributed in 11 bacterial phyla. The most abundant groups were Proteobacteria and Firmicutes. Bacterial diversity was greater in the upper section of the intestine and decreased toward the final portion of the gut. After a conservative denoising of the sequences, we found 4,436 OTUs in the gut of P. domesticus. Our data shows that the diversity of intestinal bacteria in the gut of wild birds is much larger than what had previously been estimated using fecal samples.

The Mexican highlands are areas of high biological complexity where taxa of Nearctic and Neotropical origin and different population histories are found. To gain a more detailed view of the evolution of the biota in these regions, it is necessary to evaluate the effects of historical tectonic and climate events on species. Here, we analyzed the phylogeographic structure, historical demographic processes, and the contemporary period, Last Glacial Maximum (LGM) and Last Interglacial (LIG) ecological niche models of Quercus castanea, to infer the historical population dynamics of this oak distributed in the Mexican highlands. A total of 36 populations of Q. castanea were genotyped with seven chloroplast microsatellite loci in four recognized biogeographic provinces of Mexico: the Sierra Madre Occidental (western mountain range), the Central Plateau, the Trans‐Mexican Volcanic Belt (TMVB, mountain range crossing central Mexico from west to east) and the Sierra Madre del Sur (SMS, southern mountain range). We obtained standard statistics of genetic diversity and structure and tested for signals of historical demographic expansions. A total of 90 haplotypes were identified, and 29 of these haplotypes were restricted to single populations. The within‐population genetic diversity was high (mean hS = 0.72), and among‐population genetic differentiation showed a strong phylogeographic structure (NST = 0.630 > GST = 0.266; p < .001). Signals of demographic expansion were identified in the TMVB and the SMS. The ecological niche models suggested a considerable percentage of stable distribution area for the species during the LGM and connectivity between the TMVB and the SMS. High genetic diversity, strong phylogeographic structure, and ecological niche models suggest in situ permanence of Q. castanea populations with large effective population sizes. The complex geological and climatic histories of the TMVB help to explain the origin and maintenance of a large proportion of the genetic diversity in this oak species.