Metabarcoding expands knowledge on diversity and ecology of rare actinobacteria in the Brazilian Cerrado.

Rare and unknown actinobacteria from unexplored environments have the potential to produce new bioactive molecules. This study aimed to use 16 s rRNA metabarcoding to determine the composition of the actinobacterial community, particularly focusing on rare and undescribed species, in a nature reserve within the Brazilian Cerrado called Sete Cidades National Park. Since this is an inaccessible area without due legal authorization, it is understudied, and, therefore, its diversity and biotechnological potential are not yet fully understood, and it may harbor species with groundbreaking genetic potential. In total, 543 operational taxonomic units (OTUs) across 14 phyla were detected, with Actinobacteria (41.2%), Proteobacteria (26.5%), and Acidobacteria (14.3%) being the most abundant. Within Actinobacteria, 107 OTUs were found, primarily from the families Mycobacteriaceae, Pseudonocardiaceae, and Streptomycetaceae. Mycobacterium and Streptomyces were the predominant genera across all samples. Seventeen rare OTUs with relative abundance < 0.1% were identified, with 82.3% found in only one sample yet 25.5% detected in all units. Notable rare and transient genera included Salinibacterium, Nocardia, Actinomycetospora_01, Saccharopolyspora, Sporichthya, and Nonomuraea. The high diversity and distribution of Actinobacteria OTUs indicate the area's potential for discovering new rare species. Intensified prospection on underexplored environments and characterization of their actinobacterial diversity could lead to the discovery of new species capable of generating innovative natural products.

Introgressive hybridization in a Spiny-Tailed Iguana, Ctenosaura pectinata, and its implications for taxonomy and conservation.

Introgression, the transmission of genetic material of one taxon into another through hybridization, can have various evolutionary outcomes. Previous studies have detected signs of introgression between western populations of the Mexican endemic and threatened spiny-tailed iguana, Ctenosaura pectinata. However, the extent of this phenomenon along the geographic distribution of the species is unknown. Here, we use multilocus data together with detailed geographic sampling to (1) define genotypic clusters within C. pectinata; (2) evaluate geographic concordance between maternally and biparentally inherited markers; (3) examine levels of introgression between genotypic clusters, and (4) suggest taxonomic modifications in light of this information. Applying clustering methods to genotypes of 341 individuals from 49 localities of C. pectinata and the closely related C. acanthura, we inferred the existence of five genotypic clusters. Contact zones between genotypic clusters with signatures of interbreeding were detected, showing different levels of geographic discordance with mtDNA lineages. In northern localities, mtDNA and microsatellites exhibit concordant distributions, supporting the resurrection of C. brachylopha. Similar concordance is observed along the distribution of C. acanthura, confirming its unique taxonomic identity. Genetic and geographic concordance is also observed for populations within southwestern Mexico, where the recognition of a new species awaits in depth taxonomic revision. In contrast, in western localities a striking pattern of discordance was detected where up to six mtDNA lineages co-occur with only two genotypic clusters. Given that the type specimen originated from this area, we suggest that individuals from western Mexico keep the name C. pectinata. Our results have profound implications for conservation, management, and forensics of Mexican iguanas.

Fission and fusion in island taxa--serendipity, or something to be expected?

A well-used metaphor for oceanic islands is that they act as 'natural laboratories' for the study of evolution. But how can islands or archipelagos be considered analogues of laboratories for understanding the evolutionary process itself? It is not necessarily the case that just because two or more related species occur on an island or archipelago, somehow, this can help us understand more about their evolutionary history. But in some cases, it can. In this issue of Molecular Ecology, Garrick et al. () use population-level sampling within closely related taxa of Galapagos giant tortoises to reveal a complex demographic history of the species Chelonoidis becki - a species endemic to Isabela Island, and geographically restricted to Wolf Volcano. Using microsatellite genotyping and mitochondrial DNA sequencing, they provide a strong case for C. becki being derived from C. darwini from the neighbouring island of Santiago. But the interest here is that colonization did not happen only once. Garrick et al. () reveal C. becki to be the product of a double colonization event, and their data reveal these two founding lineages to be now fusing back into one. Their results are compelling and add to a limited literature describing the evolutionary consequences of double colonization events. Here, we look at the broader implications of the findings of Garrick et al. () and suggest genomic admixture among multiple founding populations may be a characteristic feature within insular taxa.

Reproductive conflict in bumblebees and the evolution of worker policing.

Worker policing (mutual repression of reproduction) in the eusocial Hymenoptera represents a leading example of how coercion can facilitate cooperation. The occurrence of worker policing in "primitively" eusocial species with low mating frequencies, which lack relatedness differences conducive to policing, suggests that separate factors may underlie the origin and maintenance of worker policing. We tested this hypothesis by investigating conflict over male parentage in the primitively eusocial, monandrous bumblebee, Bombus terrestris. Using observations, experiments, and microsatellite genotyping, we found that: (a) worker- but not queen-laid male eggs are nearly all eaten (by queens, reproductive, and nonreproductive workers) soon after being laid, so accounting for low observed frequencies of larval and adult worker-produced males; (b) queen- and worker-laid male eggs have equal viabilities; (c) workers discriminate between queen- and worker-laid eggs using cues on eggs and egg cells that almost certainly originate from queens. The cooccurrence in B. terrestris of these three key elements of "classical" worker policing as found in the highly eusocial, polyandrous honeybees provides novel support for the hypothesis that worker policing can originate in the absence of relatedness differences maintaining it. Worker policing in B. terrestris almost certainly arose via reproductive competition among workers, that is, as "selfish" policing.