Low Predictability of Colour Polymorphism in Introduced Guppy (Poecilia reticulata) Populations in Panama.

Colour polymorphism is a recurrent feature of natural populations, and its maintenance has been studied in a range of taxa in their native ranges. However, less is known about whether (and how) colour polymorphism is maintained when populations are removed from their native environments, as in the case of introduced species. We here address this issue by analyzing variation in colour patterns in recently-discovered introduced populations of the guppy (Poecilia reticulata) in Panama. Specifically, we use classic colour analysis to estimate variation in the number and the relative area of different colour spots across low predation sites in the introduced Panamanian range of the species. We then compare this variation to that found in the native range of the species under low- and high predation regimes. We found aspects of the colour pattern that were both consistent and inconsistent with the classical paradigm of colour evolution in guppies. On one hand, the same colours that dominated in native populations (orange, iridescent and black) were also the most dominant in the introduced populations in Panama. On the other, there were no clear differences between either introduced-low and native low- and high predation populations. Our results are therefore only partially consistent with the traditional role of female preference in the absence of predators, and suggest that additional factors could influence colour patterns when populations are removed from their native environments. Future research on the interaction between female preference and environmental variability (e.g. multifarious selection), could help understand adaptive variation in this widely-introduced species, and the contexts under which variation in adaptive traits parallels (or not) variation in the native range.

Extreme mitogenomic divergence between two syntopic specimens of Arremon aurantiirostris (Aves: Emberizidae) in central Panama suggests possible cryptic species.

We report the complete mitochondrial genome of two specimens of Orange-billed Sparrow Arremon aurantiirostris from Colón Province, in central Panama. The two specimens were collected on the same day, and at the same locality; however, they showed substantial divergence (6.3% average pairwise divergence among coding genes). A survey of ND2 sequence variation across Panama suggests that this divergence is the result of geographic differentiation and secondary contact. This high level of mitochondrial divergence among co-occurring individuals raises the possibility of multiple biological species in Orange-billed Sparrows. Our results are yet another demonstration that much remains to be discovered regarding avian biodiversity in Panama and throughout the Neotropics.

Extreme sequence divergence between mitochondrial genomes of two subspecies of White-breasted Wood-wren (Henicorhina leucosticta, Cabanis, 1847) from western and central Panamá.

Prior studies of mitochondrial variation in White-breasted Wood-Wrens (Henicorhina leucosticta) have suggested that populations in South American and Mesoamerica might represent multiple species. Here we report the complete mitochondrial genomes from two individuals of H. leucosticta, representing the Panamanian subspecies pittieri and alexandri. The two sequences were 16,721 and 16,726 base pairs in size with both genomes comprised of the usual 22 tRNA genes, 2 rRNA genes, 13 protein-coding genes, and one displacement loop region in the standard avian order. Uncorrected pairwise divergence between mitogenome features was high, with the highest divergence occurring in protein-coding genes (average = 8.2%), followed by control region (6.7%). RNA features had lower pairwise divergences (average tRNA = 4.3%, average rRNA = 2.3%). The protein-coding ATPase 6 gene had a different stop codon between these two specimens. The high level of sequence variation between these subspecies suggests that Mesoamerican H. leucosticta might be comprised of multiple species. We urge a full phylogeographic survey of this widespread Neotropical forest bird.

Phylogenetic Diversity of Sponge-Associated Fungi from the Caribbean and the Pacific of Panama and Their In Vitro Effect on Angiotensin and Endothelin Receptors.

Fungi occupy an important ecological niche in the marine environment, and marine fungi possess an immense biotechnological potential. This study documents the fungal diversity associated with 39 species of sponges and determines their potential to produce secondary metabolites capable of interacting with mammalian G-protein-coupled receptors involved in blood pressure regulation. Total genomic DNA was extracted from 563 representative fungal strains obtained from marine sponges collected by SCUBA from the Caribbean and the Pacific regions of Panama. A total of 194 operational taxonomic units were found with 58% represented by singletons based on the internal transcribed spacer (ITS) and partial large subunit (LSU) rDNA regions. Marine sponges were highly dominated by Ascomycota fungi (95.6%) and represented by two major classes, Sordariomycetes and Dothideomycetes. Rarefaction curves showed no saturation, indicating that further efforts are needed to reveal the entire diversity at this site. Several unique clades were found during phylogenetic analysis with the highest diversity of unique clades in the order Pleosporales. From the 65 cultures tested to determine their in vitro effect on angiotensin and endothelin receptors, the extracts of Fusarium sp. and Phoma sp. blocked the activation of these receptors by more than 50% of the control and seven others inhibited between 30 and 45%. Our results indicate that marine sponges from Panama are a "hot spot" of fungal diversity as well as a rich resource for capturing, cataloguing, and assessing the pharmacological potential of substances present in previously undiscovered fungi associated with marine sponges.

Exploring possible human influences on the evolution of Darwin's finches.

Humans are an increasingly common influence on the evolution of natural populations. Potential arenas of influence include altered evolutionary trajectories within populations and modifications of the process of divergence among populations. We consider this second arena in the medium ground finch (Geospiza fortis) on Santa Cruz Island, Galápagos, Ecuador. Our study compared the G. fortis population at a relatively undisturbed site, El Garrapatero, to the population at a severely disturbed site, Academy Bay, which is immediately adjacent to the town of Puerto Ayora. The El Garrapatero population currently shows beak size bimodality that is tied to assortative mating and disruptive selection, whereas the Academy Bay population was historically bimodal but has lost this property in conjunction with a dramatic increase in local human population density. We here evaluate potential ecological-adaptive drivers of the differences in modality by quantifying relationships between morphology (beak and head dimensions), functional performance (bite force), and environmental characteristics (diet). Our main finding is that associations among these variables are generally weaker at Academy Bay than at El Garrapatero, possibly because novel foods are used at the former site irrespective of individual morphology and performance. These results are consistent with the hypothesis that the rugged adaptive landscapes promoting and maintaining diversification in nature can be smoothed by human activities, thus hindering ongoing adaptive radiation.

Divergence with gene flow as facilitated by ecological differences: within-island variation in Darwin's finches.

Divergence and speciation can sometimes proceed in the face of, and even be enhanced by, ongoing gene flow. We here study divergence with gene flow in Darwin's finches, focusing on the role of ecological/adaptive differences in maintaining/promoting divergence and reproductive isolation. To this end, we survey allelic variation at 10 microsatellite loci for 989 medium ground finches (Geospiza fortis) on Santa Cruz Island, Galápagos. We find only small genetic differences among G. fortis from different sites. We instead find noteworthy genetic differences associated with beak. Moreover, G. fortis at the site with the greatest divergence in beak size also showed the greatest divergence at neutral markers; i.e. the lowest gene flow. Finally, morphological and genetic differentiation between the G. fortis beak-size morphs was intermediate to that between G. fortis and its smaller (Geospiza fuliginosa) and larger (Geospiza magnirostris) congeners. We conclude that ecological differences associated with beak size (i.e. foraging) influence patterns of gene flow within G. fortis on a single island, providing additional support for ecological speciation in the face of gene flow. Patterns of genetic similarity within and between species also suggest that interspecific hybridization might contribute to the formation of beak-size morphs within G. fortis.

Reproductive isolation of sympatric morphs in a population of Darwin's finches.

Recent research on speciation has identified a central role for ecological divergence, which can initiate speciation when (i) subsets of a species or population evolve to specialize on different ecological resources and (ii) the resulting phenotypic modes become reproductively isolated. Empirical evidence for these two processes working in conjunction, particularly during the early stages of divergence, has been limited. We recently described a population of the medium ground finch, Geospiza fortis, that features large and small beak morphs with relatively few intermediates. As in other Darwin's finches of the Galápagos Islands, these morphs presumably diverged in response to variation in local food availability and inter- or intraspecific competition. We here demonstrate that the two morphs show strong positive assortative pairing, a pattern that holds over three breeding seasons and during both dry and wet conditions. We also document restrictions on gene flow between the morphs, as revealed by genetic variation at 10 microsatellite loci. Our results provide strong support for the central role of ecology during the early stages of adaptive radiation.