Environmental enrichment, sexual dimorphism, and brain size in sticklebacks

Evidence for phenotypic plasticity in brain size and the size of different brain parts is widespread, but experimental investigations into this effect remain scarce and are usually conducted using individuals from a single population. As the costs and benefits of plasticity may differ among populations, the extent of brain plasticity may also differ from one population to another. In a common garden experiment conducted with three-spined sticklebacks (Gasterosteus aculeatus) originating from four different populations, we investigated whether environmental enrichment (aquaria provided with structural complexity) caused an increase in the brain size or size of different brain parts compared to controls (bare aquaria). We found no evidence for a positive effect of environmental enrichment on brain size or size of different brain parts in either of the sexes in any of the populations. However, in all populations, males had larger brains than females, and the degree of sexual size dimorphism (SSD) in relative brain size ranged from 5.1 to 11.6% across the populations. Evidence was also found for genetically based differences in relative brain size among populations, as well as for plasticity in the size of different brain parts, as evidenced by consistent size differences among replicate blocks that differed in their temperature.Peer reviewe

Genetic diversity and detection of candidate loci associated with alternative morphotypes in a tailed amphibian

Phenotypic changes in response to environmental cues allow organisms to adapt and enhance their fitness in a given habitat. Despite the significance of phenotypic plasticity in the evolution and ecology of natural populations and the ongoing development of new genomic tools, the underlying genetic basis is still largely unknown. Herein, we examined the underlying mechanisms of genetic and phenotypic divergence among alternative morphs of a natural population of the Greek smooth newt (Lissotriton graecus). The studied population consists of fully aquatic individuals exhibiting facultative paedomorphosis, the retention of larval traits such as gills, and individuals that have passed metamorphosis (paedomorphic vs. metamorphic newts). Based on the single nucleotide polymorphisms (SNPs) obtained, we observed low genetic divergence between the two alternative morphs and similar levels of gene diversity on neutral markers. Despite the observed high gene flow between the morphs, an Fst approach for outliers detected candidate loci putatively associated with the alternative morphs that mapped to four genes. These identified genes have functional roles in metabolic processes that may mediate the persistence of alternative ontogenetic trajectories.Peer reviewe

A subtle threat: behavioral and phenotypic consequences of invasive mosquitofish on a native paedomorphic newt

Aquatic invaders often cause severe declines of native amphibian populations, either through competition, predation and/or alterations of the habitat. Such situation has raised additional concerns for the persistence of endemic species exhibiting rare and alternative phenotypes. Here, we experimentally assessed the impact of the invasive mosquitofish (Gambusia holbrooki) on adult newts (Lissotriton graecus) exhibiting paedomorphosis, the retention of larval traits such as gills, making them fully aquatic. Mosquitofish had a negative impact on paedomorphic newts by inducing both behavioral and phenotypic changes. Paedomorphic newts exhibited avoidance behavior and higher metamorphosis rates in the presence of fish. Both female and male newts responded by decreasing mobility and foraging activity. Females stopped investing in egg-laying in presence of fish and males metamorphosed earlier than females. Hence, our results show that mosquitofish introductions, particularly in areas with populations exhibiting paedomorphosis, might have detrimental consequences on the preservation of alternative developmental pathways. Both behavioral and phenotypic effects should be assessed to understand the impacts of introduced species

Phylogeographic Relationships Reveal the Origin of an Introduced Population of the Dalmatian Algyroides (Reptilia: Lacertidae) into Southern Italy

The genetic structure and dispersal dynamics of reptile populations are profoundly influenced by natural processes and human activities. While natural dispersal is shaped by species’ characteristics and paleogeographical features, human-mediated translocations have become increasingly prevalent, posing ecological challenges. Mitochondrial genetic markers have been pivotal in untangling invasion pathways for various species. Our study focuses on the Dalmatian Algyroides, Algyroides nigropunctatus (Duméril & Bibron, 1839), a lizard species endemic to the Balkan Peninsula, where recent observations in the Apulian region of Italy suggest an introduced population. Genetic analyses employing two mtDNA markers (16S and ND4 genes) elucidate the phylogenetic relationships of the Dalmatian Algyroides and trace the geographic origin of the introduced population. Our findings reveal areas in western Greece and southwestern Albania as the most probable areas of the source population, while we identify two previously undetected geographical lineages in the native range, highlighting the complex evolutionary history of the species in the region. Additionally, indications of potential glacial refugia and post-glacial dispersal patterns shed more light on the species’ demographic dynamics