Life cycle strategies have evolved extensively throughout the history of metazoans. The expression of disparate life stages within a single ontogeny can present conflicts to trait evolution, and therefore may have played a major role in shaping metazoan forms. However, few studies have examined the consequences of adding or subtracting life stages on patterns of trait evolution. By analysing trait evolution in a clade of closely related salamander lineages we show that shifts in the number of life cycle stages are associated with rapid phenotypic evolution. Specifically, salamanders with an aquatic-only (paedomorphic) life cycle have frequently added vertebrae to their trunk skeleton compared with closely related lineages with a complex aquatic-to-terrestrial (biphasic) life cycle. The rate of vertebral column evolution is also substantially lower in biphasic lineages, which may reflect the functional compromise of a complex cycle. This study demonstrates that the consequences of life cycle evolution can be detected at very fine scales of divergence. Rapid evolutionary responses can result from shifts in selective regimes following changes in life cycle complexity.

Whole genome duplication plays a central role in plant evolution. There are two main classes of polyploid formation: autopolyploids which arise within one species by doubling of similar homologous genomes; in contrast, allopolyploidy (hybrid polyploidy) arise via hybridization and subsequent doubling of nonhomologous (homoeologous) genomes. The distinction between polyploid origins can be made using gene phylogenies, if alleles from each genome can be correctly retrieved. We examined whether two closely related tetraploid Mediterranean shrubs (Medicago arborea and M. strasseri) have an allopolyploid origin – a question that has remained unsolved despite substantial previous research. We sequenced and analyzed ten low-copy nuclear genes from these and related species, phasing all alleles. To test the efficacy of allele phasing on the ability to recover the evolutionary origin of polyploids, we compared these results to analyses using unphased sequences.

Author summary The Scandinavian peninsula was the last part of Europe to be colonized after the Last Glacial Maximum. The migration routes, cultural networks, and the genetic makeup of the first Scandinavians remain elusive and several hypotheses exist based on archaeology, climate modeling, and genetics. By analyzing the genomes of early Scandinavian hunter-gatherers, we show that their migrations followed two routes: one from the south and another from the northeast along the ice-free Norwegian Atlantic coast. These groups met and mixed in Scandinavia, creating a population more diverse than contemporaneous central and western European hunter-gatherers. As northern Europe is associated with cold and low light conditions, we investigated genomic patterns of adaptation to these conditions and genes known to be involved in skin pigmentation. We demonstrate that Mesolithic Scandinavians had higher levels of light pigmentation variants compared to the respective source populations of the migrations, suggesting adaptation to low light levels and a surprising signal of genetic continuity in TMEM131, a gene that may be involved in long-term adaptation to the cold.

We sequenced the complete mitochondrial genomes of three pairs of congeneric peripheral fishes distributed on either side of the Isthmus of Panama in order to test their status as geminate species pairs. Our phylogenetic analysis did not support a sister relationship between Gobiomorus dormitor and G. maculatus and therefore they cannot be considered geminates. The average genetic distance of protein-coding genes between Sicydium altum and S. salvini was more than two times larger than between Atlantic and Pacific Awaous banana, suggesting different timings for their divergence across the Isthmus of Panama.

Aim The Tasmanian tiger, or thylacine, is an infamous example of a recent human-mediated extinction. Confined to the island of Tasmania in historical times, thylacines were hunted to extinction <150 years after European arrival. Thylacines were also once widespread across the Australian mainland, but became extinct there c. 3,200 years before present (bp). Very little is known about thylacine biology and population history; the cause of the thylacines extirpation from the mainland is still debated and the reasons for its survival in Tasmania into the 20th century are unclear. In this study, we investigate the thylacine's phylogeography and demographic history leading up to their extinction on both the mainland and Tasmania to gain insight into this enigmatic species. Location Southern Australia. Methods We generated 51 new thylacine mitochondrial DNA (mtDNA) genome sequences from sub-fossil remains and historical museum specimens, and analysed them to reconstruct the species’ phylogeography and demographic history. Results We found evidence that thylacines had contracted into separate eastern and western populations prior to the Last Glacial Maximum (c. 25,000 yr bp), and that the ancient western population was larger and more genetically diverse than the historical Tasmanian population. At the time of European arrival in c. 1800 CE, Tasmanian thylacines had limited mtDNA diversity, possibly resulting from a bottleneck event broadly coincident with an El Niño-Southern Oscillation (ENSO) associated climate event, although we find some indication that the population was expanding during the late Holocene. Main Conclusions The timing of this putative expansion, in concert with a climate event, suggests that climate change had an influence on thylacine population dynamics. Given that ENSO effects are known to have been more severe on mainland Australia, we suggest that climate change, in synergy with other drivers, is likely to have contributed to the thylacine mainland extinction.